Study Of Active Earth Pressure Of Cantilever Retaining Wall Based On The Finite Element Calculation

Cantilever retaining wall,a kind of retaining wall is familiar light retaining wall in our country over the last few years.It is widely used in river regulation,highway construction,landscape renovation and other projects because of its simple structure,light weight,easy to factory production and economy.The reasonable determination of soil pressure is the key to design for cantilever retaining wall.The past earth pressure calculation method of cantilever retaining wall is to take the attachment of wall heel points with wall vertex or the vertical plane of wall heel points as imaginary wall back,then calculate the earth pressure of imaginary wall back with Rankine's and Coulomb's earth pressure theory.This method which ignored the actual fracture surface after cantilever retaining wall,has a large gap with the actual situation of the project.In this paper,we establish the elasto-plastic finite element model of cantilever retaining wall,wall soil and foundation by using ANSYS,seek the position of the first and second fracture surface under the limit state,research the distribution law and influencing factors of the cantilever retaining wall in active earth pressure under the limit state by segmented displacement constraints and contact analysis.The main work and conclusions are as follows:(1)When the cantilever retaining wall reaches the active limit state,the first and the second fracture surface shall be produced in the fill soil.The first and second fracture surfaces are formed near the heel,go through the filling inside,respectively by the direction of away from and near the wall,run through in the "V" type.The second fracture surface is the inherent characteristics of the cantilever retaining wall,and makes the part of the backfill soil above the heel is protected against shear failure,moves with the wall.According to the geometric parameters of the cantilever retaining wall,the second fracture surface can be divided into two kinds: the straight second fracture surface which does not intersect with the wall plate and the broken line second fracture surface which intersects with the wall plate.The filling soil will produce the third failure surface which is parallel to the first failure surface and meets with the second fracture surface when second fracture surface is broken and internal friction angle and cohesive force are smaller.(2)The internal friction angle and cohesion are the shear strength indexes of soil.The stronger the shear failure capacity of soil,the greater the wall displacement required to reach the limit state with the increase of the internal friction angle and cohesion.When the displacement of the wall is certain,the area of plastic deformation decreases with the increase of internal friction angle and cohesion.The filling soil surface dip angle has no effect on the second fracture surface mainly,and effects on the first fracture surface obviously.The bigger the filling soil surface dip angle,the greater the displacement of the wall required to reach the limit state,the greater the plastic deformation area of the first fracture surface,the more destructive soil.(3)When the second fracture surface is broken,the filling between the fracture surface and the wall is protected from shear failure.When the cantilever retaining wall moves,this part of the soil will be moved together with the wall,so that it can be considered as part of the wall and the stress on the fracture surface is the earth pressure of cantilever retaining wall.The horizontal earth pressure acting on the second fracture surface decreases with the increase of soil internal friction angle,cohesion and elastic modulus.Due to the influence of ground friction,the horizontal earth pressure is gradually decreasing near the heel.The vertical soil pressure on the fracture surface increases with the increasing of the volume of the soil mass above it.The internal friction angle,cohesion and elastic modulus of the fill have little influence.When the second fracture surface is straight(the second fracture surface is outside the of ligature heel and top),the soil between the second fracture surface and the wall is not all moving with the wall,so the force of the fracture surface cannot be approximated as the retaining wall pressure.(4)No matter what kind of the second fracture surface,the horizontal resultant force decreases gradually and the resultant force point height increases,with the increasing of the internal friction angle,cohesion and elastic modulus.When the second fracture surface is rectilinear,the resultant force point height is less than the broken second fracture surface.(5)The practical example shows that the trial time in common computer calculation is about 6 ~ 15 minutes for the general size of cantilever retaining wall structure in the finite element method.Therefore it will has good application prospect to use finite element simulation of the cantilever retaining wall in engineering.The application of relevant finite element software is important to the design and check of cantilever retaining wall.