Abstract:Aiming at the key problems such as excavation,deformation and rupture of surrounding rock, and mechanism of support structure in the experimental study of deep composite stratum TBM tunnel, based on the new method of transparent rock mass test, a composite stratum was developed to meet the test requirements. Also, the tunnel boring machine (TBM) simulation experiment device and the TBM segment production device were developed. On this basis, digital photographic measurement technology was used to compare and analyze the deformation and fracture of surrounding rock with and without support, and it revealed the deformation and rupture mechanism of the surrounding rock with and without support. Combined with the deformation and fracture of the surrounding rock, the characteristics of the thrust structure were reversed. The research results show that: 1) Under the premise of axial loading and surrounding constraints, the deformation and fracture mechanism of the surrounding rock on TBM tunnel in the deep composite stratum is shear-slip type (without support) and expansion type layer deformation type (with support). 2) The supporting structure can restrain the development of deformation around the tunnel, greatly reducing the deformation of the surrounding rock, cutting down the degree of fragmentation of the surrounding rock and increasing the bearing capacity of the surrounding rock by about 2 times. Also, the stress state of the surrounding rock is changed from local tensile shear to overall vertical compression, which reduces the stress concentration and makes the shallow surrounding rock form a certain bearing capacity. Moreover, the bottom drum is effectively suppressed, thus protecting the stability and safety of the tunnel. 3) Stress concentration occurs at the corners of the two walls in the TBM tunnel. In the actual project, measures such as backfilling grouting with bean gravel and local grouting reinforcement can be used to improve the stability of the weak link.