Study On The Mechanism Of Earthquake Triggered Massive Cataclastic Structure Slope Departure Dramatically And Instability

Landslide is a common geological disaster,and it causes huge personnel and economic losses every year.Among all kinds of landslide disaster inducements,the landslide triggered by earthquake has the strongest disaster causing ability and is very common,with sudden,violent,high-speed and remote characteristics,which is significantly different from ordinary gravity landslide.Earthquake triggered high-speed remote landslide has always been an important topic in the field of landslide disaster research,but there is still a lack of systematic and complete research.Based on the typical massive cataclastic rock landslide(K24 landslide along Yingxiu—Wolong highway)triggered by Wenchuan earthquake and the high-speed long-distance landslide triggered by the shear failure of the rock mass in the locked section,this paper explores the starting dramatic mechanism of the locked slope and the instability failure mechanism of the massive cataclastic rock slope under earthquake action by combining with theoretical analysis,physical experiment and numerical simulation methods.The main research work is as follows:(1)Taking the K24 landslide along Yingxiu—Wolong highway as an example,the engineering geological conditions of the landslide area are collected and sorted out,and the landslide movement characteristics are summarized,which are divided into four stages: loosening and cracking,departure violent movement,ejection flight and impact collapse.The influence of seismic force,stratum lithology,geological structure and groundwater on the landslide is qualitatively analyzed.(2)This paper discusses the mechanical mechanism of rock mass seismic cracking failure and energy accumulation and shearing process of rock mass in the locked section,establishes the seismic dynamic calculation model of locked landslide slope,and based on the acceleration effect of clinical elastic impact and peak residual strength drop,considering the nonlinear characteristics of rock and soil materials,deduces the departure velocity meter of clinical elastic impact peak residual strength drop composite effect under the nonlinear failure criterion The calculation formula.The formula is used to calculate the departure velocity of K24 landslide,and the influence of nonlinear characteristics on the departure velocity is analyzed.(3)Based on the geological data of K24 landslide,the dynamic response of slope under earthquake is studied by shaking table test.The peak acceleration(PGA)amplification factor is used to reflect the response degree of slope model under earthquake action,and the influence of different seismic wave types,seismic input direction,acceleration amplitude,frequency and other seismic parameters on PGA amplification factor is analyzed.(4)Considering the relationship of different layers,three models of bedding layer,horizontal layer and anti dip layer are built respectively to analyze the failure process and instability mechanism of the three slope models.There are many cracks in the middle and upper part of the horizontal slope,and the rock mass disintegrates to form a loose rock mass assembly,and the tension shear sliding failure occurs along the bedding plane;the bottom of the anti dip slope is loose,and the upper rock mass is gradually toppling,The results show that there is tension crack toppling failure.(5)The failure degree of three slope models under earthquake action is compared.The results show that the anti dip slope has the weakest response,the widest failure range,a large number of disintegration in the process of failure,and the worst internal structural integrity;the bedding slope has the strongest response,less disintegration in the process of failure,the best internal structural integrity,the largest volume of sliding mass,and the most likely to form locked rock mass,which leads to ejection phenomenon;the horizontal slope has the least response Between.(6)Discrete element software PFC2 D is used to simulate the displacement field,contact bond field and contact force field of bedding slope test model with the increase of calculation time step,which shows that there is a concentrated tensile stress on the upper slope under earthquake action,the middle part is tensile and shear stress,and the lower part is compressive stress,which is corresponding to the theoretical distribution of slope stress state,and verifies the distribution of slope stress state and failure mode under earthquake action.