The rock mass disturbed by the excavation or other load will evolve from non-equilibrium state to equilibrium state with time-dependent deformation and damage. The simulation of nonequilibrium evolution is very important for evaluating the long-term stability analysis for arch dam, slope or underground engineering. This paper presents the effective driving stress based on Duvaut-Lions viscoplastic model, in which overstress exceeding yield surface is taken as the effective driving forces of non-equilibrium evolution process. The expression for finite element method has been finished based on a specific creep and damage model. It is implemented in TFINE, which is a Three-dimensional FINite Element method program, and then used in the simulation of the non-equilibrium evolution for rock mass. The distribution of driving forces and the law of evolution have been analyzed.
The large-scale and complicated rock structure is an important component of hydropower engineering and underground engineering around the world. The stability of rock structure is crucial to the safety of these projects. Excavation and reservoir impoundment for dam, slope and underground structure have an intense disturbance on natural evolution of geologic body leading to the serious stability problem of rock structure and threatening the safety of engineering (Huang 2005).
The time-dependent deformation and damage are the important factors in evaluating long-term stability of rock structure. The intense disturbance deviates the geologic body in critical stability from equilibrium state to non-equilibrium state. And then, the geologic body evolving from non-equilibrium state to equilibrium state would result in time-dependent deformation and damage of rock mass. The sustaining damage and creep will generate a large inhomogeneous deformation affecting the stability of the structure. With dynamic viewpoint, these stability problems can come down to the "non-equilibrium" evolution problem of the disturbed rock mass and structure. Stability or instability is only the intermediate state or final result of structure evolution.