The phenomenon of zonal disintegration may occur in rock mass of deep tunnels.The zonal disintegration can be regarded as a continuous phase transition process of internal structure of rock mass near deep tunnels

and thus the continuous phase transition model is used to describe the main features of zonal disintegration.In this study

a nonlinear continuous phase transition model is developed for zonal disintegration based on the continuous phase transition theory presented in references[15-16]

and classical elasticity-plasticity theories.By using the phase plane analysis method

the characteristics of solutions of the nonlinear continuous phase transition model are studied and three different types of solution are obtained.Numerical methods are applied to solve the nonlinear governing equation of the model

and results are compared with those of the linear model.Numerical results indicate that the spatial distribution of deformation of rock masses is represented well by the nonlinear model.For instance

nonlinear solutions can be used to simulate the variation of the distance between two adjacent fractured zones in the radial direction and the occurrence of inner rock burst.At last

the effects of coefficients on the solutions are given and its physical mechanism is clarified by using the elastic foundation string theory.The developed nonlinear continuous phase transition model can be served as a guidance to investigate zonal disintegration near deep tunnels.