A novel structural system to protect pipe-jacking tunnel subjected to normal faulting: Physical modeling

Tunnels are inherently susceptible to deformations induced by fault activity. However, the current state of the art lacks robust countermeasures tailored to mitigate tunnel damages. In response to this gap, this study proposed a novel structural system for the pipe-jacking tunnel to mitigate the damages during normal faulting. This system is composed of a circular pipe segment complemented by a rigid concrete shelf that is securely affixed to the segment. Seven sandbox tests are conducted to investigate the effectiveness of the novel structural system, considering different structure types and different tunnel locations. The results show that the normal fault deformation threatens the safety of the tunnel, where both great rotation and additional bending moments occur in the tunnel. The novel structural system can protect the pipe-jacking tunnel at normal faults. The tunnel rotation is reduced by the shelf through anti-rotation torque on the shelf. The additional bending moments could be decreased to some extent as well. The existence of the shelf may prevent the development of new ruptures in some situations.