ABSTRACT Buried pipelines are susceptible to earthquake‐induced damage when crossing soft‐hard rock strata in high‐intensity seismic regions. In mitigation, pipelines are usually installed within tunnels and buried under backfill materials. The existing seismic calculation method for pipelines does not consider the effects of tunnels. In this study, the pipeline‐tunnel system crossing soft‐hard rock strata is longitudinally simplified to an elastic foundation double‐beam. Green's function is employed to derive the analytical solution for the longitudinal seismic response of the pipeline‐tunnel system, whose validity is verified through numerical models and literature data. A parametric analysis is conducted through the control variable method. As the elastic modulus ratio between the hard and soft rocks increases, the peak internal forces of the pipeline and tunnel near the interface increase significantly. Specifically, the peak bending moments display a double‐peak pattern, while the peak shear forces present a single‐peak one. With the increase in the lining elastic modulus and thickness, the peak internal forces of the pipeline near the interface decrease, while those of the tunnel increase significantly. The peak internal forces of the pipeline increase sharply with the pipeline thickness, whereas those of the tunnel are hardly affected. The shaking table test results demonstrate that the tunnel crossing the interface sustained more severe damage than that in other segments, with oblique shear cracks appearing. This indicates that the sudden increase of the shear forces near the interface is one of the vital reasons for the structural damage, which verifies the rationality of the analytical solution.

ABSTRACT Tunnel excavation induces stress redistribution and deformation in the surrounding soil, weakening the lateral bearing capacity of adjacent piles and potentially resulting in engineering failures. Therefore, accurately evaluating the mechanism of lateral pile‐soil interaction induced by tunnelling is important. This study numerically investigated the pile‐soil interaction p t ‐ y t curves of a pile adjacent to tunnelling in sand (where p t denotes the soil force per unit pile length induced by tunnelling and y t represents the corresponding lateral pile displacement), clarifying the evolution mechanisms of the passive‐side (away from the tunnel), the active‐side (adjacent to the tunnel), and the resultant p t ‐ y t curves, and examining the effects of excavation parameters on the evolution of p t ‐ y t curves. The results showed that the evolution of the passive pile p t ‐ y t curves can be divided into two stages: the excavation‐induced unloading stage and the pile‐soil deformation stage. Both the passive‐side and active‐side p t ‐ y t curves evolved synchronously: the passive‐side soil force initially increased and subsequently decreased with increasing lateral pile displacement, whereas the active‐side soil resistance initially decreased and then increased. Moreover, both the passive‐side soil force and active‐side soil resistance exhibited opposite trends in response to changes in tunnel diameter, volume loss, tunnelling speed, and the pile‐tunnel distance, but exhibited similar trends in response to changes in cover depth and pile diameter.

ABSTRACT Accurately describing slurry diffusion in fracture remains challenging due to the complexity of fracture roughness and the non‐linear rheological properties of slurry. This study presents an analytical solution for the single‐hole grouting in rough fractures considering the time‐dependent viscosity of Bingham fluid. Fracture roughness is described by introducing two parameters, the fractal dimension D and the characteristic scale parameter G . The accuracy of the analytical solution is validated by comparing the slurry flow and diffusion radius from experimental results with predicted results. The corresponding slurry flow Q calculated from the analytical solution is used to delineate different areas. Variations in D and G shift the slurry flow resistance from rough ( Q < 0.1 L) to transitional (0.1–0.8 L) and smooth ( Q > 0.8 L) areas under constant other parameter conditions. Variations in yield stress and viscosity shift the slurry flow areas among low, medium, and high sensitivity areas. Additionally, numerical analysis of two‐hole grouting in rough fractures is performed to determine optimal grouting hole spacing based on the percentage of the area covered by the slurry relative to the total fracture area. During two‐hole grouting, mutual squeezing effect between slurry alternately promotes and impedes flow. The optimal grouting hole spacing of Bingham fluids with varying water‐to‐cement ratios decreases with fracture roughness and increases with grouting pressure. Bingham fluids with water‐to‐cement ratios of 1.0–2.0 exhibit greater sensitivity to grouting pressure in wide fractures due to complex flow characteristics, providing a reference for simplifying grouting process across varying geological conditions.

ABSTRACT The study of water retention and strength characteristics in unsaturated soils is an underexplored topic yet significant challenge in geotechnical engineering. This paper proposes a simplified computational model for the soil‐water characteristic curve (SWCC), incorporating the novel proposed void optimization parameters l 1 and l 2 . This model can predict SWCC under various initial void ratios and is applicable across a wide suction range. Additionally, we suggest an adjustment parameter m , which can reflect soil type, and then develop a three‐dimensional strength criterion for unsaturated soil. The strength criterion inherently allows for three expansion trends of the failure surface as the matrix suction s increases: parallel, outward non‐parallel, and inward non‐parallel. Furthermore, based on the novel SWCC model, a predictive formula for the shear strength q f of unsaturated soils is established. This formula is then applied to accurately estimate the strength of unsaturated soils under drained true triaxial conditions.

