Geotechnics doi: 10.3390/geotechnics6030074

Authors: Emil Oynakov Lyubka Pashova Petar Kirilov Mariya Popova Radan Ivanov

Subsurface faults in sediment-covered basins often lack clear surface expressions, necessitating integrated geophysical reconnaissance to identify structural complexities. The eastern margin of the Sofia Basin contains normal faults, with the geometry and activity of unmapped structures near Lozen Mountain being poorly understood. This study examines a presumed subsurface discontinuity using a ~216.2 m passive seismic profile across the Lozen Fault zone. Ambient vibrations from twelve point stations and a fixed reference station were analyzed to map structural anisotropy and wavefield variations using relative vertical-component spectral amplitudes, polarization parameters, and horizontal-to-vertical (H/V) spectral ratios. The spectral amplitude profiling revealed a significant lateral contrast of 6.21 dB across a depth interval of 0–140 m (p = 0.0043), suggesting a potential fault boundary. A two-level step model identified a horizontal transition at 109.0 m, with analyses indicating a zonal wavefield response. Southern stations recorded a more stable polarization axis (mean direction 37.32°) compared to the dispersed northern records (mean direction 60.43°, p = 0.097), while directional shifts in H/V distributions were significant (p = 0.0022). While these observations provide a clear structural indicator rather than direct proof of faulting, they effectively demonstrate that non-tectonic lithological and hydrological variations generate these identical spectral signatures. The results establish a well-constrained spatial target for future multi-profile surveys, electrical resistivity tomography, active-source seismic imaging, and paleoseismological trenches required to conclusively verify the geometry, age, and present-day activity of the fault structure.

Geotechnics doi: 10.3390/geotechnics6030073

Authors: Jaafar Abdulrazzaq Qais Sahib Banyhussan Ahmed A. Hussein Ghazi Jalal Kashesh Anmar Dulaimi Luis José Andrade Pais Luís Filipe Almeida Bernardo

Clayey soils are generally characterized with low strength and high plasticity which may affect the stability of the subgrade in road infrastructure and hence encourage research into sustainable stabilization techniques. The objective of this study was to investigate the possibility of using recycled crumb rubber (CR) mixed with biaxial geogrid reinforcement to enhance the engineering performance and interface shear behaviour of problematic clayey soil. The experiments were performed on biaxial geogrid BX1100, waste crumb rubber, clay subgrade soil, type B subbase granular material and other materials. The subgrade soil of clay has been collected from the airport area of Al-Muthanna region, Baghdad. An extensive programme of laboratory tests was conducted on soil mixtures with 5%, 10% and 15% of crumb rubber (CR) and untreated soil to determine the effect of stabilization with crumb rubber. The protocol consisted of Atterberg limits, modified Proctor compaction, California Bearing Ratio (CBR) and large-scale direct shear testing. The results showed that the engineering properties of the clay soil were improved by using CR. Maximum improvement was observed at 15% CR content where CBR increased by 56.6% and plasticity index decreased by 44% over the untreated soil. In addition, the large-scale direct shear tests showed that the interface shear strength increased with increasing CR content under geogrid reinforcement. The calculated interaction coefficients were greater than unity for all the tested mixtures indicating effective bonding and interlocking between the reinforced soil layers. The results indicate that the synergistic effect of CR and geogrid reinforcement could improve the interface behaviour of the weak clay subgrade soils with sustainable reuse of waste tyre rubber.

Geotechnics doi: 10.3390/geotechnics6030072

Authors: Shaza Soleiman Muhsin Elie Rahhal

Slope stability assessment remains a fundamental challenge in geotechnical engineering because of the complex nonlinear interactions among soil properties, slope geometry, and hydraulic conditions, particularly variations in pore-water pressure. This study investigates the reliability of Artificial Neural Network–Multi-Layer Perceptron (ANN–MLP) models for predicting the Factor of Safety (FoS) of homogeneous soil slopes through a systematic comparison of three gradient-based optimization algorithms: Adam, Mini-Batch Gradient Descent (MBGD), and Nesterov Accelerated Gradient (NAG). A database comprising 2014 slope cases, compiled from published studies and numerically generated using Limit Equilibrium Method (LEM) and Finite Element Method (FEM) analyses, was used for model development and k-fold cross-validation. Beyond statistical evaluation, the developed models were validated using two classical dry-slope benchmark frameworks based on the Taylor stability charts and Bishop–Morgenstern stability coefficients, followed by two documented engineering case studies from Hulu Kelang and Pahang, Malaysia, to assess predictive performance under both dry and variable hydraulic conditions. Adam achieved the highest cross-validated predictive accuracy (R2 = 0.988; RMSE = 0.212), whereas MBGD demonstrated the closest overall agreement with the reference LEM solutions across the validation cases and under increasing pore-water pressure ratios. NAG generally produced more conservative predictions while exhibiting greater sensitivity to hyperparameter selection. All models successfully reproduced the expected nonlinear reduction in FoS with increasing pore-water pressure, consistent with established geotechnical behaviour. The results demonstrate that optimizer selection significantly influences ANN–MLP prediction behaviour and that properly validated gradient-based ANN models can serve as efficient decision-support tools for rapid slope stability assessment under hydraulic variability.

Geotechnics doi: 10.3390/geotechnics6030071

Authors: Marwan Naeem Emran Alotaibi Tadahiro Kishida Mohamed G. Arab Tae-Hyuk Kwon George Mylonakis

Microbially Induced Carbonate Precipitation (MICP) and Enzyme-Induced Carbonate Precipitation (EICP) have emerged as promising sustainable alternatives to conventional ground improvement techniques. This paper presents a focused review of Cone Penetration Test (CPT)-based assessment of bio-cemented soils, synthesizing findings from studies spanning laboratory column tests, centrifuge models, and field trials. The review examines how CPT measurements, including tip resistance (qc), sleeve friction (fs), and pore pressure response (u), reflect the cementation mechanisms, treatment heterogeneity, soil-type effects, and scale dependency characteristic of MICP and EICP treatments. Key findings indicate that MICP and EICP produce distinct CPT responses: MICP-treated sands generally show stronger cementation-related stiffness signatures and more persistent improvement, whereas EICP-treated soils more commonly exhibit sharper near-surface qc gains that may be more susceptible to reduction with time. However, long-term field CPT evidence for EICP durability remains limited. CPT interpretation is more uncertain in fine-grained and heterogeneous soils, where low permeability, preferential flow, localized cementation, and penetration-induced disturbance can produce irregular profiles that are difficult to interpret from qc alone. Fundamental limitations of conventional qc-based CPT interpretation in bio-cemented ground are identified, including its inability to decouple cementation effects from density, stress state, and environmental variability. Multi-sensor CPT platforms integrating shear-wave velocity probes, acoustic emission monitoring, and geochemical sensors are identified as the most promising pathway toward reliable characterization. Three priority developments are outlined: standardized CPT interpretation protocols with calibrated conversion functions for major soil types, validated multi-sensor platforms deployable under field conditions, and machine-learning tools for spatial treatment quality assessment. This review provides a structured CPT-based synthesis of bio-cemented ground and establishes an interpretive basis for future standardized assessment protocols in geotechnical practice.

Geotechnics doi: 10.3390/geotechnics6030070

Authors: Sophia Einspänner Reza Taherdangkoo Christoph Butscher

Large language models are increasingly used to generate engineering code, but executable output does not establish correctness. This study examines an expert supervised workflow used to develop Python implementations for two analytical geotechnical problems: a prescribed circular slip surface calculation using the simplified Bishop method and a shallow foundation bearing capacity calculation. The workflow comprised problem decomposition, specification of geotechnical constraints, modular code generation, expert diagnosis, prompted correction, visual inspection, and comparison with independently configured reference calculations. The slope example documents implementation choices and failure modes for one prescribed slip surface. The bearing capacity study exercised five test groups and 44 calculations covering homogeneous soil, groundwater, two-layer profiles, horizontal loading, and limiting cases. The development process revealed safety-relevant failure modes, including syntax errors, unstable iterations, incorrect geometric extrapolation, and physically inadmissible failure mechanisms. These errors were not resolved reliably by autonomous model self-correction, but required expert diagnosis, modular testing, and constraint-based prompting. The results show that ChatGPT can support the development of geotechnical calculation tools for bounded analytical verification tasks, but only within a strict human-in-the-loop framework. The findings should be interpreted as a case-specific validation of one model system rather than as evidence for the reliability of large language models in general.

Geotechnics doi: 10.3390/geotechnics6030069

Authors: Xiaobao Lu Shifu Wang Meiqian Wang Zhiyi Tang Wei Xu Changxing Zhang

Transparent soil technology (TST) provides a non-intrusive visualization approach for geotechnical model experiments by matching the refractive indices of transparent particles and pore fluids. This review systematically examines recent advances in TST, from material preparation to measurement methods and engineering applications. The preparation of transparent sand and transparent clay, pore-fluid matching, degassing treatment, and mechanical similarity with natural soils are summarized. The development of optical measurement and image analysis methods, including laser slicing, particle image velocimetry, digital image correlation, speckle imaging, and three-dimensional reconstruction, is then discussed to clarify the transition of TST from qualitative observation to quantitative full-field deformation measurement. Bibliometric keyword evolution further indicates that research has shifted from early material feasibility toward engineering-oriented applications and intelligent visualization. Current applications in pile–soil interaction, tunneling, slope instability, seepage, and erosion demonstrate the value of TST for revealing displacement-field evolution, strain localization, seepage-path development, particle migration, and shear-band propagation. Remaining challenges include limited mechanical similarity, optical stability, large-scale applicability, and efficient data processing. Future work should emphasize standardized material systems, high-resolution three-dimensional visualization, multiphysics coupling, and integration with artificial intelligence.

Geotechnics doi: 10.3390/geotechnics6030068

Authors: Kakuta Fujiwara

Small-scale excavations with depths of approximately 1 to 3 m are widely conducted for purposes such as the repair of underground pipelines. In confined construction spaces, earth-retaining systems consisting of lightweight sheet-piles with struts and walers are frequently used. However, comprehensive investigations of the influence of ground conditions on member forces have not yet been conducted. Furthermore, since these temporary structures are generally not designed with seismic considerations, they may suffer damage during earthquakes depending on the soil conditions. Accordingly, this study conducted a comprehensive parametric numerical investigation to evaluate how differences in soil type, such as sandy and cohesive soils, and loading conditions during excavation and earthquake loading affect the internal forces in the supporting members. Excavation analyses using PLAXIS 3D confirmed that as the soil strength parameters (cohesion and internal friction angle) decreased, the demand on the supporting members increased and larger internal forces developed. Dynamic analyses using LIQCA 3D revealed complex behavior in which (i) earth pressure acting on the wall generated compressive forces in the struts, (ii) lateral deformation of the excavation face reduced axial forces in the struts, and (iii) when the ground liquefied, it exhibited a vibration-isolation effect, and the vibration components generated in the structural members became smaller.

Geotechnics doi: 10.3390/geotechnics6030067

Authors: Ali Ghaffarnezhad Parto Arya Assadi-Langroudi Emad Maleki Tabrizi Arash Esmatkhah Irani Masoud Hajialilue-Bonab Meghdad Bagheri

Rocking foundations reduce seismic force demand through controlled uplift and rotation, but their application remains limited by uncertainty in residual settlement and recentring capacity. Grouting is often employed to reduce these serviceability concerns, yet uncertainty in the geometry of the improvement and seismic demand constrains confident adoption. This paper examines whether strength- and serviceability-related responses of jet-grouted rocking foundations exhibit comparable epistemic uncertainty when motion amplitude and grouting layout are represented by bounded Random Set inputs. A sparse deterministic response database was generated using three-dimensional finite-difference modelling for isolated columns, directional walls, and intersecting walls beneath a 3 × 3 m2 foundation supporting a bridge-pier-type structure. The grouting layout was represented by a directional stiffness isotropy index. Motion demand was represented through bounded peak ground acceleration intervals. The deterministic results indicate that walls aligned with the excitation direction provide greater settlement reduction and energy dissipation than isolated columns or perpendicular walls. Variation in the depth of intersecting walls further reveals a trade-off between settlement reduction and recentring capacity. Random Set propagation was then used to construct uncertainty bounds for maximum moment, residual settlement, and recentring ratio. The results show that moment demand is comparatively well constrained, whereas serviceability indicators exhibit wider epistemic uncertainty.

Geotechnics doi: 10.3390/geotechnics6030066

Authors: Yan Zhang Jun Xu Miaojun Sun Bohan Zhou Mengfen Shen Honglei Sun

This study investigates marine sand collected from the southeastern coast of China through laboratory calibration chamber model tests under varying relative densities and consolidation stresses. The consolidation characteristics and cone penetration test (CPT) penetration response of soil specimens were examined, and interpretation models relating CPT parameters to soil unit weight, relative density, and shear wave velocity were established. Results show that shear wave velocity increases with relative density, with consolidation exerting a stronger enhancement. Lateral earth pressure exhibits a pronounced distance attenuation effect, with stress differences most prominent near-field and diminishing with distance. Cone tip resistance increases with both relative density and consolidation stress, with consolidation stress exerting a more significant influence on low-density specimens; sleeve friction increases linearly with relative density. The interpretation models achieve good correlations with unit weight (R2 = 0.78), normalized cone tip resistance with the square of relative density (R2 = 0.72), and shear wave velocity (R2 = 0.85), and field validation confirms higher prediction accuracy than conventional empirical formulas for terrigenous sands. The models enable rapid, cost-effective parameter estimation from routine CPT data, though they remain site-specific, being based on nine chamber tests and validated against six field layers from a single site.

Geotechnics doi: 10.3390/geotechnics6030065

Authors: Yinfeng Tang Tongxu Wang Yuxiang Ma Yaling Wang

To elucidate the active–passive reinforcement mechanisms of rock bolts and the evolution of shear strength in anchored rock joints, this study integrates theoretical analysis, laboratory direct shear tests, and numerical simulations to investigate the deformation and failure characteristics of fully grouted, end-anchored, and prestressed bolted specimens. The results show that bolt reinforcement can be classified into prestress-dominated active action and dislocation-induced passive action. The shear strength curve of anchored rock joints exhibits four distinct stages with increasing shear displacement: initial slip, elasticity, yielding, and softening. Fully grouted bolts fail primarily by tensile–shear fracture, enabling a rapid increase in shear strength at small displacements. In contrast, end-anchored bolts undergo S-shaped bending and form symmetrical plastic hinges on both sides of the joint, sustaining resistance under large displacements albeit with lower peak strength. While the laboratory tests experimentally clarified the distinct failure modes and passive shear resistance mechanisms of fully grouted and end-anchored bolts, the quantitative partitioning between active and passive contributions was derived from a numerically simulated prestressed bolt model. The simulations indicate that for prestressed bolts, the active contribution accounts for approximately 69.6% of the total shear strength enhancement, while the passive contribution is about 30.4%. These findings yield actionable design criteria: end-anchored or yielding bolts are recommended for high-geostress environments or scenarios involving large potential deformations to exploit the large-deformation bearing capacity of passive action; conversely, prestressed bolts should be prioritized where strict control of early-stage deformation is required to maximize active support efficiency.

Geotechnics doi: 10.3390/geotechnics6030064

Authors: Alaa T. Alisawi Philip E. F. Collins Ruqayah F. Alrubaye

Regional geotechnical archives contain valuable information for numerical modelling, but they are rarely organised in a form that supports traceable derivation of constitutive input parameters for advanced geotechnical analysis. This study develops a groundwater-corrected workflow for transforming regional borehole and consolidation records into finite element-ready constitutive parameter sets for shallow clayey soils, using Al Qadisiyah Governorate, Iraq, as a case study. The workflow combines data cleaning; treatment of limited missing data; derivation of λ, κ, e0; preconsolidation pressure, initial effective vertical stress; overconsolidation ratio; and correction of effective stress using observed groundwater conditions. The derived parameter set captures the compressibility, initial state, and stress history variables commonly required for Modified Cam-Clay-based finite element modelling, providing a practical workflow for parameter derivation from routine regional borehole and consolidation data. The results reveal clear vertical and lateral variability in compressibility, density state, and stress history, indicating that the investigated deposits cannot be represented adequately by a single regional parameter set. Groundwater correction was essential for realistic estimation of effective stress and OCR, particularly given the shallow groundwater table throughout the study area. The processed constitutive input dataset was translated into representative finite element material libraries in both overall and depth-specific forms, while GIS-based maps were developed to support spatial interpretation and location-informed parameter selection. The main contribution is the integrated and traceable conversion of regional borehole records into groundwater-corrected constitutive parameters and practical FE material libraries, rather than the separate application of existing empirical or mapping tools. This study demonstrates that routine borehole archives can be transformed into traceable constitutive resources for finite element modelling of shallow clay deposits, supporting preliminary material assignment, depth depth-specific interpretation, and location-informed parameter selection.

