强降雨诱发作用下岩溶山体滑坡机制研究--以关岭滑坡为例

Research on mechanism of landslides in the southwest karst mountain areas under intensive rainfall:a case study of the Guanling landslide

强降雨引起的岩溶地下水升降波动对我国西南岩溶山区的大型滑坡具有重要影响。为了明确的强降雨诱发作用下岩溶山体滑坡的机制,以关岭滑坡为例,结合现场野外调查,岩溶发育现象以及渗流场特征分析了关岭滑坡的成因机制。研究发现:在强降雨条件下,滑源区后部强烈的侧向补给抬高了地下水位,于基岩裂隙水区的坡体内形成高压水头,并作用于滑源区内的潜在软弱结构面上诱发了滑坡失稳,由此提出“岩溶山区二元岩体结构滑坡”的失稳模式。通过山体内地下水位线解析解耦合剩余推力法分析了多工况下滑体的稳定性,理论计算结果显示:岩溶管道介质的平均直径以及降雨强度对坡体稳定性有较大影响。当岩溶管道平均直径取值在0.15 m及以上时,坡体会于极端降雨工况下发生失稳。推导的岩溶山体地下水位线计算公式及稳定性分析方法可为岩溶山体滑坡的稳定性评价和防治工程提供有益参考。

The dynamic change of karst groundwater level induced by heavy rainfall has an important effect on large landslides in karst mountainous areas in southwest China.In order to clarify the mechanism of karst landslides induced by heavy rainfall,taking Guanling landslide as an example,combined with field investigation,karst development phenomenon and seepage field characteristics,this paper analyzes the genesis mechanism of Guanling landslide,and finds that,under the condition of heavy rainfall,the strong lateral recharge at the back of the slide source area raises the groundwater level,which causes the formation of high pressure water head in the slope body of the fissure water area of bedrock and induces the landslide instability on the potential weak structure plane in the slide source area.Then,the stability of the sliding body under multiple working conditions is analyzed by means of groundwater table analytic decoupling residual thrust method.The theoretical calculation results show that the average diameter of karst pipeline medium and rainfall intensity have great influence on the stability of the slope.When the average diameter of karst pipeline is 0.15 m or above,slope instability occurs under extreme rainfall conditions.The calculation formula of groundwater level and stability analysis method derived in this paper can provide useful reference for stability evaluation and prevention of karst landslides.