Impact of shield tunnel construction on the seismic responses of tunnels and stations
Disturbances caused by shield tunnel construction alter the stress state and mechanical properties of the surrounding soil,thereby affecting the seismic responses of the tunnel and sta-tion.Numerical simulations were conducted to analyze the effects of different degrees of stress state changes and shear modulus degradation on the seismic responses of the soil around the tun-nel,as well as the segment and station structures,during an earthquake.Results indicate that:(1)As the degree of stress state change(stress release rate)increases,the initial shear stress of the soil around the tunnel,shear strain at the tunnel bottom,and excess pore-water pressure also increase.In addition,the bending moment and axial force in the tunnel segment,as well as the relative horizontal displacement between the side wall and column of the station,increase.For example,the peak bending moment and peak axial force at the left arch shoulder of the segment caused by the earthquake with a 30％stress release rate are 165％and 527％higher than those with a 10％stress release rate,respectively.(2)As shear modulus degradation increases,the shear modulus of the soil around the tunnel decreases,leading to higher shear strain and excess pore-water pressure at the tunnel bottom.At the same time,the bending moment and axial force in the segment caused by the earthquake and the relative horizontal displacement between the side wall and the column of the station decreases.The larger the shear modulus degradation was,the smaller the bending moment and axial force of the segment caused by the earthquake,the smaller the relative horizontal displacements between the side wall and the column of the station.For ex-ample,the peak bending moment and axial force at the left arch shoulder of the segment caused by the earthquake with considerable modulus degradation were only 67％and 40％,respectively,of those without any modulus degradation.Therefore,the disturbance degree from shield tunnel construction evidently influences the subsequent seismic responses of the tunnel and station.Con-sequently,the influence of early shield tunnel construction on the changes in the stress state and mechanical properties of the surrounding soil should be considered in the seismic design.
万方数据
维普
