Search Results (56)

Fujian Tulou, a UNESCO World Heritage Site, is highly vulnerable to environmental and anthropogenic stresses, with its earthen walls prone to surface cracking that threatens both structural stability and cultural value. Traditional manual inspection is inefficient, subjective, and may disturb fragile surfaces, highlighting the need for non-destructive and automated solutions. This study proposes a dual-path framework that integrates lightweight crack detection with independent physical simulation. On the detection side, an improved YOLOv12 model is developed to achieve lightweight and accurate recognition of multiple crack types under complex wall textures. On the simulation side, a two-layer RFPA^3D model was employed to parameterize loading conditions and material thickness, reproducing the four-stage crack evolution process, and aligning well with field observations. Quantitative validation across paired samples demonstrates improved consistency in morphology, geometry, and topology compared with baseline models. Overall, the framework offers an effective and interpretable solution for standardized crack documentation and mechanistic interpretation, providing practical benefits for the preventive conservation and sustainable management of Fujian Tulou. Full article

In order to investigate the compression damage characteristics of the “interface section coal pillar–backfill body (ICPF)” composite structure formed after coal pillar excavation and gangue material backfill in the key technologies of coal pillar excavation and gangue material backfill replacement in the interface section of thick coal seams, an ICPF single-axis compression damage experiment under different internal dimensions of backfill was conducted using the PFC^2D numerical model, with the interface section coal pillar of a working face at a certain mine in northern Shaanxi Province as the research background. In addition, the stress–strain state, peak strength characteristics, damage mode, energy evolution, and damage characteristics of the ICPF composite were analyzed, and models for the evolution of the ICPF elastic modulus and compressive strength were established. The results showed that the stress–strain state of the ICPF changed from brittle to ductile as backfill strength decreased. The distribution of the elastic modulus is primarily influenced by backfill strength, and as the excavation–backfill width increases, the curve exhibits a distinct S-shaped distribution. The compressive strength decreases by up to 63.4% with an increase in excavation–backfill width and by up to 65.1% with a decrease in backfill strength. The sensitivity of compressive strength to backfill strength is greater than that to excavation–backfill width. Based on the established ICPF elastic modulus and compressive strength evolution model, the two mechanical properties were compared using model fitting, and the model fitting results were satisfactory. The ICPF exhibits three types of damage characteristics as the excavation and backfill width increases: oblique shear and tensile damage, edge coal stripping and X-shaped conjugate damage of the backfill body, and large-area plastic damage of the backfill body. By establishing a theoretical damage variable based on linear dissipation energy, damage factors can be quickly obtained from stress–strain curves. The damage curves all exhibit exponential growth, and their growth rates show certain dispersion as the excavation and backfill width increases and backfill strength decreases. Based on the brittleness index analysis of the ICPF composite, as the backfill strength decreases and excavation and backfill width increases, the brittleness index of the composite increases, and the tendency for impact increases. At an excavation and backfill width of 80 mm, rib damage tends to happen. Full article

The reactivation of the Longdongpo ancient colluvial landslide in Sinan County, Guizhou Province represents a typical multi-factor coupled failure. Based on detailed geological investigations and FLAC^3D fluid–solid coupling numerical simulations, this study reveals its complex reactivation mechanisms. The analysis demonstrates that long-term groundwater action has significantly weakened the slip zone at the soil–bedrock interface, causing strength degradation and inducing prolonged quasi-stable creep deformation of the slope. The artificial cut slopes formed in the middle-to-lower sections disrupted the original stress field and induced localized plastic deformation. Crucially, the numerical simulation identified a 5 m rainfall infiltration depth as the threshold triggering abrupt instability; when exceeding this critical value (simulated as 10 m and 16 m infiltration depths), pore water pressure surged (>2.7 MPa) and displacement dramatically increased (>2.2 m), reducing shear strength along the potential failure surface to critical levels. This process culminated in the full connection of the shear surface and the landslide’s catastrophic reactivation. This work quantitatively elucidates the chain-reaction mechanism of “long-term groundwater weakening → engineering disturbance initiation → critical-depth rainfall infiltration triggering”, providing vital quantitative evidence for regional ancient landslide risk prevention. Full article