Geotechnics doi: 10.3390/geotechnics6030063

Authors: Thomas Beingessner Davide Elmo

Progressive slope failures in open pit mining are characterized by accelerating deformations that can be monitored and potentially forecast. While current monitoring practice emphasizes velocity-based parameters and the inverse velocity method for failure prediction, the role of acceleration in understanding failure mechanisms and improving early warning systems remains underexplored. This paper presents a conceptual and analytical framework for characterizing acceleration in progressive slope failures. We introduce the concept of slope damage as a cumulative measure of positive accelerations over time, and demonstrate its utility in identifying the Onset of Acceleration (OOA), defined as the critical transition from regressive to progressive failure. We further examine the geotechnical conditions necessary for the inverse velocity method to be valid, proposing that a fully or nearly fully mobilized failure surface is required for sustained acceleration. The conceptual link among rock bridge degradation, fracture network connectivity, and the OOA framework is explored using the Network Connectivity Index (NCI), which is presented as a hypothesis for future numerical investigation and systematic empirical testing. This work contributes to the fundamental understanding of progressive failure mechanisms and provides practical guidance for acceleration-based slope monitoring.

Geotechnics doi: 10.3390/geotechnics6030062

Authors: Besar Abdiu Julijana Bojadjieva Lisa M. Star

Soil–Structure Interaction (SSI) is known to influence the seismic response of structures; however, its implications for the classification of dual wall–frame systems within the framework of Eurocode 8 remain insufficiently understood. This study investigates how SSI affects not only the global response but also the code-based classification of a reinforced concrete dual wall–frame system. A 9-storey prototype building is analyzed using fixed-base and flexible-base models, considering linear-elastic, nonlinear static (pushover), and nonlinear dynamic (time-history) analyses. As expected, the results show that SSI induces a significant redistribution of seismic forces, reducing the contribution of shear walls and increasing the role of frames. As a consequence, the system classification shifts from wall-equivalent dual to frame-equivalent dual, or even toward frame-dominated behavior under Eurocode 8. A comparison with ASCE/SEI 7-16 reveals that such classification changes are less pronounced due to broader system definition limits. The findings highlight that SSI influences not only structural demand but also key design parameters, including behavior factors and force distribution assumptions. This underscores the need for consistent consideration of SSI effects in both analysis and system classification within seismic design codes.

Geotechnics doi: 10.3390/geotechnics6030061

Authors: Nantapol Monthanopparat Tawatchai Tanchaisawat

Reliable construction-phase prediction of hard rock tunnel boring machine (TBM) rate of penetration (ROP) remains difficult because ground–machine interaction changes along the alignment and uniaxial compressive strength (UCS) is often incomplete or delayed at ring scale. This study proposes a construction-phase reliability framework that integrates sequence deep learning, inverse-distance-weighted UCS completion, chronological rolling evaluation, PassRate monitoring, and performance-triggered updating. The framework was developed from a granite-dominated TBM drive in northern Thailand and evaluated under a delayed-UCS information policy. In the Phase-2 forward deployment-style evaluation, the selected gated recurrent unit (GRU) model achieved a root mean square error (RMSE) of 0.1639 m/h, a mean absolute error (MAE) of 0.1186 m/h, and 62.63% within a symmetric ±10% accuracy band over 990 evaluated rings. Direct static application of representative theoretical and empirical models produced substantially lower within-band performance of 11.92–20.71%. One early reliability trigger occurred at Ring 3409, after which UCS updating, retraining, and redeployment restored the monitoring process without further intervention triggers. The results show that construction-phase TBM prediction should be managed as an auditable reliability workflow with explicit information boundaries, rather than as a single static accuracy score.

Geotechnics doi: 10.3390/geotechnics6030060

Authors: Ahmed Mneina Mohamed Hesham El Naggar Osama Drbe

Piles with continuous helix (referred to herein as “screw pile”) is a new configuration of helical piles. It features a continuous helix spiraling several pitches around a smooth shaft forming a “threaded shaft”. This study investigates the compressive capacity and behavior of helical and screw piles using 3D numerical models calibrated and validated against full-scale field testing. The bearing capacity factor, Nc, for helical piles is back-calculated from the numerical results and compared against standard theoretical assumptions to evaluate their accuracy in predicting ultimate capacity. Parametric studies are conducted considering screw piles configuration, including shaft diameter, pitch size, helix diameter, as well as soil strength. The results reveal that shaft resistance accounts for up to 89% of the total capacity. Analysis of load distribution, shear contours, and displacement contours at failure allowed for the identification of different failure modes of soil adjacent to the pile’s threaded shaft: Individual Bearing Mode (IBM), Cylindrical Shear Mode (CSM), and a combined mode. The study identifies specific parametric thresholds for these modes in both sand and clay layers. Furthermore, varying clay strength is found to alter the development of the shear surface, transitioning from localized bearing to continuous shearing along the threaded shaft. Finally, apparent shaft resistance factors, α and β, are back-calculated to provide practical parameters for evaluating the resistance of threaded shafts in layered soil.

Geotechnics doi: 10.3390/geotechnics6030059

Authors: Gabriela Mariana Dragomir Mihaela Roca Irina Rozica Mircea

While geotechnical parameter determination is fundamental to foundation engineering, traditional approaches often suffer from data fragmentation and subjective safety assessments. This research introduces an integrated framework that synthesizes multivariable regression with the Effective Random Dimension (ERD) method to bridge the gap between raw laboratory indices and structural design. By analyzing datasets from the stable Suceava Moldavian Platform (68 samples) and the tectonized Subcarpathian Flysch (50 samples), the study demonstrates that granulometric fractions, moisture content, and carbonate content can predict consistency limits with high statistical fidelity, achieving R2 = 0.98 for the Liquid Limit at Suceava and R2 ≈ 0.90 for the Plasticity Index at Doftana. The novelty of the approach lies in the generation of continuous vertical profiles transformed into code-compliant characteristic values (Xk) via Taylor series linearization and the ERD framework. The derived characteristic interval for the Plasticity Index (58.66–70.15%) quantitatively demonstrates the reduction in hyper-conservative bias compared with discrete sampling. This methodology eliminates subjective judgment and ensures a mathematically rigorous transition to Eurocode 7 and NP 122:2010 standards, optimizing both safety and economic efficiency in variable geological strata.

Geotechnics doi: 10.3390/geotechnics6030058

Authors: Haifeng Zhu Xiaolin Xu Bo Tian Honggang Li Chao Gao Tianyu Ma Fengkai Zhang Yang Yang Zhengyu Liu

“Interbedded water in thin coal seams” is characterized by its high degree of concealment and complex hydraulic connections. However, due to the confined space of underground mine tunnels and severe electromagnetic interference from metal structures, traditional geophysical methods struggle to accurately delineate the boundaries of water accumulation, making this a major and challenging water hazard in coal mines. Taking the Qinhua Coal Mine in Xinjiang, China, as the engineering context, this paper investigates the detection of water accumulation in interbedded coal seams within goaf areas using the cross-hole resistivity method. It proposes a cross-hole resistivity tomography scanning approach characterized by “progressive depth penetration and layer-by-layer traversal,” and employs an inversion method based on inequality constraints to obtain relatively detailed and reliable imaging results. Through resistivity imaging analysis, low-resistivity water accumulation anomalies were successfully delineated, and water accumulation dead zones were identified. Based on the detection results, effective drainage was carried out beneath the water-filled zones. Subsequent follow-up surveys confirmed the disappearance of the low-resistivity anomalies, thereby validating the reliability and engineering practicality of the cross-hole resistivity tomography method for precisely detecting water body boundaries under complex geological conditions in coal seams.

Geotechnics doi: 10.3390/geotechnics6020057

Authors: Michelle R. Basham Amy B. Cerato

Expansive clays exhibit shrink–swell behavior driven by microscale physicochemical interactions that are not fully captured by conventional macroscopic descriptors. This study presents a quantitative framework for evaluating microstructural evolution in expansive clays using Environmental Scanning Electron Microscopy (ESEM) combined with fractal dimension and lacunarity analysis under controlled suction paths. ESEM micrographs were collected along primary drying and secondary wetting paths across multiple magnification scales. Fractal dimension quantifies surface complexity, while lacunarity characterizes pore distribution and clustering. Fractal dimension increases with magnification and suction, reflecting greater exposure of particle surfaces as pore water is removed. Lacunarity decreases with magnification and shows soil-dependent trends with suction, indicating changes in pore heterogeneity. Hysteresis in both metrics reveals irreversible microstructural rearrangement associated with particle aggregation and fluid redistribution. These results demonstrate that fractal dimension and lacunarity provide complementary descriptors of soil fabric and establish a quantitative link between microstructure and suction-driven behavior in expansive clays.

Geotechnics doi: 10.3390/geotechnics6020056

Authors: Michelle R. Basham Amy B. Cerato Preston Larson

Expansive soils undergo structural changes in response to moisture fluctuations, often governed by suction hysteresis. This study investigates the microstructural evolution of three expansive soils using Environmental Scanning Electron Microscopy (ESEM) under controlled drying and wetting cycles across a broad suction range. Soils were prepared with varying compaction states, equilibration times, and physicochemical properties—including specific surface area (SA) and cation exchange capacity (CEC). Images captured at multiple magnifications revealed key trends in water film behavior, cracking, and fabric rearrangement. Image-derived pore-area ratios were used as comparative indicators of microstructural deformation during drying and wetting. High-activity clays (as defined by SA and CEC) displayed pronounced hysteresis and cracking, while low-activity soils exhibited minimal structural change. These findings highlight the role of microscale behavior in expansive soil performance and provide a foundation for improved predictive modeling. In addition, the study provides a framework for future quantitative microstructural characterization using fractal descriptors, enabling future analyses to capture pore complexity and scale-dependent fabric evolution during suction hysteresis.

Geotechnics doi: 10.3390/geotechnics6020055

Authors: Wenpeng Liu Shengli Wang Junbiao He Qingyun Xu Nestor Tupa Di Wang Nan Zhang

The stability of tailings dams is governed predominantly by the physical properties and geotechnical behavior of their primary construction material—tailings. Consequently, a systematic understanding of these characteristics is of great significance for the rational design and long-term stable operation of tailings dams. This review focuses on the physical properties and geotechnical behavior observed in different types of tailings. In terms of physical properties, the particle size distribution exhibits a pronounced hydraulic classification characteristic within the impoundment, consisting predominantly of silt-sized particles and displaying an overall trend toward finer gradation. The mineralogical and chemical composition is dominated by quartz, hematite, and silicates. However, significant spatial variability exists both between different tailings types and across distinct zones within the same tailings pond. Regarding geotechnical behavior, the permeability of tailings is governed by a fines content threshold: below this threshold, permeability decreases with increasing fines content, while beyond it, the permeability stabilizes. When studying consolidation and compression behavior using slurry specimens, the compression curves exhibit nonlinear characteristics, primarily described by the modified Gibson theory. The shear behavior of tailings is significantly influenced by confining pressure, drainage conditions, anisotropy and stress paths. The presence of transitional behavior leads to the critical state line determined based on a single sampling method erroneously assessing the dilation/cosntraction characteristics of in situ tailings, thereby affecting the assessment of liquefaction risk. Future research should focus on the seepage, consolidation and shear properties of clayey fine-grained tailings and unsaturated tailings, and aim to elucidate the key controlling factors of transitional behavior to enhance the reliability of tailings dam stability assessments.

Geotechnics doi: 10.3390/geotechnics6020054

Authors: Meho Saša Kovačević Mario Gazdek Lovorka Librić Danijela Jurić Kaćunić

Reliable assessment of small-strain soil stiffness is essential for geotechnical site characterization and for analysing the behaviour of embankments and other earth structures. Surface-wave methods provide an efficient non-destructive means of estimating shear-wave velocity profiles; however, their application is limited by the non-uniqueness of the inversion process. This paper implements and evaluates a PSO-based multimodal inversion framework for Rayleigh-wave dispersion curves in the context of geotechnical characterization of layered soil profiles. The procedure involves the calculation of theoretical dispersion curves for a horizontally layered medium and their matching with experimental data through a global search scheme. The implemented framework was first evaluated using two synthetic soil profiles, and its robustness was further assessed by considering perturbations of the theoretical dispersion curve of up to 10%. Particular attention was given to the influence of higher modes on the inversion results. The results indicate that including higher modes can improve the determination of shear-wave velocity profiles for the analysed cases compared with an inversion based solely on the fundamental mode. The procedure was subsequently validated on a transverse embankment profile using an experimental dispersion curve obtained by multichannel analysis of surface waves (MASW), with comparison against seismic cone penetration test (SCPT) results. Good agreement was obtained, and the eight-layer model proved to be a good compromise between accuracy and model complexity. The results indicate that the implemented PSO-based multimodal inversion framework can support the geotechnical characterization of layered soil profiles for the analysed synthetic and field cases, particularly when modal branches are clearly identified and appropriately included in the inversion.

Geotechnics doi: 10.3390/geotechnics6020053

Authors: Yong Li Shengya Zhou Fankai Liu Zhiyu Dong Xiangtai Fan Zhi Ge Chong Li Hongzhi Zhang

Enzyme-Induced Carbonate Precipitation (EICP) represents a sustainable advancement in geotechnical engineering for stabilizing fine-grained soils (e.g., silt). Utilizing plant-derived urease (~12 nm) to catalyze urea hydrolysis, this technique generates calcium carbonate (CaCO3) for soil reinforcement. Unlike Microbially Induced Carbonate Precipitation (MICP), EICP overcomes microbial size constraints (0.5–3 µm) by penetrating soil micropores, enabling uniform cementation. Its innovative single-phase low-pH method achieves >98% calcium conversion efficiency, yielding 6.41 MPa unconfined compressive strength (UCS) in sand—a 92.97% improvement over MICP. EICP demonstrates versatility: enhancing soil strength (up to 650% for silt), erosion resistance (wind erosion modulus increased ~20-fold), anti-seepage performance (permeability reduced from 10−6 to <10−9 cm/s), and heavy metal immobilization (>99%). However, challenges include unstable crystal morphologies (e.g., excessive vaterite), urease stability/cost constraints, and environmental concerns related to NH3 emissions from urea hydrolysis. The manuscript acknowledges these emissions’ impacts and introduces mitigation strategies: ammonia capture technologies, optimized dosing protocols, and exploration of alternative N-sources. Long-term durability data under complex field conditions remain insufficient. Ongoing research addresses these gaps through nucleating agents (dried skim milk, biochar), enzyme immobilization, process optimization, and byproduct treatment. As a low-carbon technology with targeted mitigation measures, EICP advances environmentally conscious soil stabilization practices. This study presents a comparative narrative analysis of EICP’s performance and challenges, integrating laboratory findings and field applications.

Geotechnics doi: 10.3390/geotechnics6020052

Authors: Ernest Daniel Olinic

Expansive soils pose significant challenges in geotechnical engineering due to their volume changes with moisture variations. A critical distinction exists between a soil’s inherent potential to swell or shrink (governed by intrinsic parameters such as clay content, plasticity index, and activity index) and its actual behaviour under specific site conditions (governed by state parameters like porosity and water content). This paper critically evaluates the reliability of widely used single-index and multi-index classification methods against direct oedometer measurements of swelling pressure. Analysis of nearly 600 tests on natural active clays from four different sites in Romania reveals that, for these soils and site conditions, no single intrinsic parameter—nor any simple pair of parameters—correlates reliably with swelling pressure, demonstrating that these indices merely indicate potential, not actual, behaviour. In contrast, state parameters provide more meaningful insights. Drawing on parallels with collapsible soil mechanics, the study introduces the concept of “saturation-independent pressure” (sip), the stress level beyond which saturated and natural-moisture soil behaviours converge. Furthermore, a practical calculation method is proposed for estimating both foundation heave (upon saturation) and shrinkage (upon drying), based on double oedometer compressibility curves. Notably, a strong correlation (R2 = 0.79–0.86) is demonstrated between swelling pressure and the specific swelling strain measured under an initial load of 12.5 kPa, offering a rapid and inexpensive screening tool for identifying potentially problematic active clays.

Geotechnics doi: 10.3390/geotechnics6020051

Authors: Nabeela Maheen Kazuhide Sawada Daisuke Ueda Hayashi Motoyuki Takahiro Yoshikawa

Rockfall is one of the most dangerous and unpredictable natural disasters that can seriously damage infrastructure. In traditional protection systems, sand is commonly used as a buffer material; however, the use of large sandbags as temporary protective structures has still not been investigated, and there are no established design guidelines available. This study aims to reveal the effect of rockfall impact on the dynamic response of a sandbag protection system for temporary restoration work in the event of a natural disaster. Initially, a numerical model based on finite element calculation was adopted to simulate the large sandbags under rockfall impact, which was verified by the full-scale experimental test data. The parameters identified were impactor velocity, acceleration, penetration depth, and sandbag displacement. After validation, the model was used for prediction analysis to examine the dynamic response and energy absorption characteristics of sandbags under different conditions, such as the influence of sand density, impactor velocity, impact height and the number of sandbags in the impact direction. The results propose an analytical basis for the establishment of performance-based guidelines for the design of sandbag walls as a temporary rockfall protection system.

