| As an ancient landslide accumulation body of Za Gu nao valley, Xishan landslide has the characteristics of loose materials and complex structure,these characteristics lead to the occurrence of slope deformation under the action of rainfall and earthquake.This artical makes Xishan landslide as the research object and will give in-depth analysis based on geology investigation, physical and mechanical experiment of rock and soil mass, high-density resistivity method and numerical simulation of Two-Dimensional and the Three-Dimensional, To find out the landslide's structure,physical and mechanical properties of different material and the trend of landslide deformation and failure. Main research results and understanding of this article are as follows:(1) Xishan landslide is a large ancient landslide accumulation body of Za Gu nao valley, presenting 'Quan yi'style on the plan, about 600 meters wide and with a difference in altitude of 1800 meters, it's slope is between 15 ° ~ 25 °. The main bedrock of Xishan Landslide include slate, phyllite from Devonian and Siluri, the occurrence of bedrock is 170 ° ? 75 °, the thickness of accumulation upon the bedrock is about 50 meters.(2) Xishan village initial slope was slow down the steep, at the foot of showed high and steep rock, slope were more than 70 degrees, suberect, steep cliff height difference of nearly 60 m, in the valley near vertical cliff top, distribution certain width are slow at the junction of the platform, platform above the slope is the valley was significantly slowed down, about 40 degrees, slope of the upper slope is below the altitude were slope gradient is reduced slightly, the formation of length is large, the trailing edge of the slope. Silurian Maoxian group bedrock occurrence for 170 °?85° degrees, Devonian system risk off group bedrock occurrence for170°?82°degrees, two sets of formation strata occurrence are basically the same and lithology are mainly for phyllite, Xishan village landslide sliding slope types for steep dip and rock slope.(3) The accumulation body of Xishan landslide contains silt with rubble, detritusand crushed-rock layer, at the same time, the accumulation has the characteristics of complex structure, piled incompact, considerable difference in destructiveness,non-uniformly distributed within the regions and so on. According to sources, the movement direction of accumulation and the motive order, we can divide the landslide into four zones.(4) In Xishan landslide, the measurement precision is inversely proportional to the electrode distance and Wenner profile method is more suitable for detecting structure in this accumulation. By comparing the borehole data with the apparent resistivity, we got the data of groundwater depth and the apparent resistivity of silt with rubble, detritus,crushed-rock layer and bedrock of this accumulation.(5) By geophysical means of the high density resistivity method, identified region III front left boundary boundary location and description I and II distinguish area structure criterion. In addition, the landslide in the upper high deformation analysis of geophysical prospecting area to determine the flat stones fault after the landslide area and by the position and accumulation body containing clasts of silt and gravel soil shear export position.(6) Crack and extrusion are the most important causes of slope failures, there are some transverse cracks in the front and rear of the accumulation. The motion direction of rear about 208 °,because lack of empty face, the motion direction of middle and front parts has changed, it's adout 178°. The dip direction of collapse plasmodiums on the landslide boundary has the trend turning to the southwest.(7) The silt with rubble is a soil of low plastic limit semi-solid inhomogeneous coarse-grained. With the increase of water content, the internal friction angle of this material decreased gradually and adapting equation is y =-0.118x2 + 0.3273x+42.144.The most cohesion is 45.5Kpa when the water content is 8%. The fitting relationship between cohesive and content of gravel is y =-0.769 x + 66.043 when the density is 0.6, besides, The fitting relationship is y =-0.947 x + 80.187 when the density is 0.8. As the same gravel content, the cohesion and internal friction angle are proportional to the density when they are different with density.(8) The elasticity and Poisson's ratio of silt is inversely proportional to the water content, the influence of water content on internal friction angle is small but has a great influence on cohesion, it has the most cohesion when the water content is about10%. The compressive strength is more big when the water content is between10%~15% compared with 3%~10% and this is advers in high confining pressure. For phyllite, the compressive strength is 66.7MPa, the elastic modulus is 12.12 GPa, thePoisson's ratio is 0.29 in natural state and the compressive strength is 54.28 MPa, the elastic modulus is 9.71 GPa, the poisson's ratio is 0.24 in saturated state and the cohesion decreased by about 70%, the internal friction angle decreased by about12.6% for strong weathering state.(9) In the natural state, the slope is dominated by compressive stress, and the distribution of the local area in the middle part of the accumulation body has a small tensile stress. The valley has a high stress concentration phenomenon, which is about4~5Mpa.(10)From the different rainfall after the plastic zone distribution, the natural state of plastic zone is mainly located in the front of landslide, the distribution area is small;the 40 mm rainfall caused edge extension of plastic zone, the central front new plastic zone, and IV area front shear outlet position of the plastic zone gradually expand upward, cover most of the surface of brecciated silt; 60 mm after rainfall, leading edge connectivity of plastic zone, plastic zone depth, trailing edge surface accumulation IV all deformation; 120 mm after rainfall, the accumulation distribution of plastic zone is divided into 2 parts, one is in the lower part of the landslide, the plastic zone distribution based on all of the above cover interface accumulation, in addition, the trailing edge of the depth of the plastic zone gradually expanded, the lower gravel layer of all plastic zone, plastic zone may be due to the increase of rainfall through a comprehensive.(11) After 40 mm and 60 mm rainfall, slope maximum principal has a small change but the minimum principal stress and shear stress increased, the shear strain continued to increase and formed high tensile stress area, it has subsurface flow in base coating interface after 120 mm rainfall, The high stress in vally further concentrated and a larger tensile stress area is formed in front of the slope, thel slope stability gradually decreased after 120 mm rainfall and slope stability was 0.92. In the saturated state, the stability coefficient of high deformation zone decreased obviously and the stability coefficient is substantially less than 1, the slope is in a deformation process: the natural state of the area I 1.077 and saturated 0.915, fall by about 15%;1.075 II in natural state, saturated 0.96, decreased by about 11%; III area under natural state stability coefficient 1.131, saturated 1.034, down about 8%... |
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