ABSTRACT The shear behavior of intermittently jointed rock masses is crucial in engineering geology, yet the widely used Jennings criterion still lacks a systematic evaluation regarding its accuracy when applied to rock with various joint geometries. This study combines physical experiments and Particle Flow Code (PFC) simulations to investigate how joint geometries influence shear strength and to further assess whether the Jennings criterion can effectively capture these influences. Both approaches reveal similar trends: peak shear stress and cohesion decrease with higher joint connectivity and number, but increase with steeper dip angles. In the present experimental conditions, no clear trend was observed between the friction angle and variations in discontinuity geometrical features, which is likely related to the relatively limited range of geometrical configurations considered in the tests. A further comparison between measured and Jennings‐derived equivalent cohesion shows a widespread discrepancy: on average, equivalent cohesion exceeds measured values by 31.4% in physical tests and 10% in numerical simulations. This overestimation, due to stress concentration and altered failure paths introduced by different joint geometries, is most significant in low‐connectivity, high‐joint‐number, and gentle‐dip‐angle scenarios. These findings suggest that the Jennings criterion's applicability is limited, as significantly overestimated equivalent parameters could lead to overly optimistic stability assessments under certain conditions. Additionally, the impact of joint geometrical features on shear strength is both systematic and potentially quantifiable, offering a valuable reference for incorporating such features into equivalent parameter estimation methods to improve the accuracy of strength assessments.

ABSTRACT Composite piles are a promising technique that improve the stability and loading capacity of soft ground, offering superior performance over traditional methods. Natural soft clays often tend to exhibit pronounced anisotropy, which can substantially affect the consolidation behavior of composite ground. This study presents an analytical consolidation model for composite ground that explicitly incorporates the anisotropic behavior of surrounding soft clay. The model is developed under the equal strain assumption, which is well‐suited for conditions beneath rigid loading platforms such as embankments or raft foundations. The annular equivalent method is employed to accommodate various practical geometries of composite piles. The mechanical behavior of the soft clay is characterized using a yield surface consistent with the S‐CLAY1 model, represented by an inclined ellipse to account for inherent anisotropy. The model integrates both size hardening and rotational hardening laws to describe the evolution of anisotropy under progressive loading. Comparative verification against existing analytical solutions confirms the accuracy of the proposed model. A detailed parametric study is conducted to investigate the influence of key anisotropic parameters, including the critical‐state friction angle , the evolution rate of rotational hardening , and the volumetric‐shear strain weighting factor , on the nonlinear consolidation behavior of the composite ground. Results indicate that higher accelerates consolidation due to increased soil stiffness, while lower values enhance system stiffness and excess pore pressure dissipation. Conversely, increasing reduces the effect of volumetric strain on rotational hardening, leading to greater compressibility and slower consolidation.

ABSTRACT Debris flows, characterized by a heterogeneous mixture of solid, liquid, and gas phases, exhibit complex mechanical behavior and pose substantial threats to infrastructure and human lives in mountainous regions. This study presents a novel three‐dimensional material point method (MPM), integrating a geographic information system (GIS) and Perlin noise functions, to model the debris flow over complex terrain as a coupled liquid‐solid system. The digital elevation models in GIS are mapped directly onto the MPM computational domain and preserve realistic terrain features. The irregular rock blocks generated by Perlin noise function in Houdini software are embedded into the source zone of debris flow to explicitly represent fluid‐solid interactions. In addition, to maintain the computational accuracy and efficiency, the sparse paged grid structure (SPGrid) is introduced to provide an efficient computational framework for large‐scale 3D hazard analysis. The proposed MPM framework is validated firstly by comparing numerical results and experimental data from previous studies, including saturated soil leakage, rockslide‐induced wave generation, and debris dam break flow. The dynamic behavior and deposition patterns of debris flows are then analyzed, revealing that these factors are significantly influenced by rock block content and the basal friction coefficient. Results show that the proposed two‐phase two‐point MPM is an effective tool to reproduce the realistic propagation of debris flows and provides a scientific reference for hazard assessment and disaster prevention in debris flow‐prone regions.

ABSTRACT Discontinuous deformation analysis (DDA) is a numerical method that is extensively utilized for simulating discrete blocks. Nevertheless, its implicit calculation approach brings in a multitude of control parameters that lack physical significance, and proper handling of these parameters is essential for obtaining accurate results. To tackle this issue, this study proposes a surrogate model‐driven parameter calibration framework that incorporates interpretability analysis. First, a Kriging surrogate model is constructed to establish an efficient substitute for DDA computations, thus accelerating forward calculations. Subsequently, the SHapley Additive exPlanations (SHAP) method is introduced to quantify global parameter sensitivity. Finally, an intelligent optimization algorithm is integrated to develop a parameter inversion mechanism, thereby forming a complete calibration system of “surrogate modeling–sensitivity analysis–parameter optimization.” Numerical examples demonstrate that this framework can effectively identify the optimal combination of key control parameters. The average errors are 1.39% in the two‐slider model and 1.63% in the elastic foundation model. This approach offers an automated parameter calibration process that doesn't require manual intervention, providing a reliable theoretical tool for DDA engineering applications in tunneling, slope stability, and rock engineering.