In this study, the influences of the thermoelastic effect and fluid viscosity-temperature effect (VTE) on hydraulic fracture growth in deep reservoirs were investigated. A computational model that integrates the thermoporoelastic effect and VTE was developed on the basis of the displacement discontinuity method (DDM). The temperature distribution within fractures is determined using a first-order upwind scheme. Using this simulator, this study systematically evaluated the impacts of the poroelastic stress, thermoelastic stress, and VTE of the fracturing fluid on fracture propagation. Furthermore, the dominant controlling factors were identified in both the viscosity- and toughness-dominated regimes. The results show that (1) the thermoelastic stress exhibits behavior opposite to that of poroelastic stress, reducing the injection pressure and increasing the fracture width. (2) Under viscosity-dominated conditions, the influence of the VTE is more remarkable, whereas the thermoelastic effect on fracture propagation is relatively weak. Under toughness-dominated conditions, the influence of the thermoelastic effect on fracture propagation remains relatively weak, and the VTE can essentially be disregarded. (3) When proppant transport is considered, for small proppant particles, the transport distance increases from 88 m to 100 m when the VTE is considered because the VTE increases the fracture length. For large proppant particles, owing to the decrease in viscosity with increasing temperature, the proppant transport distance is significantly reduced from 86 m to 70 m. These results indicate that reasonably selecting the proppant size and paying more attention to the VTE of the fracturing fluid in deep reservoir fracturing are crucial.

Borehole instability in heterogeneous rocks poses a significant challenge in geo-energy engineering. The deformation and failure around boreholes are heavily mediated by the inherent heterogeneity of rocks. Here, we examined borehole breakout under hydrostatic pressure through both laboratory tests and numerical simulations on sandstone samples. Laboratory experiments demonstrated symmetrical V-shaped failures across various borehole diameters. To replicate these observations, we developed a heterogenous UDEC Voronoi model where the material heterogeneity was interpreted by assigning Weibull-distributed inter-grain contact parameters. The rigorous-calibrated numerical modeling can effectively capture the microscopic damage process and match the observed macroscopic failure modes. Simulations showed that reducing the borehole diameter increases the critical hydrostatic pressure required for borehole failure and prompts a shift from tensile to shear-dominated failure behavior. While stress anisotropy primarily governs the overall breakout morphology, rock heterogeneity influences the specific locations of crack initiation, leading to localized stress concentrations that shape the ultimate failure patterns. These results provide valuable insights into borehole stability in heterogeneous rocks and guide engineering design and pertinent risk assessment.

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.

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.

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.

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.

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/).

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.

Supersulfated cement (SSC) is considered an environmentally friendly alternative to ordinary Portland cement (OPC), while its stabilization efficiency on dredged sediment (DS) is still unclear. Three types of SSC were prepared by combining ground granulated blast-furnace slag, alkali-activator NaOH, and a sulfate waste source, yielding SSCE (from electrolytic manganese residue), SSCP (from phosphogypsum), and SSCD (from desulfurization gypsum). To further enhance the stabilization efficiency of SSC on DS, nano-SiO₂ (NS) and nano-Al₂O₃ (NA) were incorporated individually and as a composite blend. Mechanical properties and microstructural analyses were conducted to evaluate the stabilization efficiency and elucidate the underlying mechanisms. The leaching toxicity of SSCE-stabilized DS was investigated via leaching tests. The results showed that both alkali-activation and nano-modification can significantly improve the strength development of SSC-stabilized DS. At least 15 % NaOH was required for SSC to achieve the same stabilization efficiency as OPC. The optimum NA-modified SSCD-stabilized DS demonstrated superior strength compared to OPC-stabilized DS. Composite NS/NA-modification was more efficient than using NS or NA individually. For DS stabilized with SSCE, SSCP, and SSCD, the optimal NS-to-NA mass ratios were 7:3, 3:7, and 3:7, respectively. Notably, the nano-modified SSCE-stabilized DS showed no environmental risks. Incorporating NS and NA into SSC-stabilized DS respectively promoted the formation of C-S-H gel and ettringite. A micro-mechanism model was developed to explain the strength evolution of nano-modified SSC-stabilized DS. This study provides a theoretical basis for the application of SSC in DS stabilization, and facilitates the collaborative resource utilization of industrial solid wastes and DS.