Stability Analysis Of Quasi-wedge Using 3D Discontinuous Deformation Analysis

The stability of rocky slopes is the key to engineering construction,such a cut slope formed by house construction excavation and bank slope in reservoir area of hydropower project,and road cut slopes,etc.all relate to the slope stability.The failure form of wedge in slope engineering only considers two sliding surfaces,while the bottom of Quasi-Wedge is not exposed to the slope surface.Traditional methods,such as stereographic projection method and limit equilibrium method,have some limitations in analyzing the deformation and displacement of Quasi-Wedge,while 3D DDA method has the common advantages of the finite element method and the discrete element method,and at the same time builds a bridge for the limit equilibrium method.In this paper,3D DDA method is adopted to simulate the safety factor of Quasi-Wedge stability,which is of great theoretical and value for studying various types of slope engineering and its stability.Firstly,the typical calculation methods of wedge stability are reviewed.The number of static equilibrium equations is less than the number of unknown physical quantities of the wedge,resulting in the wedge body stability problem being.By introducing different assumptions,the existing methods can transform the statically indeterminate problem to the static problem,so as to solve the safety factor of wedge.Therefore,the traditional calculation method of wedge stability is unable to solve the problem of Quasi-Wedge stability analysis.Then,the basic principle is introduced of 3D DDA.The small displacement and small strain of blocks in multiple time steps are accumulated to obtain the large displacement and large deformation of deformed blocks after a long time.And the penalty function method is used to ensure that normal blocks are not embedded in each other and the tangential blocks meets the contact conditions of Moore Coulomb's law.The 3D DDA analysis software was used to write the corresponding geometric and physical files,and the effectiveness of the3 D DDA modeling method was verified with the wedge-shaped model,arch model,and brick wall model.Follow by,the research on the stability of Quasi-Wedge bodies is carried out by using the 3D DDA analysis software.The normal contact force and tangent contact force on the three surfaces of the wedge-like structure are obtained through effective screening of the contact pairs.Based on the 3D DDA analysis software,the safety factor of the Quasi-Wedge structure is calculated.And the influence of the structural surface elevationangle and rotation angle on the safety factor is analyzed under the condition of different internal friction angle,and the law of the stability of Quasi-Wedge in rock slope is obtained.Finally,combined with an engineering example,this paper analyses the stability of the slope of the left arc section of the lower reservoir in the phase I of Fengning Pumped Storage Power Station.Based on the introduction of engineering geological conditions and the monitoring of slope status,we can analyze sliding possibility of potential unstable body and know that the sliding mode is Quasi-Wedge failure.Then the 3D DDA analysis software can be used to simulate the stability of the arc section slope.The simulation results show that the deformation trend of the slope is in the direction of NW.And the safety factor is larger than that of simplified calculation in the early stage of the project.