Chengzhi Qi

One plastic gradient model of zonal disintegration of rock mass near deep level tunnels

In the present paper zonal disintegration phenomenon is investigated within the framework of gradient theories of elastic-plastic solids. Gradient of effective plastic strain is introduced as additional internal variable. Equilibrium equation and boundary conditions are obtained by using virtual work principle. Evolution equations for internal variables are obtained by using Clausius—Duhem inequality. For circular tunnels the governing equation for effective plastic strain is obtained from the above model. Solution of the governing equation for ideal brittle rock mass model is obtained. The obtained solution may describe zonal disintegration phenomenon very well.

Strain Gradient Model of Zonal Disintegration of Rock Mass near Deep-Level Tunnels

This paper presents one strain gradient model of zonal disintegration of rock mass near deep level tunnel. The governing equations and boundary conditions of the model are established. Numerical methods (quasi-Newton method and shooting method) are adopted to solve the obtained fourth-order equilibrium equations with higher order boundary conditions in terms of displacement. The stress field in elastic and plastic zones is obtained. The effects of model parameters on stresses distribution in surrounding the tunnel rock mass are examined. The necessary conditions for the formation of zonal disintegration are elucidated.

Modeling Deformation Wave in Rock Mass near Deep-Level Tunnel

In this paper deformation wave is studied on the basis of continuous phase transition theory. Relative shear strain is taken as an order parameter. The potential energy is obtained by analogy with the Ginzburg–Landau expansion of free energy. Hamilton’s variational principle is used to obtain the motion equation by which several types of deformation waves can be modeled. The results show that the proposed model is effective in modeling deformation waves.

Modeling the zonal disintegration of rocks near deep level tunnels by gradient internal variable continuous phase transition theory

Abstract The occurrence of alternating damage zones surrounding underground openings (commonly known as zonal disintegration) is treated as a “far from thermodynamic equilibrium” dynamical process or a nonlinear continuous phase transition phenomenon. The approach of internal variable gradient theory with diffusive transport, which may be viewed as a subclass of Landau’s phase transition theory, is adopted. The order parameter is identified with an irreversible strain quantity, the gradient of which enters into the expression for the free energy of the rock system. The gradient term stabilizes the material behavior in the post-softening regime, where zonal disintegration occurs. The results of a simplified linearized analysis are confirmed by the numerical solution of the nonlinear problem.

Equilibrium equations and boundary conditions of strain gradient theory in arbitrary curvilinear coordinates

Abstract Equilibrium equations and boundary conditions of the strain gradient theory in arbitrary curvilinear coordinates have been obtained. Their special form for an axisymmetric plane strain problem is also given.

Some energy relations of rock fracture at different structural levels

There exists a complex structural hierarchy in rock mass. Intimate connection between time and spatial scales exists at each structural level. Such a connection lies in the fact that the time before the rock fracture at each structural level is proportional to the size of geoblock at that level. In the present study, the principles of constant work density, constant energy flux, and equal power are found on a basis of such connection. They can serve as a tool for the analysis of deformation and fracture of rock mass at different levels.