Analysis And Research On The Stress State And Soil Pressure Of Soil Behind Retaining Wall

The theory of earth pressure is an important content in the study of soil mechanics.It is an important basis for the design of retaining wall structure to reasonably analyze the mechanical mechanism of earth pressure and correctly calculate the earth pressure acting on the retaining wall structure.The classical Rankine theory(1857)can not be widely used b ecause of its ideal assumptions,while Coulomb theory(1776)can only get the resultant force of earth pressure,but can not get its distribution,and Coulomb’s assumption of linear distribution can not be supported by many test results at home and abroad.The distribution of earth pressure is a key problem.The research on the nonlinear distribution of earth pressure has made great progress from the discovery of soil arching effect and the application of thin layer differential method.The basic idea of the soil arching method is to assume that all elements of the sliding soil are in the limit equilibrium state,that is,the Mohr Coulomb yield condition is reached,and the Mohr circle is tangent to the shear strength line,Finally,the stress of horizontal thin layer is analyzed and solved.However,relevant research and theoretical demonstration show that when the earth pressure reaches the limit value,the internal elements of sliding soil may not reach the limit state completely.Therefore,the soil arching method based on the complete limit condition can not reflect this requirement.Moreover,when the current theory uses the principle of soil arching to study the distribution of earth pressure,it hardly studies the distribution of the reaction force on the sliding soil wedge,and does not consider whether the soil wedge can meet the overall moment balance under the corresponding earth pressure solution.Therefore,there are still some theoretical deficiencies in the current mainstream method of solving the earth pressure distribution through the soil arching effect.Correctly understanding and calculating the boundary conditions and internal stress state of the soil wedge will make theoretical progress in the calculation method of earth pressure.Based on the above research starting point,this paper puts forward different opinions that when the earth pressure reaches the stability,the soil inside the soil wedge and on the sliding surface does not completely reach the limit state(1)Analysis and Research on stress state of sliding wedge soil.According to the relevant literature at home and abroad,the ultimate failure state of soil is discussed,the behavior of soil state under the ultimate earth pressure is analyzed,and the distribution law of soil stress state under the ultimate earth pressure is explored from the perspective of experimental and numerical results.According to the assumption of complete limit state,the process of deriving the theoretical distribution of earth pressure by soil arch theory and thin layer differential method is analyzed,and the contradiction between theoretical assumptions and moment equilibrium condition is demonstrated.(2)The solution method of soil stress state and earth pressure distribution considering incomplete limit state is established.Based on the basic condition that the soil on the sliding surface reaches the limit state,but the soil elements inside the soil wedge and behind the wall do not reach the limit state completely,according to the two-dimensional equilibrium differential equation,through reasonable assumptions,combined with the improved stress state boundary conditions,the non limit stress state is described by the principal stress ratio parameter,The distribution of active and passive earth pressure on the back of the wall is shown.Furthermore,the resultant forces and the moment relative to the heel of the wall are solved by the integral of the distribution solution,and the static equilibrium and moment equilibrium equations of the sliding wedge soil are substituted to unify the micro stress and the macro static equilibrium,and the corresponding sliding surface dip angle and the non limit state parameters of the soil behind the wall are solved,So that the stress state of soil can meet all the basic mechanical conditions at the same time,the theoretical calculation model of active and passive earth pressure of cohesionless soil and the analysis method of stress state of soil behind the wall are established.(3)An extended method for calculating the active earth pressure of cohesionless soil is established.Based on the relevant conclusions of the stress analysis of cohesionless soil,the application scope of the theory is extended to the condition that the back of the wall is inclined and the filling behind the wall is cohesive soil.Considering the shear stress between horizontal thin layers,combined with the soil arch theory and coordinate translation method,the improved solution of sliding surface dip angle considering cohesion an d the calculation formula of active earth pressure are obtained.At the same time,the application scope of the theory is expanded.