Geotechnics doi: 10.3390/geotechnics6020050

Authors: Yuxuan Zeng Jun Guo Wangyu He Yueying Chen Meng Ma

In the assessment of bearing capacity for in-service bridge pile foundations, static load tests are costly, destructive, and difficult to scale. The traditional dynamic formula approach relies heavily on an empirical dynamic–static conversion coefficient that introduces considerable uncertainty. To address these limitations, this study proposes a non-destructive evaluation method for pile foundation bearing capacity based on measured dynamic stiffness and machine learning algorithms. Using data from a highway bridge inspection project, a dataset comprising 680 piles was compiled, including measured dynamic stiffness, geometric parameters, and design load information. An end-to-end binary classification model was constructed to map multidimensional physical features to an engineering decision target, namely, whether the bearing capacity meets the design requirement. The performance of several algorithms was compared, including logistic regression, random forest, and gradient boosting decision tree (GBDT). Among the evaluated models, the GBDT model demonstrated the best capability for capturing the complex nonlinear pile–soil interactions. On an independent test set, it achieved an accuracy of 96.3% and an F1 score of 0.96, with a very low false-negative rate, satisfying the high precision required for engineering safety screening. Feature importance analysis indicates that measured dynamic stiffness contributed approximately 42% to the classification outcome, establishing it as the dominant indicator for detecting capacity deficiencies and reinforcing its physical relevance as a key health indicator for pile foundations. This study demonstrates that data-driven methods can effectively circumvent the uncertainty associated with traditional empirical coefficients, providing a promising approach to the health monitoring and rapid evaluation of in-service bridge pile foundations.

Geotechnics doi: 10.3390/geotechnics6020049

Authors: Danabek Saduakassov Annaguly Deryaev Anvar Eshmuratov Ernazar Sanetullaev

This article considers the causes of inter-column pressures (ICP) in wells and their impact on operational reliability. The analysis of Karachaganak field well stock for the period from 2001 to 2024 demonstrates that inter-column pressures manifest in a time frame of five to six years following drilling. These pressures are characterized by a spontaneous emergence and subsequent dissipation. This study proposes a mechanism where the formation of ICP is influenced by multiple factors, including cementing defects, as well as physical and chemical processes. Additionally, the geological heterogeneity of the section has been identified as a contributing factor. The results of studies employing a mobile laboratory and pumping unit are presented. The mobile laboratory unit (MLU) operates with pressure sensors in the range of 0–100 MPa (accuracy ±0.5%), a pump rate of 0.5–20 L/min, and an injection pressure up to 70 MPa; fluid sampling is performed by a discrete sampler with a volume of 500 mL. These allow the identification of sources and channels of fluid migration into the inter-column space, as well as the carrying out of technological operations to reduce and eliminate ICP. This paper sets out a risk-oriented method of inter-column pressure assessment. The proposed risk-based method classifies wells into three risk levels (low, medium, high) based on a composite index R = (P/Pmax) + (V/Vmax) + (C/Cmax) where P is annulus pressure, V is escaped fluid volume per day, C is concentration of H2S, CO2, or mercaptan, respectively, and threshold values are Pmax = 35 MPa (API RP 90), Vmax = 50 m3/day, and Cmax = 10 ppm for H2S. This method takes into account not only the pressure value, but also the volume of escaping fluid and the concentration of aggressive components. It is concluded that an integrated approach to diagnostics and management of inter-column pressures is necessary. This approach should be supported by technological solutions that ensure increased reliability and environmental safety of well operation.

Geotechnics doi: 10.3390/geotechnics6020048

Authors: Henrique Milan André Luis Meier Gracieli Dienstmann Helena Paula Nierwinski Murilo da Silva Espindola Orlando Martini Oliveira Rafael Augusto dos Reis Higashi

Penetration rate effects and partial drainage can govern piezocone (CPTu) response in intermediate permeability geomaterials, but field testing at a fixed standard rate limits systematic evaluation. This study presents the development and laboratory validation of a miniature piezocone system and testing framework to investigate rate-dependent penetration response in laboratory-prepared silty sand. Baseline dry and flooded specimens were tested using a triaxial-based configuration at penetration velocities of 9.6, 0.28, 0.10, and 0.03 mm/s, including selected holding periods for dissipation. A dedicated servo-controlled penetration system was then implemented for slurry-prepared specimens, enabling continuous constant-velocity penetration over a wider velocity range (0.004–15 mm/s). Cone resistance was interpreted using normalized net resistance (Q) and normalized velocity (Vh), and pore pressure using normalized excess pore pressure (Δu2/σ′v0). The results show a monotonic rate dependency, with Q increasing as Vh decreases, while Δu2/σ′v0 progressively decreases toward zero at intermediate-to-low Vh; at the lowest rates, pore-pressure readings were affected by instrument signal limitations. A hyperbolic-cosine backbone fitted to the normalized response provided good agreement for resistance (R2 = 0.99, RMSE = 3.41) and more limited agreement for pore pressure (R2 = 0.30, RMSE = 0.23). The drainage transition for the tested material occurs in an interval of approximately Vh ≈ 0.3~30. The study provides a reproducible laboratory approach—combining miniature instrumentation, controlled specimen preparation, and variable-rate penetration—to generate normalized drainage-transition trends for rate-effect investigations in intermediate geomaterials.

Geotechnics doi: 10.3390/geotechnics6020047

Authors: Abilash Pokhrel Sean Rees Ali Tasalloti Gabriele Chiaro

Shear wave velocity (VS) measurements are widely used to characterize geomaterials, evaluate small-strain stiffness, and develop indirect approaches for estimating the liquefaction resistance of various soil types. In this study, the bender element method was employed to investigate the VS characteristics of sand–gravel mixtures (SGMs), with the aim of clarifying the combined effect of key factors such as gravel content (GC), relative density (Dr), packing state, and soil fabric. Laboratory tests were performed on reconstituted specimens composed of two sandy soils and pea gravel with GC of 0, 10, 25, 40, 60, 80 and 100% and Dr of 20, 30, 45 and 60%. Specimens were prepared using wet tamping (WT) and air pluviation (AP) techniques. VS measurements were conducted under effective confining stresses (σ′0) of 50, 100, 150 and 200 kPa. The results show that the VS of SGMs increases with increasing Dr and p′0, whereas the influence of GC depends on the limiting and threshold sand contents. The effect of soil fabric was found to be marginal. Furthermore, the combined effects of GC and Dr on VS can be uniquely captured using the equivalent void ratio approach for SGMs with sand-dominated microstructures, while the skeleton void ratio approach is more appropriate for SGMs with gravel-dominated microstructures.

Geotechnics doi: 10.3390/geotechnics6020046

Authors: Ivan Sakhno Svitlana Sakhno Oleksandr Kyrsanov Serhii Bashynskyi Oleksandr Nosach Liubov Shaidetska Denys Darmostuk

In the case of pillarless coal mining, the floor uplift reaches 60–80% of the total vertical convergence in gob-side entry, while total convergence often exceeds 1.0 m. This is one of the key factors impedimental to pillarless mining in deep coal mines. Traditional methods of floor heave control in gob-side entry are not effective enough, so they need to be improved. This paper is devoted to the improvement of the anti-shear pile method in gob-side entry retaining. Finite element analysis was used as the main study method. The influence of pile diameter and its design on the stress–strain distribution in the surrounding rock and on the floor uplift magnitude was determined. It was found that the filled piles are the most efficient in reducing floor heave magnitude, asymmetry of floor uplift, and size of post-peak strain in the immediate floor. In filled piles, the steel tube prevents the concrete core from fracturing, while the concrete core prevents the steel tube from plastic yielding. Therefore, with the same diameter and elastic modulus, filled piles are 1.06–1.7 times more effective in floor heave control than comparable analogs.

Geotechnics doi: 10.3390/geotechnics6020045

Authors: Gregorii Iovlev Andrey Katerov Anna Andreeva Alisa Ageeva

Maintaining the integrity of impermeable strata between mine workings and overlying aquifers is critical, because seepage pathways may cause mine flooding and surface subsidence. In the Upper Kama potash deposit, the impermeable sequence is a 50–140 m thick layered sequence of evaporites and clays overlying mined-out chambers. Under long-term loading, salt rocks tend to creep, soften, and localize damage, which can cause failure in the impermeable strata. In this paper, the Concrete damage-plasticity model, supplemented by the N2PC-MCT viscoplastic creep model, is applied to simulate the initiation and evolution of seepage pathways in the Upper Kama impermeable strata. Model parameters are obtained from published laboratory tests (uniaxial and triaxial compression and tension) and validated using observed ground-surface subsidence. A plane-strain finite-element model incorporates the stratified lithology, interface elements between layers, and sequential excavation. Long-term simulations up to 50 years investigate two operational scenarios: with and without backfilling. The calibrated model reproduces the main stages of surface subsidence and chamber closure. Without backfilling, simulations indicate that tensile damage localizes mainly in a stiff central salt layer of the impermeable strata, with most cracks appearing approximately between 33 and 37 years after the start of mining. With backfill, tensile crack propagation stops and damage remains stable. A hypothetical homogeneous impermeable strata case confirms that the observed central-layer cracking is associated with stiffness contrasts and composite bending in the stratified system. An approximate analytical multilayer beam solution, based on energy minimization, predicts bending stress concentration in stiff intermediate layers and is consistent with the numerical stress distribution. The combined numerical and analytical results provide insight into the mechanisms of long-term conductive fracture initiation in stratified impermeable strata and may serve as a basis for preliminary hazard indication and for planning mitigation measures, including backfilling and focused monitoring of stiff central layers. Because the study is based on a 2D plane-strain model, the quantitative estimates should be regarded as preliminary and require verification by 3D modelling and further field observations.

Geotechnics doi: 10.3390/geotechnics6020044

Authors: Bibi Wang Wenbing Guo Yi Tan Dan Chen Erhu Bai Yatao Li Zhibo Ge Yixiang Feng Chaoqun Hu

Coal mining beneath rivers in thick collapsible loess areas involves prominent risks of surface subsidence, riverbed damage, and water inrush, which threaten both mining safety and land–water ecological stability. Taking the Dan River Coal Mine in Shanxi Province, China, as a case area, this study establishes a systematic safety assessment and adaptive remediation framework for longwall mining under complex geological conditions involving collapse columns, dynamic river hydrology, and collapsible loess. A multi-method analytical approach integrating theoretical calculation, 3DEC numerical simulation, and engineering analogy is used to determine the development height of water-conducting fracture zones and the stability of collapse columns. On this basis, a 55 m wide waterproof coal–rock pillar is designed, and the secondary open-off cut is optimized. Surface deformation monitoring shows a maximum surface subsidence of 3.9 m and reveals key movement angles specific to thick collapsible strata. These results support the formulation of adaptive mining control strategies and integrated river protection measures, including composite geomembrane anti-seepage, gabion reinforcement, and overburden grouting for subsidence mitigation. The integrated technical system of pre-mining evaluation, dynamic process control, and post-mining remediation effectively protects river integrity, controls land deformation, and reduces environmental impacts. This study provides a replicable model for safe coal resource extraction, subsidence management, and land–water environmental protection in similar mining areas under rivers and thick collapsible loess conditions.

Geotechnics doi: 10.3390/geotechnics6020043

Authors: Jaafar Abdulrazzaq Qais Sahib Banyhussan Ahmed A. Hussein Anmar Dulaimi Hugo Alexandre Silva Pinto Luís Filipe Almeida Bernardo

This study considers the potential of utilizing waste glass powder as a sustainable additive to improve the characteristics of clay subgrade soils. A comprehensive experimental program was designed, wherein a selected clay soil was amended with four distinct contents of glass powder that were finely ground: 0%, 3%, 6%, and 9% by weight. The primary objective was to evaluate the resultant improvements in soil strength and the enhanced interfacial bond between the treated subgrade and an overlying Type B granular subbase layer, which was further reinforced with an SS2 Geogrid. To characterize these effects, a suite of laboratory tests was performed, including the Modified Proctor Test, Atterberg Limits Test, California Bearing Ratio (CBR) test, and a large-scale direct shear test. A specially made large-scale instrument for direct shear was employed for the interface testing. The results demonstrate a clear positive correlation between the proportion of glass powder and the improvement in geotechnical properties. The most significant enhancement was observed at the 9% inclusion rate, which yielded a 6.6% increase in the maximum dry density and a substantial 49% improvement in the CBR value. Concurrently, this optimal mix design resulted in a 14% reduction in optimum moisture content, alongside notable decreases in the swelling and plasticity indices by 33% and 39%, respectively, confirming the efficacy of glass powder in stabilizing the clay subgrade.

Geotechnics doi: 10.3390/geotechnics6020042

Authors: Faouzia Kharrachi Adam Hamrouni Daniel Dias Madani Sid

This study investigates the undrained bearing capacity of strip foundations subjected to inclined loading on two-layer cohesive slopes using finite element limit analysis (FELA). Both lower bound (LB) and upper bound (UB) theorems with adaptive mesh refinement are employed to conduct comprehensive parametric analyses examining the influence of key geotechnical and geometric factors on the bearing capacity factor Nci and associated failure mechanisms. The parameters investigated include the interlayer shear strength ratio cu1/cu2, load inclination angle α, upper layer thickness ratio D/B, setback distance b/B, normalized undrained shear strength of the upper layer cu1/γB, and slope angle β. The results demonstrate that load inclination and interlayer strength contrast have a pronounced effect on the bearing capacity, while the failure mode transitions between foundation failure and overall slope failure depending on the geometric configuration. The numerical results are validated against existing published data, showing excellent agreement with a maximum relative error of 1.19%. Comprehensive design charts are provided to facilitate the bearing capacity estimation and failure pattern identification under various geometric and loading configurations, offering practical guidance for geotechnical engineers dealing with foundations on stratified slopes.

Geotechnics doi: 10.3390/geotechnics6020041

Authors: Zijing Song Chunyang Hu Zhixing Ren Hongwei Guo Chengshun Xu

Rapid landslide susceptibility screening is important for linear engineering projects because long corridors, numerous slope units, limited data, and tight schedules often restrict the use of data-intensive models. This study develops an engineering-oriented reduced-factor screening framework based on the Information Value (IV) model and applies the framework to the Beijing-Zhangjiakou Railway corridor. A conventional 10-factor IV model was first established as the reference model. Reduced-factor models were then screened under the same study area, the same landslide inventory, the same modelling workflow, and the same factor classification scheme. The 10-factor model reached an accuracy of 94.87%. Two reduced five-factor models reached the same accuracy: Slope + Aspect + Elevation + Lithology and Engineering Rock + NDVI, and Slope + Aspect + Elevation + Lithology and Engineering Rock + Distance to Rivers. The comparison shows that the full-factor model can be simplified without loss of validation accuracy when a stable terrain–geological framework is retained and a suitable external factor is added. Because the available inventory contains only 45 landslides and does not distinguish failure mechanisms consistently, the proposed model should be regarded as a preliminary probabilistic screening tool rather than a mechanism-specific prediction model. The proposed framework provides a practical approach for corridor-scale hazard screening under incomplete data conditions.

Geotechnics doi: 10.3390/geotechnics6020040

Authors: Juan Carlos Ruge Carlos J. Slebi-Acevedo

Volumetric collapse, a critical phenomenon in clayey soils, is characterized by a sudden reduction in volume when subjected to wetting under a specific effective vertical stress. This behavior is primarily caused by the breakdown of cementing bonds between particles in the soil’s interstitial spaces. Our study, which examines the impact of unit weight and wetting on the collapse potential of clayey soils under various stress conditions, has practical implications for geotechnical engineers. We evaluated three-unit weights spanning from loose to compacted states and assessed collapse behavior at various stress levels. Even in the observations of the microstructure under a scanning electron microscope, which corroborated the images, the pathology is evident. The results demonstrate an explicit dependency between unit weight and collapsibility. Statistical analysis revealed that unit weight was the predominant factor influencing the outcomes, with the magnitude of applied stress being identified as a secondary yet notable determinant. Furthermore, the non-linear interactions, as elucidated through ANOVA and Tukey’s HSD tests, serve as instrumental methodologies in this analytical framework. The findings underscore a significant correlation between applied stress and collapse potential, underscoring the crucial role of soil densification in mitigating the risks associated with collapse phenomena.

Geotechnics doi: 10.3390/geotechnics6020039

Authors: Ching-Chuan Huang

This study re-examines two geologically and geotechnically similar geosynthetic-reinforced soil walls with modular block facings (GRS-MBs) that exhibited markedly different seismic performances during the 1999 Chi-Chi earthquake (ML = 7.3). Integrating a multi-wedge failure mechanism that captures soil–facing–reinforcement interactions with a nonlinear hyperbolic soil model representing shear stress–displacement behavior along the slip surface, the Force–equilibrium-based Finite Displacement Method (FFDM) provides consistent and robust displacement evaluations over a wide range of input seismic inertial forces. A systematic sensitivity investigation confirms that the FFDM framework responds to parameter variations in a physically meaningful manner, and that displacement predictions remain stable with respect to reasonable uncertainties in soil, reinforcement, and facing properties. The analysis clarifies why two similar GRS-MBs responded so differently during strong shaking and demonstrates the broader applicability of FFDM for displacement-based seismic assessment, including under shaking levels (e.g., kh ≈ 0.3) that would drive conventional limit–equilibrium calculations to Fs < 1.0, a physically impossible state requiring shear resistance greater than the soil’s ultimate strength. A comparative evaluation of seismic displacement predictions using the Newmark method and FFDM shows that FFDM successfully generates displacement-based seismic resisting curves and reproduces field-observed displacements. In contrast, the Newmark method yields order-of-magnitude variability in predicted movements and may be unsuitable for displacement-sensitive engineered slopes where deformations on the order of several 10−3–10−2 m are practically significant. For interaction-rich GRS-MBs with high values of khc, beyond the predictive capability of Newmark’s equation, FFDM offers a practical and physically grounded tool for seismic displacement assessment of reinforced soil structures.

