Numerical Investigation of Time-Dependent Deformation in Rock Based on Numerical Manifold Method

Abstract

In this paper, the extended Nishihara model (ENM) is incorporated into numerical manifold method (NMM) to study time-dependent deformation of stressed rock, this model uses a nonlinear viscoelastoplastic component to achieve the tertiary creep of rock by using ENM based on numerical manifold method. The improved NMM based creep model is a combination of creep theory for the time-dependent deformation of rock and traditional NMM. Using time step-initial strain method, the improved NMM program divides viscous strain and large creep time into a series of increment time-step values to calculate creep problems. Parameter sensitivity analysis is performed and the Improved NMM program is validated against experimental data. Meanwhile, the influence of axial stress and confining pressure on time-dependent deformation of rock is also investigated. The fact that numerical simulations agree well with experimental results shows that improved NMM program is suitable for modelling time-dependent creep deformation of rocks.