The Influence of Scale and Spacing Distance of the Lateral Karst Cave on the Surrounding Rock Deformation of a Shield Tunnel

According to the construction of the metro running tunnel in the carst region, with the method of the three-dimensional elastoplastic simulation for dynamic construction process of the shield tunnel, the influence of the cave size and spacing between the cave and the tunnel on the deformation and stress of surrounding rock is analyzed. The study results indicate: the cave has great influence on the surrounding rock deformation during the shield tunnel construction, the radial displacement of surrounding rock and its release rate show an increase tendency when there exists a cave, and the increase is found with the growth of the cave size; The cave size and spacing between the cave and the tunnel have great influence on the deformation of surrounding rock, the plastic zone distribution range and distribution form, mechanical characteristics of lining structure. The minimum safety spacing between the cave and the shield tunnel should not be less than the cave size through repeated demonstration. These results are instructive for the construction of the metro tunnel in carst regions.