The Temporal And Spatial Distribution Of Zonal Disintegration Of Surrounding Rock Mass In Deep Tunnel

Due to the complexity of the environment of deep rock mass, the mechanism of deep rock deformation and failure is greatly different from the shallow rock mass. Zonal disintegration is one of the typical phenomenon in deep rock mass engineering. Meanwhile the deformation of the surrounding rock in the process of tunnel excavation would be influenced by each construction step. Therefore the zonal disintegration phenomenon shows obvious spatial temporal features. Owing to the poor consciousness for the failure process and characteristic of zonal disintegration, the accurate evaluation on stability of surrounding rock couldn’t made. These cause so many problems such as unreasonable support design and supporting opportunity after excavation. So far, the mechanism of zonal disintegration is not yet clearly known. But less effort has been made on the temporal and spatial distribution of zonal disintegration in the process of tunnel excavation. So it is urgent to do some study on the temporal and spatial distribution of zonal disintegration phenomenon.Aiming at the main influence factors of zonal disintegration, which are the post-peak softening rule of deep rock mass and the impact of stress rotation of surrounding rock during excavation, some study on zonal disintegration are made here:① By considering the post-peak rule of deep rock mass, internal variable gradient theory has been introduced. The term of internal variable gradient is added to constitutive model to analyze the influence of interaction between surrounding area. Based on the plane-strain analysis, the solution of inelastic equivalent strain of surrounding rock mass under hydrostatic and non-hydrostatic pressure is obtained. Then the distribution of inelastic equivalent strain of surrounding rock mass is determined.② Due to the underground tunnel forming in a gradually process, the stress around the excavation face would rotate under unloading condition. The stress of surrounding rock would change with the advancement of excavation face. In this case the simulation of process of a circle tunnel excavation is performed by using finite difference software. The analysis of longitudinal stress curve of tunnel with different initial stress level and different spatial position is conducted. Then the mass ahead of excavation face is assumed to be the half space problem. The solution of this part is solved using Hankel integral-transform method. Based on the analysis above, the temporal and spatial distribution of zonal disintegration is obtained, finally a 3D model of zonal disintegration in deep rock mass during tunnel excavation is established.③ According to the 3D model of zonal disintegration, the main influence factors of zonal disintegration is conducted. By analyzing the factors such as initial in-situ stresses, internal variable parameters and excavation velocity, the change law of size, length and quantity and evolution law during excavation of fractured zone is acquired.④ Finally the 3D model is applied to the roadways of Suncun coal mine to simulate the zonal disintegration which distribute in surrounding rock mass. Through comparison with the survey results, the reliability and feasibility of the present model is verified. Then the mechanism and influence factors of zonal disintegration occurred in the actual engineering are discussed.