Study On Earth Pressure On Retaining Wall Under Finite Displacement

Classical Coulomb and Rankine earth pressure theory is characterized by clear concepts and simple calculations,so it is widely accepted and applied to engineering practice.In actual working conditions,the filling soil behind the retaining wall is not allowed to reach the limit state,nor is it allowed to reach the limit state at all depths.So the calculation of non-limit equilibrium earth pressure is an urgent problem to be solved.Therefore,this paper finds a new way to study earth pressure.By improving the previous theory,a definite formula for calculating the non-limit earth pressure with theoretical support is obtained.The main research work and conclusions are as follows:(1)In this paper,it is considered that earth pressure is a kind of force that reacts on retaining wall when filling soil is subjected to various forces.So the mechanical properties of fill is the key to study the earth pressure.The theory of non-polar pressure proposed by the research group establishes the relationship between soil-filled elongation of retaining walls and earth pressure based on the constructive Duncan-Chan model.Based on this theory,this paper has made improvements to find the relationship between the displacement of the retaining wall and the soil pressure.Therefore,the theory in this study also takes into account the mechanical properties of the filling.(2)In this paper,Rankine’s theoretical sliding crack surface is used as the deformation boundary of the backfill of the retaining wall,and the triangular area surrounded by the deformation boundary,the back of the retaining wall and the backfill surface is used as the deformation area in the displacement process of the retaining wall.The fill behind the wall is not uniformly deformed.This paper assumes the deformation law of the fill behind the retaining wall.Based on reasonable assumption,the deformation area and law of backfill are defined.(3)Based on the assumption of the range and law of the fill deformation,the relationship between the strain of the fill behind the wall and the displacement of the retaining wall is established.Then the relation between the displacement of retaining wall and earth pressure under the condition of finite displacement is deduced.Thus,This completes the theory of earth pressure under limited displacement conditions of its predecessor.(4)The calculation formula of the Unlimited earth pressure improved in this study is equal to the active and passive limit soil pressure of rankin,which calculates the displacement amount according to each depth of the retaining wall when calculating the boundary equilibrium state.The ultimate displacement of active and passive soil at different depths behind the retaining wall can be calculated.(5)With the help of discrete element software PFC,retaining wall models are created,and the four working conditions of the filled soil are discontinuous soils and clay soils under limited displacement conditions.By comparing the calculation results of theoretical and numerical model experiments in this study,it can be seen that the deformation area and the law of deformation of the filling coincide with the assumptions of this paper when the retaining wall leaves the filling.If the retaining wall moves in the direction of the fill,the deformation area of the fill is not exactly a triangular area,but the main deformation is within the triangle surface that we assume in this article.The calculation of earth pressure in theoretical model experiments and numerical model experiments is basically the same,confirming the rationality of the theory in this paper.