Stability Analysis Of Pile Reinforced Slope By Upper Bound Method And Numerical Simulation Considering Three-Dimensional Effect

At present,the slope stability analysis mainly adopts the two-dimensional(2D)method,ignoring the influence of three-dimensional(3D)effect.In mountainous urban and infrastructure construction,the slope mostly locates in complex geologic environment with a large scale and shows remarkable 3D effect.How to quickly and reliably evaluate the 3D stability of slopes and guide the design of slope reinforcement is an urgent problem to be solved in related projects.In this paper,the upper bound limit method and the numerical simulation method are taken as basic means to conduct a series of stability analysis of 3D slopes,including derivations of upper bound solutions,example analyses,case studies,constitutive model development and numerical modelling studies.As a result,a 3D upper bound limit analysis method for evaluating stability of slope reinforced with piles is proposed,and 3D numerical simulation of slopes considering nonlinear characteristics of soil strength is implemented.The main work and achievements of this paper are as follows:1.The 3D rotational failure mechanism for stability analysis of slope reinforced with piles,including the effect of slope crest inclination and the failure mode of through toe and below toe,is established.The external power and internal energy dissipation equations are derived,and the upper bound solution to the 3D safety factor of the pile reinforced slope is obtained.To find the minimum value of safety factor,this slope stability problem is transformed into nonlinear programming problems.The corresponding constraints are given and the minimum safety factor is optimized by using the interior point method.Afterwards,the influence of crest inclination,slope angle,pile space,pile position and soil shear strength on 3D safety factor of the slope and the geometric characteristics of the critical slip surface are studied through a series of parametric analysis.2.A method to determine the critical buried depth of embedded anti-slide piles in 3D failure mode is proposed,which avoids the difficulty of directly determining the 3D secondary sliding surface through the top of pile.The failure characteristics of slope reinforced with embedded piles are analyzed.The calculation method of resistance power provided by embedded piles is discussed.The energy balance equation and the upper bound solution of 3D safety factor are deduced.The specific procedure of determining the critical depth of pile top is given,and the critical depth of pile top is obtained,which satisfies the requirements of both overall and secondary sliding stability.The effect of pile top depth on the 3D stability of reinforced slope is analyzed through examples.Moreover,the design parameters of embedded pile for stabilizing an engineering slope are put forward.3.The numerical analysis method of 3D slope stability considering the nonlinearity of soil strength is realized,and the stability characteristic of 3D slope under nonlinear failure criterion is studied.The nonlinear variation of soil strength with confining pressure is described by the generalized nonlinear failure criterion of power-law type.The selection of yield function and its numerical realization in principal stress space are discussed,and the elastic-plastic model associated with generalized nonlinear failure criterion is implemented in a finite difference program.The influence of nonlinear parameters c0/σtand m on the stability of 3D slope is analyzed by numerical examples.Finally,the numerical method combining strength reduction technique is applied to the stability analysis of 3D slope stabilized by anti-slide piles,and the difference between the 3D stability results of the slope under the linear and nonlinear criteria is analyzed.