Abstract: The stability and safety of the soil slope will be threatened when the thrust at front end of slope change due to rainfall infiltration. Rainfall simulation system and monitoring system are used to make a comprehensive and real-time monitoring of rainfall-induced slope failure process of unsaturated residual soil. The real-time response of thrust at front end of slope with different locations, slope angles, densities and rainfall conditions are analyzed. Results show that the changing of water content, matric suction, body strain and thrust at front end of slope in the upper part of slope is with great range and speed, while the bottom part of slope with less range and speed. The change of thrust at front end of slope can be divided into slow increase, rise accelerate and attenuation three stages, compared with less angle and lower density slope, the changing of residual thrust in larger angle and higher density slope is more strong and with a higher peal value. The new slope is easier to fail than the old one under rainfall since a greater growth force in a new slope. The internal high stresses of larger angle and higher density slope inside can be fully released after repeated rain, i.e., a high level of residual slide force will be happened, and the effect of soil softening will be even more significant. The results are useful and meaningful for further revealing the influence mechanism of unsaturated soil slope under rainfall infiltration in Southeast of Fujian, to further understand the weakening effect of unsaturated soil strength and stability.

Key words: thrust at front end of slope, unsaturated residual soil slope, real-time response, residual slide force, effect of soil softening