Search Results (464)

This study aimed to investigate vertical variations in dissolved organic matter (DOM) properties, humus (HS) composition, humic acid (HA) characteristics, and clay mineral dynamics, with a particular focus on the vertical distribution of HS components and mineral composition across Dark-brown, Meadow, and Paddy soil profiles. Results indicated that: (1) DOM in all three soil types was predominantly endogenous, primarily derived from microbial metabolism with minimal contributions from plant residues. (2) Vertical trends in DOM carbon content (C_DOM) were specific to soil type: in Dark-brown soil, C_DOM slightly increased from the Ap to Bt layer, followed by a sharp increase in the C layer; Meadow soil exhibited a significant decrease in C_DOM in the AB layer but remained relatively stable in other layers; Paddy soil showed a consistent decline in C_DOM with increasing depth. (3) HS and its fractions exhibited vertical variability: Paddy soil showed higher HS content in surface layers; carbon contents of water-soluble substances, HA, and humic-extracted acid (C_WSS, C_HA, and C_HE) decreased with depth in Dark-brown and Paddy soils, whereas they remained relatively stable in deeper layers of Meadow soil. (4) HA characteristics, including C/N ratio, functional groups, and aromaticity, were influenced by both depth and soil type: the Ap2 layer of Paddy soil effectively restricted the downward movement of organic matter; Fe³⁺ complexation played a key role in HA stabilization in Dark-brown soil; Meadow soil exhibited transitional HS properties. (5) Clay mineral assemblages were dominated by 2:1 type minerals (illite, smectite, illite–smectite interstratifications), showing distinct vertical weathering patterns: illite content decreased with depth due to hydrolysis, while proton-driven dissolution promoted kaolinite formation in surface layers, particularly in Dark-brown soil 2:1 minerals enhancing organic–mineral complexation in Meadow soil. The findings of this study provided a scientific basis for optimizing soil carbon pool management and offer insights into organic–mineral interactions that can enhance organic matter sequestration in agricultural soils. Full article

This research presents the results of studies on the physical and mechanical properties of the soil–polymer composites developed by the Scientific and Production Company “Special Polymer Technologies” SPT^® by injecting polyurethane material into clay soils to strengthen the foundations of erected structures. A novel method is proposed to determine the strain characteristics of these composites, embracing the preparation of model specimens in cylindrical containers with subsequent static and dynamic load testing. The results of static tests showed a significant increase in the strain modulus in comparison to that of the soil, resulting in soil stabilization due to a decrease in the initial content of moisture squeezed out of the modified soil. A coefficient of increase in the deformation modulus (K_E) is introduced to quantitatively assess the soil stabilization efficiency. An original technique is also proposed for assessing composite durability, and it is based on analyzing the mass loss after cyclic wetting and drying. The proposed soil stabilization approach promotes and improves digital construction technologies such as Building Information Modeling (BIM) by enabling the accurate simulation and prediction of the behavior of loaded soil in foundation systems. The introduced quantifiable metrics can be integrated into Digital Twin- or BIM-based project planning tools, contributing to sustainability, safety, and reliability in modern construction practices. Full article

Dynamic compaction has been widely applied to reinforce soft soils in port areas due to its high efficiency and cost-effectiveness. However, a comprehensive understanding of the deformation mechanisms and stiffness evolution of treated soils under static and dynamic loading remains limited. This study integrated one-dimensional consolidation tests, resonant column tests, and bender element tests to systematically investigate the mechanical behavior of soft clay before and after dynamic compaction under varying stress levels and loading frequencies. The results show that dynamic compaction significantly enhances the compression modulus and consolidation stability of soft clay while reducing the settlement rate during primary consolidation. The shear modulus exhibits nonlinear degradation with increasing strain, whereas the damping ratio increases rapidly before reaching a plateau, indicating typical strain-dependent behavior. A three-parameter model and a second-order polynomial model effectively characterize the degradation of the shear modulus and the evolution of the damping behavior, respectively. Moreover, the strong consistency between the resonant column and bender element test results enables continuous characterization of the shear stiffness across small- to intermediate-strain ranges. These findings provide theoretical insight and practical guidance for modeling the dynamic response of soft clay and evaluating the effectiveness of dynamic compaction as a ground improvement technique. Full article

