降雨诱发填方路堤边坡变形机制物理模拟研究

填方路堤变形失稳是西部山区工程建设的常见问题。重庆某高速公路边坡为典型的堆载条件下降雨诱发型滑坡，填方堆载后，填方边坡在连续降雨条件下，沿基岩之上的软弱面产生滑动破坏。定性分析认为，降雨在滑坡形成中起着关键作用，为了研究填方边坡在降雨条件下的变形破坏机制及孔隙水压力与变形之间的关系，采用物理模拟方法研究边坡变形失稳的全过程，分析孔隙水压力随降雨时间的变化规律及其与变形破坏的关系。研究结果表明：边坡后缘大方量堆载，改变了其应力条件，是滑坡产生的主要因素。场地施工改变了原有的地表水环境，连续强降雨致使大量下渗的雨水，不仅显著改变坡体应力条件，而且雨水沿着滑面运移软化滑带，是滑坡产生的重要诱发因素。孔隙水压力在坡体失稳过程中起着关键作用，填方体土碎屑、泥质含量大，下渗的雨水携带上部细小颗粒及滑带泥质成分至滑带附近，堵塞地下水消散通道，表现为坡体变形积累，孔隙水压力增加；边坡变形陡增，孔隙水压力降低。该滑坡破坏分为降雨下渗、滑带饱水软化、后缘产生裂缝、裂缝贯通-整体滑动4个阶段，为蠕滑-拉裂式滑坡。

Physical model studies on fill embankment slope deformation mechanism under rainfall condition

Deformation of filled embankment and its stability are common engineering problems of the western mountains area construction. A typical slope of one expressway in Chongqing slides along the weak stratum on the bedrock after stacking fill, under the condition of continuous heavy rain. To study the failure mechanism of the landslide, physical simulation is adopted to study the rainfall influence on slope deformation. We also analyze pore water pressure change with the rainfall time and its relationship with the deformation and failure. The results show that the landslide deformation and failure is due to large amount of stack at trailing edge, changing the slope stress condition greatly. Secondly, the construction changes the original hydrological environment, and continuous heavy rains cause a lot of rain infiltration into the slope. Pore water pressure in the process of the landslide plays a key role. Embankment has a mass of debris and argillaceous, which can be carried to the slide zone with rainwater. And argillaceous of slide is the same. These substances can block the dissipate of groundwater. This phenomenon is the accumulation of slope deformation and pore water pressure. Deformation suddenly increase and pore water pressure decrease. The landslide can divide four phases: rainfall infiltration, slide with full water softening, trailing edge cracks, crack through whole sliding. The final landslide deformation failure mode is creeping-cracking.