Soil Arch Effect Analysis And Earth Pressure Calculating Method Research Of Soil With Limited Width Behind The Retaining Wall

In the field of soil mechanics,the solution of earth pressure acting on retaining wall has always been one of the major topics of the discussion,and it is also a key problem in geotechnical engineering design.At present,classical Rankine and Coulomb methods or modified expressions based on classical theory are mostly used in traditional earth pressure calculation,but they must be based on the basic premise that the soil behind the retaining wall is a semi-infinite space.However,there are a lot of working conditions of filling with limited width behind retaining walls in practical projects have emerged,such as the foundation pit adjacent to the underground building,the slope support near the bedrock surface and so on.At this time,the classical earth pressure theory is obviously not applicable.In addition,the back of retaining wall with finite width is not absolutely smooth.The classical Rankine and Coulomb methods consider that the back of retaining wall is smooth and frictionless,thus ignoring the influence of wall-soil frictional force.However,according to the mechanism of soil arching effect,it can be seen that the friction between retaining wall and soil interface will cause the deflection of the main stress direction of backfill behind the wall,thus forming soil arching to further influence the distribution of soil pressure intensity.Therefore,it is necessary to introduce the analysis of soil arching phenomenon into the calculation of earth pressure with finite width.On the basis of previous studies,this paper has carried out theoretical research and laboratory tests on the calculation of earth pressure considering soil arching effect under the translational mode of finite width soil behind retaining wall.The main work is as follows:Firstly,considering the effect of friction between retaining wall and soil on the stress distribution of soil pressure,the stress state of soil is studied,so as to explain the deflection of principal stress direction and the mechanism of soil arch formation in the case of finite width soil.At the same time,three different soil arching forms,catenary,arc and parabolic,are compared and studied,and the expression of arc soil arching trace in this paper is determined.In addition,this paper summarizes the research results of previous methods for calculating the earth pressure of finite fill,and focuses on three typical methods,including limit analysis method,limit equilibrium method and horizontal layer analysis method.The advantages and disadvantages of these three methods are also analyzed.Secondly,the finite earth pressure model test of rigid retaining wall under active translation mode is carried out by using cohesionless sand soil samples.The failure modes and distribution of active earth pressure strength under different filling widths are studied,and a comparative study is carried out with Coulomb's method.The experimental results show that when the soil behind the retaining wall is of finite width,the failure surface of the fill is a continuous curve passing through the heel of the wall and the vertex of the fixed wall,and the failure surface of the fill moves outward with the increase of the width of the fill,and finally stabilizes at a fixed point,its position is always in the interior of the classical Coulomb failure surface.Finally,based on the results of laboratory model tests and variational theory,the failure modes of sandy soils with finite width in translational mode are discussed in this paper.The results show that the failure surface of the finite sand behind the retaining wall is a logarithmic spiral curve.On the basis of the slip surface,the phenomenon of soil arch is introduced to influence the soil pressure intensity.Assuming that the small principal stress arch is a circular arc soil arch,the theoretical formulas of the active earth pressure resultant force and its action point of the finite fill are derived by using the thin layer element method.The comparison with the monitoring results in the test and other scholar's academic results shows that the theoretical calculation results in this paper coincide with the monitoring results in the test.It can be applied to engineering practice.And then the parameters of active earth pressure of finite soil are analyzed.The results show that the distribution of active earth pressure of finite width filling along the depth of retaining wall is unchanged,which increases with the depth of retaining wall at first,then decreases gradually at a certain depth.In addition,at the same depth of retaining wall,the value of active earth pressure of finite width filling increases with the angle of internal friction and the angle of wall-soil friction.The value increases and decreases.After that,in the light of the characteristics of the finite width fill behind the wall,a reasonable definition method of the finite and infinite width fill is established.