Vertical low-permeability barriers are widely used to improve the stability and seepage resistance of flood embankments. The present study evaluates three barrier technologies—vibrating beam slurry walls (VBSWs), deep soil mixing (DSM), and low-pressure grout injection (LPG)—through a series of consolidated drained triaxial tests and permeability coefficient tests on soil samples collected from the sites where different barrier installation technologies were used. All three barrier installation methods produced substantial improvements in both mechanical and hydraulic performance: the effective angle of internal friction (φ′) increased by 3–6° in samples with a plasticity index near 3.5%, and coefficients of permeability dropped from 10⁻⁸–10⁻⁷ m/s in untreated soils to below 10⁻⁹ m/s in treated specimens. The key finding of the study is that the barrier performance varies by the technology and the soil type. According to the result, DSM is the most effective technology used in clay-rich soils (φ′ increased up to 4°); LPG achieved the lowest permeability (7 × 10⁻¹¹ m/s) in granular soils; and VBSWs balanced strength and impermeability, most effective in silty sands. Flow-pump tests further demonstrated that treated soils required much longer to stabilize under a constant flow rate and could sustain higher hydraulic gradients before reaching equilibrium. These findings show the importance of matching barrier technology to soil plasticity and liquidity characteristics and highlight saturation as essential for reliable laboratory evaluation. The results provide a scientific basis for selecting and designing vertical barriers in flood-preventing infrastructure, offering performance benchmarks for improving hydraulic and geotechnical structures. Full article

This study aims to develop environmentally friendly soil-stabilization materials by investigating the synergistic enhancement mechanism of industrial by-product lignin fibers (LFs) and sodium sulfate (Na₂SO₄) on the mechanical and micro-structural properties of cement-stabilized soil. A systematic evaluation was conducted through unconfined compressive strength (UCS), splitting tensile strength, and capillary water absorption tests, supplemented by microscopic analyses including XRD and SEM. The results indicate that the optimal synergistic effect occurs at 1.0% LF and 0.10% Na₂SO₄, which increases UCS and splitting tensile strength by 9.23% and 18.37%, respectively, compared to cement-stabilized soil. Meanwhile, early strength development is accelerated. Microscopically, LF physically bridges soil particles, forming aggregates, reducing porosity, and enhancing cohesion. Chemically, Na₂SO₄ acts as an activator, accelerating cement hydration and stimulating pozzolanic reactions to form calcium aluminosilicate hydrate and gypsum, which fill pores and densify the matrix. The synergistic mechanism lies in Na₂SO₄ enhancing the interaction between the LFs and clay minerals through ion exchange, facilitating the formation of a stable spatial network structure that inhibits particle sliding and crack propagation. This technology offers substantial sustainability benefits by utilizing paper-making waste LF and low-cost Na₂SO₄ to improve soil strength, toughness, and impermeability. Full article

The dataset presented in this manuscript consists of three distinct sets of data collected during a laboratory experiment aimed at quantifying the emissions of greenhouse gases (GHGs), specifically methane (CH₄), carbon dioxide (CO₂), and nitrous oxide (N₂O). The experiment was conducted in three phases, each initiated at different times. The first phase began on 6 June 2022, using a biocover composed of 60% fine-fraction waste, 20% clay soil, and 20% stabilized compost. The second phase commenced on 26 August 2022, with two biocover variants: one composed of 50% fine-fraction waste and 50% clay soil, and the other consisting of 40% fine-fraction waste, 40% clay soil, and 20% shredded paper. The final phase started on 27 October 2022, introducing two biocovers: one containing 25% dried algae, 25% fine-fraction waste, 25% gravel (0–20 mm), and 25% ash, and the other composed of 40% fine-fraction waste, 40% dried algae, and 20% chernozem. Emission assessments were conducted three weeks after the biocover installation to allow for settling and stabilization, followed by weekly measurements two to three days before irrigation with 250 mL of water to simulate field conditions. GHG emission quantification was carried out using the Cavity Ring-Down Spectroscopy gas measurement device, Picarro G2508. This dataset offers substantial scientific value for advancing biocover technologies aimed at reducing GHG emissions in landfill environments, particularly for mitigating methane emissions. In addition to initial experimental use, the dataset offers a wide range of possibilities for reuse, including modeling landfill gas emissions, validating gas flow measurement methods, developing machine learning models, and performing meta-analyses. Its detailed structure facilitates multi-faceted environmental research and supports optimization of landfill management. Full article

