Model Test Study On Evolution Process Of Accumulated Layer Landslide Induced By Rainfall In Zhashui County

Zhashui County is located in the hinterland of Qinling Mountains.The geological environment conditions are complex and diverse.In addition,the climatic conditions in the area are relatively poor,the frequent occurrence of extreme rainfall events,combined with human unreasonable human engineering activities and other factors,have resulted in a large number of geological hazards in Zhashui County,which are widely distributed and frequently occurring.Zhashui County has become one of the counties with relatively developed geological hazards in Shaanxi Province.Rainfall is the most important and active factor to trigger the accumulation layer landslide.The landslide and debris flow disasters often occur in this area during the flood season,which is a typical rainfall landslide area.Therefore,it is of great significance to analyze the formation and evolution process of the accumulation layer landslide induced by rainfall in this area for disaster prevention and mitigation in Zhashui County.The research work and results are as follows:(1)Based on the investigation and analysis of 85 accumulative landslides in Zhashui County,it is found that the landslides in the area are mainly shallow,small,modern and accumulated landslides.The development and distribution characteristics of the landslides are analyzed in detail from the aspects of geomorphological features,slope thickness characteristics,landslide slope characteristics,and material characteristics of Sliding Body On this basis,the Fengchai Highway Landslide in Chaizhuang Town,which is the typical landslide representative in the area,was selected as the landslide prototype to carry out the model test on the formation mechanism of accumulation layer landslide induced by rainfall.(2)According to the similarity theorem,and based on the physical size of the landslide and the size of the model box,the similarity ratio of the test is C_l=50.Using the uniform design method,the similar materials of the sliding body have been tested several times and finally determined(fine sand:40%,barite powder:35%,double fly powder:15%,water:10%)as similar materials for sliding soil.On the basis of previous studies,a layer of kraft paper was selected as the similar material of sliding zone soil,and the slurry block stone was used to simulate the bedrock of sliding bed.(3)In the model test process,the pore water pressure and horizontal soil stress data during the landslide test were obtained by six pore water pressure sensors and six soil pressure sensors,and the change characteristics are analyzed by combining the landslide deformation and damage image information.It is found that the changes of pore water pressure and horizontal soil stress are synchronized with the rainfall process in time.Pressure and horizontal soil stress increase gradually with the beginning of rainfall,and decrease gradually with the stop of rainfall in the intermittent period of rainfall.(4)According to the model test characterization change and internal displacement change characteristics,the deformation process of this test can be divided into three stages:the slope foot deformation and collapse stage,the middle crack development stage,and the landslide model overall sliding stage.The evolution process is as follows:rainfall-rainfall infiltration-slope deformation and slippage--cracking in the middle-fracture expansion.