Geotechnics doi: 10.3390/geotechnics6020038

Authors: Kaustav Chatterjee Mohak Desai Joshua Li

Over the last two decades, there has been a paradigm shift in geotechnical engineering driven by advances in sensing, communication, and data-driven techniques. These advancements enhanced the safety and reliability of geotechnical infrastructure through real-time monitoring and automated decision-making. In recent times, Large Language Models (LLMs) have emerged as advanced data-driven techniques contributing to automated risk assessment of geotechnical infrastructure. LLMs are advanced deep learning models widely used to solve complex numerical problems, analyze large volumes of data, and generate human language. This paper presents a critical review of the application of LLM in geotechnical engineering. The integration of LLMs into geotechnical engineering has demonstrated significant advances in slope stability analysis, bearing capacity computation, numerical analysis, soil–structure interaction, and underground infrastructure. By summarizing the latest research findings and practical applications, this research paper underscores the potential of LLMs to advance and automate various processes in geotechnical engineering. The findings presented in this paper not only provide insights into the current LLM-based geotechnical practices but also emphasize the instrumental role that LLM can play in advancing geotechnical engineering, ultimately ensuring a safer and more sustainable future. Lastly, this paper highlights the different LLM capabilities which can be used to empower geotechnical engineers.

Geotechnics doi: 10.3390/geotechnics6020037

Authors: Takaji Kokusho Tomohiro Ishizawa Jiro Mori Michinori Mizuhara

Slope displacements (δ) have been shown to correlate uniquely with the earthquake energy (Eeq) contributing to slope sliding, regardless of input motion characteristics. Based on this principle, this study applies the Energy-Based Newmark Method to infinitely long slopes subjected to ten diverse earthquake records with stepwise scaled amplitudes. As the earthquake wave energy (Eᵤ) increases, the energy ratio (Eeq/Eᵤ) exhibits a distinct peak followed by a monotonic decrease. The peak values and corresponding Eᵤ levels strongly depend on the predominant frequencies (fp) of the motions, consistent with results from harmonic wave analyses. A unified design diagram is developed to correlate Eeq/Eᵤ with Eᵤ, incorporating fp and slope parameters. Since both Eᵤ and fp can be determined from design motions or empirically predicted using earthquake magnitudes and source distances, the slope displacement δ can be directly obtained from the diagram, eliminating the need for time-domain numerical simulations used in the conventional Newmark approaches. This method is recommended to conduct seismic zonation and hazard mapping in mountainous and hilly regions for regional authorities and infrastructure planners.

Geotechnics doi: 10.3390/geotechnics6020036

Authors: Ekrem Bektašević Luka Crnogorac Kemal Gutić Vancho Adjiski Rade Tokalić Ahmed Mušija

This study investigates road tunnel stability in heterogeneous flysch formations using the Zenica Tunnel as a case study. A hybrid research framework integrating empirical classification, analytical modeling, and numerical simulation was applied. The approach combines the Rock Mass Rating (RMR) system, the Convergence–Confinement Method (CCM), and nonlinear two-dimensional finite element (FEM) analyses. Statistical evaluation of the results reveals a strong exponential relationship between the stability factor Ns and measured tunnel convergence, with coefficients of determination (R2) between 0.89 and 0.96. Particular attention was given to sections classified as Category V rock mass. The analysis indicates that when RMR values fall below 25, the stability factor Ns exceeds the critical value of 5, marking the onset of pronounced squeezing behavior. The results show that analytical methods provide conservative estimates of tunnel stability, while numerical modeling enables improved calibration of support system stiffness. The proposed integrated methodology contributes to more reliable stability assessment and support design in road tunnels excavated in complex flysch formations.

Geotechnics doi: 10.3390/geotechnics6020035

Authors: Huanxiao Hu Shifan Shen Huatang Shi Wenqin Yan

To address the critical challenges of geological hazards, such as water and mud inrush, encountered during the construction of deep-buried tunnels in China, this study investigates the hydraulic properties of remolded mud-infill materials. A multi-scale approach, integrating indoor variable-head permeability tests with scanning electron microscopy (SEM), was employed to characterize the evolutionary patterns of the permeability coefficient (k). Specifically, the research evaluates the independent influences of moisture content, dry density, and confining pressure, alongside the synergistic coupling between dry density and hydration state. The results demonstrate the following: Under independent variable conditions, k exhibits a monotonic decline with increasing dry density and confining pressure while showing a positive correlation with moisture content, with the sensitivity varying significantly across different parameter regimes; under coupled effects, the permeability in both low- and high-moisture ranges manifests a distinct “increase–decrease–increase” fluctuation as dry density rises, reaching a local peak at 2.20 g/cm3. Notably, a relative minimum k (6.12 × 10−7 cm/s) is achieved at the optimum moisture content (5.8%); micro-mechanistic analysis reveals that low-moisture samples are characterized by randomized angular particles and well-developed interconnected macropore networks, facilitating higher k values. Conversely, high-moisture samples exhibit preferential plate-like stacking dominated by occluded micropores, resulting in a substantial reduction in hydraulic conductivity. This study elucidates the multi-factor coupling mechanism governing the seepage behavior of remolded mud, providing essential theoretical benchmarks for the prediction and mitigation of water–mud outburst disasters in deep underground engineering, thereby ensuring the structural stability and operational safety of tunnel projects.

Geotechnics doi: 10.3390/geotechnics6020034

Authors: Nelson García Per Gunnvard Tan Manh Do Jan Laue

Sulphide soil is an organic soil characterised by high water content and poor geotechnical properties. When excavated, it oxidises and becomes an environmental hazard due to leached metals and acid drain. To avoid excavation, methods for utilizing more sulphide soil as a subgrade material are being developed. However, precise characterisation of sulphide soil is challenging, as its inherent properties make it prone to sample disturbance, introducing large scatter into geotechnical test results. To minimise the scatter in laboratory test results, a portion of the characterisation could be based on reconstituted samples. This study explores the applicability of the slurry deposition method to produce homogeneous, repeatable and representative sulphide soil samples. The reconstituted samples were assessed by comparing their initial index properties and triaxial behaviour against those of the intact samples. The index properties of the tested reconstituted samples precisely and accurately matched the average results of the intact samples. The undrained triaxial behaviour and derived critical state line of the reconstituted samples and the intact samples were found to be comparable. Neither type of sample reached critical state in drained triaxial testing. In conclusion, this study suggests that the slurry deposition method is suitable for reconstituting sulphide soil samples.

Geotechnics doi: 10.3390/geotechnics6020033

Authors: Vachan Vanian Pavlos Asteriou Theodoros Rousakis Ioannis P. Xynopoulos Constantin E. Chalioris

The integration of vertical greenery systems (VGSs) into existing reinforced concrete (RC) buildings raises questions regarding interface kinematics and the permanent displacement of soil-retaining elements under seismic excitation. This study experimentally investigates the residual displacement of façade-mounted living walls and rooftop planter pods anchored to a deficient RC frame under shake table excitation. A 1:3 scale reinforced concrete frame was tested in two distinct phases: initially as a deficient, unretrofitted structure (Phase A), and subsequently as a retrofitted system integrated with vertical greenery elements (Phase B). High-precision terrestrial laser scanning (TLS) was employed before and after successive seismic excitation stages to generate dense three-dimensional point clouds. Cloud-to-cloud comparison techniques were used to quantify global structural displacement and local kinematic behavior of greenery components, while results were validated against conventional displacement sensors. The RC frame exhibited millimeter-scale permanent displacements consistent with draw-wire measurements. In contrast, planter pods demonstrated configuration-dependent behavior, including up to 8 cm translational sliding and rotational responses reaching 13° under repeated excitation, whereas living wall panels remained stable. Notably, a 95% reduction in point cloud density reproduced global deformation patterns with an RMSE of 3.03 mm and quantified peak displacements with only ~2% deviation from full-resolution results. The findings demonstrate the capability of TLS-based monitoring to detect differential kinematic behavior of integrated VGSs, while highlighting the variability in performance of friction-based rooftop anchorage utilizing different robust planter pod fixing systems.

Geotechnics doi: 10.3390/geotechnics6020032

Authors: Rafika Lachache Salim Kouloughli Ana Bras Halima Belhadad

Dredged reservoir sediments (DRS), generated in large volumes during dam desilting operations, pose significant stockpiling and land-use challenges in Mediterranean regions. Owing to their high fines content and moderate plasticity, these sediments present potential for reuse as compacted hydraulic barrier materials. This study evaluates the feasibility of using DRS as a liner material and, for the first time, provides a direct comparative assessment of natural (wheat straw fibers, WSF) and synthetic (polypropylene fibers, PPF) reinforcement within the same sediment matrix under liner-relevant conditions. Fiber contents of 0–0.9% (by dry mass) were investigated. Mechanical and consolidation behaviors were assessed using direct shear and oedometer tests. Fiber inclusion significantly improved shear strength, with an optimal response at 0.6%. At this dosage, PPF reduced the compression index by ~50%, while WSF provided moderate but consistent improvement. Estimated hydraulic conductivity increased slightly with fiber addition but remained within the range typically reported for compacted barrier materials. FTIR analysis indicated distinct reinforcement mechanisms, with lignocellulosic interactions for WSF and mechanical bridging for PPF. These results demonstrate that DRS can be effectively valorized as liner materials, while highlighting the contrasting performance of biodegradable and synthetic fibers, with 0.6% identified as a balance between mechanical efficiency and material sustainability.

Geotechnics doi: 10.3390/geotechnics6020031

Authors: Abdullah O. Baarimah Madhusudhan Bangalore Ramu Aiman A. Bin Mokaizh Ahmed Wajeh Mushtaha Aawag Mohsen Alawag Arsalaan Khan Yousafzai Tharaa M. Al-Zghoul

Simple shear testing is a widely used method in geotechnical engineering for evaluating soil liquefaction susceptibility, deformation characteristics, and shear strength under controlled loading conditions. This study presents a bibliometric analysis of research trends in simple shear testing based on 367 publications indexed in the Scopus database between 2000 and 2024, analyzed using VOS-viewer. It appears that the current research output on this topic has greatly increased lately. The number of research articles reached a peak in 2024 with a total of 42 research articles. The most frequently cited journals on this topic are Soil Dynamics and Earthquake Engineering, with a total of 48 research articles (1173 citations); the Journal of Geotechnical and Geo-environmental Engineering, with a total of 34 research articles (772 citations); and the Canadian Geotechnical Journal, with a total of 10 research articles (250 citations). This indicates substantial research interest in earthquake engineering and soil mechanics. The output shows that there is a major emphasis on research done in the USA, with a total of 104 research articles (1215 citations). The highest average citations per document belong interestingly to the research done by Taiwanese, with a total of 36.73 citations. Similarly, it appears that there is a good impact on soil liquefaction studies. The research findings show that confining pressure, strain rates, and volume ratio affect the shear strength of the soil. Advances in boundary control and shear testing techniques have improved the reliability of experimental results. The study underscores the growing need for more sophisticated numerical modeling techniques and field verification to bridge the gap between laboratory findings and real geotechnical applications. These findings contribute to improving soil characterization methods, which enable safer and more efficient geotechnical designs for infrastructure development.

Geotechnics doi: 10.3390/geotechnics6010030

Authors: Sevki Ozturk Mehmet Ufuk Ergun

This study experimentally investigates the shear strength behavior of interfaces formed between granular soils and clay under drained conditions, with particular emphasis on peak-to-residual strength evolution. Large and small-scale direct shear tests were performed on clay, granular soils (sand and gravel), and their interfaces, and shearing was continued to large displacements to reliably capture residual behavior. Unlike most previous studies that focus on soil mixtures, this study explicitly quantifies interface-specific shear strength parameters and highlights their distinct mechanical response. The results show that while interface cohesion remains comparable to that of clay, the interface friction angle is consistently higher. Specifically, under residual conditions, the friction angle of the clay (12.9°) increased to 16.4° for the sand–clay interface and to 19.8° for the gravel–clay interface. These findings demonstrate that adopting clay residual parameters for granular soil–clay interfaces may be overly conservative and that interface-specific residual friction angles should be considered in stability analyses of slopes and earth structures.

Geotechnics doi: 10.3390/geotechnics6010029

Authors: Thibault Badinier Siegfried Maiolino Habibou Maitournam

The geometry of ballasted railway tracks is crucial for ensuring railway safety and efficiency. This paper introduces the use of innovative steady-state algorithms designed to compute plastic strains in linear geotechnical structures like railway ballast layers, within Finite Element Methods (FEMs). Facing the specificities of moving loads, traditional step-by-step algorithms, while simple and adaptable, are computationally expensive and time-consuming. In contrast, the proposed steady-state algorithms leverage an Eulerian approach to describe the movement of loads significantly reducing computational time while maintaining accuracy. This paper proposes these algorithms as a methodological improvement and demonstrates the applicability and efficiency of the method for non-periodic structures, as well as for periodic structures, such as railway tracks with evenly spaced sleepers. This paper demonstrates the applicability and efficiency of theses algorithms through comparative studies with traditional methods on typical railway structures. The results show that the presented algorithm not only matches the accuracy of step-by-step methods but also drastically reduces computation time and data storage requirements. This advancement has practical applications for railway infrastructure managers, enabling more efficient and accurate predictions of track geometry evolution and preventing incidents through improved maintenance strategies.

Geotechnics doi: 10.3390/geotechnics6010028

Authors: Konstantinos Syngros George Mylonakis

Viscoelastic solutions are developed for the axial dynamic response of single piles in soil profiles that are inhomogeneous both vertically (with depth) and horizontally (with radial distance from the pile). While vertical soil inhomogeneity has been well explored, horizontal inhomogeneity has received limited research attention. In this work, the problem is treated in the realm of linear elastodynamic theory by employing a rigorous finite-element formulation specifically developed by the authors for the problem at hand. The effect of double soil inhomogeneity is investigated with reference to: (1) pile head stiffness; (2) pile-head radiation damping; (3) soil reaction along the pile; and (4) variation of the above with loading frequency. To this end, four different soil profiles are considered in conjunction with different levels of soil inhomogeneity, pile lengths, pile–soil stiffness contrasts, and boundary conditions at the pile tip. It is shown that the effect of inhomogeneity has unique features that cannot be captured by using a substitute homogeneous profile. Modeling an inhomogeneous soil as a homogeneous layer providing equal pile-head stiffness (to be referred in this work to as “stiffness-equivalent soil”) may grossly overestimate wave radiation, leading to dampened estimates of dynamic pile response. Simulations of two field experiments are reported, and implications of radiation damping in design are discussed.

Geotechnics doi: 10.3390/geotechnics6010027

Authors: Nazim Hussain Guoxin Zhang Songhui Li Yongrong Qiu Arifullah

Seepage through construction joints is a major factor affecting uplift pressure and long-term safety of concrete dams. Pre-existing joints with millimeter-scale openings provide preferential flow paths, where hydraulic pressure can induce joint opening and permeability escalation. In this study, seepage-induced joint-opening behavior is investigated using a coupled hydromechanical numerical framework with damage-dependent aperture evolution. The impacts of initial crack width, interface cohesiveness, and interface tensile strength on the evolution of crack opening displacement (COD) and hydraulic instability are comprehensively isolated by parametric studies. The results show that, once tensile opening is activated, variations in cohesion have a negligible influence on pressure–COD responses and failure pressure, indicating that cohesion degradation does not control seepage-induced instability in pre-existing cracks. In divergence, interface tensile strength strongly governs damage initiation, the onset of rapid crack opening, and the critical hydraulic pressure at failure. Larger initial crack widths act as geometric accelerators, leading to earlier instability and enhanced permeability evolution under increasing seepage pressure. A dimensionless, pressure–tensile strength ratio is shown to unify the observed responses, revealing a transition from a geometry-controlled regime to a damage-dominated failure regime. These findings indicate that seepage-induced instability in concrete dams is primarily controlled by tensile resistance of construction joints rather than cohesion degradation, providing guidance for uplift pressure assessment and seepage control design.

Geotechnics doi: 10.3390/geotechnics6010026

Authors: Jinxing Ma Xiaogang Zhang Jiabang Yu Yonghong Jia Xinyu Huang

Global climate change has intensified the need for clean and stable energy sources. Geothermal energy, with its consistent availability, is crucial for the transition to renewable energy systems. This study aims to numerically evaluate the enhancement of heat extraction in a mid-deep coaxial geothermal heat exchanger (GHE) when using water-based Al2O3 and SiO2 nanofluids. A comprehensive 1D pipe flow- and 3D subsurface heat transfer-coupled model was developed and validated against field experimental data. The results demonstrate that the nanofluids significantly enhanced heat extraction. The water–SiO2 nanofluid achieved the highest outlet temperature, exceeding pure water by approximately 0.2 °C after 2000 h. A lower inlet temperature of 5 °C increased heat extraction by 88.57% compared to 25 °C, despite a lower outlet temperature. The thermal influence radius expanded from <2 m at 300 h to ~6 m at 1800 h. This study provides quantitative insights and a validated framework for optimizing GHE performance through nanofluid selection and operational control.