This study introduces an innovative deflection-controlled design method (DCM) for evaluating the bearing capacity of offshore mono-bucket foundations (MBFs) in clay, integrating advanced numerical simulations using FLAC3D with the modified cam clay (MCC) soil model. Departing from conventional ultimate bearing capacity approaches, the proposed method prioritizes serviceability limits by constraining foundation deflections to ensure optimal structural performance and turbine efficiency. A systematic investigation revealed that the MBF performance is predominantly governed by eccentricity ratios and soil–structure interaction, with vertical loads exhibiting a minimal impact in a serviceability limit state. Key findings include the following: (1) the rotation center (RC) stabilizes at approximately 0.8 times the skirt length (L) under loading; (2) thin, deep MBFs (aspect ratio > 1.0) exhibit up to a 30% higher bearing capacity compared to wide, shallow configurations; (3) increasing eccentricity ratios (ε = 0.31–1.54) enhance the moment capacity but reduce the allowable horizontal force by 15–20%; (4) compressive vertical loads (υ = −0.30) slightly reduce the normalized bending moments (ω) by 5–10% at low eccentricities (ε < 0.5). The numerical framework was rigorously validated against centrifuge test data, demonstrating high accuracy (error < 3%) in predicting foundation behavior. By bridging geotechnical mechanics with practical engineering requirements, this study provides a robust and efficient design framework for MBFs, offering significant improvements in reliability and cost-effectiveness for offshore wind turbine applications. The proposed DCM successfully guided the design of an MBF in southeastern China, demonstrating its efficacy for use with homogeneous clay. Full article

To address the critical challenge of ensuring bottom water-inrush stability during the excavation of ultra-deep foundation pits for riverside suspension-bridge anchorages under complex geological conditions involving high-pressure confined groundwater, we investigate the application of D-RJP high-pressure rotary jet grouting pile technology for ground improvement. Its effectiveness is systematically validated through a case study of the South Anchorage Foundation Pit for the North Channel Bridge of the Zhangjinggao Yangtze River Bridge. The D-RJP method led to the successful construction of a composite foundation within the soft soil that satisfies the permeability coefficient, interface friction coefficient, bearing capacity, and shear strength requirements, significantly improving the geotechnical performance of the anchorage foundation. A series of field experiments were conducted to optimize the critical construction parameters, including the lifting speed, water–cement ratio, and stroke spacing. Core sampling and laboratory testing revealed the grout columns to have good structural integrity. The unconfined compressive strength of the high-pressure jet grout columns reached 5.45 MPa in silty clay layers and 8.21 MPa in silty sand layers. The average permeability coefficient ranged from 1.67 × 10⁻⁷ to 2.52 × 10⁻⁷ cm/s. The average density of the columns was 1.66 g/cm³ in the silty clay layer and 2.08 g/cm³ in the silty sand layer. The cement content in the return slurry varied between 18% and 27%, with no significant soil squeezing effect observed. The foundation interface friction coefficient ranged from 0.44 to 0.52. After excavation, the composite foundation formed by D-RJP columns was subjected to static load and direct shear testing. The results showed a characteristic bearing capacity value of 1200 kPa, the internal friction angle exceeded 24.23°, and the cohesion exceeded 180 kPa. This study successfully verifies the feasibility of applying D-RJP technology to construct high-performance artificial composite foundations in complex strata characterized by deep soft soils and high-pressure confined groundwater, providing valuable technical references and practical insights for similar ultra-deep foundation pit projects involving suspension bridge anchorages. Full article

