Shaking Table Test And Finite Element Analysis Of Seismic Response Of Rectangular Tunnel Structure In Soft Clay

In recent years,along with the advancement of urbanization,the floor space is far cannot meet the needs of the People’s Daily life,no longer pursue the speed of urbanization and to focus on quality at the same time,the last of the circular tunnel due to the low space utilization has been replaced with the rectangular tunnel,as a result,China urgently needs to speed up the transformation development and utilization of underground space.China is located between the Asia-Europe seismic belt and the Pacific Rim seismic belt,with extensive and frequent seismic activities,and is a country with many earthquake disasters.However,due to the huge cost and irreversibility of subway engineering,the earthquake disasters in the past show that once the earthquake damage occurs,the underground tunnel structure destroyed by earthquake will bring great difficulties to the earthquake emergency and post-disaster repair work.Weak foundation in soft clay will increase the damage of earthquake,so the study of seismic performance of underground tunnel in soft clay area is becoming an important subject.In this paper,the main structure and material of open-cut rectangular tunnel in a certain area are used for reference.The dynamic response law of rectangular tunnel under earthquake action in soft clay area is deeply studied,and the seismic dynamic response of rectangular tunnel under the influence of different tunnel wall thickness,different tunnel buried depth and different maximum shear modulus of soil is discussed.By analyzing the data of horizontal displacement and strain response of the whole tunnel,some conclusions are obtained which are of reference significance to practical engineering.The main research contents and analysis results are as follows:1.Shaking table scale test of rectangular tunnel in soft clay area with geometric similarity ratio of 1:50 was carried out,and the acceleration response,tunnel displacement response and tunnel strain response of the model were obtained.The dynamic response characteristics of tunnel structure under earthquake action were analyzed in detail,which provided a reliable factual basis for finite element simulation.2.through the soft clay constitutive model,selection of material properties,the determination of the damping coefficient of the tunnel,tunnel and soil contact surface setting,setting of boundary conditions,the initial ground stress balance and a series of steps to establish the rectangular tunnel-three-dimensional dynamic finite element model of soft clay,and the test and the simulation of acceleration,displacement and strain comparison found that the two results are in good agreement,Prove the correctness of finite element modeling.3.By analyzing the acceleration,displacement and strain of the tunnel under the action of three kinds of seismic waves with different seismic intensity,it can be seen that the seismic wave has a certain delay in the propagation process;With the increase of seismic wave intensity,the acceleration amplification coefficient decreases gradually.Soft clay has obvious amplification effect on seismic wave,and the amplification effect of soil in the upper part of the tunnel is particularly severe.The rectangular tunnel slows down the peak acceleration of the surrounding soil layer to some extent.The maximum strain in both the tunnel and the middle column is located at the bottom,and the minimum strain in the middle.The interlayer displacement ratios of the weak position at the corner of the tunnel section are all within the limit value of the code,which can meet the design requirements.4.The prototype numerical model was established and the parameters were analyzed.The results showed that the change of parameters had little influence on the distribution trend of displacement and strain.The thicker the tunnel wall is,the shallower the buried depth is,the smaller the relative displacement and the tunnel strain value are.With the increase of soil shear modulus,the interlayer relative displacement and strain response of tunnel first increase,while when reaching a certain critical value,the interlayer relative displacement and strain response of tunnel gradually decrease.