Theoretical Calculation Of Stress And Deformation Of Circular Pit Retaining Wall And Its Stability Analysis

The classical Rankine and Coulomb theories are proposed to be used for the earth pressure problem of the plane earth pressure.However,they are not suitable for the calculation of the earth pressure of the circular foundation pit retaining wall due to the earth arch effect of a wall in space.This paper adopts the limit equilibrium analysis of the sliding wedge,and considers the equilibrium relationship between the positive pressure acting on the two radial sections of a sliding wedge,the self-weight of a sliding wedge,the sliding surface reaction force,and the force imposed by the retaining wall,thereby develops a new mathematical theory for calculating the earth pressure distribution of the circular retaining wall in a circular foundation pit.Based on a calculation example,it is found that the active earth pressure obtained from the new theory of this paper is 13.3%～14.1% smaller than that given by the classical theories for the retaining wall of a circular foundation pit within 30 m depth,and the degree of smallness enlarges with the increase in depth.In addition,along the vertical direction,the variation of the horizontal component of soil pressure intensity in the classical theory is linear while the variation obtained from the new theory of this paper is nonlinear,which is consistent with the actual situation of a circular retaining wall.The theory in this paper is a more economical and safe method of calculating earth pressure on curved retaining walls,which can be applied to the engineering design to ensure the safety of circular foundation retaining wall during construction and use,while significantly reducing the cost of construction and maintenance.According to the theoretical basis of shell buckling in the elastic stability theory of Timoshenko and the basic formulas of elastic mechanics,the differential equations of displacement,bending moment and shear force of the retaining wall of a circular foundation pit are established.Using the weighted residual method to set up a system of functions and solve the differential equations with the help of MATLAB,to obtain the calculation formulas of displacement,bending moment and shear force of the retaining wall of a circular foundation pit.By comparing the displacement semianalytical solutions obtained by the weighted residual method and the displacement calculation results of ABAQUS,it is found that the trends of both are consistent and the values are relatively close.Therefore,the semi-analytical solution proposed in this paper can be applied to practical engineering problems to assist in the design calculation of foundation pit projects.With the use of ABAQUS,an elasto-plastic model is established to analyze the stress and displacement of the specific circular foundation excavation and support project.The Concrete Damaged Plasticity(CDP)model and the Mohr-Coulomb Plasticity model are used to describe the concrete diaphragm wall and the soil,respectively.By analyzing cloud diagrams of stress and deformation of the diaphragm wall and the soil,the changes in stress and displacement during the excavation of the circular foundation pit are discussed and summarized.