Study On Formation Mechanism Of Loess-bedrock Landslide Based On Creep Characateristics Of Slip Zone Soil

The Loess Plateau is a region with frequent disasters in China,and landslides are typical natural disasters in this region.In recent years,with the rise of the western economy,the scope of human activities has continued to expand,infrastructure has risen,the natural environment has been destroyed,and natural disasters caused by human activities have also followed.The geological environment in Yan'an area is complex and changeable,and good land resources are scarce.In order to reclaim more flat land for engineering construction,for the loess area with ravines and ravines,mountain construction has become a more convenient method,and slope excavation will occur,when the natural stress field of the slip mass is changed,the stability of the slip mass also changes,and it is easy to cause natural disasters such as landslides and collapses.In order to better analyze the formation and evolution process of this type of landslide and better control this type of landslide,a typical creep loess-bedrock landslide in Yan'an City was selected as the research object,and the creep characteristics and strength of the landslide soil were selected.The characteristics are analyzed in detail,and based on the experimental data,the entire evolution process from landslide to development is simulated and analyzed,and finally the formation mechanism of such landslides is revealed.The main conclusions of this article are as follows:(1)Through analysis of the creep test data of the slip zone soil,the landslide slip zone soil has three stages in the direct shear creep experiment,which are instantaneous deformation,low-speed attenuation creep and steady-state creep,and the whole landslide.The evolution is similar,indicating that the mechanical characteristics of the landslide soil play a controlling role in the overall evolution of the landslide.(2)Through the direct shear test,direct shear creep test and repeated shear test,the instantaneous peak strength,long-term strength and residual strength of the slip zone soil were obtained,and the relationship between the three was compared and analyzed.Under the same water content and the same normal stress,the peak strength is the largest,the long-term strength is the second,and the residual strength is the smallest.Therefore,when determining the safety factor of this type of landslide,the long-term strength parameter is the most suitable to provide parameters for the later long-term stability calculation.(3)On the basis of creep test data,four creep models including Burgers model,Singh-Mitchell model,generalized Kelvin model and self-built empirical model were established.The four models were compared and analyzed.The results showed that:generalized Kelvin model and self-developed model The empirical model is more suitable for describing the creep characteristics of this kind of landslide sliding zone soil;Burgers model is suitable for describing the creep characteristics of sliding zone soil under higher shear stress;Singh-Mitchell model is more suitable for?(0.2,0.8).(4)Through the traditional Bishop method and Midas software analysis of landslide stability,combined with field survey and deformation monitoring data,it is learned that the main factor of landslide formation is manual excavation,and the factor that affects the further deformation and damage of the landslide is rainfall.The entire simulation process of the cause is:the early slope foot excavation,the stability of the landslide is reduced,because of the small excavation,the slope body is in a stable state at this stage;the continuous excavation in the middle period,the stability of the landslide is reduced,due to the large amount of excavation,this At this stage,the slope body is in an unstable state;the stability of the landslide after the slope reduction has been improved,but it is still in an unstable state;it is predicted that if the landslide does not take timely control measures and encounters heavy rain,the landslide will undergo rapid deformation.Therefore,it is recommended that the landslide be treated in time before the rainy season,so as not to cause damage to the engineering construction below.