Study On The Formation Mechanism Of Gedi Landslide Of Yinjiang County Guizhou Province

Gedi landslide is located in Huangmu Town, Yinjiang County, Tongren City, Guizhou Province. Due to the impact of heavy rains, at 4:30 on July 17, 2014, it formed a large-scale overall slippage and took shape of a small barrier lake. Landslide developed in the bedding gently inclined structure slope which is made of the marl and shale clip in, before the landslide occurred, the nature slope is gentle about 15 °. In the rock developed the weak interlayer, in different parts of the landslide movement shows different motion residues. Therefore, this gently dipping structural slope characteristics of landslide motion certain significance. Through detailed field geological survey, based on the identification of landslide geological conditions, established the Gedi landslide structure model. Based on this, combining with two-dimensional and three-dimensional discrete element method studied on the motion features of landslide, integrated analysis of the Causes and evolution of Gedi landslide. The main results are as follows:(1) Gedi landslide developed in bedding gently inclined slope made of the mudstone contains weak interlayer, lithology of slope mainly is Ordovician Dawan under the EC marl, rock occurrence of N4°E / NW∠16°, in marl sandwiched two shale weak interlayer. Landslide was toe-shaped and elevation range of 850 ~ 890 m, the trailing edge is nearly like the arc, with an elevation of 1020 ~ 1040 m, the maximum height of about 190 m.The width of landslide accumulation body is about 500 m, a longitudinal length of it is about 750 m. The slope of landslide is 10 ° ~ 48 °, The lower flat and the upper steep,in the middle exposed fake bedrock, the leading edge forming a high-piled, blocking the river, take shape of a small barrier lake, the main direction of slide is 282 °, landslide volume of it is about 200 million m3, sliding distance is about several hundred meters.(2)Signs of landslide deformation and failure mainly for trailing edge cracking and the whole of the bedding slip.Landslide distribution of trailing edge multiple cracks and the downstream side of the border is obvious scratch, steep hills and leading edge is covered by deposit is not visible, upstream side landslide boundary trees lush, originally to slip at the bottom of the slope rock mass, become warped on here to rock, crack along the structural plane.According to the field of surveying and mapping and high-density electrical method physical detection methods to analyze results, sole landslide sliding surface depth of 1 m to 40 m, most deep place located at the top of the slope, there are a large number of empty in geophysical profile form and deposit shows that the central distribution have a large number of cracks.(3)The discrete element method, the sole landslide deformation and failure process and the movement characteristics of the landslide.Appear at the top of the slope at the beginning of cracking damage, displacement of slope toe appear,Central and trailing edge and then play the decomposition slip phenomenon in a slope, trailing edge of the deep fractures, and started to pull the tank, and also the crack front slope penetration to the sliding surface, causes the front slope began to collapse sliding phenomena, and trailing edge of slot elevation difference reached 15 m,In the end, the decomposition of whole sliding slope.(4) The deformation and failure mechanism of the whole Gedi landslide is slidin g and fracturing, and slide-bending in partial because of the different slide body speed s. The deformation and failure process is divided into four stages: The first stage, the mechanical strength of argillaceous weak intercalations is reduced, results in the decre ase of slope stability, and the rock mass in slope toe are sliding out. The second stage, the preferred plane L1 developed in the marl that is located in the central and upper sl ope, forming the fractured and the fractures along the structural plane development to the slope surface. The third stage, the rock mass that is located in the upper slope surf ace are sagged, forming the trailing edge boundary, and the rock mass toppling defor mation to the backward direction. The fourth stage, the slope completely disintegrate,sliding to the leading edge and blocked the river, forming a barrier lake.