Geotechnics doi: 10.3390/geotechnics6010025

Authors: Mahsa Gharizadehvarnosefaderani Md. Fazle Rabbi Debakanta Mishra

The structural and geotechnical characteristics of railroad tracks change abruptly at transition zones. At these locations, a change from ‘rigid’ to ‘flexible’ track conditions or the opposite leads to amplified dynamic responses, large deformations, accelerated track deterioration, and increased maintenance expenses. Researchers have conducted numerous field and numerical studies into track transitions’ behavior; however, their investigations are often limited by point-based and short-term measurements and assumptions that overlook critical mechanisms in track transitions. This review presents current sensor-centric knowledge achieved by integrating insights from field instrumentations and numerical modellings of transition zones. The objective is to expose the overlooked behavioral aspects of track transitions and identify the limitations of conventional monitoring systems. To address these gaps, this review introduces optical fiber sensors (OFSs) as an emerging technology for track condition monitoring. Focusing on recent OFS applications, this study demonstrates how OFSs can improve the quantity and quality of field data through spatial continuity, multiplexing, and higher sensitivity, thus marking a significant practical improvement. This review also outlines OFS-based monitoring challenges, such as sensor durability, measurement quality, temperature-strain cross-sensitivity, and lack of a standardized data interpretation framework. Altogether, this work’s novelty is in connecting transition zone behavior, monitoring limitations, and the inherent potential of OFS systems.

Geotechnics doi: 10.3390/geotechnics6010024

Authors: Jonatas Sosnoski Gracieli Dienstmann Helena Paula Nierwinski Edgar Odebrecht Graziella Maria Faquim Jannuzzi Fernando Artur Brasil Danziger

Limitations of the cone penetration test, especially to accurately determine undrained shear strength (Su) in soft soil deposits with high in situ stresses, have motivated the development of alternative devices, such as the T-bar and ball penetration tests, commonly referred to as flow penetrometers. These devices can estimate, in a single test, both the undrained shear strength (Su) and the remolded strength (Sur). When equipped with pore pressure sensors, they also provide valuable information on soil stratigraphy and consolidation parameters, making them versatile tools for characterizing soft soils. This study presents the development of two flow penetrometers, piezoball and piezo-T, highlighting relevant aspects of their design and calibration, followed by experimental campaigns conducted in two Brazilian clay deposits (Tubarão/SC and Sarapuí/RJ). Field tests enabled a direct comparison between the flow penetrometers and conventional methods, both in terms of Su and Sur. The investigation also examined the coefficient of consolidation of the soft soils. The results demonstrate good repeatability and consistent values for the bearing capacity factors (Nb and Nt) and remolded behavior (Nb-rem and Nt-rem). Regarding the performance of the pore pressure transducers, the piezoball test demonstrated good performance in pore pressure measurements and derived coefficients of consolidation. In contrast, despite the proposed design modifications, the piezo-T exhibited instability in the readings. Although the findings are derived from specific sites, the discussion is framed in light of the ranges reported internationally, highlighting potential local implications and reinforcing the need to expand robust geotechnical databases to support future applications.

Geotechnics doi: 10.3390/geotechnics6010023

Authors: Yuamar Imarrazan Basarah Mirna Dwi Lestari Salamah Masyhur Irsyam Dedi Apriadi Endra Susila Sugeng Krisnanto Juan Marvel

The geological complexity of Java Island, Indonesia, has resulted in the extensive distribution of very soft clay soils, posing significant challenges to geotechnical design and construction. A reliable estimation of the geotechnical properties of these soils is therefore essential to address these challenges and ensure the safety and sustainability of construction projects. The cone penetration test with pore pressure measurement (CPTu) is a reliable in situ test for soil characterization, providing a continuous shear strength profile. However, the determination of a representative cone bearing factor (Nkt) to estimate undrained shear strength (Su) is critical for geotechnical design. Although several studies on CPTu have been conducted in Indonesia, there has been a lack of emphasis on establishing Nkt values for local soft, high-plasticity clays in Indonesia. This study aims to fill this gap in the literature by proposing updated correlations for Nkt specific to the soft, high-plasticity clays of Java, Indonesia, derived from the statistical analysis of combined field and laboratory data obtained from two representative sites in Western Java. These sites correspond to a coastal plain deposit in Central-North Jakarta and an alluvial deposit in Gedebage, Bandung. A comprehensive database was compiled, consisting of 20 CPTu boreholes, 84 depth points of vane shear test (VST), 29 samples of consolidated undrained (CU) triaxial tests, 26 samples of unconsolidated undrained (UU) triaxial tests, and 18 standard penetration test (SPT) boreholes. The results indicate that the representative Nkt value for these soft, high-plasticity clays in the investigated sites in Western Java ranges from 14 to 16. A refined empirical correlation between Nkt and the pore pressure ratio (Bq) is proposed, demonstrating consistent trends with recent data. Additionally, a reasonable correlation between the undrained modulus (Eu) and undrained shear strength of Eu = 276–323 Su was identified, enabling the derivation of a continuous profile of the undrained modulus from CPTu data. This study also further highlighted the absence of significant relationships between Nkt and other parameters such as OCR, PI, and NSPT. These findings provide practical insight and a regionally calibrated reference that can be useful for engineers working in similar soft, high-plasticity clay environments with characteristics comparable to the investigated sites in Western Java.

Geotechnics doi: 10.3390/geotechnics6010022

Authors: Wendy L. Puente-Castillo Lorenzo Borselli Damiano Sarocchi Azalea J. Ortiz-Rodriguez Dino Torri

Reliable field estimation of near-surface soil hydraulic parameters remains challenging, particularly in heterogeneous or stony soil environments. Conventional drip infiltrometers (DI) are widely used, but their field deployment may limit mobility and testing efficiency. This study presents a portable drip infiltrometer (PDI) methodology that enhances field applicability while reducing testing time without compromising parameter robustness. The approach enables estimation of saturated hydraulic conductivity (Ks), effective net capillary drive (G), and sorptivity (S) by integrating image-based analysis of ponded surface areas using the Portable Drip Infiltrometer Software (PDIS v1.5) with linear and non-linear infiltration formulations optimized through evolutionary algorithms. A total of 34 PDI field tests were conducted across two Mexican regions with contrasting climatic and soil conditions. In semi-arid environments, Ks ranged from 1.07 to 12.82 mm h−1 and G from 89.1 to 1999.99 mm, whereas in semi-warm sub-humid settings, Ks ranged from 30.68 to 117.68 mm h−1 and G from 2.65 to 121.64 mm. Results indicate that linear formulations perform adequately under relatively homogeneous conditions, while non-linear PDI formulations become necessary as surface structural complexity increases. The PDI–PDIS framework provides a rapid, repeatable, and physically grounded tool for parameterizing near-surface hydraulic processes in heterogeneous soils.

Geotechnics doi: 10.3390/geotechnics6010021

Authors: Asha U. Rao Narayana Sabhahit Lathashri U. Ananda Radhika P. Bhandary

The laterite formations consist of top layers that are highly porous, followed by a lithomargic soil layer over the weathered residual soil and parent rock. The excavated slopes are stable during summer, but the slopes with exposed lithomargic soils have failed during rainy season even when safety factor was more than one. The present study considers the effect of erosion in the lithomargic layer of soil while analyzing the stability of slopes. Janbu’s GPS (Generalized Procedure of Slices) method in conjunction with a genetic algorithm is used to analyse the slope stability and to locate the noncircular critical slip surface. A failed slope from the Yekkur site was considered for the study considering three possible failure mechanisms (Mechanism I, II and III) of slopes due to progressive erosion of fines in the lithomargic soil layer. It is observed that the lithomargic soil’s vulnerability to erosion depends on a critical combination of sand content and hydraulic gradient causing piping. Mechanism III is more critical as compared to other mechanisms and a similar observation was made from failed slopes in the field. The failure in lateritic soil slopes is mainly due to piping of lithomargic soil, which reduces the length of the critical slip surface, and failure due to erosion is progressive.

Geotechnics doi: 10.3390/geotechnics6010020

Authors: Yunfeng Zhang Ahmet Darilmaz

This study investigates how incorporating physical constraints can enhance the performance of machine learning models by ensuring that geotechnical drilling data predictions align with known physical conditions at the site. Machine learning-predicted soil property point cloud data has significant value for geotechnical project planning. The base model was trained on extensive borehole datasets of soil properties collected from an area of 32,133 square km covering five distinct physiographical regions. To incorporate physics-based constraints, a custom loss function was defined to penalize the model training loss whenever it violates known physical principles. Two distinct types of machine learning models—classification and regression models—are considered in this study for categorical and numerical geotechnical drilling datasets, respectively. Feature variables play a critical role in determining the accuracy of machine learning models and feature variables including location, geology, surface elevation, soil parent material, physiographical information (codes) and soil layer depth are adopted for training the machine learning models after parametric study of various feature variable combinations. Two case studies were conducted to demonstrate the effectiveness of incorporating physical constraints into machine learning models for categorical and regression datasets respectively. The study results demonstrate strong potential for applying physics-constrained machine learning models to generate reasonable estimated values across large regions, while also providing a better understanding of the historical data within the geotechnical drilling inventory.

Geotechnics doi: 10.3390/geotechnics6010019

Authors: Farzaneh Farahbakhsh Hadi Shahir

Lateral pressure on a retaining wall could be a critical parameter that affects the stability and efficiency of the wall design. Traditional methods to estimate active lateral earth pressure is often inadequate in cases where geometric constraints, or arching effects play significant roles. An analytical method has been used in this study to estimate soil and geotextile stresses in reinforced retaining walls by considering the arching effect. It presents a clear analytical solution for calculating lateral earth pressure in narrow Mechanically Stabilized Earth (MSE) walls. The model includes bilinear failure surfaces and nonlinear stress paths, which better reflect real soil behavior in comparison to the traditional methods with linear failure surfaces. The proposed method demonstrated excellent agreement with both field data and centrifuge test results. According to the proposed analytical approach, the distribution of horizontal soil pressure is not linear. The lateral soil pressure is zero at the top and bottom, while the maximum pressure is between 0.4 and 0.9 of the wall height. The formulation further indicates that the higher the friction at the interfaces, the greater the arching effect, so reducing the lateral earth pressure on the retaining wall. Moreover, narrowing the backfill space leads to a significant reduction in lateral earth pressure.

Geotechnics doi: 10.3390/geotechnics6010018

Authors: Ahmed Khamiss Usama El Shamy

A three-dimensional discrete element method (DEM) framework was developed and applied to investigate the time-domain seismic response of a soil–pier system embedded in stratified dry sand. The numerical model was validated against analytical solutions to determine the ultimate vertical load capacity and internal forces when subjected to a lateral load at the pier head. Simulations were conducted to explore the influence of different excitation frequencies and amplitudes on soil–foundation interaction. Dynamic p–y curves were extracted at multiple elevations along the shaft to examine variations in lateral stiffness with depth. The results show that seismic loading significantly increases lateral displacement, and the residual response is strongly governed by the input motion amplitude. Peak lateral deformation and internal forces were observed when the excitation frequency coincided with the pier’s natural frequency. Both cyclic shear strain and ground settlement reached their maximum near the natural frequency of the soil deposit, and increased substantially with shaking amplitude.

Geotechnics doi: 10.3390/geotechnics6010017

Authors: Saurav Sharma Netra Prakash Bhandary

This study explores the effect of cation adsorption on the shear strength and mineralogical characteristics of smectite-rich landslide clay collected from the Nishinotani landslide in Ehime Prefecture, Japan. Laboratory experiments were conducted using aqueous solutions of calcium, magnesium, and potassium chlorides at concentrations of 1000, 6000, and 12,000 mg/L. Ion chromatography, X-ray diffraction (XRD), and ring shear tests were conducted to evaluate the interaction between ion uptake and its influence on the change in shear strength. The results showed that calcium and potassium ion adsorption increased with both concentration and time, leading to enhanced residual shear strength and crystallinity, primarily due to stronger Coulombic interactions and favorable ionic size compatibility with smectite. Conversely, magnesium ions exhibited adverse effects, including reduced strength and mineral ordering, attributed to calcium leaching and weaker interparticle bonding. The findings indicate that selective cation exchange can be an effective, sustainable alternative to conventional landslide stabilization methods, especially in fine-grained, expansive clay systems. This work contributes to the development of geochemically engineered landslide mitigation strategies based on microstructural and mineralogical reinforcement.

Geotechnics doi: 10.3390/geotechnics6010016

Authors: Ioan Gheorghe Crișan Octavian Bujor Nicolae Har Călin Gabriel Tămaș Eduárd András

This study evaluates the swelling potential in clayey soils of the Paleogene Brebi, Mera, and Moigrad formations in the Transylvanian Basin (Romania) by integrating direct free-swelling tests (FS; STAS 1913/12-88) with indirect index-property diagrams and semi-quantitative X-ray diffraction (XRD; RIR method). The indirect analysis combines three swelling-susceptibility classification charts—Seed et al. (AI–clay), Van der Merwe (PI–clay), and Dakshanamurthy and Raman (LL–PI)—with mineralogical trends from the Casagrande plasticity chart, complemented by Holtz and Kovacs’s clay-mineral reference fields and Skempton’s activity concept (AI = PI/% < 2 µm). The geotechnical dataset comprises 88 Brebi, 46 Mera, and 263 Moigrad specimens (with parameter counts varying by test), an XRD was performed on a representative subset. The free swell (FS) results indicate that Brebi soils range from low to active behavior (50–135%) without reaching the very active class; most Brebi specimens fall in the medium-activity range. Moigrad spans the full FS spectrum (20–190%) but is predominantly in the medium-to-active range. In contrast, Mera soils exhibit predominantly active behavior, covering the full range of activity classes (30–170%). The empirical classification charts diverge systematically: clay-sensitive schemes tend to assign higher swell susceptibility than the LL–PI approach, especially in carbonate-influenced soils. XRD results corroborate these patterns: Brebi is calcite-rich (mean ≈ 53.5 wt% CaCO3) with minor expandable minerals (mean ≈ 3.1 wt%); Mera is feldspathic (orthoclase mean ≈ 55.3 wt%) with variable expandable phases; and Moigrad has a higher clay-mineral content (mean ≈ 38.8 wt%). Overall, swelling is controlled by the combined effects of clay-fraction reactivity, clay volume continuity, and carbonate-related microstructural constraints.

Geotechnics doi: 10.3390/geotechnics6010015

Authors: Miguel Trinidad Moe Momayez

Factor of Safety (FOS) is a significant index to measure the stability condition of a rock slope in mining or civil engineering. In this paper, we evaluate and compare four different machine learning models, Gaussian Process Regressor (GPR), Support Vector Regressor (SVR), Random Forest (RF), and a hybrid genetic algorithm–multi-layer perceptron (GA-MLP), using two separate real-world datasets. The two separate datasets used in this study are from a previously conducted study on highway excavation with rock cutting in China, and another one in a mining site in Peru, with five geotechnical properties used as inputs, including slope height, slope angle, unit weight, cohesion, and friction angle. The two separate datasets were separated into training, validation, and testing datasets. The testing dataset of the models is unseen data used to assess model performance in an unbiased manner. The result shows that the SVR had the highest prediction accuracy, followed by GPR for the mining dataset, and GPR had the highest performance among all the models for the highway excavation dataset. From the boxplot, we can see that SVR, while having the highest predictive accuracy, has a larger variance in prediction compared to GPR for the mining dataset.

Geotechnics doi: 10.3390/geotechnics6010014

Authors: Zihan Zhang Chaoshui Xu Zhao Feng Tian Feng Xiong John Centofonti

Underground coal gasification (UCG) is an emerging energy technology that involves the in situ conversion of coal into syngas through controlled combustion within a subsurface excavation. The geomechanical processes associated with UCG can lead to significant overburden caving and surface subsidence, posing risks to surface infrastructure and groundwater systems. To accurately predict the size of overburden caving zones and associated surface subsidence, a prediction model was developed based on simulation results using discrete element method (DEM) numerical models. The main purpose of developing such a model is to establish a systematic and computationally efficient method for the rapid prediction of the height of overburden caving and its associated surface subsidence induced by underground excavation. The model is broadly applicable to different types of underground excavations, and UCG is used in this study as a representative application scenario to demonstrate the relevance and performance of the model. Sensitivity analysis indicates that excavation span, tensile strength, and burial depth are the primary controls on the height of the caving zone within the ranges of parameters investigated. Rock density is retained as a secondary background parameter to represent gravitational loading and its contribution to the in situ stress level. The derived model was validated using published numerical, experimental, and field measurement data, showing good agreement within practical ranges. To further demonstrate the application of the model developed, the predicted caving geometries were incorporated into finite element method (FEM) models to simulate surface subsidence under different geological conditions. The results highlight that the arch structure formed by overburden caving can help redistribute stresses and thereby reduce surface deformation. The proposed model provides a practical, parameter-driven tool to assist in underground excavation design, environmental risk evaluation, and ground stability management.

