| In the Loess Plateau,rainfall induced landslides have the characteristics of frequent occurrence,mass occurrence and large scale,which cause huge potential safety hazards to the local people.It is of great significance to conduct in-depth and systematic research on such landslides.Based on the "geological disaster risk investigation and evaluation demonstration project in Suide County of Shaanxi Province",this paper takes the rainfall induced landslide in Tianshuigou village of Suide County as the typical research object,carries out the field geological disaster investigation,mapping,monitoring,exploration,field sampling and indoor test,and obtains the basic physical properties,geological characteristics and geological characteristics of loess in the study area through indoor test Through the finite element analysis software,the seepage field and stability of the slope under different rainfall conditions are discussed.The main research results are as follows:(1)Through the triaxial creep test of loess samples,it is found that the confining pressure has a great influence on the development of primary cracks and the axial strain is relatively small when the deviatoric stress level is low;With the increase of deviatoric stress,the influence of confining pressure is relatively weakened.Coupled with the promotion of moisture,the crack fully develops,evolves and penetrates,and the axial deformation is relatively large.The difference of long-term strength determined by isochronal stress-strain curve method and transition creep method is small,and it is negatively correlated with water content.(2)The ring shear test of different influencing factors of the landslide soil in Tianshuigou village of the exploration area shows that:(1)The effect of moisture content on residual strength is mainly reflected in the change of matric suction,the change of water film on the surface of soil particles,the dissolution of connecting structure between soil particles and the weakening of pore arrangement;(2)In the range of medium shear rate,the residual strength changes from "neutral effect" to "negative effect" with the increase of shear rate,and the effect of shear rate on the residual strength is significant under the "interference" of normal stress;(3)Comparing the single-stage shear,pre shear and multi-stage shear,it is found that the pre shear and multistage shear basically do not experience peak strength and insignificant strain softening stage,and the soil soon reaches the residual strength,while the single-stage shear is relatively backward,and the accuracy of residual strength obtained by single-stage shear test is higher.(3)Through the finite element simulation analysis of long duration weak rainfall and short duration heavy rainfall,it is found that:(1)There are large saturated areas in the upper loess area and the junction of the three loess layers,and the saturated areas gradually develop and increase with the continuous rainfall,becoming the most likely area to produce sliding surface shear in.(2)In the process of rainfall,because the infiltration of long-term weak rainfall is more sufficient,the range of critical sliding surface under long-term weak rainfall is larger than that under short-term strong rainfall;The rapid growth stage of short duration heavy rainfall displacement is in the early stage of rainfall,while the rapid growth stage of long duration weak rainfall displacement is relatively backward.(3)In terms of failure mode,in the early stage of rainfall,with the infiltration of rainwater,the soil mass in the potential sliding zone increases in gravity,the soil mass in the potential sliding zone compresses the slope toe,and the stress concentration and failure appear at the toe of the slope.With the failure of the slope toe,the anti sliding force further decreases,The sliding surface develops along the potential sliding direction towards the top of the slope until a fully connected overall sliding surface is formed,which is the typical failure mode of the traction landslide. |
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