STUDY AND PREDICTION OF SLOPE FAILURE BY HEAVY RAIN

(1)降雨降低土体强度的机理研究通过研究孔隙水对非饱和土体强度的影响，探讨了降雨过程中土体强度降低的机理。提出了几种毛细管水在地下的作用模型，并通过数值分析讨论了孔隙水体积的变化与土体抗剪强度的关系。(2)雨水入地渗流。对暴雨过程中的入地渗流进行了数值分析。并了解降雨过程中和降雨后地表含水率变化的时变过程。(3)现场吸力的测量发展了土壤吸力的监测方法，以掌握降雨过程中和降雨后地面土体强度条件的变化。(4)边坡失稳的数值分析研究了降雨前后边坡稳定性程度的变化。用降雨强度、土性、坡体形状等参数模拟了降雨与边坡稳定性的关系，确定了吸力测量作为边坡稳定性监测的有效方法。

The following four topics of research have been carried out to understand the mechanism of the slope failure during heavy rain and to develop a method to predict the slope failure due to the heavy rain.(1) Mechanism of the strength reduction of the soil by the rainThe mechanism, that the strength of the soil decreases during the rain, has been investigated by studying the effect of the pore water to the strength of the unsaturated soil. Some models were suggested to express the action of the capillary water in the ground, and the relation between the change of volume of the pore water and the shear strength of the soil was discussed with the numerical analysis.(2) Seepage of the rain water into the groundThe numerical analysis have been carried out to investigate the seepage of the water into the ground during heavy rain, and to understand the time-depending process of the change in the water containing conditions of the ground during and after the rain.(3) Measurement of the suction on the fieldThe monitoring method of the suction of the soil has been developed to grasp of the change of the strength conditions of the soil in the ground during and after the rain.(4) Numerical analysis for the slope failureSome numerical simulations have been carried out to study the change in the degree of the stability of the slope during and after the rain. The relation of the rain to the stability of the slope was simulated with the parameter of the rain strength, soil properties and the shape of the slope, and the measurement of the suction was confirmed to be effective as the monitoring method of the slope stability.