Geotechnics doi: 10.3390/geotechnics6010013

Authors: Binghai Li Yang Chen Taibing Liu Guoqing Fu Jingeng Li Ao Lu Xiaoguang Jin

To accurately analyze the time-dependent stability of large-span tunnels traversing the F2 fault fracture zone, this study focused on the deep-buried red-bed mudstone of the Jishan Tunnel. Rock cores were retrieved from the critical Grade V surrounding rock section (depth 370 m). Uniaxial and triaxial compression tests were conducted to determine basic mechanical parameters. Through step-loading creep tests, the creep characteristics were analyzed, and a long-term strength of 19.2 MPa was identified. Analysis revealed that the deformation aligns well with the stress-dependent Burgers model, where parameters evolve with stress level. Using the Levenberg–Marquardt algorithm, the variable model parameters were derived. Finally, three-dimensional creep parameters were obtained for numerical validation. Engineering recommendations for support timing and yielding mechanisms are proposed to mitigate rheological risks in fault-affected zones.

Geotechnics doi: 10.3390/geotechnics6010012

Authors: Ioan Gheorghe Crișan Octavian Bujor Nicolae Har Călin Gabriel Tămaș Eduárd András

The Transylvanian Basin is an intra-Carpathian sedimentary unit displaying complex tectonic and sedimentary evolution that started in the Late Cretaceous. This study presents a geotechnical characterization of three Paleogene lithostratigraphic units located in the northwestern part of the basin, i.e., Brebi, Mera, and Moigrad. These formations record the transition from marine carbonate facies to brackish and subsequently fluvial environments, controlled by tectonic uplifts, marine regressions, and fluctuations in sediment supply. A total of 583 soil samples were collected through geotechnical boreholes and analyzed in the laboratory according to EN ISO standards, assessing natural moisture content, bulk density, grain size distribution, Atterberg limits, carbonate content, unconfined compressive strength, and shear strength parameters. Characteristic values of these properties were determined based on probabilistic distributions. The analyzed formations exhibit well-differentiated lithological and geotechnical characteristics, primarily governed by the degree of plasticity and the presence of calcium carbonate. The Brebi Formation predominantly consists of medium-plasticity clays with highly to very highly carbonate content, indicating a partially cemented microstructure. The Mera Formation is mainly composed of high-plasticity clays having a variable content of carbonates, with frequent sandy intercalations, resulting in significant variability in mechanical properties. The Moigrad Formation consists of two distinct lithological complexes: a clay-rich complex composed of variably plastic calcareous clays spanning all four plasticity classes and a sandy unit made up of weakly cohesive sediments with a granular structure and locally developed carbonate microcementation.

Geotechnics doi: 10.3390/geotechnics6010011

Authors: Gernot Beer Nicola Grillanda Vincenzo Mallardo

Using current approaches, which are almost entirely based on volume methods, 3D simulations of complex underground excavations can be cumbersome and time-consuming. This is because the rock mass, which for practical purposes is of infinite extent, has to be discretised. This leads to very large meshes, which have to be truncated at a distance assumed to be “safe”. Consequently, the demand for human and computer resources can be significant. To ascertain the quality of the result is difficult because it depends on the fidelity of the volume mesh and the truncation distance. The aim of this paper is to present a novel approach that does not require volume discretisation. Using the isogeometric boundary element method (IGABEM), only excavation surfaces need to be defined. The geometry of the excavations can be defined in a highly accurate and smooth manner with computer-aided design (CAD) data, eliminating the requirement for mesh generation. Volume effects, such as nonlinear, anisotropic, and heterogeneous ground conditions, as well as the effect of ground support, can be considered. On several examples, related to real projects, it is shown that excavations of high complexity can be simulated, and highly refined results can be obtained in a mesh-free setting.

Geotechnics doi: 10.3390/geotechnics6010010

Authors: Baitak Apshikur Temyrbay Chigambayev Alizhan Almas Murat Alimkulov Bisenbay Makhanov Yerbulan Abaikhan

Seasonal groundwater rise of 2.5–3.0 m leads to full saturation of the lakeside slope of the railway embankment, significantly reducing the strength of clayey–sandy loam layers. Laboratory shear tests showed that saturation decreases the internal friction angle from 24–26° to 16–19°, while effective cohesion drops from 12–18 kPa to 0–3 kPa, identifying the 3–6 m depth interval as the critical weak zone. These parameters were incorporated into PLAXIS 2D/3D hydro-mechanical models to assess the embankment behaviour under three scenarios: natural conditions, high water level, and reinforced configuration. Under elevated water levels, lateral displacement toward the lakeside increased to 0.16–0.21 m, and the plastic strain zone expanded by a factor of 2.4, reducing the safety factor from FS ≈ 1.32 to below 1.10. The proposed stabilization system—replacement of a 1.5 m weak layer, installation of geotextile reinforcement, and application of a bituminous waterproofing layer—substantially improved stability, reducing maximum lateral displacement to 0.12 m (≈43% reduction) and restoring the safety factor to FS = 1.25–1.40. The results demonstrate that low-cost geosynthetic barriers provide an effective and practical engineering solution for maintaining the long-term stability of railway embankments exposed to seasonal inundation.

Geotechnics doi: 10.3390/geotechnics6010009

Authors: Kei Katayama Takashi Matsushima

This study aims to investigate the tip resistance mechanism of open-ended steel pipe piles under partially plugged conditions by decomposing the load-sharing contribution of the ring zone and the internal soil core. A virtual static loading test was performed using the two-dimensional discrete element method (2D-DEM). Note that the findings of this study were obtained within the range of the 2D-DEM analysis conditions and do not intend to directly reproduce the three-dimensional arching mechanism or to establish equivalence between 2D and 3D responses. Quasi-static conditions were ensured by identifying loading parameters such that the energy residual remained ≤5% during driving, rest, and static loading phases, and the sensitivity criterion |Δq_b|/q_b ≤ 3% was satisfied when the loading rate was halved or doubled. The primary evaluation range of static loading was set to s/D = 0.1 (10% D), corresponding to the displacement criterion for confirming the tip resistance in the Japanese design specifications for highway bridges. For reference, the post-peak mechanism was additionally tracked up to s/D = 0.2 (20% D). Within a fixed evaluation window located immediately beneath the pile tip, high-contact-force (HCF) points were binarized using the threshold τ = μ + σ, and their occupancy ratio φ and normalized force intensity I* were calculated separately for the ring and core regions. A density-based contribution index (“K-density share”) was defined by combining “strength × area” and normalizing by the geometric width. The results suggest that, for the sand conditions and particle-scale ratios examined (D/d_50 = 25–100), the ring zone tends to carry on the order of 85–90% of the tip resistance within the observed cases up to the ultimate state. Even at high plugging ratios (CRs), the internal soil core gradually increases its occupancy and intensity with settlement; however, high-contact-force struts beneath the ring remain active, and it is suggested that the ring-dominant load-transfer mechanism is generally preserved. In the post-peak plastic regime, the K-density share remains around 60%, indicating that the internal core plays a secondary, confining role rather than becoming dominant. These findings suggest that the conventional plug/unplug classification based on PLR can be supplemented by a combined use of plugging ratio CR (a kinematic indicator) and the ring contribution index (K-density share), potentially enabling a continuous interpretation of plugged and unplugged behaviors and contributing to the establishment of a design backbone for tip resistance evaluation. Calibration of design coefficients, scale regression, and mapping to practical indices such as N-values will be addressed in part II of this study. (Note: “Contribution” in this study refers to the HCF-based density contribution index K-density share, not the reaction–force ratio.)

Geotechnics doi: 10.3390/geotechnics6010008

Authors: Yue Chen Yinsheng Wang Yongqiang Li Guoshun Lv Quan Dai Le Liu Lianheng Zhao

To investigate the shear behavior of rock mass joint surfaces with varying roughness and lithology, this study introduces a novel experimental framework that combines high-precision 3D printing and direct shear testing. Ten artificial joint surfaces were fabricated using Barton standard profiles with different joint roughness coefficients (JRC) and were cast using two representative rock-like materials simulating soft and hard rocks. The 3D printing technique employed significantly reduced the staircase effect and ensured high geometric fidelity of the joint morphology. Shear tests revealed that peak shear strength increases with JRC, but the underlying failure mechanisms vary depending on the lithology. Experimental results were further used to back-calculate JRC values and validate the empirical JRC–JCS (joint wall compressive strength) model. Numerical simulations using FLAC3D captured the shear stress–displacement evolution for different lithologies, revealing that rock strength primarily influences peak shear strength and fluctuation characteristics during failure. Notably, despite distinct lithologies, the post-peak degradation behavior tends to converge, suggesting universal residual shear mechanisms across rock types. These findings highlight the critical role of lithology in joint shear behavior and demonstrate the effectiveness of 3D-printing-assisted model tests in advancing rock joint characterization.

Geotechnics doi: 10.3390/geotechnics6010007

Authors: Abdulnaser Alamari Adel Hanna

Pile foundations are widely used to transfer axial loads to deeper strata, where uplift resistance is critical for offshore structures, towers, and retaining systems. Uplift capacity is governed primarily by shaft resistance mobilized along the pile–soil interface, yet its behavior in sand remains inadequately defined. This study investigates the shaft resistance of vertical model piles subjected to pure pullout loading in dry sand, using instrumented steel piles in a rigid steel tank with reaction beams and earth pressure sensors to capture lateral stress distribution. The effects of pile diameter D, embedment ratio L/D, and sand relative density Dr on uplift performance were systematically examined. The results show that higher relative density produces higher earth pressure coefficients Ks and, accordingly, higher uplift capacity. An analytical model was developed to predict the earth pressure coefficient Ks and shaft resistance, introducing a friction-based critical depth ratio linked to the sand friction angle. The critical depth ratio increases with friction angle and is greater in denser sands under uplift loading. This study contributes in the following ways: (1) developing an improved analytical framework for uplift prediction, (2) introducing a friction-based critical depth ratio concept, and (3) establishing an empirical OCR relationship for sand.

Geotechnics doi: 10.3390/geotechnics6010006

Authors: Ambrosios-Antonios Savvides

Uncertainty quantification in science and engineering has become increasingly important due to advances in computational mechanics and numerical simulation techniques. In this work, the relationship between uncertainty in soil material parameters and the variability of failure loads and displacements of a shallow foundation is investigated. A Drucker–Prager constitutive law is implemented within a stochastic finite element framework. The random material variables considered are the critical state line slope c, the unload–reload path slope κ, and the hydraulic permeability k defined by Darcy’s law. The novelty of this work lies in the integrated stochastic u–p finite element framework. The framework combines Drucker–Prager plasticity with spatially varying material properties, and Latin Hypercube Sampling. This approach enables probabilistic prediction of failure loads, displacements, stresses, strains, and limit-state initiation points at reduced computational cost compared to conventional Monte Carlo simulations. Statistical post-processing of the output parameters is performed using the Kolmogorov–Smirnov test. The results indicate that, for the investigated configurations, the distributions of failure loads and displacements can be adequately approximated by Gaussian distributions, despite the presence of material nonlinearity. Furthermore, the influence of soil depth and load eccentricity on the limit-state response is quantified within the proposed probabilistic framework.

Geotechnics doi: 10.3390/geotechnics6010005

Authors: Bochen Wang Hongqian Lu Weiming Gong Jiaqing Shu Xiaoqing Gu Geng Cao

Soil–structure interaction (SSI) under torsional loading plays a critical role in the dynamic performance of foundations supporting offshore structures and machine foundations. However, existing simplified or semi-analytical approaches often idealize the pile tip boundary and may not adequately capture the frequency-dependent torsional impedance induced by finite soil thickness beneath the pile tip in layered deposits. This study develops a Hamilton-based variational solution for dynamic torsional soil–pile interaction in layered viscoelastic soils by explicitly incorporating a fictitious soil pile (FSP) beneath the pile tip within an energy-consistent framework. Admissible torsional displacement fields for the pile, layered soil, and FSP are adopted to establish a frequency-domain variational functional, and an iterative scheme is used to obtain the convergent frequency-dependent torsional impedance at the pile head. The formulation is verified against an existing semi-analytical solution for piles in layered soils and shows excellent agreement. Parametric results indicate that introducing a finite FSP reduces torsional stiffness and increases damping compared with a rigid base condition, while the thickness and stiffness of the bearing stratum govern the variation in impedance, providing physical insight into torsional SSI in layered ground.

Geotechnics doi: 10.3390/geotechnics6010004

Authors: Hui Lu Qiyao Zhang Zhixiao Bai Liwei Guo Zeyu Shao Erbing Li

Offshore wind farm construction faces significant geotechnical challenges posed by tidal mudflat sediments, including high moisture content, low bearing capacity, and high sensitivity to disturbance. Utilizing MgO—a material characterized by abundant raw materials, low embodied energy, and environmental compatibility—for the stabilization of such soft soils represents a promising and sustainable approach worthy of further investigation. This study elucidates the carbonation-induced stabilization mechanism of coastal mucky soil from Ningbo, Zhejiang Province, through systematic monitoring of reaction temperature and unconfined compressive strength (UCS) testing under varying levels of reactive MgO content, carbonation duration, and initial moisture content. Microstructural characterization was performed using X-ray diffraction (XRD), scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) to reveal the evolution of mineralogical and pore structure features associated with carbonation. The results indicate that increasing MgO content leads to higher peak reaction temperatures and shorter time-to-peak values. However, the rate of reduction in time-to-peak diminishes beyond 20% MgO. A secondary temperature rise is commonly observed between 3–3.5 h of carbonation in most specimens. When the MgO content is below 30%, UCS peaks within 6–10 h, with the peak time decreasing as MgO content increases. When MgO exceeds 45%, strength deterioration occurs due to structural damage. The correlation between deformation modulus and UCS is found to be comparable to that of conventional cement-stabilized soils. Microstructural analysis reveals that, with increased MgO dosage and prolonged carbonation, carbonation products progressively fill voids and bind soil particles, resulting in reduced total porosity and a refinement of pore size distribution—evidenced by a leftward shift in the most probable pore diameter. Nevertheless, at excessively high MgO levels (e.g., 50%), crystallization pressure from rapid product formation may generate macro-pores, compromising soil fabric integrity. This study presents a low-carbon and efficient ground improvement approach for access road construction in tidal mudflat wind farm developments.

Geotechnics doi: 10.3390/geotechnics6010003

Authors: Pengfei Guo Weiquan Zhao Linxiu Qu Xifeng Li Yahui Ma Pan Li

Overburden layers, composed of unconsolidated sediments, are widely distributed in construction, transportation, and water conservancy projects, but their inherent defects (e.g., developed pores, low strength) easily induce engineering disasters. Grouting is a core reinforcement technology, yet traditional design relying on empirical formulas and on-site trials suffers from high costs and low prediction accuracy. Numerical simulation has become a key bridge connecting grouting theory and practice. This study systematically reviews the numerical simulation of overburden grouting based on 82 core articles screened via the PRISMA framework. First, the theoretical system is clarified: core governing equations for seepage, stress, grout diffusion, and chemical fields, as well as their coupling mechanisms (e.g., HM coupling via effective stress principle), are sorted out, and the advantages/disadvantages of different equations are quantified. The material parameter characterization focuses on grout rheological models (Newtonian, power-law, Bingham) and overburden heterogeneity modeling. Second, numerical methods and engineering applications are analyzed: discrete (DEM) and continuous (FEM/FDM) methods, as well as their coupling modes, are compared; the simulation advantages (visualization of diffusion mechanisms, parameter controllability, low-cost risk prediction) are verified by typical cases. Third, current challenges and trends are identified: bottlenecks include the poor adaptability of models in heterogeneous strata, unbalanced accuracy–efficiency, insufficient rheological models for complex grouts, and theoretical limitations of multi-field coupling. Future directions involve AI-driven parameter optimization, cross-scale simulation, HPC-enhanced computing efficiency, and targeted models for environmentally friendly grouts. The study concludes that overburden grouting simulation has formed a complete “theory–parameter–method–application” system, evolving from a “theoretical tool” to the “core of engineering decision-making”. The core contradiction lies in the conflict between refinement requirements and technical limitations, and breakthroughs rely on the interdisciplinary integration of AI, multi-scale simulation, and HPC. This review provides a clear technical context for researchers and practical reference for engineering technicians.

Geotechnics doi: 10.3390/geotechnics6010002

Authors: Giuseppe Tropeano Anna Chiaradonna

This review aims to provide a complete and comprehensive state of the art of the SCOSSA computer code, which is a one-dimensional nonlinear computer code used for the analysis of seismic site response and soil instability. Indeed, among the effects of earthquakes, the activation of landslides and liquefaction constitute two of the predominant causes of vulnerability in the physical and built environment. The SCOSSA computer code (Seismic Code for Stick–Slip Analysis) was initially developed to evaluate the permanent displacements of simplified slopes using a coupled model, and introduced several improvements with respect to the past, namely, the formulation for solving the dynamic equilibrium equations incorporates the capability for automated detection of the critical sliding surface; an up-to-date constitutive model to represent hysteretic material behavior and a stable iterative algorithm to support the solution of the system in terms of kinematic variables. To address liquefaction-induced failure, a simplified pore water pressure generation model was subsequently developed and integrated into the code, coupled with one-dimensional consolidation theory. This review retraces the main features, developments, and applications of the computer code from the origin to the present version.

