Strength and failure mechanism of highly interlocked jointed pillars: Insights from upscaled continuum grain-based models of a jointed rock mass analogue

Abstract

An optimum design of mine pillars necessitates a reliable estimation of the rock mass strength. It is known that the Hoek-Brown failure criterion, with its strength parameters obtained using the Geological Strength Index, tends to underestimate the confined strength of interlocked jointed hard rock masses. Therefore, geomechanical designs based on this approach could lead to oversized pillars due to the underestimation of the pillar core strength. In this study, a two-dimensional finite element program was used to investigate the strength and failure mechanisms of jointed pillars. For this purpose, a previously calibrated grain-based model of heat-treated marble, an analogue for a highly interlocked jointed rock mass, was upscaled to simulate jointed pillars of various width-to-height ratios. The simulation results showed that the slope of the pillar stability curve obtained from this approach is steeper than those of existing continuum and discontinuum models of jointed pillars. This is attributed to the high degree of block interlock leading to higher rock mass strength at the pillar core. It is demonstrated that this modeling approach provides more realistic results in terms of pillar failure process compared to other continuum models, in which the rock mass is simulated as a homogeneous material.