Taking the Banbiyan dangerous rock mass as the focus, this study employs field investigations, model experiments, and numerical simulations to explore the instability mechanisms of dangerous rock masses on bank slopes containing a single shear band under the deterioration of reservoir water. The results indicate that the failure mode of the dangerous rock mass is collapse of rock mass in the hydrofluctuation belt (HFB) - internal damage to the dangerous rock mass - development and through-going of fractures on both sides - sliding failure of the lower rock detaching from the parent rock. As the shear band gradually deteriorates, stress concentration develops around it near the highest water level. Within the rock mass close to the highest water level, a phenomenon of unloading occurs, and the pore water pressure at the shear band-bedrock interface eventually exceeds that within the rock mass of the HFB. In the numerical simulation, before 40 dry-wet cycles, the damage zone is concentrated near the shear band above the highest water level. Afterward, it concentrates around the fractures on both sides of the dangerous rock mass. The sensitivity of different shear band characteristics to the stability of the dangerous rock mass is ranked as follows: the height-length ratio of the shear band-bedrock interface, followed by the filling material thickness, dip angle, width, and degree of fragmentation. The findings can provide valuable reference for the stability and prevention of such dangerous rock masses.

In the natural environment, the soil structure can be weakened by temperature fluctuations and climatic changes. Nevertheless, the dynamic behavior of expansive soils, especially those with high swelling and pronounced fissure properties, subjected to wetting-drying-freeze-thaw (WDFT) cycles has been rarely investigated. Undisturbed and remolded samples, made of Xinjiang's highly expansive soils, were evaluated in this study through comprehensive resonant column tests conducted at several confining pressures and WDFT cycles. A typical hyperbolic model demonstrated the decay law of shear modulus with strain. An estimated model of the maximum shear modulus, incorporating the two factors, was developed, and it was found to be in good agreement with the measurement results. The results reveal that strain, WDFT cycle, and confining pressure have qualitatively uniform effects on the shear modulus of natural soils containing fissures and recompacted samples. However, the maximum shear modulus of the undisturbed samples is lower by 0.83-13.24 MPa due to the presence of initial fissures, except for the confining pressure of 400 kPa. Also, their responses to confining pressure are more significant, with the shear modulus increased by up to 20 %-124 % relative to that at 25 kPa. Furthermore, the relative difference in the shear modulus (up to about 60 %) between the two samples tested under low confining pressure conditions deserves special attentions. The quantitative differences in shear modulus and cumulative damage effect of the tested samples are attributed to the initial fabric and microstructural evolution, as observed by Scanning Electron Microscope (SEM). This research enriches the theoretical framework for analyzing the ability of soils to resist shear deformation under small strain, which is instructive for disaster prevention and mitigation in expansive soil regions, considering the effects of climate change.

Callovo-Oxfordian (COx) claystone has been selected as the host rock formation for the deep geological disposal of radioactive waste in France, called the Cigéo project. The excavation of drifts in the COx formation induced damage zones with an anisotropic shape, while the stress state around the drifts is almost isotropic. This is due to the anisotropic properties of the host rock formation and the instability caused by the brittle damage. In this study, the mechanical anisotropy of COx claystone was investigated through a triaxial shear test, where the axial stress was maintained while the lateral stress was decreased. Such a method was proposed for simulating one of the possible unloading paths involved during the excavation. The triaxial samples were prepared along different directions based on the angle between the axial loading direction and the one perpendicular to the bedding plane. Results show that the stress-strain curve exhibited an elasto-plastic pattern. With increasing deviatoric stress, a minor decline in Young's modulus E was observed, suggesting progressive damage behaviour. The shear strength changed with increasing the loading angle, showing the anisotropic property of COx claystone. Moreover, the results in this study and collected from other works show a time-dependent behaviour of COx claystone. It is attributed to the coupled effect of creep and pore pressure dissipation inside claystone.

Landfill cover system plays a crucial role in reducing leachate generation by limiting rainwater infiltration. This paper evaluates the field performance of a polymer-enhanced three-layer cover system at a leather sludge dump site in Xinji city, China over a 1-year monitoring period. Waste soil (WS), sand-bentonite mixture (SB), and sand-polymer-bentonite mixture (SPB) were used as the low-permeability layer, respectively, in three test areas, above which the fine-grained cultivated soil and gravel were used in the top and middle layers to form a capillary barrier. During the 1-year monitoring period, the recorded cumulative rainfall was 452.1 mm, and the volumetric water content (VWC) at the top layer fluctuated significantly from 0.13 to 0.45 in response to rainfall and evaporation, but that of the low-permeability layer maintained stable for both cover SB and SPB. No water percolation was detected during the 1-year monitoring period. Furthermore, numerical simulations were carried out to assess the anti-seepage performance under more extreme climatic conditions (i.e., higher rainfall intensity and long-term deterioration of soil permeability). Numerical simulations corroborated the field observations that the SPB layer effectively minimized percolation even under extreme climatic conditions. For example, under the most unfavourable conditions, the computed annual percolation through the cover SPB was 4.7 mm, as low as 27.2% and 8.1% that through the cover SB (=17.3 mm) and WS (=57.9 mm). Overall, the results suggest that the polymer-enhanced three-layer soil cover is a promising alternative to traditional geomembrane-based covers and/or thick composite soil covers.