Geotechnics doi: 10.3390/geotechnics6010001

Authors: Donata N. W. Wardani Nils Hoth Sarah Amos Kofi Moro Johanes Maria Vianney Carsten Drebenstedt

Spontaneous liquefaction in the Lusatian lignite dump sites has raised significant geotechnical and environmental concerns. While mechanical influences have been extensively studied, hydrochemical investigations suggest an inner initial that is highly correlated to CO2 generation, attributed to buffering reactions, which lays the foundation for this study. This study aims to understand the process behind and to quantify the transient evolution of excess pore-pressure induced by CO2 accumulation, both dissolved and as free gas, in saturated medium using a series of column experiments. Excess pore-pressures up to 7.7 kPa were recorded following a period of buffering reaction, with discharged gas confirmed as CO2. The results demonstrate that the buffering process strongly influences the elevated pressure, while, in turn, elevated pressures affect the chemical conditions within the column. Secondary mineral precipitation, as one of the effects, was observed to reduce buffering reactivity and modify pore structure, thereby altering pore-pressure response. These findings highlight hydrochemical feedback as critical internal triggers and amplifiers in liquefaction events, complementing mechanical explanations and advancing understanding of coupled hydro-chemo-mechanical processes in dump site stability.

Geotechnics doi: 10.3390/geotechnics5040087

Authors: Sandra A. A. O. Donkor Mehrdad Razavi Claudia Mara Dias Wilson Benjamin Abankwa Richard Otoo Abraham Armah

Soil permeability is an important factor in the mining and geotechnical industry, impacting slope stability and tailings management. It directly influences the stability of structures, the control of water in tailings ponds, and the safety of workers. Various additives, such as cement kiln dust (CKD), bentonite, fly ash, polymers, lime, and asphalt, are incorporated into soil structures to improve permeability and stability. Any significant changes in soil permeability will alter the soil’s behavior. However, the long-term effect of most additives on structures remains unexplored. This study investigates the long-term impact of CKD on the permeability of a CKD-treated slope. The slope surface was treated with 0%, 5%, 10%, and 15% of CKD by the dry weight of the soil in 2008 and was evaluated in 2024. The permeability test results of the collected soil sample from the slope (2024) showed that the permeability of the soil decreases with an increase in the soil CKD content. The coefficient of permeability, k, is more than 100 times less for a CKD content of 15% by the dry weight of the soil compared to the permeability of the untreated native soil. The treated soil becomes almost impermeable when the CKD content increases to 20% (by the dry weight of the soil). However, the treated slope’s permeability increased over time, possibly due to erosion, resulting in a reduction in CKD content. The surface permeability of the slope exhibits an irregular distribution, resulting from the evolving spatial distribution of Cement Kiln Dust over time.

Geotechnics doi: 10.3390/geotechnics5040086

Authors: Keith Mandisodza David Williams

Tailings dams, critical for storing mine waste and water, must maintain stability and functionality throughout their lifespan. Their design and risk assessment are complicated by significant uncertainties stemming from multivariable parameters, including material properties, loading conditions, and operational decisions. Traditional dam design and risk assessment procedures often rely on first-order probabilistic approaches, which fail to capture the complex, multi-layered nature of these uncertainties fully. This paper reviews the current tailings dam design practice and proposes the application of Bayesian networks (BNs) to analyse the epistemic and aleatory uncertainty inherent in tailings dam design parameters and risk assessment. By representing these uncertainties explicitly, BNs can facilitate more robust and targeted design strategies. The proposed approach involves several key steps, including parameterisation—design input variable probability density function and uncertainty, knowledge elicitation, and model assessment and integration. This methodology provides a sophisticated and comprehensive approach to accounting for the full spectrum of uncertainties, thereby enhancing the reliability of tailings dam designs and risk management decisions.

Geotechnics doi: 10.3390/geotechnics5040085

Authors: Azemeraw Wubalem Chiara Caselle Anna Maria Ferrero Gessica Umili

Environmental stressors, such as freeze–thaw (F–T) cycling and acid rain, affect the durability of carbonate rocks used in engineering and cultural heritage structures. This study investigates the mechanical degradation and strain evolution of Carrara marble subjected to 10 F–T cycles and immersion in a simulated sulfuric acid solution (pH 5) for 3, 7, and 28 days. The mechanical strength of the samples was tested under uniaxial compression using a displacement-controlled loading rate, while full-field deformation and fracture evolution were analyzed with Digital Image Correlation (DIC). Results show that F–T cycling led to a substantial reduction in uniaxial compressive strength (UCS) and a very large decrease in tangent Young’s modulus. Acid exposure also caused progressive degradation, with both UCS and stiffness continuing to decline as exposure time increased, reaching their greatest reduction at the longest treatment duration. Additionally, DIC strain maps revealed a change in deformation response as a function of the treatment. The findings provide the integrated assessment of Carrara marble mechanical response under both F–T and acid weathering, linking bulk strength loss with changes in strain localization behavior, highlighting the vulnerability of marble to environmental stressors, and providing mechanical insights relevant to infrastructure resilience and heritage conservation.

Geotechnics doi: 10.3390/geotechnics5040084

Authors: Markus Kaspar Christine Latal Gerhard Pittino Volker Reinprecht

Soft and weak rocks present challenges for construction activities in various environments. Their genetic origin, geological and tectonic evolution, and exposure to atmospheric conditions control their weathering and degradation over time. Therefore, a sound characterization of the associated rock parameters is essential. Numerous tests have been developed and standardized or defined in recommendations to assess various geomechanical, petrological, and mineralogical parameters. However, these tests are still subject to modification or extension to address project-specific issues. Additionally, standardized tests do not consider regional climatic conditions that may affect weathering, meaning they do not reflect the degradation behavior that is observed in the field. The present study investigates the slaking resistance and degradability of a range of soft rocks. The workflow of widely used tests is employed to evaluate their representativeness for different rock types in practical applications. Depending on their genetic origin and mineral composition, fabric alterations affect the rate and style of rock disintegration differently. Soft sedimentary rocks react already to static slaking, i.e., water immersion, whereas crystalline and grain-bound rocks slake under dynamic action while undergoing attrition in a rotating slake durability drum. Zones of structural weakness, such as foliation planes, are responsible for material removal in the latter; sedimentary rocks, on the other hand, are subject to surface particle separation (suspension) and suction due to the presence of clay minerals. This study presents an approach that combines the results of several routine tests to help identify and refine the slaking susceptibility of different rock types. A routine for inspecting and documenting the evaluated slaking characteristics for infrastructure maintenance is proposed, and the wider implications in light of climate change are discussed. Some limitations of the transferability of laboratory values to field sites still have to be evaluated and validated in the future.

Geotechnics doi: 10.3390/geotechnics5040083

Authors: Kakuta Fujiwara

Slope failures frequently occur during rainfall, earthquakes, and long-term weathering, and reinforcing bar insertion is widely used worldwide to prevent such failures. In this method, steel bars are installed in pre-drilled holes and bonded to the ground with grout, with a pressure plate resisting deformation; however, tensile forces generated during slope movement may crack the hardened grout and reduce performance. To address this issue, we propose an Early-stage Prestressed Reinforcing Bar Insertion Method, in which tensile load is applied to the bar before grout hardening. Grout is injected while maintaining tension, allowing the bar to remain prestressed after construction and inducing compressive stress in the grout, which is expected to improve resistance against tensile loading. A field construction test and numerical finite-element analysis were conducted to verify performance. The test confirmed constructability within half a day and retained tensile force of 42 kN after 30 days. The numerical model reproduced measured axial forces and indicated that the hardened grout remained in compression, with an average compressive stress of 3680 kN/m2. These results demonstrate that prestressing can enhance grout tensile resistance. The method shows promise for future application and potential extension to similar anchoring systems.

Geotechnics doi: 10.3390/geotechnics5040082

Authors: Ömer Ündül Enes Zengin

Understanding the strain rate behavior of rock materials is key to geomechanical engineering. However, in numerical tools such as the Particle Flow Code (PFC), the chosen bonded-particle contact model also fundamentally dictates the mechanical response. A systematic comparison of how quasi-static strain rates affect different contact models, Parallel-Bonded (PBM), Soft-Bonded (SBM), and Flat-Jointed (FJM), using a common calibration baseline, has been lacking. This study addresses that gap by first calibrating all three models against identical laboratory data from the siltstone of Paleozoic-aged Trakya formation in Cebeciköy-Istanbul, Türkiye. Subsequently, numerical uniaxial loading simulations were conducted on the calibrated models at three distinct quasi-static strain rates (0.01, 0.005, and 0.001 s−1) to compare their stress–strain response, crack evolution, and failure patterns. The results demonstrate that while the initial elastic stiffness was largely insensitive to the applied strain rates across all models, the post-peak behavior and failure mechanism remained fundamentally distinct and model dependent. PBM consistently produced an abrupt, localized brittle failure, SBM exhibited more gradual softening with distributed tensile damage, and FJM displayed the most widespread, mixed-mode failure pattern. It is concluded that within the quasi-static loading conditions, the intrinsic formulation of the chosen contact model is a more dominant factor in controlling the failure style, damage localization, and post-peak characteristics than the specific strain rate applied.

Geotechnics doi: 10.3390/geotechnics5040081

Authors: Takumi Iijima Tomohiro Toyoda Toshihiro Noda

Yamamoto’s theoretical solution for a two-dimensional wave-induced response of an elastic seabed with finite permeability needs a simultaneous equation to be solved. Analysis of the dimensionless simultaneous equation demonstrated that it becomes unsolvable due to the singularity of its matrix when the permeability coefficient of the seabed approaches infinity and zero, representing (elementwise) fully drained and undrained conditions, respectively. To address this limitation and thus expand the verifiable drainage condition for a finite element analysis code, theoretical solutions for seabed responses under the fully drained and undrained conditions were derived. The feasibility of these solutions was discussed through comparison of the forms of these solutions with the one of Yamamoto. Furthermore, characteristics of seabed behaviors explained by these solutions were obtained. Finally, these theoretical solutions and Yamamoto’s solution were utilized to verify a finite element analysis code by considering horizontally periodic seabed behavior in the numerical analysis. It turned out that the numerical code was capable of expressing seabed behavior in any drainage condition without any approximation to a governing equation as made in the derivation of the fully drained and undrained solutions. Therefore, the numerical analysis code is now reliably used for further studies on wave-induced seabed behaviors even out of the verifiable range of drainage conditions by Yamamoto’s solution.

Geotechnics doi: 10.3390/geotechnics5040080

Authors: Mohammad Ossama Waseem Dave Sego Lijun Deng Nicholas Beier

Partially frozen soil (PFS) is comprises of coexisting unfrozen water and ice within its pores at subzero temperatures. The review paper examines how unfrozen water content (UWC) and pore ice content interact during phase changes under near-freezing conditions, governed by microscopic thermodynamic equilibrium. Key theories describing why UWC persists (premelting, disjoining pressure) and the soil freezing characteristic curve (SFCC), along with measurement techniques, including the gravimetric approach to advanced nuclear magnetic resonance for characterization of water content. The influence of the water–ice phase composition on mechanical behavior is discussed, signifying pore pressure and effective stress. Various modelling approaches categorized into empirical SFCC, physio-empirical estimations, and emerging machine learning and molecular simulations are evaluated for capturing predictions in PFS behavior. The relevance of PFS to infrastructure foundation, tailings dams, permafrost slope stability, and climate change impacts on cold regions’ environmental geotechnics is also highlighted as a challenges in practical application. Hence, understanding pore pressure dynamics and effective stress in PFS is critical when assessing frost heave, thaw weakening, and the overall performance of geotechnical structures in cold regions. By combining micro-scale phase interaction mechanisms and macro-scale engineering observations, this review paper provides a theoretical understanding of the underlying concepts vital for future research and practical engineering in cold regions.

Geotechnics doi: 10.3390/geotechnics5040079

Authors: Vladimir Leonidovich Trushko Vladimir Yakovlevich Klimov Elena Konstantinovna Baeva Anatoly Yurievich Ozhigin

Existing pile foundations in the Arctic face significant limitations regarding bearing capacity, environmental impact, and dismantling capabilities. This study proposes and geomechanically justifies a novel technology for constructing dismantlable modular pile foundations in permafrost using a pile with a dome-plug (PDP). Comparative numerical modeling was conducted to analyze the bearing capacity of the proposed PDP versus a conventional pile without a dome-plug (PWDP) across six types of frozen rocks (clays, loams, sandy loams), specifically accounting for salinity. The results indicate that the dome-plug effectively transforms the shell pile into a combined pile-column, providing a bearing capacity increase ranging from 35% to 63%. Notably, the highest relative improvement was observed in the weakest saline rocks. The proposed technology serves as a superior alternative to traditional piling methods, enabling the deployment of modular foundations as a cost-effective and eco-friendly substitute for artificial soil islands.

Geotechnics doi: 10.3390/geotechnics5040078

Authors: Wenjia Xu Catrina Brüll

This study investigates the influence of stratification—the vertical layering of particles with different sizes—on porosity in granular sediment packings. Conventional porosity models are typically formulated for homogeneous, well-mixed grain assemblies; however, natural riverbed sediments often exhibit stratification, leading to deviations from these idealized conditions. Part I established empirical relationships describing transition layer geometry and porosity in systems composed of low-friction glass beads. Building on this foundation, Part II extends the analysis by incorporating the higher inter-particle friction characteristic of natural sediments, using discrete element method (DEM) simulations to quantify its effect on packing structure and porosity. A refined method is used to extract porosity and density distributions from simulated packings, enabling accurate identification of transition layers. Empirical formulas are developed to predict key transition-layer parameters (thickness, average porosity, and minimum porosity) as functions of the grain-size ratio. A density-based porosity prediction model is introduced and coupled with an existing model for well-mixed sediments, allowing for a quantitative comparison between stratified and homogeneous packing scenarios. Results show that stratification can increase porosity by 44–57% relative to well-mixed samples of an identical grain-size composition. These findings highlight the importance of considering sediment stratification when modeling riverbed porosity and pave the way for improved sediment transport and hydraulic predictions.

Geotechnics doi: 10.3390/geotechnics5040077

Authors: Wenjia Xu Catrina Brüll

This study investigates how stratification—layering of particles of different sizes—affects porosity in granular sediment packings. While most existing porosity models are developed for well-mixed, homogeneous grain structures, natural riverbed sediments can be stratified, which may lead to significant deviations in porosity. To address this, a novel, cost-effective, and non-destructive laboratory method was developed to measure the vertical porosity distribution in stratified samples using glass beads. Results confirmed the presence of transition layers at the interface between coarse and fine sediments, where porosity follows a distinct trend of decrease and recovery. A Discrete Element Method (DEM)–based simulation model (Particula 1.3) was calibrated and validated against laboratory results, enabling broader parameter studies beyond the physical experiments. An improved algorithm based on a density threshold was also introduced to efficiently and objectively determine the transition layer extent in simulations. Empirical formulas linking transition layer thickness and porosity metrics to the grain-size ratio were derived, enabling the calculation of the average porosity of a stratified sample. Part I focuses on the experimental setup, model validation, and foundational insights into transition zone formation. A companion paper (Part II) will build on these results to develop predictive models for porosity in stratified sediment.

Geotechnics doi: 10.3390/geotechnics5040076

Authors: Chuheng Wu Youhu Zhang Peng Guo Di Lei

The offshore wind industry is expanding from shallow water to deep water. As a cost-effective and efficient anchoring solution, drag embedment anchors have been widely used for mooring floating offshore structures. However, there is currently no well-established method for predicting the installation trajectory and holding capacity of drag anchors in sand. This paper reports an integrated anchor–chain–soil large-deformation finite-element model for simulating the complete installation of drag anchors in sand. The proposed approach restores the effects of anchor chains and detailed structures of the anchor, which is essential for detailed anchor design. Sensitivity analysis is conducted to investigate the convergence of model parameters. The performance of the numerical model is benchmarked against a centrifuge test conducted at the University of Western Australia (UWA), which demonstrates satisfactory accuracy and reliability. Installation simulations are then performed using a popular commercial anchor design in sands of different friction angles. Three characteristic stages during the drag embedment process are identified. The results highlight the significant influence of the soil resistance to the shank on the anchor penetration performance. The large-deformation analysis approach proposed provides a powerful tool for further investigation on drag anchor installation behavior in sand.

Geotechnics doi: 10.3390/geotechnics5040075

Authors: Angela Fiamingo Gabriele Chiaro

The reuse of rubber inclusions obtained from End-of-Life Tires (ELTs) offers both environmental and technical benefits in civil engineering applications, reducing landfill disposal and enhancing the dynamic properties of geomaterials. The use of well-graded Gravel–Rubber Mixtures (wgGRMs), produced by blending well-graded gravel with granulated rubber, has been investigated for use in different geotechnical applications. The percentage of rubber inclusions included in wgGRMs significantly modifies the mechanical response of these mixtures, influencing stiffness, strength, dilatancy and dynamic properties. Due to the material heterogeneity (i.e., stiff gravel and soft rubber), the effective implementation of wgGRMs requires the development of constitutive models that can capture the non-linear stress–strain response of wgGRMs subjected to representative in situ loading conditions. In this study, a critical state-based generalized plasticity model is presented and tailored for wgGRMs. Calibration is performed using experimental data from isotropically consolidated drained triaxial tests on wgGRMs with different rubber contents. It is shown that the model accurately reproduces key features observed experimentally, including post-peak strain softening, peak strength variation, and volumetric changes across different confining pressure levels and rubber content fractions. This model represents a useful tool for predicting the behavior of wgGRMs in engineering practice, supporting the reuse of ELT-derived rubber.

