Experimental Study on Deformation Failure Mechanism of Surrounding Rocks for the Deep-Buried Twin Tunnels in Inclined Layered Strata During the Excavation

The paper conducts a physical model test to study the deformation mechanism of twin tunnels excavated in deep-buried inclined thin-layered rock strata. During the excavation process, the infrared temperature measurement system and non-contact displacement monitoring system were used to obtain the deformation and the thermal response of the surrounding rock. Meanwhile, the strain monitoring was arranged in a circular pattern in the surrounding rock of each tunnel to acquire the strain characteristic. The deformation and failure mechanism of surrounding rock during twin tunnels excavation was studied through the comprehensive analysis of the experimental process images, displacement field evolution photos, infrared temperature evolution pictures, and strain change characteristics. Based on the experiment, a numerical calculation model was established to verify the displacement results of the physical model. The results showed that during the twin tunnels excavation, the deformation of the surrounding rock of the twin tunnels is asynchronous, and the deformation of the same tunnel is asymmetric. The maximum deformation was located in the left arch shoulder and the top area of the twin tunnels. The change of temperature field and strain field in the excavation process could reflect the change of surrounding rock deformation behavior.