Failure Model And Stability Prediction Of Loess Plateau Slope With Cracked Under Earthquake

The Loess Plateau is one of the main areas in which moderate and strong earthquakes occur frequently and geological disasters occur frequently in China.In history,earthquakes caused more than 1.4 million deaths in the region,and earthquake-induced landslides(mountain walks)buried in groups in cities and towns.The village is the main cause of huge casualties,so the loess earthquake landslide disaster in this area has become the focus of geotechnical engineering.In this paper,the typical fractured slope and non-fissured slope on the north bank of Jinghe River in Kongtong District,Pingliang City,Gansu Province are selected as the research objects,and the comprehensive utilization of data collection,field investigation,indoor triaxial test and direct shear test are carried out.The large-scale shaking table test and numerical simulation,etc.,are analyzed and studied in this paper.Based on the characteristics of landform,geological structure,earthquake and landslide in the study area,the dynamic response characteristics of fractured slope and non-fissured slope on loess tableland are compared and analyzed considering the structure and seismic action of slope body with and without fissures on the edge of loess tableland.The instability failure model and the simplified model of stability prediction for fractured slopes on loess tableland are put forward in this paper.Key results include:(1)The seismic dynamic response characteristics of loess slopes with two kinds of structures,fracture development and no crack,are studied in this paper.Based on the theory of similarity,the results of laboratory triaxial test and direct shear test,two kinds of structural slopes with and without fissures on the loess tableland of Pingliang Kongtong district,Gansu Province,are selected to determine the proportion of similar materials,and to consider the slope structure and earthquake action two kinds of factors.The large-scale shaking table comparative model tests of two types of structural slopes with the dimensions of 1:25 are carried out.The general dynamic response characteristics and variation rules of the loess slopes with and without cracks on the edge of the loess tableland under earthquake action are studied.The process of instability and failure of the slope with cracks on the edge of thetableland under different intensity earthquake loads is observed emphatically in this paper.The results show that loess is the site of fracture development under earthquake.The most sensitive part of the plateau slope is affected by dynamic disturbance.(2)Numerical calculation and Analysis of dynamic response of Loess Plateau Slope using Abaqus finite element Software.Two kinds of structural slope models with and without fissures on the loess tableland are established.The dynamic time-history analysis of the two types of structural slopes is carried out using the infinite element-finite element coupling boundary and the Wenchuan Tangyu seismic wave input to the bottom of the model.Comparing the numerical results with the shaking table test results,the reliability of the test results can be well verified.The results show that the dynamic response characteristics of acceleration and displacement are basically consistent with the results of shaking table test.In addition,the second plastic zone is formed in the crack-developed slope near the crack on the edge of the tableland.The depth of the fracture is approximately the same as the depth of fracture development,which is due to the compression of the soil at the posterior margin by the development of the fracture.The spatial position results in the deformation tendency of the soil at the back edge of the soil.(3)Stress distribution,dynamic instability failure model and stability prediction and analysis model of fractured slopes in loess tablelandBased on the numerical results and the stress distribution characteristics of the horizontal site under the condition of gravity field,the stress distribution characteristics of the slope with cracks on the edge of the loess plateau under the condition of gravity field are given.Combined with shaking table test phenomenon and dynamic time history analysis of numerical calculation,it is concluded that under the action of earthquake,The failure modes of fractured slopes on loess tableland are as follows: earthquake induced-crack expansion-high longitudinal fissure development-high shear out of small mass soil mass,low shear out of large mass soil mass-accumulation slope foot.Finally,based on the characteristics of fractured slope in loess plateau,a simplified model suitable for the stability prediction and analysis of this kind of slope is put forward.