Numerical Research For Nonlinear Continuous Phase Transition Model Of Zonal Disintegration Of Rock Masses Near Deep-Level Tunnels

With the increasing needs for development and utilization of deep underground resource, there are numerous underground chambers having been built in recent years. Compared to the shallow rock mass, rock mass near deep-level behave remarkable non-linear mechanical characters when deformation and fracture are involved. Zonal disintegration, as a typical non-linear feature of deep-level rock mass, has coursed an increasingly widespread awareness. Many experts and scholars have conducted a series of researches on this phenomenon, and a plentiful conclusion have been draw in the fields of in-situ observations, model testing, theoretical researches and numerical simulations.In this paper, the non-linear governing equation of continuous phase transition model for rock masses near deep-level tunnels, which has a significant theoretical direction to analysis zonal disintegration of rock mass, is researched under the framework of second order phase transition and internal variable theory. The major research contents of this paper are as following:(1) The non-linear governing equation, which is a diffusive-like partial differential equation, of phase transition model is analyzed by utilizing phase plane analysis method. Taking the coefficients varing with the dynamic process of micro cracks into account, three basic solutions to non-linear equation can be solved: periodic solution, soliton solution and divergent solution which are corresponding to the phenomena of stable zonal disintegration, the propagation of strain wave and inner rock brust.(2) The stable periodic solution is solved by using finite difference method and the effluences of non-linear items on period and attenuation velocity are analyzed. The non-linear solution can describe zonal disintegration phenomenon better, when compared to linear solution.(3) The sensitivity of coefficients of non-linear equation are discussed. Combined with elastic foundation string theory, the physical mechanism of the coefficients are studied. Taking equivalent stiffness as a starting point, the effects exerted by coefficients on the solution have been given qualitatively.(4) The evolutional solution can be obtained with adopting appropriate initial condition, boundary condition and step length. The strain wave will propagate into the rock mass as a kink wave. The solution obtained can describe strain wave propagating as a kink wave exactly. The sensitivity of coefficients is studied. The influences of coefficients on the propagation velocity and amplitude of kink wave are researched.