Chashushan landslide is located in the intersection of Batang fault and Jinshajiang fault.With the complex geological structure and intense neotectonic movement,large landslides occur frequently in this area.Chashushan landslide originates from ancient landslide mass.The sliding deformation of the landslide first appeared in July of 2001,followed by creep deformation.Deformation velocity of the landslide was accelerating continuously because of deformation.Then a lot of distortion evidences appeared in the landslide mass.Finally,the landslide occured severely sliding on January 7,2006.The landslide is in unstable condition,and the deformation and failure of the landslide are obvious,and it is potential that the deformation and failure will last.Through field investigation,large-scale direct shear tests on slipping soils were carried out,then the shear strength was obtained under the condition of different water contents,which revealed the cohesion and internal friction angle decreased with the increase of water content.In this paper,based on the analysis of field geological survey,geophysical prospecting,drilling,and large-scale direct shear tests,the authors consider that the formation mechanism of Chashushan landslide is complicated:rocks affected by the fault structure have the intensive development of rock mass structures and poor mechanical properties of rock and soil masses;the stratum system of landslide has a hydrogeologic structure of groundwater rich in the upper and poor in the lower,which is very vulnerable to landslide disasters.The stability of the landslide body is in critical condition due to heavy rainfall.Canal water infiltration influence of freezing-thawing action induced the occurrence of landslide.FLAC3D was used to simulate the stability of the landslide body.Results indicate that the landslide body has obvious signs of deformation under heavy rainfall and has formed intact slip surface,and the landslide is likely to occur again.Taking into account the formation mechanism of the landslide,it is effective for controlling the stability of the landslide body to strengthen the drainage and to avoid infiltration of the canal water.%川西巴塘茶树山滑坡位于金沙江断裂带和巴塘断裂带的交汇处,区内地质构造复杂,新构造活动强烈,大型滑坡频发.茶树山滑坡为一古滑坡堆积体复活形成的滑坡.该滑坡自2001年7月首次出现滑动变形之后以蠕滑变形为主,不断的变形作用促使滑坡变形速度加快,滑坡体上出现了各种滑动形迹,于2006年1月7日发生大规模滑动.该滑坡目前仍处于不稳定状态,滑坡体变形破坏迹象较为明显,有进一步发生变形破坏的可能.在野外调查的基础上,对茶树山滑坡滑带土进行了大型直剪试验研究,获得了不同含水率条件下的滑带土抗剪强度变化规律,结果表明随含水率增大滑带土强度有明显减小的趋势.综合野外调查、物探钻探以及试验分析认为茶树山滑坡的形成机理为:受断裂构造作用,岩体结构面密集发育,岩体破碎程度高,岩土体力学性质差;上部透水层和下部隔水层的二元结构为滑坡体的富水提供了有利条件,强降雨作用使滑坡稳定性处于临界状态,渠水入渗和冻融作用直接诱发滑坡的发生.采用FLAC3D对目前茶树山滑坡的稳定性进行模拟,结果表明,在强降雨条件下滑坡体出现明显的变形迹象,滑移面即将贯通,可能再次发生大的滑动.从滑坡形成机理角度考虑,加强排水、避免渠水再次入渗可以有效地控制坡体稳定性.
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