Geotechnics doi: 10.3390/geotechnics5040074

Authors: Vincenzo Canzoneri Alessandro Bonfardeci Simona Bongiovanni Lavinia Coletta Enrico Paolo Curcuruto Maurizio Gasparo Morticelli Attilio Sulli Alessandro Canzoneri

In recent years the Government of the Sultanate of Oman has planned the construction of recharge dams in the semi-desert region of Wilayat Ibri, according to the growing domestic water demand for drinking and agricultural use. For this reason, the Engineering Company SERING International planned the construction of rockfill dams, well positioned according to the local morphological and geological context. Using temporary floodwaters and releasing them slowly downstream, these dams increase the water flow of the Aflaj. The latter is the existing traditional irrigation system devised to manage the scarce water resources of the Sultanate. In this paper, we describe the IBRI 14 Dam, namely Wadi Sulayf Dam, with a total length of about 3200 m and lying close to the settlements of Ibri Town, the largest one among those projected. This paper shows the criteria that guided the design studies of the dam linked to the geological and geotechnical features of the area, the main dam characteristic and the activities developed until the work was completed in 2020. This work represents an interesting and useful case study about the complete cycle of realization of a dam, in particular considering that it had been affected by huge flooding during the construction but reporting no significant damage.

Geotechnics doi: 10.3390/geotechnics5040073

Authors: Carlo Vidotto Claudio Cappellaro Eric Puntel

This work stems from the curiosity stimulated by a paper by Yttrup and Abramsson, which appeared in the journal Australian Geomechanics in 2003. Their work proposes a kinematic limit analysis method to compute the ultimate strength of steel screw piles in sand when first the bending and then the plastic collapse of the pile helix occurs. It is accompanied by insightful comments drawn from geotechnical design experience. The paper has both academic and professional impact as it is cited in scientific journals and used in engineering practice in Australia and New Zealand. However, the original paper is quite brief in its exposition. Here, Yttrup and Abramsson’s model is critically reconstructed, providing guidance that can help avoid potential pitfalls in its application. A variation of the model is proposed. Then, the calculated results are discussed and compared with experimental results, starting with those of the original paper. This work hopes to contribute to enhancing the appraisal, adoption, and utility of Yttrup and Abramsson’s model in design practice and in subsequent studies.

Geotechnics doi: 10.3390/geotechnics5040072

Authors: Luís Miranda Laura Caldeira João Bilé Serra Rui Carrilho Gomes

Many immersed tunnels are constructed in alluvial formations within earthquake-prone regions, making seismic resistance a critical aspect of their safety design. During an earthquake, tunnel displacements can lead to slippage between the tunnel and surrounding soil and may be further amplified by liquefaction. This phenomenon can cause severe structural damage, including tunnel flotation. This paper examines the seismic performance of immersed tunnels, starting with an overview of the deformation mechanisms affecting tunnels, including those induced by ground shaking and failure. Given its significance in large foundation deformations and its impact on tunnel integrity, liquefaction is analyzed alongside potential mitigation strategies. The seismic design process for immersed tunnels is discussed in detail, covering analytical approaches, numerical modeling techniques (such as finite element and finite difference methods), and physical modeling. Real-world examples are provided to illustrate key concepts. Finally, this paper summarizes the core factors influencing the seismic response of immersed tunnels and highlights future research directions to enhance their resilience in seismic environments.

Geotechnics doi: 10.3390/geotechnics5040071

Authors: Madhusudhan Bangalore Ramu Abdullah O. Baarimah Aiman A. Bin Mokaizh Ahmed Wajeh Mushtaha Al-Baraa Abdulrahman Al-Mekhlafi Aawag Mohsen Alawag Khalid Mhmoud Alzubi

Improper disposal of waste tires has led to significant environmental and economic challenges, including pollution and inefficient resource utilization. The growing focus on sustainable solutions in geotechnical engineering highlights the potential of sand–rubber tire shred mixtures for applications such as soil stabilization, embankment reinforcement, seismic isolation, and drainage. This paper presents a bibliometric study analyzing research trends, methodologies, and applications of these mixtures from 2000 to 2025, based on 366 relevant publications. The findings indicate a substantial increase in publications after 2015, reflecting heightened academic and industrial interest in sustainable construction materials. Keyword co-occurrence analysis reveals key research themes, including optimization of shear strength, enhancement of compressibility, and mitigation of seismic impacts. Citation network maps illustrate influential studies and collaborative research networks that are propelling advancements in this field. Despite the advantages of sand–rubber mixtures, challenges such as compaction difficulties, variability in rubber particle size, and long-term durability remain to be addressed. Future research should focus on large-scale field applications, standardization of design methodologies, and the integration of advanced computational modeling for performance optimization. This study contributes to the development of sand–rubber mixtures, positioning them as viable and ecological solutions within the framework of circular economy principles and sustainable construction practices.

Geotechnics doi: 10.3390/geotechnics5040070

Authors: Davor Marušić Vedran Jagodnik

This study investigates the behaviour of dense silty sands with kaolinite clay under static drained/undrained conditions at low confining stress. Conventional laboratory tests assessed the mixtures’ physical properties, but standard void ratio methods proved inadequate for silty sands with kaolinite. Despite targeting 80% relative density, specimens exhibited loose sand behaviour in both drained and undrained tests. With increasing kaolinite content, conventionally reconstituted mixtures exhibit reduced peak stress ratios up to 10% fines, with little change beyond, while critical ratios generally rise at 25 kPa but remain unchanged or decrease slightly at 50 kPa. Analytical redefinition of minimum/maximum void ratios (based on sand–clay volumetric fractions) improved specimen reconstitution, yielding dense behaviour matching that of the host sand. The alternatively reconstituted mixtures display increasing drained peaks and minor changes in undrained peaks with increasing kaolinite content, with critical ratios increasing markedly at 25 kPa and only slightly at 50 kPa. However, this analytical void ratio determination method is limited to non-expansive, low-plasticity clays. Void ratios in silty sands with clay mineras are influenced by confining stress, drainage, saturation, clay content, and the sand skeleton structure. Unlike pure sands, these mixtures exhibit variable void ratios due to changes in the clay phase under different saturation levels. A new evaluation method is needed that accounts for clay composition, saturation-dependent consistency, and initial sand skeleton configuration to characterise these soils accurately. The findings highlight the limitations of conventional approaches and stress the need for advanced frameworks to model complex soil behaviour in geotechnical applications.

Geotechnics doi: 10.3390/geotechnics5040069

Authors: Rayed Almasoudi Abolfazl Baghbani Hossam Abuel-Naga

Accurate prediction of soil–structure interface shear strength (τmax) is critical for reliable geotechnical design. This study combines experimental testing with interpretable machine learning to overcome the limitations of traditional empirical models and black-box approaches. Ninety large-displacement ring shear tests were performed on five sands and three interface materials (steel, PVC, and stone) under normal stresses of 25–100 kPa. The results showed that particle morphology, quantified by the regularity index (RI), and surface roughness (Rt) are dominant factors. Irregular grains and rougher interfaces mobilised higher τmax through enhanced interlocking, while smoother particles reduced this benefit. Harder surfaces resisted asperity crushing and maintained higher shear strength, whereas softer materials such as PVC showed localised deformation and lower resistance. These experimental findings formed the basis for a hybrid symbolic regression framework integrating Genetic Programming (GP) with Shapley Additive Explanations (SHAP), Fourier feature augmentation, and physics-informed constraints. Compared with multiple linear regression and other hybrid GP variants, the Physics-Informed Neural Fourier GP (PIN-FGP) model achieved the best performance (R2 = 0.9866, RMSE = 2.0 kPa). The outcome is a set of five interpretable and physics-consistent formulas linking measurable soil and interface properties to τmax. The study provides both new experimental insights and transparent predictive tools, supporting safer and more defensible geotechnical design and analysis.

Geotechnics doi: 10.3390/geotechnics5040068

Authors: Akira Ofuchi Daisuke Fujiwara Tomohiro Watanabe Noriaki Mizukami Yasuhiro Kuwahara Koji Miyoshi Kojiro Iizuka

Currently, Japan’s fishing industry is facing a severe decline in its workforce. As a response, fishing mechanization using small underwater robots is promoted. These robots offer advantages due to their compact size, although their operating time is limited. A major source of this limited operating time is posture stabilization, which requires continuous thruster use and rapidly drains the battery. To reduce power consumption, anchoring the robot to the seabed with anchors is proposed. However, due to neutral buoyancy, the available thrust is limited, making penetration into the seabed difficult and reducing stability. To address this, we focus on composite-shaped anchors and vibration. The anchors combine a conical tip and a cylindrical shaft to achieve both penetrability and holding force. However, a trade-off exists between these functions depending on the tip angle; anchors with larger angles provide better holding capacity but lower penetrability. To overcome this limitation, vibration is applied to reduce soil resistance and facilitate anchor penetration. While vibration is known to aid penetration in saturated soft soils, the effect of tip angle under such conditions remains unclear. This study aims to clarify the optimal tip angle for achieving sufficient penetration and holding performance under vibratory conditions. Experiments in underwater saturated soft soil showed that vibration improves both penetration and holding. This effect was strong in anchors with tip angles optimized for holding force. These findings support the development of energy-efficient anchoring systems for autonomous underwater operations in soft seabed environments.

Geotechnics doi: 10.3390/geotechnics5040067

Authors: Koohyar Faizi Robert Evans Rolands Kromanis

Accurate evaluation of subgrade behaviour under dynamic loading is essential for the long-term performance of transport infrastructure. While the Light Weight Deflectometer (LWD) is commonly used to assess subgrade stiffness, it provides only a single stiffness value and may not fully capture the time-dependent response of soil. This study presents an image-based vision system developed to monitor soil surface displacements during loading, enabling more detailed analysis of dynamic behaviour. The system incorporates high-speed cameras and MATLAB-based computer vision algorithms to track vertical movement of the plate during impact. Laboratory and field experiments were conducted to evaluate the system’s performance, with results compared directly to those from the LWD. A strong correlation was observed (R2 = 0.9901), with differences between the two methods ranging from 0.8% to 13%, confirming the accuracy of the vision-based measurements despite the limited dataset. The findings highlight the system’s potential as a practical and cost-effective tool for enhancing subgrade assessment, particularly in applications requiring improved understanding of ground response under repeated or transient loading.

Geotechnics doi: 10.3390/geotechnics5030066

Authors: Juan Carlos Ruge Diego Caballero-Rojas Fausto Molina-Gómez Renato Pinto da Cunha Diego Meléndez-Suarez

The insertion into the soil stratum to be evaluated is the factor that most affects the results obtained by the vane shear test (VST). According to the literature, it has been identified that there is a disturbance in the fabric and even in the movement of soil particles around the probe. The current study allowed the VST to be carried out on kaolinitic clayey soils reconstituted in the laboratory at different historical preconsolidation artificial stresses. The influence of the disturbance on the alteration of the soil analysed is directly linked to the thickness of the vane blades and their corresponding vane area ratio (VA). For this reason, a digital image correlation (DIC) technique was proposed to analyse images taken during the test’s development. The alteration produced by the disturbance was recorded, and the result obtained was compared with previous studies. This analysis established the effect on the reconstituted samples by employing a disturbance parameter specific to this study.

Geotechnics doi: 10.3390/geotechnics5030065

Authors: Nabanita Daimary Devabrata Sarmah Arup Bhattacharjee Utpal Barman Manob Jyoti Saikia

The increasing difficulty of handling industrial and agricultural wastes has generated interest in reusing materials such as Cement Kiln Dust (CKD) and Rice Husk Ash (RHA) for sustainable soil stabilization. This study examined the enhancement of lateritic soil with the incorporation of CKD (0–12%) and RHA (0–25%) by weight. An integrated experimental and Artificial Neural Network (ANN) methodology was utilized to evaluate and forecast geotechnical features. Laboratory assessments were conducted to measure Atterberg limits, Maximum Dry Density (MDD), Optimum Moisture Content (OMC), and Unconfined Compressive Strength (UCS) at 0, 7, and 28 days of curing. The results indicated significant enhancements in soil characteristics with CKD-RHA combinations. Artificial Neural Network models, including GELU, LOGSIG-3, and Leaky ReLU activation functions, accurately predicted the UCS, MDD, and OMC, achieving R2 values as high as 0.980. This work underscores the efficacy of CKD-RHA mixtures in improving soil stability and the promise of ANN models as excellent prediction instruments, fostering sustainable and economical construction methodologies.

Geotechnics doi: 10.3390/geotechnics5030064

Authors: Robi Sonkor Mozumder Maalvika Aggarwal Md Jobair Bin Alam Naima Rahman

Soil moisture is one of the key hydrologic components indicating the performance of landfill final covers. Conventional compacted clay (CC) covers and evapotranspiration (ET) covers often suffer from moisture-induced stresses, such as desiccation cracking and irreversible hydraulic conductivity. Engineered turf (EnT) cover systems have been introduced recently as an alternative; however, their field-scale moisture distribution behavior remains unexplored. This study investigates and compares the soil moisture distribution characteristics of EnT, ET, and CC landfill covers at a shallow depth using one year of field-monitored data in a humid subtropical region. Three full-scale test Sections (3 m × 3 m × 1.2 m) were constructed side by side and instrumented with moisture sensors at a depth of 0.3 m. Distributional characteristics of moisture were evaluated with descriptive statistics, goodness-of-fit tests such as Shapiro–Wilk (SW) and Anderson–Darling (AD), Gaussian probability density functions, Q–Q plots, and standard-normal transformations. Results revealed that Shapiro–Wilk (W = 0.75–0.92, p < 0.001) and Anderson–Darling (A2=1.63×103to6.31×103,p<0.001) tests rejected normality for every cover, while Levene’s test showed unequal variances between EnT and the other covers (F>5.4×104,p<0.001) but equivalence between CC and ET (F = 0.23, p = 0.628). EnT cover exhibited the narrowest moisture envelope (95%range=0.156to0.240m3/m3;CV=10.6%), whereas ET and CC covers showed markedly broader distributions (CV = 38.6 % and 33.3 %, respectively). These findings demonstrated that EnT cover maintains a more stable shallow soil moisture profile under dynamic weather conditions.

Geotechnics doi: 10.3390/geotechnics5030063

Authors: Luis Castillo-Suárez Jesús Redondo-Mosquera Vicente Mercado Jaime Fernández-Gómez Joaquín Abellán-García

This research presents the calibration of a constitutive model to replicate the cyclic performance of soils using a Bayesian framework. This study uses data from laboratory-conducted consolidated undrained isotropic cyclic triaxial tests and numerical tools to estimate optimal parameters by the application of Slice Sampling in a Bayesian analysis and to determinate the uncertainty of the model. For each calibrated parameter in the model, a probability distribution was obtained from the Markov chain. The means and the standard deviations from the distributions are compared with the laboratory results by the simulation of a series of consolidated undrained isotropic cyclic triaxial tests and a numerical model for a deposit that replicates the Wildlife’s stratigraphic characteristics. The calibrated model response offers a good approximation of the recorded data and the uncertainty due to the model is evaluated. The results of this study demonstrate that Bayesian calibration can reliably quantify parameter uncertainty, reveal parameter correlations that deterministic methods overlook, and improve confidence in liquefaction assessments. This probabilistic framework provides a robust basis for extending calibration to other soil types and site conditions.

Geotechnics doi: 10.3390/geotechnics5030062

Authors: Adel Belmana Victor Cavaleiro Mekki Mellas Luis Andrade Pais Hugo A. S. Pinto Vanessa Gonçalves Maria Vitoria Morais André Studart Leonardo Marchiori

Internal erosion is a significant issue caused by water flow within soils, resulting in structural collapse of hydraulic structures, particularly in coarse soils located near rivers. These soils typically exhibit granulometric instability due to low clay content, resulting in poor hydraulic and mechanical properties. To mitigate this problem, cement treatment is applied as an alternative to soil removal, reducing transportation and storage costs. The hole erosion test (HET) and Crumbs tests, shearing behaviour through consolidated undrained (CU) triaxial, and microstructure analyses regarding scanning electron microscopy (SEM), mercury intrusion porosimeter (MIP) and thermogravimetric analysis (TGA) were conducted for untreated and treated coarse soil specimens with varying cement contents (1%, 2%, and 3%) and curing durations (1, 7, and 28 days). The findings indicate a reduction in the loss of eroded particles and overall stability of treated soils, along with an improvement in mechanical properties. SEM observations reveal the development of hydration gel after treatment, which enhances cohesion within the soil matrix, corroborated by TGA analyses. MIP reveals the formation of a new class of pores, accompanied by a reduction in dry density. This study demonstrates that low cement addition can transform locally unsuitable soils into durable construction materials, reducing environmental impact and supporting sustainable development.