Abstract:

To investigate the impact of rainfall on the stability of granite residual soil slopes, indoor model box tests were conducted at three rainfall intensities (30, 60, 90 mm/h) and two rainfall durations (3, 12 h). The variations in wetting front and vertical displacement were monitored. PFC discrete element software was used to simulate direct shear tests of granite residual soil, calibrate the mesoscopic parameters of granite residual soil for varying moisture contents, and develop a discrete element slope model. The analysis concentrated on the displacement and rotation fields, instability indicators, force chains, and fabric anisotropy to reveal the mesoscopic deformation and mechanical mechanisms underlying slope instability in the model box tests. The results show that when the rainfall intensity reaches 60 mm/h or above, the slip and disturbance range of the slope expand significantly, and the slip body exhibits a circular arc shape along the slope face. The slip loss rate of the slope initially decreases and then increases with prolonged rainfall; short-term low-intensity rainfall can stabilize the slope, but continuous rainfall significantly increases the slip loss rate. After 9 hours of rainfall, the displacement and rotation angle of soil particles in the slope increase markedly, forming a distinct circular arc slip failure surface. Furthermore, after 9 hours of rainfall, the distributions of force chains and contact force anisotropy within the slope change significantly, with force chains on the slip surface breaking and densely concentrating in stable regions.

Key words: granite residual soil, slope, rainfall conditions, discrete element analysis