Physical model tests of the surrounding rock deformation and fracture mechanism of mixed-face ground under TBM tunneling

Abstract

To investigate the surrounding rock deformation and fracture mechanism of mixed-face ground under tunnel boring machine (TBM) tunnelling, tests of a mixed-face ground model with TBM tunnelling were conducted by using a self-developed 3D large-scale simulation test machine and TBM excavation equipment. A fibre Bragg grating sensor and a distributed optical fibre sensor have been installed along the micro-pressure cell and are used to monitor the variation of stress, strain and displacement in the surrounding rocks while ‘uncoordinated deformation is observed at the interface’ during the excavation process. By comparing the experimental observation obtained in the soft and hard rocks located near the interface, a significant difference is observed in the deformation and stress measurement. The fractures observed in the shallow layer of the surrounding rock mass were mainly tensile fractures and tensile shear fractures, and pressure shear fractures were observed at a certain depth of the surrounding rock during TBM tunnelling. The results not only provide reference data on the mechanical behaviour of mixed surrounding rocks during tunnelling by TBM but also can guide construction units to prevent and control the disaster of TBM in tunnelling through mixed-face ground.