Effect of Flexibility Ratio on Seismic Response of Cut-and-Cover Box Tunnel

Shamsher Sadiq,Duhee Park,Quang Van Nguyen,Hyunil Jung

doi:10.1155/2019/4905329

Shamsher Sadiq, Duhee Park + Show 2 more

Open Access

https://doi.org/10.1155/2019/4905329

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Abstract

Equivalent linear time history analyses are conducted to calculate the seismic response of various types of cut-and-cover single box tunnels. A finite-element numerical model is calibrated against the results of centrifuge tests. The calculated tunnel responses compare favourably with the measurements. A validated model is then used to quantify the seismic response of box tunnels. The flexibility ratio (F) is illustrated to have a governing influence on the tunnel response. It is shown that the previously developed relationship betweenFand the racking ratio (R) is applicable for a wide range ofFup to 20. It is also shown that an increase inFaccompanies corresponding increase inR, the spectral acceleration in the tunnel lining, and the shear stress along the tunnel lining-soil interface. The thrust in the tunnel lining is also revealed to increase withF, although the calculated value is significantly lower than the pressure on yielding walls. Additionally, the surface settlement is shown to increase with an increase inF.

Highlights

Tunnels constitute an integral part of the transportation infrastructure in urban areas
A two-dimensional (2D) plane strain finite-element analysis was performed on a cut-and-cover tunnel using the equivalent linear (EQL) soil properties. e numerical model was calibrated against the centrifuge results of Gillis [9]. e effect of F on the pattern of the deformation shapes, distribution of mobilized shear stress along the tunnel lining, thrust in the lining, and corresponding surface settlement are investigated
Where Δtunnel is calculated as the relative horizontal displacement between the tunnel top and bottom and Δfree−field represents the relative free-field displacement at corresponding depths. e calculated values of F and R are compared with the F-R curve presented in NCHRP-611 [47] in Figure 12. e measured responses from the centrifuge test performed by Gillis [9] are shown. e calculated F-R values fit very well with both NCHRP-611 [32] curve and Gillis [9] data points

Summary

Introduction

Tunnels constitute an integral part of the transportation infrastructure in urban areas. A wide range of studies using centrifuge tests [2,3,4,5,6,7,8,9,10,11], shaking table tests [12,13,14,15,16,17,18,19], and numerical simulations [7, 20,21,22,23,24,25,26,27,28,29,30] have been performed. A suite of linear dynamic analyses was performed for rectangular tunnels for which analytical solutions were not available in the guidelines of the National Cooperative Highway Research Program (NCHRP-611) [32]. A two-dimensional (2D) plane strain finite-element analysis was performed on a cut-and-cover tunnel using the EQL soil properties. A two-dimensional (2D) plane strain finite-element analysis was performed on a cut-and-cover tunnel using the EQL soil properties. e numerical model was calibrated against the centrifuge results of Gillis [9]. e effect of F on the pattern of the deformation shapes, distribution of mobilized shear stress along the tunnel lining, thrust in the lining, and corresponding surface settlement are investigated

Numerical Model

Conclusions

B21: Two-node beam element

H: Height of the tunnel