| The colluvial landslide is defined as the landslide occurring in the loose layer of the Quaternary strata,and the sliding body material is generally formed by the accumulation of the collapse,the collapse and accumulation of the slope,the alluvial and the collapse slope.The cover layer of Muchuan County is mainly composed of red layer silty clay,which has the characteristics of loose structure,high porosity and high permeability.It is easy to crack under the action of rainfall and earthquake.On the basis of field investigation of 131 landslides in Muchuan,the paper selects the landslide of the 63 layers as the research object.Based on the field data and other related data collection and collation,the paper lists the landslide elements of each accumulation layer and summarizes the distribution law of landslide development.For the Formation Regularities of distribution of landslide essential maps by using Arcgis software,then on the basis of indoor experiment,discusses the effect of rainfall on landslide,with the earthquake process,finally on the early achievements,highlighting the region deposit slip rupture deformation and failure mechanism,the failure mechanism of the proposed earlier by Geo-studio verify.The content and innovation of this paper are as follows:? Compared to the 63 accumulation landslides were researched,we found out that the obvious difference between the researched accumulation landslide and the others landslides is the slopes ranging from 15°to 25°,and the maximum slopes are no more than 30°.In addition,according to the enclosing rectangle criterion and the length-width ratio of landslide,the plane shape of the landslides can be divided into horizontal type,equiaxial type and longitudinal type.Through XRD and other experiments,it is concluded that the material composition of the accumulation layer mainly consists by montmorillonite minerals and there are three structural combinations of sliding bodies.Through the investigation,it is found that the sliding surface shape,dip angle and the spatial distribution direction of landslide are obvious.? The regional accumulation landslide mainly lies in structural erosion,denudation,low mountains and fluvial erosion valley landform units,it is mainly controlled by fold structure and the cluster is obvious,which many composes of Wudu-Lidian cluster and Wuzhishan-Muchuan cluster.These landslides occurred after Wenchuan earthquake with obvious time node,what's more,some landslides occurred in July,August at the height of the monsoon rains.So according to the study,the most important reasons for the instability of the landslide are the earthquake and rainfall.The landslides are distributed in the area of the three basins,but mainly in the Mabian River basin.? The coupling action of rainfall and earthquake can greatly induce instability of accumulation layer landslide.There are 54 accumulation landslides in all researched accumulation landslides located in the area where the rainfall is from 1300 mm to 1400 mm,the investigation result shows that there is continuously different intensity of rainfall before and after landslide instability.Based on the experiments,the shear stress-shear displacement curve,variation curve of internal friction angle with different water content and variation curves of cohesive force with different water contents we can learn that the sensitivity of the three to water content change is cohesion > internal friction angle.Under the action of earthquake wave.The surface of the thicker accumulation layer landslide will produce a tensile shear crack perpendicular to the driving direction of the transverse wave,the interface slope front base cover of the deformation of cover appears,showing creep shear appeared slope table.? Earthquake,rainfall and disturbance of human engineering activity are the mainly causes of accumulation landslide in the study area,4 coupling models are proposed based on the evolution process of accumulation landslide including rainfall-gravity coupling model,seismic-rainfall coupling model,erosion-gravity coupling model and artificial disturbance-rainfall coupling model.? According to the structure of landslide,the dip of slip surface and constouctional material the 63 landslide in study area can be generalized by 3 elasses,and 7 small classes which cover 7 types of deformation failure modes,including erosion-slip,vibration-creep,shatter-slip,plastic flow-slippery,creep-lapse,creep-traction,creep-slip.In this paper,7 models are discussed in detail about the landslide formation and evolution process.? Vibration-creep model is simulated by using Geo-studio,QUAKE and SIGMA are used to analyze the dynamic response and fracture formation of stacked deposits under seismic,and SEEP was used to study the change of underground site under different rainfall,rainfall intensity and duration. |
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