This study investigated the freeze–thaw resistance of ordinary and nano-TiO₂-modified concrete (NTC) based on mass loss, ultrasonic velocity, compressive strength, and fracture toughness. The compressive behavior and internal damage evolution were further analyzed using particle flow code in two dimensions (PFC^2D) simulations. The results show that, although neither material exhibited structural collapse after freeze–thaw cycling, visible surface damage was observed, particularly in ordinary concrete. After 100 cycles, NTC showed a 52.17% reduction in mass loss and a 37.31% increase in ultrasonic velocity compared to ordinary concrete. Compressive strength of ordinary concrete decreased by 24.28 MPa (from 41.53 MPa to 17.25 MPa), while that of NTC decreased by only 13.37 MPa, demonstrating that the incorporation of nano-TiO₂ effectively improves the compressive performance of concrete under freeze–thaw conditions. Fracture toughness after 100 cycles decreased by 89.7% in ordinary concrete and 80.9% in NTC, suggesting that while nano-TiO₂ mitigates damage, its effect on maintaining fracture load-carrying capacity remains limited. The PFC^2D simulations were consistent with the experimental results, effectively capturing peak compressive behavior and validating the model’s applicability for freeze–thaw degradation analysis. Full article

Cyclical footage, a fundamental parameter in tunnel construction, has received limited attention despite its critical role in ensuring excavation stability and safety. To investigate the underlying mechanisms by which different cyclical footage values influence the stability of deeply buried tunnels, the Fast Lagrangian Analysis of Continua in Three Dimensions (FLAC^3D) was employed to simulate the spatiotemporal evolution of tunnel responses during excavation. The simulation results reveal that each cyclical footage scenario produces a “segmental decline” pattern in tunnel displacement. Unlike shallow tunnels, where peak displacement typically occurs near the tunnel face, in deep tunnels the maximum Y-direction displacement appears at the center of the excavation face. Furthermore, as cyclical footage increases, the displacement extent first expands and then contracts. The stress release process is found to be minimally affected by cyclical footage, with vertical strain in the tunnel roof nearly fully released within 1 m ahead of the excavation face. Therefore, deploying tunnel support structures beyond this 1 m zone may enhance their effectiveness. This study provides a theoretical reference for optimizing excavation parameters in deep tunnels and contributes to reducing the likelihood of support failure during underground construction. Full article

The instability of mine roadways is significantly influenced by the coupled effects of groundwater seepage and non-uniform loading. These interactions often induce localized plastic deformation and progressive failure, particularly in the roof and sidewall regions. Seepage elevates pore water pressure and deteriorates the mechanical properties of the rock mass, while non-uniform loading leads to stress concentration. The combined effect facilitates the propagation of microcracks and the formation of shear zones, ultimately resulting in localized instability. This initial damage disrupts the mechanical equilibrium and can evolve into severe geohazards, including roof collapse, water inrush, and rockburst. Therefore, understanding the damage and failure mechanisms of mine roadways at the mesoscale, under the combined influence of stress heterogeneity and hydraulic weakening, is of critical importance based on laboratory experiments and numerical simulations. However, the large scale of in situ roadway structures imposes significant constraints on full-scale physical modeling due to limitations in laboratory space and loading capacity. To address these challenges, a straight-wall circular arch roadway was adopted as the geometric prototype, with a total height of 4 m (2 m for the straight wall and 2 m for the arch), a base width of 4 m, and an arch radius of 2 m. Scaled physical models were fabricated based on geometric similarity principles, using defect-bearing sandstone specimens with dimensions of 100 mm × 30 mm × 100 mm (length × width × height) and pore-type defects measuring 40 mm × 20 mm × 20 mm (base × wall height × arch radius), to replicate the stress distribution and deformation behavior of the prototype. Uniaxial compression tests on water-saturated sandstone specimens were performed using a TAW-2000 electro-hydraulic servo testing system. The failure process was continuously monitored through acoustic emission (AE) techniques and static strain acquisition systems. Concurrently, FLAC^3D 6.0 numerical simulations were employed to analyze the evolution of internal stress fields and the spatial distribution of plastic zones in saturated sandstone containing pore defects. Experimental results indicate that under non-uniform loading, the stress–strain curves of saturated sandstone with pore-type defects typically exhibit four distinct deformation stages. The extent of crack initiation, propagation, and coalescence is strongly correlated with the magnitude and heterogeneity of localized stress concentrations. AE parameters, including ringing counts and peak frequencies, reveal pronounced spatial partitioning. The internal stress field exhibits an overall banded pattern, with localized variations induced by stress anisotropy. Numerical simulation results further show that shear failure zones tend to cluster regionally, while tensile failure zones are more evenly distributed. Additionally, the stress field configuration at the specimen crown significantly influences the dispersion characteristics of the stress–strain response. These findings offer valuable theoretical insights and practical guidance for surrounding rock control, early warning systems, and reinforcement strategies in water-infiltrated mine roadways subjected to non-uniform loading conditions. Full article

