Abstract
For the seismic safety of tunnels with cavity behind lining, based on the finite element method, the viscoelastic artificial boundaries are introduced to study the influence of the location of cavity behind lining on the seismic response of tunnel structure under vertically incident SV wave. The analysis results show that the cavity behind the lining has a significant effect on the seismic response of tunnel structure, and the appearance of cavity behind lining will significantly change the dynamic characteristics of tunnel structure; when the incidence frequency of wave is close to the natural vibration frequency of tunnel structure, the lining stress has the largest amplification when the cavity appears behind the vault; Regardless of the cavity location, the maximum of lining stresses always appears at the arched foot, and the vault stress has the largest amplification; Under the Taft wave, the maximum stress 1.642 MPa of lining without cavity appears at the arched foot, and the minimum 0.118MPa at the arched waist, the stress amplification at the vault can reach about 760 %, which is unfavorable to tunnels. In addition, the soil property also has a great influence on the tunnel; the layered site will lead to the obvious change of the seismic wave, hence the geological data should be collected in detail in the seismic design of tunnel. Meanwhile it is proposed that the PE material can be filled back into the cavities behind the tunnel lining to reduce the earthquake damage of tunnels.
Highlights
A large number of tunnel earthquake damage investigations have shown that strong earthquakes will cause various degrees of damage to the tunnel lining structure, and the tunnel earthquake damage may be more serious when there exist some cavities behind the lining [1]
Zhao [47] analyzed the influence of different earthquake intensities on the acceleration and strain of the tunnel structure through the shaking table test and the finite element simulation when a cavity appears behind the lining vault, and the results show that the acceleration, stress and strain of the lining structure near the cavity will increase significantly
Taft seismic wave is introduced in the time domain solution
Summary
A large number of tunnel earthquake damage investigations have shown that strong earthquakes will cause various degrees of damage to the tunnel lining structure, and the tunnel earthquake damage may be more serious when there exist some cavities behind the lining [1]. Kamel and Meguid [39] used the finite element method to investigate the influence of different cavity size and position on the tunnel lining, and believed that the appearance of cavity would cause the damage of tunnel lining structure. Wang et al [42] used the elastic-plastic finite element numerical method to analyze the influence of cavities with different sizes, positions and depths on the lining, the results show that the cavity may lead to lining cracks or even damage, and change the stress distribution of surrounding rock, which is prone to greater damage. Zhao [47] analyzed the influence of different earthquake intensities on the acceleration and strain of the tunnel structure through the shaking table test and the finite element simulation when a cavity appears behind the lining vault, and the results show that the acceleration, stress and strain of the lining structure near the cavity will increase significantly. The method of applying equivalent nodal forces on the viscoelastic boundary nodes is adopted to accurately simulate the ground motions of two-dimensional tunnel with cavity behind lining at both time domain and frequency domain, and the reinforcement measures for the cavity will be proposed
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