The actively-heated fiber-optic (AHFO) method can near-continuously measure soil water content along the AHFO sensors by sensing the temperature variation during an actively heated pulse. Different heating materials, structures, and fiber-optic temperature sensing techniques significantly impact the measurement performance of AHFO sensors. However, there has been no systematic evaluation regarding the measurement performance of soil water content by different AHFO sensors. To address this issue, this study focuses on the measurement performance and monitoring potential of six different AHFO sensors (i.e. actively-heated fiber Bragg grating (AH-FBG) alundum tube, AH-FBG cable, carbon fiber heated cable (CFHC), copper metal heated cable (CMHC), CFHC sensing tube, and CMHC sensing tube). Numerical models were built first for simulating the thermal response process of six AHFO sensors to quantify the measurement accuracy and sensitivity of soil water content. Then, the in situ applications of six AHFO sensors were carried out in Yan'an, China. The numerical and in situ monitoring results indicate that the measurement accuracy and sensitivity of soil water content are both highest by using CFHC sensing tube and CMHC sensing tube. CMHC sensing tube is most suitable for fine and accurate monitoring of in situ soil, while AH-FBG alundum tube and AH-FBG cable are best suited for long-term real-time remote monitoring. In practical applications, it is recommended that geotechnical engineers, when selecting AHFO sensors for a specific site project, should take into account a variety of factors, including measurement performance, spatial resolution, monitoring duration, site installation, and power supply conditions.

The stress-strain behavior of brittle siliceous mudstone coarse-grained soils (SMCGSs) under penetrating erosion critically affects the stability of SMCGS-filled embankments in erosion-prone areas, yet remains insufficiently understood, particularly regarding particle crushing and critical state behavior under low confining pressures. This study proposes a modified constitutive model to characterize erosion-induced mechanical degradation and nonlinear critical state evolution. A normalized parameterϑ, derived from the principle of crushing equivalence, is introduced to capture the coupled effects of particle breakage and critical state shifts under varying erosion intensities. Along with a nonlinear tuning index δ, this parameter is integrated into the unified hardening model for low confining pressure (UH-L), resulting in the N-UH-LE model. Consolidated drained (CD) triaxial tests under confining pressures of 100-400 kPa are conducted for model calibration and validation. The model predictions exhibit strong agreement with experimental results, with a maximum relative error of 7.76 %. The N-UH-LE model successfully reproduces key mechanical responses, including hardening, softening, shear dilation, and volumetric changes across different erosion levels. Furthermore, erosion-induced degradation decreases with lower confining pressures and higher initial void ratios (e₀ = 0.3, 0.5, and 0.7), while variations in interlocking strength (τ₀cotφ = 40 kPa, 80 kPa, and 120 kPa) show limited influence.© 2026 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

The soil-water retention and soil shrinkage characteristics are both crucial constitutive relations for unsaturated soils. Although existing research has explored the correlation between these two characteristics to some extent, the underlying mechanisms remain inadequately investigated. To investigate the correlation between the soil-water retention and soil shrinkage behavior, a series of soil-water retention and soil shrinkage tests is performed on compacted clays over a wide suction range (0-367 MPa). The test results show that the pore water in compacted clays is first expelled from large pores in low suction range. The drainage of pore water at low suctions is predominantly responsible for the phase of structural shrinkage in the soil shrinkage curve. The consistency between the characteristic transitional water contents in the soil shrinkage curve (SSC) and the inflection points in the soil-water retention curve (SWRC) is identified for all the compacted clays. The bimodal pore-size distributions (PSDs) of different clayey soils are obtained using the mercury intrusion porosimetry. The bimodal pore-size distribution characterization is the intrinsic factor in shaping the bimodal morphology in the SWRC over a wide suction range. The low proportion of micropores in clays is responsible to the indistinct zero-shrinkage stage of the SSC. The microstructure measured by the scanning electron microscope indicates the manifestation of aggregation effects during desaturation process. The results demonstrate that soil shrinkage is primarily caused by the contraction of inter-aggregate pores, rather than the evolution of intra-aggregate pores. The findings can greatly enhance the understanding of the soil-water retention and mechanical behavior of compacted clays in varying water content conditions.

