Study On The Mechanism Of Expansive Soil Landslide

Expansive soil is widely distributed in our country.In recent years,landslide disasters frequently occur,causing huge losses to the country and people.The expansive soil landslide zone in the mountainous area of southern Shaanxi Province has the characteristics of large quantity and wide distribution,its forming characteristics and occurring mechanism are more complex,and there are many factors affecting the landslide,which cause great trouble to the engineering activities and human life.In this paper,the mechanism of landslide is studied on the expansive soil in the south of Shaanxi Province.According to the characteristics of regional landslide,the effect of fracture development on the mechanism of landslide is analyzed.According to the characteristics of regional landslide,an experimental model of landslide is designed for in-depth study.According to the principle of landslide,the indoor landslide model test and direct shear test are designed by using prepared expansive soil,in order to summarize the formation mechanism of expansive soil landslide,the crack development of expansive soil under dry-wet cycles and the Shear Strength Change of expansive soil under different dry-wet cycles were studied,the conclusions are as follows:(1)the development characteristics of expansive soil landslide in the south of Shaanxi Province are summarized based on the analysis and induction of landslide data in this area and the in-depth study of related literatures.Landslides are distributed in areas with serious rainfall erosion and low topography.The orientation and shape of landslides show the characteristics of sunward slope with slope between 10°? 40°.The rainfall is more in the West and less in the east,more in the south and less in the north.(2)Based on the mechanism of expansive soil landslide in southern Shaanxi Mountain area,a laboratory landslide model test was designed to study the growth and development of cracks on the surface of expansive soil landslide under different dry-wet cycles.Through the vectorization of the fracture image obtained and the image analysis using software,the water content gradient will be formed in and out of the soil under the action of the dry-wet circulation,and the area ratio,length ratio and width of the fracture will be increased,will increase with the number of dry-wet cycle,but the dry-wet cycle is limited,cracks will not infinite growth.(3)as the number of dry-wet cycles increases,during the drying process,the surface of the sliding body is in direct contact with the hot air generated by the drying device,which leads to the heating of the surface of the soil body,while the heat received by the deeper the soil body is,the less the heat is,resulting in uneven heating,thus,the water loss rate of the internal and external soil bodies is different,the surface soil body is dehydrated,the color becomes lighter,gradually dries out,the internal soil body changes slowly,thus causes the soil body's uneven contraction,causes the soil body to crack;The crack develops gradually until it runs through,causing the stress and strain unbalance,which finally leads to the landslide.(4)the direct shear test was carried out on the samples of the expansive soil ring with different vertical loads by controlling the water content,in order to explore the relationship between the strength parameters and the development of the fissures,according to the data,the mechanical properties and General Laws of expansive soil samples are analyzed.With the increase of dry-wet cycles,the expansive soil samples have destructive cracks and the internal structure is destroyed,which leads to the decrease of cohesion and the change of internal friction angle.(5)according to the results of laboratory landslide test and direct shear test of expansive soil under the condition of dry-wet Circulation,the mechanism of expansive soil landslide is studied and analyzed.Under the action of drying,cracks appear from outside to inside,and they develop constantly.In addition,under the action of rainfall,rainwater seeps through the cracks to the interior of the landslide body,and the expansive soil becomes soft by absorbing water,repeated cycles cause the cracks in and out of the soil to run through,the soil to be broken,the shear strength becomes low,and the landslide occurs.