Dynamic Response of Composite Lining Tunnel with Buffer Layer: An Analytical and Experimental Investigation

Kaixiang Fan,Peng Min,Shuaishuai Wang,Yusheng Shen,Bo Gao,Gaoming Yan,Qing Zheng,Kaiming Bi

doi:10.1155/2020/5453138

Abstract

Composite lining is often designed for the mountainous tunnels in high-intensity earthquake areas. The application of the buffer layer will bring more advantages, while the shock-absorbing mechanism is still unclear currently. In this paper, based on the Fourier-Bessel series expansion method, the dynamic stress concentration factor of composite lining tunnel with buffer layer subjected to plane SV waves in the half-space is obtained. Then, the influence of geometric and mechanical parameters of the buffer layer on composite lining was systematically analyzed. Finally, the correctness of the analytical solutions is verified by series shaking table tests and numerical simulations. Results suggest that the buffer layer can play the role of “redistributing” the seismic load, and it can effectively reduce the dynamic responses of secondary lining but amplify in primary support. There is an optimal interval of the stiffness and thickness for the buffer layer. When the stiffness ratio of the buffer layer to surrounding rock is 1/10 ∼ 1/50 or the ratio of buffer layer thickness to inner diameters of secondary lining is 1/40 ∼ 1/20, the shock-absorbing performance is remarkable. The general damage observations in tests show that the crown, arch springing, and invert of composite lining in case of no buffer layer are prone to cracking under a strong earthquake. The invert of the composite lining is more susceptible to be damaged after adopting the buffer layer. In general, the analytical results were consistent with experimental and numerical results. The above study results may provide theoretical support and experimental data for the seismic design of composite lining tunnels.

Highlights

The underground structure has been considered to have better seismic performance compared with surface structure
It suggests that the buffer layer can reduce the dynamic stress of the secondary lining, but it will increase the dynamic stress of primary support greatly
Reducing the stiffness of buffer layer is beneficial to protect secondary lining, but it will increase the dynamic stress of primary support. erefore, the stiffness of buffer layer should not be too low

Summary

Introduction

The underground structure has been considered to have better seismic performance compared with surface structure. In terms of analytical methods, wave function expansion has been widely used in the dynamic stress concentration of tunnel structures, which can reveal the mechanical response mechanism of composite lining tunnel with buffer layer in essence and can be used to verify the numerical calculation and test results. In this paper, the wave function expansion method is adopted to study the dynamic stress concentration of composite lining tunnel with buffer layer subjected to plane SV waves at different incident angles in elastic half-space. The correctness and reliability of the analytical solution are verified by shaking table tests and numerical simulation Such studies could provide a reference for the seismic design of shallow-buried composite lining tunnel in high-intensity area. Where cp,s and cs,s are the wave velocities of P and SV in halfspace, respectively

When the Angle of Incidence of Plane SV Waves Is

Shaking Table Test and Numerical Simulation

Primary support4

So rock A5

Findings

Conclusions