MECHANISM AND ASSESSMENT METHODS FOR PLASTIC FLOW AND TENSILE CRACK-TYPE COLLAPSE
WANG Genlong1，2，WU Faquan2，QI Shengwen2，YU Guoqiang1，SU Tianming3
(1. Key Laboratory for Geo-hazards in Loess Area of Ministry of Land and Resources，Shanxi Center of Geological Survey，China Geological Survey，Xi?an，Shaanxi 710054，China；2. Key Laboratory of Engineering Geomechanics，Institute of Geology and Geophysics，China Academy of Sciences，Beijing 100029，China；3. Research Institute of Highway，Ministry of Transport，
Beijing 100088，China)
Abstract：The plastic-flow and tensile crack-type collapse or soft foundation-type collapse are very common in Southwest mountain region and Three Gorges reservoir area in China. These types of collapse occur frequently when weak layer distributes under the perilous rock mass. Suffering from the influence of gravity，water softening，long-term weathering and spalling，the weak layer will generate horizontal plastic flow towards free face. Meanwhile，the hard rock will generate tensile cracks. At last，perilous rock mass will generate uneven deformation in a weak layer. The deformation and failure processes of numerical simulation by discrete element method(DEM) are mudstone weathering and sheet-like peeling，hard rock falling，weak pedestal squeezing out，tension crack opening，deformation increasing and collapse occurring. According to two different failure modes of perilous rock mass caused by inhomogeneous deformation of weak layer，the computing formula of stability coefficient of plastic flow and tensile crack-type collapse is deduced by means of the method of geomechanics. Taking a typical rock slope in Wanzhou area of the Three Gorges area for example，the serious contrast and analysis of ratio of compressive strength to compressive stress and stability analysis of inhomogeneous deformation of weak layer are conducted. The results show that under static condition，the perilous rock mass is stable in a short term，on the contrary，it is unstable under high seismic intensity conditions.
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2013, Vol. 32 
