甘肃舟曲牙豁口多级滑坡变形特征及复活机理

Deformation Characteristics and Revival Mechanism of Yahuokou Multi-stage Landslide in Zhouqu,Gansu Province

2019年7月19日,甘肃舟曲县牙豁口发生多级滑坡,该滑坡是牙豁口老滑坡中部凹槽内的复活滑动,其体积约215.5×10^(4)m^(3)。该滑坡从斜坡体顶部崖口处启动,呈“流塑”状自上而下缓慢滑落至岷江,导致岷江河道被阻塞,水位上升,严重威胁附近居民以及下游城镇的安全。为探究该滑坡的变形特征及复活机理,本研究通过野外勘察、历史资料调研,查明了滑坡的地质环境背景与变形历史;通过对遥感解译、滑坡监测以及降雨数据等分析,探讨了滑坡的启动及演化过程,揭示了滑坡的复活机理。研究结果显示牙豁口多级滑坡的复活具有逐级加载、逐级传递应力、逐级启动的特点。滑坡的复活分为3个阶段:(1)上部滑体开始缓慢的塑性流动;(2)缓坡中部平台受到上部滑体的预压,形成“切填”效应,其破坏形式为蠕滑-拉裂-滑移;(3)下部坡体滑动。

On July 19th,2019,a multi-stage landslide(volume:215.5×10^(4)m^(3))with a reactivated sliding in the middle groove of the paleo-landslide occurred in Yahuokou(Zhouqu County,Gansu Province).The landslide started from the cliff mouth at the top of the slope body,and slowly slid down to the Minjiang River with flow shape.This blocked the Minjiang River channel and raised the water level,seriously threatening the safety of nearby residents and downstream towns.To study the deformation characteristics and revival mechanism of the landslide,the landslide geo-environmental background and deformation history were first investigated through field survey and historical data analysis.With data interpretation on remote sensing,landslide monitoring and rainfall,the landslide initiation and evolution processes were elucidated,and the landslide revival mechanism revealed.The multistage landslide resurrection is characterized by stepwise loading,stress transfer,and initiation.The landslide revival comprises three stages:(1)the upper slide began to flow slowly in a plastic form;(2)the middle platform of the gentle slope was prepressed by the upper sliding body,forming the“cut-fill”effect.Its failure mode is creep slip-tensile crack-sliding;(3)the lower block slid.