四川省万源市毛坝子老滑坡变形特征及复活机制分析

Analysis of Deformation Characteristics and Resurrection Mechanism of Maobazi Old Landslide in Wanyuan City,Sichuan Province

老滑坡复活失稳主要是以基覆界面附近的滑带土作为滑面失稳的,万源市地形起伏较大,雨量充沛,发生过多起滑坡事件.通过工程地质调查及相关地质灾害监测手段对毛坝子滑坡的失稳过程分析得出,毛坝子滑坡的诱发首要因素为滑坡前缘基坑开挖,基坑开挖导致整个坡体应力分布表现为坡脚应力集中,出现剪切破坏带,滑坡开始蠕动变形;在持续的暴雨条件下,地下水位急剧上升,由于拉张裂缝的存在使雨水容易进入坡体内,滑体的抗剪强度降低,因粉质黏土的存在,使得孔隙水压力的消散产生较大的滞后性,基岩的隔水作用使坡体局部产生扬压力对滑坡产生托顶作用;人工开挖诱使滑坡发生蠕动变形,在持续暴雨条件下进行加速变形阶段,最终导致滑坡失稳.

The resurrection instability of old landslides is mainly based on the sliding zone soil near the base cover interface functioning as the sliding surface.Wanyuan City has large topographical fluctuations,abundant rainfall,and too many landslide events.This paper analyzes the instability process of the Maobazi landslide through engineering geological survey and related geological disaster monitoring methods:The primary cause of the Maobazi landslide is the excavation of the foundation pit at the front edge of the landslide,and the excavation of the foundation pit leads to the entire slope.The stress distribution is manifested as the stress concentration at the foot of the slope,the shear failure zone appears,and the landslide begins to creep and deform;under continuous heavy rain conditions,the groundwater level rises sharply,and the existence of tensile cracks makes rainwater easily enter the slope.The shear strength of the sliding body is reduced,and the existence of silty clay causes a larger hysteresis in the dissipation of pore water pressure.The water barrier of the bedrock causes the local uplift pressure of the slope body to support the landslide;manual excavation induces creep deformation of landslide,and accelerates the deformation under continuous heavy rain,which finally causes instability.