Study On Calculation Method Of Active Earth Pressure For Limited Soils Considering Shear Stress Effect

In the process of rigid retaining wall deviating from backfill in translation mode,the soil in contact with the retaining wall has a tendency to slide along the back of the wall,which results vertical shear stress produced.The analysis of the soil stress state behind the retaining wall shows that horizontal shear stress should be exist.And the shear stress has a great influence on the distribution of active earth pressure,the resultant force of active earth pressure and the height of resultant force.Sliding plane is the critical factor to solve the active earth pressure of retaining wall.Not only the soil property of backfill should be considered,but also the width of backfill or longitudinal length of retaining wall should be considered when solving the angle of sliding plane.This can truly calculate the distribution of active earth pressure according to the specific engineering conditions.In this paper,the formula for calculating the angle of sliding plane of the limited soil after the retaining wall was firstly determined by the limit equilibrium theory.Then based on the horizontal differential element method,considering the shear stress deflection caused by the soil arching effect,the calculation about lateral earth pressure coefficient and mean shear stress coefficient was deduced.Additionally,a method was created to calculated active earth pressure distribution formula,and the method was proved reasonable by combining with a model test results.The results show that active earth pressure distribution is smaller and the height of resultant force is higher by the calculation without consideration of shear stress.The sliding plane deduced by the limit equilibrium theory approaches the Coulomb sliding plane with the increase of the distance between the parallel vertical walls.The finite element software ABAQUS was used to simulate the active earth pressure of the limited soil and the semi-infinite soil behind the rigid retaining wall.The theoretical values calculated by calculation method were compared by the simulation values in active earth pressure distribution and the resultant force of active earth pressure and overturning moment with the difference of parallel vertical wall distance.The rationality of the calculation method was further verified.Then the influence of the distance between the parallel vertical wall,the displacement of the retaining wall and the cohesion on the active earth pressure of the limited backfill soil was analyzed.On the basis of the above,the theoretical method of this paper was extended to the calculation of space active earth pressure.This paper determined the formula of limit height of spatial sliding soil and the distribution of active earth pressure.The results show that the distribution of active earth pressure at the same section of the retaining wall had obvious difference under the different longitudinal length of the wall.The shear stress has obvious influence on the distribution of the earth pressure near the sliding soil.It's not safe without considering shear stress.