滑坡对降雨的动态响应及其监测预警研究

以福建德化县彭坑滑坡为例,基于非饱和土力学理论,结合滑坡实际监测数据,利用有限元法对坡体在雨水入渗条件下的渗流、变形特性和稳定性进行计算和分析,研究滑坡对降雨的动态响应和不同工况下安全系数和位移的关系。结果表明:滑体结构松散,易于雨水入渗,改变基质吸力空间分布,弱化岩土体参数; 持续降雨会使地下水位上升,坡脚发生变形,牵引坡体后缘产生拉裂,直至在降雨期间产生以非饱和区域为主的滑坡。强降雨初期,边坡安全系数下降较快,易发生滑坡; 雨停后安全系数会因雨水持续下渗而进一步降低,应注意雨后滑坡的产生; 同样水分在不同坡体部位对稳定性影响不同,安全系数有消有涨,存在时空效应。最后为反映地下水位线和降雨条件变化对边坡产生危害的程度,提出危险系数概念,建立危险系数与增量位移的关系,实现边坡测点位移变化的阶段式预警。研究结果和方法可为类似工程的治理和监测预警提供有意义的参考。

DYNAMIC RESPONSE OF PENGKENG LANDSLIDE TO RAINFALL AND ITS MONITORING AND EARLY WARNING

This paper takes Pengkeng landslide as a case study on the basis of the theory of unsaturated soil mechanics. The finite element method is used to calculate and analyze the slope seepage, deformation properties and stability under rainfall infiltration. The calculation results are utilized to study dynamic response mechanism of landslide due to rainfall and the relationship between safety factor and displacement under different real working conditions. Results show that the loose structure of the slip mass has provided a convenient condition for rainwater infiltrated. Thus it changes the spatial distribution of matrix suction and weakens the rock-soil mass parameters. The ground water level is risen under sustained rainfall. Deformation instability occurs in the zone of slope toe, then pulls the slope rear edge and causes the tensile fissures, which forms partial landslide in unsaturated area during rainfall period. In the initial stage of the heavy rainfall, the safety factor of the slope drops rapidly, which easily causes the landslide. The safety coefficient reduces further due to the continued infiltration of rainwater. Landslide occurrence after rainfall should be paid more attention. Safety factor is affected and vibrated with water in different parts of the slope. Finally, the concept of risk factor is proposed to reflect the harmful degree of slope under groundwater level and rainfall condition variation. The relationship between the risk factor and incremental displacement is established to describe the changes of surface displacement of slope measure point at different time periods. The above research and method will be useful and meaningful as reference for the management and early warning of the similar projects.