Analysis and Application of Surrounding Rock Mechanical Parameters of Jointed Rock Tunnel Based on Digital Photography

The strength, deformation characteristics and failure mechanism of tunnel surrounding rock are affected by the rock mass discontinuity. In order to explore the influence of the existence of rock mass discontinuity on the mechanical parameters and the instability mechanism of surrounding rock mass, the 3D digital photogrammetry system is used to measure the rock mass of Guangshan No. 1 tunnel to obtain the geometric information of discontinuities and its probability distribution model. Based on the information of rock mass discontinuity obtained by digital photography technology, the volumetric joint count (J(v)) and joint roughness coefficient (JRC) are introduced to quantitatively study the geological strength index (GSI), and Hoek-Brown strength criterion is used to analyze the mechanical parameters of tunnel rock mass. According to the strength parameters of tunnel rock mass, the numerical simulation of excavation stability of the tunnel is carried out. The research results show that 3D digital photography can accurately locate the joints exposed by rock excavation in tunnel site, and the quantitative GSI method can accurately determine the rock strength parameters in Hoek-Brown strength criterion, which is conducive to the accurate simulation analysis of tunnel surrounding rock stability. The research realizes the digital identification of information of jointed rock mass, quantitative analysis of rock mass mechanical parameters and numerical simulation of tunnel stability, which provides a fast and practical method for stability analysis of tunnel with joint development.