# Investigation into the Construction Response of Tunnels through Fault: Model Test
## 1 Introduction
Currently, two main research methods are applied: model testing and numerical simulation. Numerical simulation is a useful tool to analyze the stress and deformation of fault tunnels by changing the parameter settings. It is widely used to comprehensively analyze the construction response of fault tunnels under different influencing factors. For example, [PERSON] et al. [12] explored the surrounding rock stability of the Wuzhuling tunnel under different fault dips and thicknesses. [PERSON] et al. [20] established models for faults with different locations and thicknesses and discussed the stress, displacement, plastic zone distribution of surrounding rock, and lining stress of the tunnel. [PERSON] and [PERSON] [26] focused on the surface subsidence of the fault area during shallow tunnel excavation. [PERSON] et al. [27] studied the stress distribution of the surrounding rock in a deep tunnel in the fault zone. Some scholars [28; 29] have explored the construction response of reverse fault tunnels and found that the fault dip, fault movement, and overburden thickness can affect the tunneling process. [PERSON] and [PERSON] et al. [30; 31; 32] studied the influence of strike-slip faults on tunnel displacement relative to the surface and its own deformation. Model test and numerical simulation are both valuable methods for investigating the mechanical response of fault tunnels. While numerical simulation can analyze the stress and deformation of fault tunnels under different parameter settings, model tests provide more realistic results and are more intuitive in reproducing the actual construction project. Figure 1: Survey of tunnel fault fracture zone issues. For instance, [PERSON] [18] and [PERSON] et al. [33] conducted model tests to study the sand tunnel structure deformation in normal fault zones. [PERSON] et al. [34] pointed out that the normal fault could not cause the sudden destruction of tunnel lining structure, and the tunnel stability will increase with the increase of overburden thickness. [PERSON] et al. [35; 36] and [PERSON] et al. [37] investigated the construction response of the tunnel lining structure in reverse faults. [PERSON] et al. [38] simulated the shear failure process of dextral strike-slip fault tunnel. [PERSON] et al. [39] studied the occurred mechanism and evolution law of leakage water in operating tunnels crossing intersecting faults. [PERSON] et al. [40] used DLC technology to monitor the displacement and strain field, revealed the failure mechanism of deep tunnel lining in fractured zone. However, it has certain limitations to test the fault only as a smooth shear section. [PERSON] et al. [41; 42] concluded that smaller fault dip angles will lead to stronger dynamic response after studied the dynamic response of deep tunnels under different fault dip angles. Currently, there are numerous studies on the mechanical response of tunnel construction in various geological conditions, including tunnels in cold regions [43], loess tunnels [44; 45], karst tunnels [46], urban interaction tunnels [47], and so on. However, there is comparatively less research on the construction methods of highway tunnels in fault areas, and there is a lack of research on the coupling effect of different faults and construction methods. One commonly used method in the excavation of large-span highway tunnels is the center diaphragm (CD method), which can reduce the span of the excavation face and decrease the deformation of the surrounding rock. In this context, this paper proposes a three-dimensional model test method to investigate the construction mechanical response of highway tunnel excavation using the CD method under different fault dip angles, as well as to obtain the mechanical response laws of the surrounding rock and tunnel support structure under various fault dip angles. The results of the model test will provide valuable suggestions for the construction of tunnels crossing fault zones using the CD method.