Traditional active earth pressure evaluations considering seepage are typically deterministic, assuming uniform soil layers. However, soil hydraulic properties exhibit the obvious spatial variability due to geomorphological processes or poor construction control. To address this, the random limit analysis method (RLAM) is employed to investigate the influence of spatial variability of saturated hydraulic conductivity on active earth pressure. To combine random field simulations with the limit analysis-based evaluation method, this study discretizes the conventional three-dimensional (3D) rotational failure mechanism. Owing to the energy dissipation principle, the explicit expression of 3D active earth pressures can be derived. The proposed method's validity is demonstrated through comparisons with available analytical solutions, deterministic numerical calculations, and random finite difference method (RFDM). RLAM integrating with Monte Carlo simulations (MCS) in MATLAB, facilitates the probabilistic analysis of the active earth pressure to be evaluated. The findings indicate that the present method not only incorporates the spatial variability of hydraulic properties, but also enhances the computational efficiency of calculating active earth pressures compared to the RFDM. Based on extensive uncertainty analyses, this study proposes a system reliability evaluation method for semi-gravity retaining walls, accounting for the spatial variability of saturated hydraulic conductivity. The results reveal that under different random field design scenarios, all decay curves of system failure probabilities for a semi-gravity retaining wall intersect within a specific range, referred to herein as the "turning region". Furthermore, as the normalized horizontal autocorrelation distance, anisotropic ratio and coefficient of variation increase, the effective influence zone of the wall design index on system failure probability gradually expands, offering valuable guidance for the design and construction of semi-gravity retaining walls.

This research introduces a powerful tool, the automatic parametrization of hardening soil (HS) model (APHS), designed to make the HS model parameterization process easier and faster than conventional methods while maintaining high accuracy. Traditional parameterizations rely on oedometer tests, unloading-reloading data, or domain-specific assumptions. Existing optimization-based models often assume uniform parameter weighting, potentially overlooking the distinct sensitivity of each parameter. APHS addresses these limitations as a standalone tool that relies exclusively on conventional triaxial loading test data. To achieve this goal and address the scarcity of labeled datasets, this study integrates numerical modeling with deep learning. The study focuses on a typical shallow Hong Kong soil with parameter ranges derived from field data and relevant literature. Latin hypercube sampling generated diverse parameter values within theoretical bounds for reliable input, while a two-dimensional (2D) axisymmetric finite element model (SIGMA/W) simulated laboratory tests to create a comprehensive, labeled dataset. Seven novel multi-parallel deep long short-term memory (LSTM) networks were trained and validated, achieving an accuracy of 99.4 %. Validation against a conventionally parameterized reference case confirmed 99.6 % accuracy, while an experimental laboratory case study demonstrated strong agreement between simulated and measured results. APHS accelerates HS model parameterization, delivering accurate results in seconds. It can seamlessly integrate with finite element models for automated laboratory data processing and physically informed models to refine calibration parameter ranges. Future work will expand its applicability to various conditions and parameters.

Compacted bentonite blocks are proposed for buffer barriers in deep geological repositories for high-level radioactive waste (HLRW) disposal. These blocks, manufactured through uniaxial compression in molds, exhibit heterogeneity that may impact long-term buffer performance. This study focuses on the physical and hydro-mechanical heterogeneity of full-scale blocks induced by the compaction process. Sector-shaped blocks, with radii of 600 mm and 1200 mm and a height of 200 mm, were axially compressed. Key parameters, including water content, dry density, elasticity modulus, swelling pressure, and permeability, were measured to assess the heterogeneity. Results show that the heterogeneity in the upper layer is primarily caused by differences in drainage and gas expulsion pathways. As depth increases, water content and dry density become more correlated. Hydro-mechanical behavior is largely controlled by dry density, but its fluctuation ratio is much higher than that of dry density. Regarding the microstructure, pore structure heterogeneity follows the order: corner regions > edge regions > center regions, and upper layer > middle layer > lower layer. Vertical microcracks also develop to varying degrees, increasing the anisotropy of the blocks. Upon these observations, the study thoroughly discusses the feasibility and challenges of reckoning the hydro-mechanical properties of blocks using dry density distribution alongside laboratory-scale data. Additionally, it proposes an indicator to evaluate the overall heterogeneity of buffer blocks. These findings highlight the inherent heterogeneity of compacted bentonite blocks at the engineering scale, providing valuable insights for future experiments and simulations.