Study On Revival Formation Mechanism And Stability Of Shaojiwo Landslide In Yuli Town Of Beichuan County

Shaojiwo old landslide is located in sanping village, beichuan county of mianyang city of sichuan province, in the longmen Mountain fracture zone, structure is complex bedding phyllite occurs in middle steep dip.qianmei rock in mass slope, the deformation and failure mode for "sliding and bending", instability of the scale of about 7 million m3. In "5.12" wenchuan earthquake, the old landslide on several short tension crack; After years of rainfall effect after the earthquake, especially for July 2013 after heavy rainfall, slope on the development of multiple transverse tensile cracks grown up and signs of resurrection. Resurrection of the old landslide on the down slope threatening people life and property safety, important traffic disruption leads to the upstream villages, and old suede GouGou residents as a threat. Study, therefore, the resurrection of the landslide mechanism and stability has important practical significance, at the same time complement the earthquake-induced landslide deposit study, the resurrection of the similar to the resurrection of the old landslide deposit and the analysis of its stability has a certain reference value.Based on collecting relevant geological data, in the study area exploration data, to the engineering geological condition of landslide, the landslide structure characteristics, on the basis of the analysis of its deformation characteristics, adopt the method of geological and mechanical analysis of the old landslide formation mechanism, through the geological analysis combined with numerical simulation method to study the mechanism of the resurrection of the landslide under earthquake and the heavy rain, then use both qualitative and quantitative methods to evaluate the stability of the landslide the whole and local, and prevention measures are put forward. The main research results are as follows:(1) Analysis of the basic characteristics of the landslide are similar to those of landslide peripheral phyllite slope deformation characteristics, combined with the slip- curved geological mechanical model calculating the limit bending length, determine the seive litter of landslide for dipping phyllite quality bedding slope instability damage accumulation and become, after deformation failure mode for "slip- bending- breaking".(2) in the "5.12" earthquake, the old landslide deposit under the action of seismic wave deformation damage main cash for loose, rupture, the part of the high and steep in the back of the front microtopography of protuberance part produce several short transverse crack. After the earthquake under the rainfall effect for many years, especially during the rainstorm in July 2013, the resurrection of landslides have obvious signs, mainly brought up multiple transverse cracks to appear on the slope with fault scarp, and has a certain partition. According to the characters of slope body structure and deformation characteristics of the old landslide can be divided into 1 #, 2 #, 3# three raised area.(3) The structure of the old landslide is loose, and provides the landslide revival adverse geological basis, under seismic action, the slope with cracks, and the structure is looser, late for rainfall seepage channel into the good.After the rainfall infiltration into ground water, slope loading, hydrostatic pressure and permeation, and soften the sliding zone, cause slide force increases with the sliding resistance is reduced, the landslide deposit started to creep deformation, leading to the resurrection of the old landslide. Deposit according to the deformation characteristics of the landslide, concluded that degree of landslide deformation and failure model for creep, cracking of the partition- cutting pattern.Flac3D finite difference method is used to simulate analysis under earthquake and storm deposit landslide revival mechanism, through the numerical simulation results analysis: under the seismic action, the smaller displacement of deposit, plastic deformation appears almost everywhere in the landslide deposit, only the surface of the plastic damage, earthquake promotes the resurrection of the old lands. Displacement of the old landslide deposit under the action of rainfall amount is larger, in a certain area of the plastic damage, and at the rear and front form relatively concentrated landslide shear strain zone, deposit rainfall effect induced by the resurrection.(4) Through the qualitative analysis with the Morgenstern- Price limit equilibrium method and old deposit landslide and local and global stability.Old landslide under natural conditions in the whole stable state, under heavy rain and earthquake conditions in a basically stable steady state.The resurrection of the body under natural conditions in the basic stability- unstable state, in the working condition of heavy rain and earthquake touchpad and unstable- unstable state. By the sensitivity of the stability analysis, the stability coefficient of cohesion and internal friction Angle is on the rise, but the internal friction Angle of a greater influence on the stability of the landslide.Two-dimensional seepage field and stress field coupling numerical simulation analysis of 50 years of single maximum rainfall and maximum rainfall in 5 days under the condition of seepage. Single rainfall results show that the single largest rainfall pattern of vertical infiltration, and stress and strain of the slope table in, easy to cause surface skid.Five days continuous rain results show: 2 days before the rain rain effect way as the main vertical infiltration cause slippery body density increase, for 3 days after osmosis and certain floating supporting role;Coupling calculation according to rainfall effect increases the overall stress of slope body, the back and the front of the displacement increases, the back of the displacement is the anterior displacement of large, sliding zone of maximum shear stress increases, formed in the rear and front two run-through shear strain band, the maximum shear strain at the back of the value to see the front of a big, the maximum shear strain band as a whole, shows before and after the instability and failure of landslide is divided into two parts, push back the front, the failure mode is on type.(5) On the basis of the landslide stability calculation, and combined with the feature of landslide deformation, failure mode, rock and soil characteristics, the space development characteristics and suffer object characteristics of the distribution of the proposed control scheme for the pile and cut drains.