土坡前端推力对降雨入渗响应的试验研究

Experimental study on rainfall infiltration of slope under thrust at front end

降雨入渗可引起坡体前端推力发生显著改变,影响土坡的稳定和安全。利用构建好的降雨模拟和监测系统,对降雨诱发非饱和残积土坡失稳过程进行全方位、多参量的实时监测,着重分析不同位置、坡度、密实度和不同降雨条件下坡体前端推力的时变规律。结果表明:边坡上部土体含水率、吸力、坡体变形和下滑推力变化幅度较大,速度较快,而下部土体变化幅度较小,速度较慢;坡体前端推力变化可分为缓慢增加、加速上升和雨后衰减3个阶段,降雨过程中陡坡和高密实度边坡反映较为强烈,下滑推力峰值大于缓坡和低密实度边坡;降雨作用下新边坡坡体应力状态变化明显,较易失稳,而老边坡则相对比较稳定;高密实度和陡坡坡体内部的高应力区域在二次或多次降雨后可完全释放,边坡具有高水平的雨后剩余下滑力和更显著的土体软化效应。研究成果对进一步揭示闽东南地区降雨入渗对非饱和土坡的影响机制及对非饱和土强度与稳定性的弱化作用具有重要的理论及实际意义。

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.