۱- Introduction

۲- Field investigation and analysis of tunnel damage through fault zone

۳- Design idea of sectional tunnel lining with flexible joints through fault

۴- Experimental method and apparatus

۵- Model test results and discussion

۶- Conclusions

References

Abstract

Tunnels often suffered severe seismic damage when passing through the active fault in high intensity earthquake area. The fault movement might be divided into fault movement and seismic motion under the strong earthquake action, and both of them could have the significant influence on the stability of tunnel structure. To improve the seismic performance of the mountain tunnel through fault, a design idea or method of the between sectional tunnel structures with the flexible joint were put forward to run through the active fault and verified or analyzed by using the shaking table test. Firstly, the typical seismic damage characteristics of the tunnel passing through the fault were analyzed after Wenchuan earthquake; secondly, the sectional tunnel linings with the flexible joint were designed in the active fault zone under the strong seismic motion, and the basic theory of this design method was presented in detail. Thirdly, the scaled model shaking table test was carried out to study the seismic performance of flexible joints of tunnels under the normal fault action, and some key parameters of the test was designed, including similarity relationship, boundary condition, sensor layout, input earthquake wave and flexible joint design. The test results showed that the joints between sectional linings could make structure localize damage rather than global damage, and compared to seismic motion, the fault movement suffered more serious damage for the tunnel structure. The tunnel lining at hanging wall was more susceptible to damage or destroy than that at the footwall under the normal fault action, and the flexible joint could adapt to the differential deformation of fault during the strong earthquake. Lastly, the dynamic response of the tunnel lining demonstrated that the upper-structure of the tunnel mainly suffered the severe seismic load, while the lower-structure might experiences the imposed deformation of fault movement under strong earthquake motion. So the design method of the sectional tunnel lining with the flexible joint would be applied to tunnel structure design to improve the adaptive deformation ability of tunnel structure through active fault.

Introduction

For a long time, the underground structure has been generally considered to suffer a lower level of damage in comparison with the surface structure during an earthquake (Asakura et al., 2007). The tunnel engineering project will be prior to be recommended due to the advantages of shortening lines, smoothing the curve of traffic lines and resisting geological hazards and earthquake disaster (Yan et al., 2020a, 2020b). However, tunnels located in the active fault area are easily vulnerable to damage by shear deformation under strong ground motion (Kun and Onargan, 2013). A lot of tunnels are designed or constructed in China Western and inevitably cross through active fault zones in mountainous area with some disasters. Therefore, the damage mechanism of the tunnel through fracture zone should be firstly demonstrated under the strong ground motion, and some seismic design method need to be studied to improve the seismic performance of the tunnel running through fault zone in the high intensity earthquake area. A number of related researches have been carried out to investigate the damage mechanism and seismic design method for tunnels crossing the fault section including numerical simulation (Anastasopoulos et al., 2008; Wang and Zhang, 2013), theoretical analysis (Zhang et al., 2018) and model tests (Su et al., 2019; Wang et al., 2019a, 2019b). Researches have shown that the most severe earthquake damage occurs in fault fracture zones, followed by tunnel entrances and public road sections (Lai et al., 2017; Yu et al., 2016).