Multiscale analysis of tunnel surrounding rock disturbance: A PFC3D-FLAC3D coupling algorithm with the overlapping domain method

Under the condition of high in-situ stress, the instantaneous excavation disturbs surrounding rocks, which shows different internal mechanisms on the different scales. At present, there still lacks numerical simulation algorithms for multiscale analysis in this field. A PFC3D-FLAC3D coupling algorithm with the overlapping domain method (ODM) was proposed. ODM can optimize the problem of energy reflection between different coupling domains and improve the accuracy of calculation. ODM was verified to a certain extent, including the velocity transmission and the mechanical deformation of models. In addition, the coupling algorithm with ODM was applied to the tunnel excavation under the assumption of the Kastner formula and the Songhua–Changchun diversion tunnel in China. In the tunnel excavation simulation, the simulation results showed that the coupling algorithm can characterize the stress distribution of surrounding rocks on the macro-scale, and reveal the phenomena of crack initiation propagation and large deformation on the micro-scale. By comparing with the empirical formula and the engineering data, it can be found that the coupling algorithm accurately and effectively realized the multiscale simulation of rocks disturbance. This research have some reference value for the multiscale investigation, which is the disturbance of surrounding rock caused by tunnelling.