Quantitative design method for anti-dislocation joints for tunnels passing through active faults

Abstract

Given the rapid development of Chinese transportation networks, a substantial number of tunnels are under construction or will be built in mountainous areas. However, certain tunnels must be constructed through active fault zones and will be destroyed by the dislocation of active faults. In the present Chinese codes, three measures are suggested, including over cutting the cross-section, setting up anti-dislocation deformation joints, and strengthening the lining, but there is a lack of quantitative design method. In this study, we present a design method for anti-dislocation deformation joints to improve the anti-dislocation ability of the tunnel passing through active fault. First, formulae related to the design method for anti-dislocation deformation joints were proposed to consider different fault and tunnel parameters. Then, the proposed method and the formulae were validated by experimental model tests and numerical analyses. The experimental models were prepared according to the geological data of the Beichuan-Yingxiu fault in Sichuan Province, China. Models on 1:30 scale were subjected to fault dislocation tests in two cases: tunnels with ordinary linings and tunnels with anti-dislocation deformation joints. The test results show that the longitudinal strain of the lining with anti-dislocation deformation joints in the fault fracture zone decreased to 32% of that of the ordinary lining, and the transverse strain also significantly decreased. The maximum normal stress between the surrounding rock and lining was approximately 80% of the value for the ordinary lining. The lining with anti-dislocation deformation joints experienced less damage than the ordinary lining. The results of numerical calculation suggest that anti-dislocation deformation joints determined by the proposed method could effectively reduce the forces and bending moments of the lining. The proposed method for anti-dislocation deformation joints could be used to mitigate the seismic damage of tunnels passing through active fault zones.