Tardigrades, also known as “water bears”, are microscopic invertebrates capable of surviving extreme conditions, including extreme temperatures, intense radiation, and the vacuum of space. Recent studies have unveiled a novel nucleosome-binding protein in the tardigrade Ramazzottius varieornatus, known as the damage suppressor protein (Dsup). This protein has proven essential for enabling tardigrades to thrive in the most challenging environmental conditions, highlighting its pivotal role in their remarkable survival capabilities. Dsup is a highly disordered protein with DNA-binding abilities that reduces DNA damage and enhances cell survival and viability caused by several stresses such as oxidative stress, UV exposure, and X-ray and ionizing radiation. In this review, we summarized articles describing the protective role of Dsup upon different stressors across diverse organisms, including bacteria, yeast, plants, and animals (cell lines and organisms). The multifaceted properties of Dsup open avenues for biotechnological applications, such as developing stress-resistant crops and innovative biomaterials for DNA manipulation. Furthermore, investigations into its potential in space exploration, particularly in protecting organisms from space radiation, underscore its relevance in extreme environments. Full article

The distribution of in situ stress fields in reservoirs is critical for the accurate exploration and efficient exploitation of hydrocarbon resources, especially in deep, fault-developed strata where tectonic activities significantly complicate stress field patterns. To clarify the perturbation effects of faults on in situ stress fields in deep reservoirs, this study combines dynamic–static parameter conversion models derived from laboratory experiments (acoustic emission Kaiser effect and triaxial compression tests) with a coupled “continuous matrix–discontinuous fault” numerical framework implemented in FLAC^3D6.0. Focusing on the BKQ Formation reservoir in the MH area, China, we developed a multivariate regression-based inversion model integrating gravitational and bidirectional tectonic stress fields, validated against field measurements with errors of −2.96% to 9.07%. The key findings of this study include the following: (1) fault slip induces stress reductions up to 22.3 MPa near fault zones, with perturbation ranges quantified via exponential decay functions (184.91–317.74 m); (2) the “continuous matrix–discontinuous fault” coupling method resolves limitations of traditional continuum models by simulating fault slip through interface contact elements; and (3) stress redistribution exhibits NW-SE gradients, aligning with regional tectonic compression. These results provide quantitative guidelines for optimizing hydrocarbon development boundaries and hydraulic fracturing designs in faulted reservoirs. Full article

