Infiltration regulation and stability analysis of soil slope under sustained and small intensity rainfall

LIU Zi-zhen(刘子振)^{1, 2, 3}, YAN Zhi-xin(言志信)^{1, 2}, DUAN Jian(段建)^{1, 2}, QIU Zhan-hong(邱战洪)³

(1. Key Laboratory of Mechanics on Disaster and Environment in Western China of Ministry of Education
(Lanzhou University), Lanzhou 730000, China;
2. School of Civil Engineering and Mechanics, Lanzhou University, Lanzhou 730000, China;
3. School of Civil Engineering and Architecture, Taizhou University, Taizhou 318000, China)

Abstract:Rainfall infiltration depth and mode can severely influence slope stability. With the sustained rainfall, the influenced region of slope gradually expands. By using the Green-Ampt model to the soil slope, infiltration regulation was discussed under sustained and small intensity rainfall. And the infiltration rate of unsaturated soil was proposed according to the saturated infiltration theory. Because of the changing of initial moisture content in depth of slope, the saturated or unsaturated infiltration rate and depth could also be changeable with the sustained rainfall infiltration. Based on the principle of strength reduction, the calculation model of slope safety factor was established under different initial moisture contents and infiltration modes. Then, the slope stability was quantitatively analyzed through software FLAC^3D. The calculation results of soil slope engineering show that there is a shorter period for slope stability under different initial moisture contents and unsaturated infiltration ways at the slope wetting front. The stability period of slope is 33.3% according to different initial moisture contents of wetting front less than that of the same initial moisture content of wetting front. And the slope is easier to fail under the unsaturated infiltration. The results agree well with the actual situation under sustained and small intensity rainfall.

Key words:small intensity rainfall; soil slope; infiltration depth; safety factor