Repeated freeze-thaw cycles in seasonally frozen regions significantly degrade the mechanical properties of clay, posing serious challenges to geotechnical infrastructure stability. This study investigates the compressibility behavior of lignin fiber-reinforced clay under freeze-thaw conditions through one-dimensional consolidation tests and microstructural analysis. Clay specimens containing 0.0%, 0.5%, 1.0%, 1.5%, and 2.0% lignin fibers by mass were subjected to 0, 1, 4, and 10 freeze-thaw cycles to simulate typical seasonal variations. The results indicate that reinforcement with lignin fibers markedly enhances the soil’s resistance to freeze-thaw-induced degradation. Specifically, in unreinforced clay, 10 freeze-thaw cycles reduced the pre-consolidation pressure from 139 kPa to 97 kPa. With 2.0% lignin fiber, the pressure increased to 186 kPa under unfrozen conditions and remained at 120 kPa after 10 cycles. SEM and MIP analyses revealed that lignin fibers form interconnected networks that inhibit the formation and expansion of strip pores and constrained pore coarsening caused by freeze-thaw action, effectively stabilizing the soil structure. A model incorporating both fiber content and freeze-thaw cycle effects was proposed to predict compression behavior, and the model accurately captured the experimental compression curves across all test conditions. This study provides a theoretical and experimental basis for the application of natural fiber-reinforced clay in cold-region geotechnical engineering, offering a sustainable and effective alternative to traditional stabilization methods. Full article

This study investigates sedimentation dynamics and microstructural evolution of silty clay and mucky sediments from the immersed tube tunnel trench of the Shunde Tanzhou Waterway. Experiments examined different initial unit weights (11.5–12.6 kN/m³) and heights (10–60 cm) through sedimentation tests (N = 30, representing five heights × three unit weights × two soil types) and scanning electron microscopy (SEM) imaging. Results identified two sedimentation patterns: consolidation (inverse “S” curve) and hindered (three-stage) types. Key findings reveal that silty clay exhibits height-dependent transition between patterns (critical height = 30 cm at γ = 12.6 kN/m³). Mucky soil demonstrates stable hindered settlement across conditions (rate = 0.09 ± 0.01 cm/min at γ = 12.0 kN/m³). Moisture distribution analysis reveals that unstable structures in low-unit-weight slurries exhibit slow drainage and steady moisture content changes. Microstructural analysis uncovered height-dependent porosity increases and pore complexity in mucky soils, alongside reduced honeycomb-like cavities and enhanced particle aggregation in silty clay under lower unit weights. These results provide novel insights into the interplay between initial slurry conditions and sedimentation behavior, offering a theoretical foundation for optimizing dredging strategies and ensuring long-term sediment stability in immersed tube tunnel projects. Full article

Soybean (Glycine max (L.) Merrill) is globally valued for protein, oil, and biofuel applications. Thailand imports 99.8% of its soybean consumption due to declining cultivation areas. Northeastern Thailand presents substantial potential for expanding soybean production through integrated seed rotation systems in post-sugarcane (upland) and post-rice (lowland) environments. This study evaluated the newly developed ‘Morkhor 60’ soybean variety compared to three commercial varieties (SJ 5, 223*Lh-85, and CM 60) across thirteen diverse environments in Northeastern Thailand during 2022–2023. Field experiments employed a randomized complete block design with four replications per site. The ‘Morkhor 60’ demonstrated favorable yield stability and competitive performance across most environments. The variety showed broad adaptability across soil types (sandy loam to clay) and seasonal conditions (rainy and dry seasons) with minimal genotype-by-environment interactions. Chemical analysis revealed favorable protein content (39.63%) and oil content (14.66%). These findings support the cultivation of ‘Morkhor 60’ in integrated seed rotation systems, offering a viable strategy to reduce national soybean seed shortages while enhancing domestic production and agricultural sustainability. Full article

