Elastoplastic analysis of jointed rocks using a coupled finite element and boundary element method

Abstract

SUMMARYThis paper presents a coupled, elastoplastic, finite element and boundary element method for the twodimensional, non-linear analysis of anisotropic jointed rock. The non-linear and anisotropic behaviour of a jointed rock mass is simulated by representing the mass as an equivalent anisotropic, elastoplastic continuum, so that the influence of the jointing system is 'smeared' across the continuum, i.e. the individual joints are not modelled as discrete entities. Numerical examples have been solved to verify the capability, accuracy and efficiency of the present technique. The proposed technique has also been applied to the analysis of tunnel excavation problems in plane strain. The effects of anisotropy and non-linearity of the jointed rock mass during excavation have been investigated in some detail.

Micromechanical approach to effective viscoelastic behavior of jointed rocks

“…Similarly to the elastic upscaling problem, the viscoelastic concentration problem (20) admits the following homogeneous stress solution…”

A triangular caving subsidence model

“…The key parameter to be determined in this subsidence model is the value of the volumetric strain, which may be estimated either from measurements or calculations of void ratio, which depends on effective stress and vice versa, observations and past experience, or from rigorous analyses of jointed rock masses. 7 Notice that, this model is mainly based on the assumption that only the rock in the caved triangular zone will certainly collapse into the seam void. In other words, this model is unable to predict or study the complex behaviour and localised progressive failure (due to deformation and fracture), of both the overburden layers of the rock mass and the coal lateral pillars, for which rigorous and rational numerical methods of analysis are essential.…”

“…However, most methods introduced to the practical mining engineer are either highly empirical and site specific, 2 or highly theoretical or impractical in terms of parameters to be measured or assumed. [3][4][5][6][7] There is certainly a gap between these two extreme approaches in order to aid engineers who are looking for a simple and widely applicable analytical tool. This short paper presents a simple model for estimating potential maximum ground surface subsidence over underground coal mines and the required volume of remedial fill or grout materials for reducing subsidence.…”

Nonlinear analysis of NATM tunnel construction with the boundary element method

“…The usual approach consists in using the FEM to simulate the tunnel lining and the zones around the tunnel which undergo plastic deformation and in using the BEM to simulate the elastic zones of the rock mass. However, most of this work focuses on 2D modelling only [22,26,29]. Furthermore, the use of the BEM for the nonlinear zone and the direct coupling of the boundary elements with the finite elements for the tunnel lining has -to the best of the authors' knowledge -never been discussed in 3D.…”