四川泸定昔格达组滑坡灾害运动过程模拟分析

Simulation analysis of landslide disaster movement process in Xigeda Formation,Luding County,Sichuan Province

四川泸定昔格达组以半成岩为主,工程地质特性复杂,在高陡斜坡中常发生浅层蠕滑变形,在强降雨作用下失稳后可转化为泥石流。本文以四川省泸定县海子坪环环村滑坡为例,基于遥感解译、地面调查、数值模拟等方法,对滑坡发育特征、潜在失稳模式和滑坡-泥石流运动过程进行分析。结果表明,环环村滑坡主要发育于昔格达组内,以深度3~5 m的浅层变形为主,整体处于蠕滑变形阶段。滑坡平面上分为强变形区(A区)和弱变形区(B区),体积分别约为5.5×10^(4) m^(3)、5.8×10^(4) m^(3),在不同降雨条件下,存在仅有A区下滑和A区牵引B区一起下滑并转化为沟道泥石流2种致灾模式。当仅有A区失稳下滑时,最远运动距离可达1325 m,最大堆积厚度为5.2 m,最大运动速度41.6 m/s,滑坡破坏沟口居民区及道路。当A区和B区同时失稳下滑时,最远运动距离可达1345 m,最大堆积厚度为7.7 m,最大运动速度为44.3 m/s,滑体最远能够冲至河流对岸,形成高约3 m的滑坡坝。研究结果对于深化浅层滑坡-泥石流远程致灾效应的认识和防灾减灾具有一定的指导意义。

The Xigeda Formation developing in Luding County,Sichuan Province,is mainly composed of semi-diagenetic rocks,which has complex engineering geology properties.Shallow creep deformation of the Xigeda Formation often occurs in the slope with high and steep terrain.It can transform into debris flow after destabilization under the action of heavy rainfall.In this paper,the Huanhuancun landslide in Haiziping developing in the Xigeda Formation was selected as a study case.Based on remote sensing interpretation,field investigation and numerical simulations,we analyzed and calculated the development characteristics of landslides,potential instability modes and the process of landslide-debris flow movement.This study has shown that the Huanhuancun landslide is mainly developed in the Xigeda Formation,mainly in the shallow deformation with a depth of 3~5 m,and is in the creep deformation stage as a whole.The landslide in plane can be divided into strong deformation zone(A)and weak deformation zone(B)with the volume of approximately 5.5×10^(4) m^(3) and 5.8×10^(4) m^(3).Under different rainfall conditions,there are only two forming patterns of disasters:zone A sliding and zone A pulling zone B sliding together and transforming into gully debris flow.When only the zone A slides downslope,the longest movement distance can reach 1325 m,the maximum thickness of deposits is 5.2 m,the maximum velocity is 41.6 m/s,and the sliding body will damage the residential areas and roads.When the zone A and B slides together,the maximum movement distance can reach 1345 m,the maximum thickness of deposits is 7.7 m,the maximum velocity is 44.3 m/s,and the sliding body can rush as far as the other side of the river,forming a landslide dam with a height of about 3 m.The research results have certain guiding significance for deepening the understanding of remote disaster effect of shallow landslide-debris flow and disaster prevention and mitigation.