华南典型巨厚层红层软岩边坡降雨失稳的模型试验研究

 针对华南巨厚层红层软岩边坡在强降雨条件下极易致灾的问题，采用相似理论，通过制备可表征软岩遇水软化特性的相似材料，构建巨厚层红层软岩边坡相似模型，研究其在中小雨(雨强Id＜25 mm)、大雨(25 mm≤Id＜ 50 mm)、暴雨(50 mm≤Id＜100 mm)等降雨模式下的灾变过程和规律。结果表明：(1) 该类型边坡的变形破坏受降雨模式的影响较大，大雨和暴雨等强降雨条件下边坡岩体逐渐崩解软化，在坡脚处首先达到饱和，产生初始裂缝，在重力及渗透力作用下，裂缝进一步扩展贯通，产生局部破坏，这样，坡脚之上的部分失去支撑，导致整个坡体产生牵引式滑坡。(2) 降雨入渗主要分为无压渗流、有压渗流与饱和渗流3个阶段，边坡表面裂缝主要出现在无压渗流阶段并在有压渗流阶段逐渐扩展贯通、在饱和渗流阶段发生破坏；降雨过程中超孔隙水压力的累积和消散改变了边坡有效应力场的分布，从而引起其位移。(3) 临滑阶段，有效应力和孔隙水压力比位移、位移变化速率等参数对边坡的破坏响应更敏感，因此提出基于应力监测的边坡灾变过程安全预警新思路。

Model tests for failure mechanism of typical soft rock slopes of red beds under rainfall in South China

The similar materials representing the softening feature of the soft rock in water were prepared and the similar model for the thick red-bed soft rock slope was built in order to study the disaster caused by the failure of the thick soft rock under the rain condition in Southern China. The softening process was monitored and its mechanisms were studied under different rainfall patterns，including the medium-weak(Id＜25 mm，Id is intensity of rainfall)，heavy(25 mm≤Id＜50 mm) and torrential rainfall(50 mm≤Id＜100 mm). The failure of the slope was found to be closely related to the rainfall patterns. Heavy and the torrential rains tended to soften rocks on the slope. At first，the bottom of the slope was saturated and then the initial cracks were generated. Along with the expansion of cracks，local failure occurred due to the influence of the gravity and seepage forces，caused the collapses of the upper part and finally resulted in the pull-type landslide. The infiltrating process of rain water includes three main steps，i. e. the unconfined seepage，the confined seepage and the saturated seepage. The cracks on the surface of the slope were mainly generated during the unconfined seepage and gradually expanded during the confined seepage. The failure of the slope occurred during the saturated seepage. The accumulation and dissipation of the excess pore water pressure in the thick red-bed rock layer slope changed the distribution of the effective stress field during the raining process and caused the movement of the slope. The response of effective stress and water pressure in pores was more sensitive than displacement，displacement rate and other parameters to the failure of slopes near the sliding stage. The safety precaution in terms of slope disaster was proposed on the basis of the effective stress and water pressure in pores.