Rainfall infiltration frequently triggers slope failures by elevating pore water pressure and compromising the shear strength of unsaturated soil layers. Modeling these severe geological events remains computationally challenging. Standard grid-based techniques, such as the Finite Element Method (FEM), typically fail due to severe mesh distortion under large deformations, whereas the Discrete Element Method (DEM) demands excessive computational resources. Addressing this gap, we develop an advanced theoretical framework utilizing the Material Point Method (MPM) integrated with a liquid-solid-gas three-phase mechanics model. We first verify the algorithmic accuracy using a 1D unsaturated soil column test. Subsequently, the framework is deployed to capture the dynamic displacement and mechanical responses of a 2D rainfall-induced landslide. Benchmarking against FEM data confirms that our multiphase MPM accurately models the infiltration process and subsequent structural collapse. Ultimately, this approach offers a highly robust computational strategy for analyzing large-scale landslide deformations and improving predictive assessments.
Steep, highly fractured rock slopes, characterized by lithological heterogeneity, intense fracturing, and sensitivity to rainfall-induced hydraulic perturbations, pose challenges that are not covered by classical sliding-surface models. This study integrates multiphysics monitoring, laboratory experiments, and probabilistic inversion to investigate a representative slope at the Luanchuan Longyu open-pit mine. A positive feedback loop was found between seepage and fracture development: elevated pore pressure induced by rainfall or increased groundwater levels drives fracture propagation, enhances permeability and seepage velocity, reduces effective stress, and initiates a self-accelerating “seepage → fracture → rock weakening” chain, even in the absence of a continuous slip surface. Lithological analysis reveals that marble and gneissic granite exhibit high strength (UCS ≈ 57-58 MPa, c ≈ 6.2-6.8 MPa, ϕ ≈ 39°-43°), whereas quartz-mica schist is a highly weathering-sensitive weak layer (saturated UCS = 9.78 MPa, with 35 % strength loss and SDI = 58.96 % after 11 wetting-drying cycles). Parameter back-analysis (with 80 % confidence intervals) reveals schist ( c = 24.5 kPa, ϕ = 34.4°) as the dominant weak stratum and faults ( c = 8.9 kPa) as potential slip surfaces, clarifying the lithology-structure controls on failure patterns. Rainfall infiltration triggers a nonlinear hydraulic response and preferential toe flow, causing pore pressure to propagate downward and shifting slope degradation from surficial to whole-slope failure-a dynamic "surface-to-depth" progression modeled in this study. These findings provide a quantitative mechanistic framework for assessing steep, heterogeneous slopes and support intelligent hazard mitigation through rainfall thresholds and real-time monitoring.
The efficient development of unconventional reservoirs is fundamentally challenged by strong geological heterogeneity and variations in rock mechanical properties. To address this, we present an integrated workflow for high-resolution 3D geomechanical modeling to optimize hydraulic fracturing design. The methodology begins with developing a centimeter-scale mechanical profile to construct a high-precision 1D Mechanical Earth Model (MEM). This detailed 1D model is then upscaled and embedded into a 3D geomechanical model, which explicitly incorporates seismically interpreted faults and discrete fracture networks. This workflow was applied to optimize stimulation treatments in the Bai Jiantan Formation, with a detailed case study on the Bai818 well and representative offset wells (84009, D84005, 84010). Hydraulic fracturing simulations were performed at various pumping rates (0.8, 0.6, 0.4 m3/min for Bai818) to identify the most effective design. The simulation results confirm that the hydraulic fractures propagate perpendicular to the minimum horizontal stress direction of 135°. Furthermore, a stress sensitivity analysis was integral to the process, ensuring operational safety and borehole stability throughout the design. This study demonstrates that the presented integrated workflow provides a robust and precise account of the hydraulic fracturing operation, directly addressing the challenges posed by reservoir heterogeneity. The workflow establishes a critical foundation for optimizing stimulation designs and enhancing recovery in complex unconventional reservoirs.
Intense rainfall and the resulting increase in ground saturation can significantly modify the mechanical performance of rock masses in natural slopes, particularly when fractured material is present. Extended infiltration reduces shear strength along discontinuities and increases pore-water pressures, raising the probability of large-scale landslides. When a tunnel is built within or near an unstable slope, the response of both structures becomes coupled, and this tunnel–slope interaction has proven to be an important aspect in the design and safety assessment of underground infrastructure in mountainous regions. This study evaluates the static and seismic performance of a tunnel–slope system in a fractured shale–limestone slope that failed after heavy rainfall. Since ground exploration was limited, the observed failure was reproduced through a back-analysis within a performance-based design (PBD) framework to calibrate representative geomechanical parameters. These parameters were then used in three-dimensional finite difference models to simulate the tunnel construction process and the seismic response of the system. During construction, the interaction between the tunnel and the slope was found to be minor. Under seismic loading, however, the simulations revealed notable interaction effects: slope displacements accumulate in the zone where the tunnel runs closest to the unstable critical section, and the stresses in the tunnel lining increase as a result of both the interaction with the slope and the curvature of the alignment. These results indicate that tunnel–slope interaction should be explicitly considered in the analysis and design of underground infrastructure whenever the tunnel lies within about four diameters of an unstable slope.
Rainfall-induced instability of highway slopes with a soil–rock binary structure may be strongly influenced by the hydraulic barrier effect of low-permeability shale. This study investigated the right-side slope along the D-ramp section from DK0+230 to DK0+660 at Deze Interchange on the Zhanhui Expressway, China. A two-dimensional coupled seepage–stress model was developed based on the engineering geological conditions and rainfall records to simulate the slope response under a 72 h extreme rainfall scenario with an intensity of 175.6 mm/d. Field displacement monitoring data were used to validate the modeled deformation pattern under natural conditions. Under natural conditions, the reinforced toe zone remained stable, deformation was concentrated along the interface between the block-stone layer and strongly weathered limestone in the middle and rear portions of the slope, and the factor of safety was 1.1344, indicating a basically stable state. During prolonged rainfall, infiltrating water accumulated near the interface between the strongly weathered shale and the underlying shale owing to the hydraulic barrier effect of the low-permeability shale, forming a continuous transient saturated zone. The plastic zone progressively extended from the upper shallow weak interface to the lower deep interface and eventually became fully connected, while the factor of safety decreased to 0.9886, indicating overall instability. The results reveal a coupled mechanism involving interfacial water accumulation, increased pore-water pressure, the formation of a transient saturated zone, and a shift in the controlling zone of slope deformation and failure from shallow to deeper layers. These findings provide a reference for disaster prevention and mitigation of similar soil–rock binary-structure slopes.
