Model test of landslide of hanging rock wall under the action of reservoir water and rainstorm

Abstract

[Objective] Water level fluctuations in the Three Gorges Reservoir area and rainfall are recognized as major triggers of landslides. To investigate the deformation and failure mechanisms of reservoir landslides under the coupled effects of reservoir drawdown and heavy rainfall, [Methods] a 1:87 scaled physical model of the Diaoyanbi landslide was constructed. Changes in internal stress and deformation processes within the landslide were detected using pore water pressure sensors, soil pressure sensors, and displacement sensors. Five scenarios were designed, and a two-stage loading test was conducted, combined with numerical modeling using geotechnical simulation software. A stability evaluation model for the Diaoyanbi landslide was established based on the limit equilibrium method. [Results] The result indicated that heavy rainfall increased the pore water pressure within the sliding body by 126.7%, significantly exceeding the water pressure under single rapid drawdown scenarios. Soil pressure exhibited varying changes across different positions of the landslide; at the front edge, rapid water drawdown reduced the soil pressure from 3.5 kPa to 2.84 kPa, while in the middle-upper section, rainfall loading increased the soil pressure from 2.02 kPa to 2.83 kPa. Displacement monitoring revealed that cumulative displacement under Scenario 5 reached 0.848 m, 5.65 times greater than that of the single water drawdown scenario. Numerical simulations showed that the influence of reservoir drawdown on stability accounted for 48.6%, while the impact of heavy rainfall accounted for 51.4%. [Conclusion] The findings demonstrated that rapid reservoir drawdown predominantly deteriorates landslide stability, inducing frontal traction failure through the gradient of seepage pressure, while rainfall intensifies shear band softening and drives rear-edge push deformation. The coupling of these factors produces a chain failure effect, with the safety factor under the “175 m to 145 m water level drawdown + heavy rainfall” scenario decreasing by 8.1%, representing the most adverse condition.

Keywords

Diaoyanbi landslide / pore water pressure / rapid reservoir drawdown / rainfall coupling / model test / numerical simulation / progressive failure / rainfall