To investigate the mechanical response characteristics of damming rockfill materials under different confining pressure conditions, this study integrates laboratory triaxial compression tests and PFC^2D numerical simulations to systematically analyze their deformation evolution and failure mechanisms from both macroscopic and microscopic perspectives. Laboratory triaxial test results demonstrate that as the confining pressure increases, the peak deviatoric stress rises significantly, with the shear strength of specimens increasing from 769.43 kPa to 2140.98 kPa. Under low confining pressure, rockfill exhibits pronounced dilative behavior, whereas at high confining pressure, it transitions to contractive behavior. Additionally, particle breakage intensifies with increasing confinement, with the breakage rate rising from 4.25% to 8.33%. This particle fragmentation alters the granular skeleton structure, thereby affecting the overall mechanical properties and leading to a reduction in shear strength. Numerical simulations further reveal the micromechanical mechanisms governing rockfill behavior. The simulation results show a shear strength increase from 572.39 kPa to 2059.26 kPa, exhibiting a trend consistent with experimental findings. The shear failure mode manifests as a characteristic “X-shaped” shear band distribution, while at high confining pressures, shear fracture propagation is effectively inhibited, enhancing the overall structural stability. Furthermore, increasing confining pressure promotes denser interparticle contacts, with contact numbers increasing from 16,140 to 18,932 and the maximum contact force rising from 12.19 kN to 59.83 kN. The quantity and frequency of both strong and weak force chains also increase significantly, further influencing the mechanical response of the material. These findings provide deeper insights into the mechanical behavior of rockfill materials under varying confining pressures and offer theoretical guidance and engineering references for dam stability assessment and construction optimization. Full article

Group 11 metals form with pyrazolate ligand complexes with a general formula of [MPz]_n. The value of “n” varies depending on the type of substituent in the ligand and the metal atom. Copper(I) and silver(I) ions mainly form cyclic di-, tri-, and tetra-nuclear complexes or polymeric structures. Cyclic trinuclear d¹⁰ metal pyrazolates [MPz^m]₃ (M = Cu(I) and Ag(I); Pz = substituted pyrazolate ligand) are of particular interest because their planar structure allows them to form supramolecular aggregates via noncovalent metal–metal, metal–π, and metal–electron donor interactions. Designing complexes based on these interactions has been a focus of research for the last two decades. The ability of cyclic trinuclear copper(I) and silver(I) pyrazolates to form coordination and supramolecular structures determines their properties and potential applications in catalysis, gas sensing, molecular recognition, and photoluminescence. In this review, we discuss noncovalent interactions between cyclic trinuclear silver(I) and copper(I) complexes with various types of ligands. Full article

Fault fracture zones, characterized by high weathering, low strength, and a high degree of fragmentation, are common adverse geological phenomena encountered in tunneling projects. This paper performed a series of large-scale triaxial compression tests on the cohesive soil–rock mixture (SRM) samples with dimensions of 500 mm × 1000 mm to investigate the influence of rock content P_BV (20, 40, and 60% by volume), rock orientation angle α, and confining pressure on their macro-mechanical properties. Furthermore, a triaxial numerical model, which takes into account P_BV and α, was constructed by means of PFC^3D to investigate the evolution of the mechanical properties of the cohesive SRM. The results indicated that (1) the influence of the α is significant at high confining pressures. For the sample with an α of 0°, shear failure was inhibited, and the rock blocks tended to break more easily, while the samples with an α of 30° and 60° exhibited fewer fragmentations. (2) P_BV significantly affected the shear behaviors of the cohesive SRM. The peak deviatoric stress of the sample with an α of 0° was minimized at lower P_BV (<20%), while both the deformation modulus and peak deviatoric stress were larger at high P_BV (>60%). Based on these findings, an equation correlating shear strength and P_BV was proposed under consistent α and matrix strength conditions. This equation effectively predicts the shear strength of the cohesive SRM with different P_BV values. Full article

