Meso fracture characteristics of granite and instability evolution law of surrounding rock in deep cavern.

In order to analyze the influence of meso-structure and meso-parameters on deep granite characteristics, a construction method of variable radius proportional clump model was proposed with particle flow method. The clump particle flow structure was constructed which suited the mechanical characteristics of granite. The deep cavern numerical calculation model of gradual particle density was constructed using the variable radius proportional clump model construction method, and the macroscopic fracture law of deep cavern surrounding rock was analyzed. The results show that meso parameters have lower effects on the compressive and tensile ratios of particle structures in the ball and clump models. It is also found that clump structure is greatly influenced by particle proportion and size while ball model is only slightly influenced by particle size. Furthermore, the compressive and tensile strength curves and fracture modes of numerical simulations and laboratory tests are in good agreement. In addition, the calculated results of the tunnel after simulated excavation are very close to the engineering practice. There are obvious shear failure areas on the right vault and left wall of the tunnel, and the shape and depth of the fracture area are basically the same.