Study On The Influcence Of Foundation Condition On Seismic Response Of Retaining Wall And The Parameters Of Cushion Layer On The Back Of Retaining Wall

As a typical retaining structure to support slope and ensure soil stability,retaining wall is related to smooth stability and safety of traffic lifeline.Gravity retaining wall is still the most widely used retaining structure due to its rich material source and convenient construction.In order to ensure the safety of people’s lives and property,it is necessary to study the seismic performance of gravity retaining wall in high intensity earthquake area.This paper focuses on the vertical retaining wall as the research object,using ABAQUS finite element software to establish a numerical calculation model,on the basis of reasonable definition of the most adverse conditions of retaining wall displacement,analysis of earth pressure,acceleration,dynamic displacement and residual displacement,residual earth pressure and other seismic response data.The influence of soil foundation and rock foundation conditions on seismic response characteristics of retaining wall model is studied.In order to reduce the load and limit the displacement,the reasonable stiffness of the damping layer is studied and applied to the back of invert and bent retaining wall to verify the applicability of its damping effect.The main research contents and results are as follows:(1)The acceleration amplification coefficient of the back of the wall presents a concave curve distribution,which keeps constant or even decreases at the bottom of the wall,and then increases nonlinearly with the increase of elevation,and reaches the peak at the top of the wall.The acceleration amplification coefficients of soil foundation(0.90～1.50)are generally higher than those of rock foundation(0.74～1.20).When the peak acceleration reaches 0.6g,the displacement of high wall in soil foundation will exceed the allowable value.The displacement of rock foundation is less than that of soil foundation to a large extent before,at the epicenter or after the earthquake,so the allowable wall height can be up to 8m.(2)The dynamic earth pressure of the retaining wall at the most disadvantageous and dangerous moment shows that the dynamic component of earth pressure presents a triangular distribution along the wall height of"large in the middle and small at both ends".The positions of the resultant forces vary little,and the resultant forces are about 0.38～0.4 of the relative wall height in soil foundation,and about 0.45 of the relative wall height in rock foundation.The epicentral earth pressure of rock foundation is about 1.6～3.4 times that of soil foundation under the same condition,and the compressive stress of foundation is greater than that of soil foundation under the same condition.The compressive stress peak occurs at the toe of the wall and the rock foundation will be empty.Commonly used in engineering,the earth pressure time series peak value space line of each elevation measurement point has a large earth pressure resultant force,which is too conservative and wasteful.(3)Under the two kinds of foundation conditions,the displacement and earth pressure on the back of the wall change inversely and positively with the decrease of the stiffness of the cushion,and the load reduction rate of earth pressure increases gradually.Under the condition of soil foundation,when the peak acceleration reaches 0.6g,the compression deformation of cushion increases sharply,and its applicability is poor in high seismic intensity region,but stronger than that of rock foundation.Rock foundation is more sensitive to elastic modulus parameters of cushion with load reduction rate ranging from 30%to 60%.Combined with good load reduction rate and displacement control,it is suggested that the elastic modulus of the new cushion is 2MPa and the stiffness is6.67×10~3 k N/m under the condition of soil foundation.Under the condition of rock foundation,it is recommended to use buffer cushion of 0.5mpa～2MPa with rigidity of1.7×10~3～6.67×10~3k N/m.(4)The acceleration,displacement and earth pressure responses of the inverted and inclined retaining wall and the vertical retaining wall are similar under the two kinds of foundation conditions.The addition of cushion cushion has the effect of shock absorption and buffering on the inverted/inclined retaining wall,and the effect is good.Under the condition of soil foundation,the load reduction rate of inverted retaining wall and inclined retaining wall can reach 36%and 24%respectively.Under the condition of rock foundation,the load reduction rate of inverted retaining wall and inclined retaining wall can reach 32%and 35%respectively.