Effect of soil strength degradation on slope stability

Abstract

Under the influence of water, the strength of rock-soil material changes over time. The strength degradation conforms to varied laws in different areas of the slope. This paper carries out lab experiments on the strength degradation laws of slip zone soil under long-term saturation in a bank slope of the Three Gorges Reservoir (TGR) area. The experimental results show that the strength attenuation weakened with the growing saturation time. Based on the experimental data, the authors established the formulas about the variation of strength parameters with saturation time. As the saturation time increased from 2, 5, 10 to 30 days, the cohesive force decreased by 18.8%, 28.1%, 36.1%, and 41.3%, while the friction angle narrowed by 22.9%, 31.9%, 36.5%, and 39.4%, respectively. Hence, both cohesive force and the friction angle declined exponentially with the elapse of saturation time. In addition, numerical simulation was carried out under long-term saturation to reflect the effect of strength parameter degradation on slope stability. It is learned that the stability coefficient dropped from 1.377 to 1.005 over 17 years, and the annual difference of the factor of safety dropped exponentially to the equilibrium level.