Theoretical modeling and engineering case analysis of reservoir landslide initiation considering thermal–hydro-mechanical coupling and hydrodynamic pressure

The high-speed movement characteristics of landslides represent a core scientific challenge in the fields of geotechnical engineering and geological hazards. Their essence lies in uncovering the physical mechanism underlying the reduction in shear strength during the sliding process. Existing thermal–hydro–mechanical (THM) coupling models often overlook the influence of hydrodynamic pressure on the dynamics of reservoir landslides, leading to discrepancies between simulation results and real-world scenarios. To address this gap, this study develops a theoretical framework for THM-coupled landslide dynamics that incorporates hydrodynamic pressure, grounded in the principles of mass conservation, energy conservation, and momentum. The framework employs the Crank–Nicholson finite difference scheme for discretizing the governing equations and utilizes the Thomas algorithm to solve the resulting tridiagonal matrix system, enabling dynamic simulation of temperature distribution in the shear zone, pore water pressure, and landslide kinematics. Furthermore, the effectiveness of the proposed model is validated through engineering case studies of the 2017 Xinmo landslide and the Yanshangou landslide in the Baihetan Reservoir, while the mechanism driving the high-speed movement of these landslides is analyzed in depth. Simulation results reveal two distinct softening mechanisms during landslide instability: frictional softening and THM coupling softening. These mechanisms exhibit phase-dependent dominance and synergistic effects throughout the sliding process. In conclusion, the proposed model provides reliable theoretical support for predicting the landslide dynamics in reservoir areas.