# Model Test on Effect of Ground Fissure on the Behavior of Oblique Two-Section Subway Tunnel
## 4 Conclusions  
In this study, a physical model test is performed to investigate the dynamic interaction between the ground fissure and an oblique two-section horseshoe-shaped subway tunnel under the subway dynamic load. The main conclusions are drawn as follows:  
1. The vibration-induced soil acceleration attenuates when crossing the ground fissure and the degree of attenuation has nothing to do with the propagation direction (from one side of the ground fissure to the other side). Nevertheless, for the scenario that the hanging wall of the ground fissure descends from the original place, a more significant attenuation is observed when the vibration propagates from the footwall to the hanging wall, while the enhancement phenomenon is observed with an opposite propagation direction;
2. The vibration near the ground fissure is stronger in the soil layer below the tunnel than that of the upper soil layer. The rapid attenuation of vibration intensity is identified when the vibration propagates from the lining to the lower and the upper stratum;
3. The additional contact pressure at the tunnel bottom is relatively larger than that at the tunnel crown when the hanging wall of the ground fissure does not move, and the minimum value is identified on both sides of the tunnel. A relatively larger additional contact pressure is also identified at the place on the same side as the vibration exciter. Additionally, when the hanging wall moves downward, an increase in additional contact pressure is observed at the tunnel crown in the hanging wall, while that at the tunnel bottom significantly decreases to a negative value. The additional contact pressure at the tunnel bottom in the footwall increases in such a condition, and that at the tunnel crown nearly decreases to zero. Notably, the additional contact pressure at the tunnel bottom decreases with the movement of vibration exciter from the footwall to the hanging wall, and the movement of the ground fissure has little effect on the additional contact pressure on both sides of the tunnel;
4. The excitation-induced additional strain at the crown and bottom of the tunnel are approximately zero with a condition of an inactive ground fissure. When the hanging wall of the ground fissure descends from the original place, negative and positive additional strain is identified at the crown and bottom of the tunnel in the hanging wall, respectively, implying a compression state. Meanwhile, positive and negative additional strain is observed at the crown and bottom of tunnel in the footwall, respectively, implying a tensile state.  
Funding acquisition, J.-K.Y.; Investigation, Z.-H.W.; Methodology, T.M.; Writing--original draft, L.L. All authors have read and agreed to the published version of the manuscript.  
Figure 24: Distribution of the maximum longitudinal additional strain at the tunnel bottom: (**a**) vibration exciter at 60 cm; (**b**) vibration exciter at 100 cm.  
**Funding:** The authors would like to give sincere thanks to the funding agencies that supported this research. This work was supported by China Geological Survey Project (Grant nos. DD20211314).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Not applicable.  
**Conflicts of Interest:** The authors declare no conflict of interest.