Research On Upper Bound Method Of Plastic Limit Analysis For Geotechnical Slope Under Earthquake

China is in the tackling period of eliminating poverty and building a moderately prosperous society in all respects.In recent years,China has carried out large-scale infrastructure construction in various parts of the country.A large number of geotechnical slope projects have inevitably appeared in transportation,water conservancy and hydropower,mining and other projects.The stability of slope shoulders the responsibility of ensuring the safe operation of the project and the safety of people's life and property.The instability of rock and soil slopes is caused by the combined effect of internal causes(geotechnical structure and physical and mechanical properties of materials)and external causes(earthquake,artificial engineering action,etc),and the instability often presents a variety of failure modes such as sliding and toppling.In this paper,with the support of NSFC project(51564026),the upper bound method of plastic limit analysis was applied to the field of limit state solution of geotechnical slope which can consider both sliding and toppling failure modes under earthquake action.The upper bound method of rock slope,rock-soil composite slope and masonry retaining wall slope under earthquake was studied in depth.The main research work of this paper was as follows:(1)Explained the research background and practical significance of this topic.The development and research status of slope stability research method,plastic limit analysis method,slope toppling failure research method,and seismic research method were introduced respectively.Aiming at the problems in the above studies,it is pointed out that it is necessary to use pseudo-dynamic method combined with upper bound theorem of plastic limit analysis to study the limit state of geotechnical slope under earthquake considering both sliding and toppling failure.(2)The basic concepts and basic principles of plastic limit analysis were systematically introduced,the upper bound theorem of plastic limit analysis was proved,the inference of the upper bound theorem was given,and the upper bound method of plastic limit analysis for studying the limit state of structures was introduced.(3)The pseudo dynamic method was introduced into the field of limit state analysis of slope under earthquake action.The earthquake action was simplified as the seismic inertia force acting on the centroid of slope element varying with time and space.The seismic acceleration and seismic inertia force of any slope element at any time can be obtained,which well simulated the seismic dynamic action.(4)Taking rock slope as the research object,the mechanical mechanism of interaction between rock block and interface under earthquake action was studied.Based on the upper bound theorem of plastic limit analysis,an upper bound method for plastic limit analysis of rock slope under seismic dynamic action,which can consider both translational and rotational mechanical effects of rock mass,was proposed by combining pseudo dynamic method,rigid block element dispersion idea and mathematical programming method.(5)Taking the geotechnical composite slope or masonry retaining wall slope under the action of seismic dynamics as the research object.Based on the upper bound theorem of limit analysis,the pseudo dynamic method was used to simulate the earthquake action.Combining the idea of rigid block element discretization with the method of mathematical programming,the upper bound method of geotechnical composite slope or masonry retaining wall slope which can consider both sliding and toppling failure under the action of earthquake was proposed.(6)The numerical solution strategy of upper bound method was put forward,the corresponding calculation program was compiled,and the simplex method of linear programming software CPLEX was used to optimize the solution.The upper bound solution of the ultimate bearing capacity(or safety factor)and the corresponding failure mechanism can be obtained when the geotechnical slope reaches the ultimate state.Based on calculation examples and practical engineering example,the calculation theory,numerical method and calculation program which were established in this paper were verified.The influence of seismic dynamic parameters,physical and mechanical parameters of slope material on the limit state and failure mode of the slope were also investigated.