Mechanical performance of shared rock of neighborhood tunnels

Based on the Laojie-Shaibulu shield tunnels of Shenzhen Metro Line 3, and considering the complicated and three-dimensional stress state in the shared rock of neighborhood tunnels, the yield approach index (YAI) function on the basis of Mohr-Coulomb shear yield criterion and tensile yield criterion is introduced, and two methods, i.e. numerical analysis and centrifugal model test, are employed to analyze the mechanical characteristics of shared rock of the two styles of neighborhood tunnels, which are overlap tunnels and parallel tunnels. The results indicate that YAI value of the middle part is larger than that of the side parts both in the shared rock of the overlap tunnels and parallel tunnels, namely the middle part is relatively far from a failure state compared with the side parts. But the main reason is different. The former is mostly due to the reduction of the ‘radius’ of stress circle, and the latter is mainly due to the move-out of the ‘center’ of stress circle to improve the stress state of the middle part of the shared rock relatively. For shallow buried tunnel, the shared rock of overlap tunnels is in better stress state than that of parallel tunnels under the same static conditions.