Numerical Calculation Method Of Reinforced Earth Retaining Wall Based On EFG-FEM

The reinforced soil technology has greatly improved the overall strength and stability of reinforced earth retaining wall,and has been widely used in China.At present,the finite element method(FEM)is the most common method to analyze the reinforced soil problems,which has high economy and reliability.However,the mesh of FEM is prone to distortion in the analysis of large deformation problems,which reduces the computational accuracy and computational efficiency.The Mesh-free methods(MFMs)only needs the node information and get rid of the grid constraint in the calculation process.MFMs has good precision and is suitable for solving the problems of large deformation of reinforced soil.However,it is difficult to apply the essential boundary conditions of the MFMs.The coupling of the MFMs and FEM can solve the problem well and give full play to the advantages of the two methods.Based on the above ideas,the Duncan-Chang model is applied to element-free Galerkin method(EFG)as a constitutive model of soil in the reinforced soil.The equivalent additional stress method is applied to EFG to simulate the reinforcement effect,and a hybrid numerical method of EFG-FEM is proposed.In this paper,all codes are compiled by FORTRAN and applied to centrifuge model test and field test of the reinforced soil retaining wall for the numerical analysis.The main conclusions are as follows:(1)In this paper,the directed coupled FEM-EFG method is used to calculate the reinforced soil problems,which simplifies the calculation process without constructing the shape function of the transition elements.FEM elements are arranged at the essential boundary,and uniform nodes of EFG are distributed in the rest area,which give full play to the advantage of FEM to apply the essential boundary conditions and the advantage of EFG to calculate the deformation.(2)In this paper,the Duncan-Chang model is used as the constitutive model of soil,and is applied to EFG for the numerical analysis of reinforced soil.The method for calculating the elastic matrix of background units in EFG is proposed.The formula of the nodal stiffness matrix is derived,and the application of Duncan-Chang model is realized in EFG.(3)The equivalent additional stress method is extended to EFG,and the equivalent additional stress method based on EFG is proposed in the paper.It is only necessary to add the equivalent additional matrix of reinforcements to the elastic matrix of soil in the calculation.The reinforcement effect is reflected on the additional stiffness matrix ultimately,and the stiffness matrix of reinforced soil can be obtained by superimposing it with the stiffness matrix of soil.(4)A new numerical method of reinforced soil ——EFG-FEM mixed numerical method is presented in this paper.In the method,the coupling boundary between EFG and FEM is calculated by the direceded coupled EFG-FEM method,the reinforcement effect is calculated by the equivalent additional stress method,and the Duncan-Chang model is used as the constitutive model of soil.The method results is in good agreement with the results of the centrifugal test and field test of reinforced soil retaining wall,which proves the correctness of the method a nd the ability to solve the engineering problems.