Home – Home – Jornals – Journal of Mining Sciences 2013 number 2

It is difficult to numerically reproduce the common failure modes of the circular tunnel surrounding rocks, such as the slabbing or delamination in hard rock, and the zonal disintegration at great depth, based on continuum and homogeneous elastoplastic models. In the present paper, a grain-interface-matrix model is proposed based on continuum elastoplastic theories, and implemented in FLAC. Rock is simplified as a compound of the circular grains, rectangular interfaces, and remaining matrix. These components are modeled by squared elements with the same size. Results show that shear strains exhibit intersecting and multiple shear bands or slip lines extending intergranularly. High principal stresses in compression are found to form rings around the tunnel surface. For fine grains, the intensive rings are found, similar to the slabbing; while for coarse grains, the spacing between rings becomes large, analogous to the zonal disintegration. Thus, a unified mechanism of two kinds of phenomena is explained as the self-organization process of dominant microstructures subjected to forces. Nevertheless, the scale of dominant microstructures regarding or governing the process is different. For hard rock without joints, the scale corresponds to actual grains; while for jointed rock mass under high compressive stresses at great depth, the scale of rock blocks is dominant.