Study On Deformation And Fracture Of Surroundin Rrocks In Deep Tunnel

With the increase of mining depth of a lot of coal mines and other undergrounds, exerted by the high in-situ stress and complicated environment in deep geology,the surrounding rocks of tunnel has complex deformation phenomenon with the excavation disturbance, the problem of deformation and fracture of surrounding rocks under excavation in deep tunnel has aroused widespread concern and attention, it has became a hot topic of rock mechanics discipline in recent years. This paper takes the deep tunnel as study object, the method of theoretical analysis and numerical were used to study the deformation and fracture law of surrounding rocks under excavation, the chief contents and results of this paper as follows:(1) For the problem of excavation in a deep and circular tunnel, it regards the excavation of surrounding rocks as dynamic process. In the theoretical analysis, this problem was decomposed into two problems: the force of the hole edge and the outer boundary; Quadratic parabolic function curve was used to simulate the change process of excavation unloading with time, Laplace transform method was adopted to obtain excavation force load, then carry on numerical calculation of inverse Laplace transform by the method of Den Iseger, the deformation and fracture law of surrounding rocks under excavation could be obtained by summing the two computing solutions. The static analytical solution of tunneling was obtained by the method of elastic and elastic-plastic mechanics from the perspective of static mechanics; Finally, the differences of the dynamic and static solution for the influence of the excavation dynamic load was obtained by comparing the two mechanical analysis results.(2) For the phenomenon of zonal disintegration in deep tunnel, mechanics analysis model was built whose surrounding rocks were divided into four regions that are a cracked region,an elastic region, a cracked region and an elastic region, with Mohr-Coulomb yield criterion, the mechanical behavior of the surrounding rocks was simulated by an elastic-plastic model and the analytical solutions for the stress, strain and displacement in the four regions were derived in a theoretically consistent way by using non-associated flow rule. Finally, the forming conditions of zonal disintegration for surrounding rock was derivsd by the different regions’ s boundary conditions and the existence states of stress and deformation.(3) Numerical simulations were carried out to study the deformation and fracture law of surrounding rocks after excavated with the influence of single factors such as tunnel depth, side pressure coefficient and angle between maximum horizontal principal stress and tunnel axial direction at first. Secondly, considering the effect of excavation unloading in circular tunnel, the study of deformation and failure mode of surrounding rocks at different side pressure coefficients and initial ground stresses was carried out which bases on the condition of physical and mechanical parameters’ s changing of surrounding rock during excavation process. It provides the theoretical foundation in order to analyze the stability of deep tunnel and to reinforce the cracked surrounding rock.