降雨作用及坡脚开挖激发路堑滑坡的灾变效应

Catastrophic effect of landslide under rainfall condition and excavation at foot

山地丘陵地区,暴雨是一种灾害性天气,其持续性强降雨可诱发山体滑坡。对于因高等级公路建设而实施坡脚开挖的斜坡条件,其在连续性强降雨作用下的暂态渗流场及暂态安全稳定性的变化情况是值得探讨的问题。基于浙南山区某路堑斜坡实际工况,针对已经实施坡脚开挖的条件,采用数值模拟和极限平衡计算,研究斜坡在不同强降雨雨型作用下的饱和-非饱和暂态渗流场,并对其安全稳定性变化规律进行流固耦合分析。研究表明:在坡脚开挖的激发作用下,坡体达到失稳破坏的时间大大缩短;坡体暂态渗流场和强降雨雨型密切相关,强降雨持时越长,强降雨量越大,暂态渗流场向坡体表面扩散的趋势越明显,则滑体饱水面积比越大,基质吸力越小,坡体稳定系数的下降幅度也越大;坡体稳定系数的变化趋势与暂态渗流场的扩展变化情况密切相关,暂态渗流场越向坡体表面扩展则坡体稳定系数越低,可见在坡脚开挖和强降雨激发的综合作用下,斜坡极易失稳破坏。此规律性成果可为相应滑坡整治提供参考依据。

At mountainous area,rainstorm is a disastrous weather. Moreover,the continuity intensive rainfall can induce landslide. For the condition of excavation at slope foot because of high-grade highway construction,the variation of transient seepage and stability of slope is an important research topic. Based on the actual working condition of cut slope at mountainous area in south of Zhejiang province,adapting numerical simulation and limit equilibrium calculation,the saturated and unsaturated transient seepage under different intensive rainfall patterns is numerically computed,then the slope stability is coupling analyzed. The research results show that the time which the slope reaches to instability state under the effect of excavation at foot is greatly reduced. The transient seepage field of slope is closely related to the intensive rainfall patterns. The intensive rainfall duration is longer and the rainfall quantity is greater,then the tendency which the transient seepage field diffuses toward to the surface of slope is more obvious,the water-saturated area ratio of landslide is greater,the matric suction of landslide is smaller,and the descend amplitude of stability factor of slope is greater. Moreover,the trends of stability factor of slope is closely related to the expansion of transient seepage field,the expansion magnitude of transient seepage field is greater,then the stability factor of slope is smaller. Therefore,under the combined effects of excavation at slope foot and intensive rainfall condition,the slope is easily in the state of instability and failure. The regularity research results can provide a reference basis for landslide treatment.