This study aimed to evaluate the impact of vineyard cultivation time and the use of metal-based fungicides on the chemical fractions of soil organic matter (SOM) as well as their interactions with Cu, Zn, and Mn in vineyard soils from Southern Brazil with varying histories of fungicide application. Soil samples were collected in 2017 from vineyards aged 35, 37, and 39 years in the Serra Gaúcha region and 13, 19, and 36 years in the Campanha Gaúcha. In each region, samples were also collected from a non-anthropized reference area. In the oldest vineyards, sampling was conducted both within and between the rows of planting. Chemical fractionation of SOM was performed: non-humic substances (nHSs), particulate organic matter (POM), fulvic acid (FA), humic acid (HA), and humin (Hu). Fourier-transform infrared (FTIR) spectra were obtained for the HA, from which the aromaticity index (AI) and relative intensities (RIs) were calculated. In each SOM fraction, total organic carbon and the concentrations of Cu, Zn, and Mn were determined. Changes in land use alter the forms and distribution of soil organic carbon (SOC) and, consequently, of metals. Elemental and spectroscopic analyses of HS revealed that HA in the reference areas (forest and native grassland) was more aliphatic and had higher concentrations of polysaccharides, indicating fractions with a lower degree of stabilization. However, in vineyard areas, HA exhibited greater humification and aromaticity. Increasing cultivation time gradually increased soil carbon content, indicating that viticultural agroecosystems can sequester carbon in the soil over time, reaching levels similar to those observed in the reference areas. When comparing vineyard areas alone, with row collections and inter-row collections, we observed an increase in SOC levels in areas managed with cover crops, demonstrating the importance of conservation management in these areas. When evaluating the distribution of metals in these soils, we could observe the high affinity of Cu for the functional groups of SOM, with FA and HA responsible for the complexation of these elements in the soil. For Zn and Mn, the greatest accumulations were observed in the Hu fraction due to their greater affinity for soil clay minerals. This shows that soil organic matter is a key component in the complexation of metals in soils, reducing their availability and potential toxicity to cultivated plants. Full article

One type of pore fundamental to water dynamics is the intra-aggregate pore, which holds water vital for plant and root system development, mainly in finer-textured soils such as clays. The distribution of intra-aggregate pores also influences the redistribution of water. Thus, it is important to study the dynamics of the intra-aggregate pore network under processes such as wetting and drying cycles (WDC). Changes in these pore types can play essential roles in organic matter protection, water movement, microbial activity, and aggregate stability. To date, there are few studies analyzing the impact of WDC on intra-aggregate pore dynamics. This study aims to provide results in this regard, analyzing changes in the pore architecture of a subtropical Oxisol under no-tillage (NT), conventional tillage (CT), and forest (F) after WDC application. Three-dimensional X-Ray microtomography images of soil aggregate samples (2–4 mm) subjected to 0 and 12 WDC were analyzed. The results showed that WDC did not affect (p > 0.05) the imaged porosity, number of pores, fractal dimension, tortuosity, and pore connectivity for the different soil management types. To analyze the permeability and hydraulic conductivity of the soil pore system, the most voluminous pore (MVP) was examined. No differences were observed in the imaged porosity, fraction of aggregate occupied by the MVP, connectivity, tortuosity, hydraulic radius, permeability, and hydraulic conductivity between 0 and 12 WDC for the MVP. Comparing soil management types after 12 WDCs, for example, F samples became more porous than CT and NT samples. In contrast, the pore system of NT had a lower fractal dimension and was more tortuous than that of CT and F samples. Our results show that for highly weathered soils such as the Brazilian Oxisol studied, the intra-aggregate pore network proved resistant to changes with WDC, regardless of the type of management adopted. Full article