In order to consider the effect of fabric anisotropy in the analysis of geotechnical boundary value problems, this study proposes a modified model based on a fabric-based modified Cam-clay model, which can account for the anisotropic response of soil. The major modification of the original model aims to simplify the equations for numerical implementation by replacing the SMP strength criterion with the Lade’s strength criterion. This model comprehensively considers the inherent anisotropy, induced anisotropy, and three-dimensional strength characteristics of soil. The model is first numerically implemented using the elastic trial–plastic correction method, and then it is encapsulated into the FLAC^3D 6.0 software, and tested through conventional triaxial, embankment loading, and tunnel excavation experiments. Numerical simulation results indicate that considering anisotropy and three-dimensional strength in geotechnical engineering analysis is necessary. By accounting for the interaction between microstructure and macroscopic anisotropy, the model can more accurately represent soil behavior, providing significant advantages for geotechnical analysis. Full article

The vibration waves generated by pressure fluctuations can substantially impair and jeopardize the structural integrity of roadway anchorage within adjacent rock formations, thereby presenting a significant risk to the safety and operational efficiency of mining activities. In order to address this issue and elucidate the response characteristics of roadway-anchored surrounding rock subjected to P-wave and S-wave influences, this study employs a roadway that is experiencing actual impact instability within a mine situated in Xinjiang as the engineering context. The synchrosqueezing wavelet transform, enhanced by a Butterworth filter, is utilized to isolate and filter seismic wave data, thereby facilitating the extraction of time-frequency signals corresponding to both P-waves and S-waves. Subsequently, a dynamic numerical model is developed to simulate the propagation of these vibration waves. An analysis of the dynamic behavior and response characteristics of P-waves and S-waves is performed, focusing on their interaction with roadway anchoring within the surrounding rock at various stages of propagation. The results indicate that weak rock and plastic zones can absorb vibrational waves, with S-waves exhibiting a stronger absorption effect than P-waves. S-waves contribute to increased stress and displacement in the surrounding rock, leading to the accumulation of elastic energy and an expansion of the plastic zone. The rapid fluctuations in the axial force of bolts along the roadway, caused by S-waves, can result in instability within the roadway. The research findings possess considerable reference value and practical applicability for the design of anti-scour support systems in roadways. Full article

This study investigates the micro-mechanical behavior of mortar under uniaxial compression using a three-phase model in PFC^3D. By simulating mortar as a composite of cement, sand, and the interfacial transition zone (ITZ), the research examines the impact of particle size on stress–strain behavior, crack propagation, porosity distribution, contact forces, and energy transformation. The simulations reveal that reducing sand particle size from 1–2 mm to 0.25–0.5 mm leads to a significant increase in uniaxial compressive strength, with peak strength values rising from 65.3 MPa to 89.6 MPa. The elastic modulus similarly improves by approximately 20% as particle size decreases. The study also finds that tensile cracks dominate failure, accounting for over 95% of total cracks, with their onset occurring at lower strains as the particle size is reduced. Porosity analysis shows that smaller particles result in a more uniform distribution, with the final porosity at peak strength ranging between 0.26 and 0.29, compared to 0.22 to 0.31 for larger particles. Additionally, energy dissipation patterns reveal that as particle size decreases, the boundary energy transformation into strain energy becomes more efficient, with a 15% increase in strain energy storage observed. These findings provide critical insights into optimizing mortar microstructure for enhanced mechanical performance in construction applications. Full article

Due to the thin bedrock, typical geological characteristics, and the high-intensity underground mining in western China, the water and sand inrush pour into the panels through the broken rock fragmentations in the caving zone, which could result in serious financial losses or even casualties. This paper investigated the influence of the height of the caving zone and the size of sand particles on the speed of water and sand inrush by the methods of laboratory tests and numerical simulation. The test results reveal that the speed of sand flow decreases with an increase in the height of the caving zone until the height of the caving zone approaches a certain value, and the speed of sand flow decreases with the increase in sand particles. The particle flow (PFC^3D) method was used to simulate the experiment to study the dynamic changes in the force chain during the process of water and sand inrush. The simulation results show that the process of water and sand inrush is a continuous and variable process of force chain formation and break. Sand particles only flow through the gap between the caving zones, and during this process, some sand particles remain, which makes the force chain gradually become stable and the speed of water and sand inrush slow. Full article