Large-diameter rock-socketed monopiles supporting offshore wind turbines in soft clay strata face significant geotechnical risks from negative skin friction (NFS) induced by construction surcharges. While the effects of NFS on axial drag loads are documented, the critical interaction between horizontal pile loading and NFS development remains poorly understood. This research bridges this gap using a rigorously validated 3D finite element model that simulates the complex coupling of vertical substructure loads (5 MN), horizontal loading, and surcharge-induced consolidation. The model’s accuracy was confirmed through comprehensive verification against field data for both NFS evolution under surcharge and horizontal load–displacement behavior. The initial analysis under representative conditions (10 MN horizontal load, 100 kPa surcharge, 3600 days consolidation) revealed that horizontal loading fundamentally distorts NFS distribution in the upper pile segment (0 to −24 m), transforming smooth profiles into distinct dual-peak morphologies while increasing the maximum NFS magnitude by 57% (from −45.4 kPa to −71.5 kPa) and relocating its position 21 m upward. This redistribution was mechanistically linked to horizontal soil displacement patterns. Crucially, the NFS neutral plane remained invariant at the clay–rock interface (−39 m), demonstrating complete independence from horizontal loading effects. A systematic parametric study evaluated key operational factors: (1) consolidation time progressively increased NFS magnitude throughout the clay layer, evolving from near-linear to dual-peaked distributions in the upper clay (0 to −18 m); NFS stabilized in the upper clay after 720 days while continuing to increase in the lower clay (−18 to −39 m) due to downward surcharge transfer, accompanied by neutral plane deepening (from −36.5 m to −39.5 m) and 84% maximum axial force escalation (12.5 MN to 23 MN); (2) horizontal load magnitude amplified upper clay NFS peaks at −3.2 m and −9.3 m, with the shallow peak magnitude increasing linearly with load intensity, though it neither altered lower clay NFS nor neutral plane position; (3) surcharge magnitude increased overall NFS, but upper clay NFS (0 to −18 m) stabilized beyond 100 kPa, while lower clay NFS continued rising with higher surcharges, and the neutral plane descended progressively (from −38 m to −39.5 m). These findings demonstrate that horizontal loading critically exacerbates peak NFS values and redistributes friction in upper pile segments without influencing the neutral plane, whereas surcharge magnitude and consolidation time govern neutral plane depth, total NFS magnitude, and maximum drag load. This research delivers essential theoretical insights and practical guidelines for predicting NFS-induced drag loads and ensuring the long-term safety of offshore wind foundations in soft clays under complex multi-directional loading scenarios. Full article

As an intensive eco-agricultural model, the rice–crayfish co-culture (RCC) system has been widely adopted in recent years due to its remarkable advantages in resource use, efficiency, and economic benefits. However, the long-term mechanisms by which this system affects the quantity and stability of soil aggregate, as well as the vertical distribution of soil organic carbon (SOC) within aggregate across soil profiles, remain unclear. This study investigated the effects of varying duration (4 and 8 years) of RCC in Qianjiang City, Hubei Province. Soil samples were collected from six depth layers (0–10 cm, 10–20 cm, 20–30 cm, 30–40 cm, 40–80 cm, and 80–120 cm) to analyze the distribution characteristics of soil aggregate and SOC. The results demonstrated that, compared to the field which used RCC for a duration of 4 years, the field which used RCC for a duration of 8 years significantly reduced bulk density (BD) by 16.3% in the 40–80 cm layer. However, prolonged flooding has led to a 9.6% increase in the BD of the plow pan layer (10–20 cm) due to hydrostatic pressure and mechanical disturbances. Furthermore, the use of RCC for a duration of 8 years significantly enhanced the mass fractions of water-stable aggregates > 2 mm in the 0–80 cm soil layer at 0–10 cm (25.9%), 10–20 cm (30.2%), 20–30 cm (141.8%), 30–40 cm (172.4%), and 40–80 cm (112.9%), and improved aggregate stability throughout the entire soil profile. In terms of SOC distribution, the SOC concentration increased significantly with prolonged RCC usage across all soil layers, particularly in the 0–20 cm layer. The SOC was primarily derived from >2 mm (Large aggregate). Notably, although < 0.053 mm (Silt and clay) constituted a small proportion of the 0–20 cm layer, their SOC concentration reached 15.3–20.55 g kg⁻¹. Overall, extended RCC duration reduced BD in nearly all soil layers, promoted the formation of macro-aggregate, enhanced aggregate stability, and increased the SOC concentration within macro-aggregate, while strengthening the SOC stocks capacity of the 80–120 cm soil layer from 2.58 kg C m⁻² to 4.35 kg C m⁻², an increase of 68.6%. Full article