Simulating Large-Scale Supported Pillar Laboratory Experiments in 3DEC

ABSTRACT: Underground mine pillars are typically supported using rockbolts, wire mesh, shotcrete liners, or a combination of these methods to enhance stability and maintain their load-bearing capacity. The design of these supports is generally based on field experience, which is often site-specific, making them less applicable to all geological and loading conditions. Advancements in computational power have made it feasible to utilize numerical tools to simulate and analyze complex deformation behavior effectively. Discrete Element Methods (DEM) are more suitable than continuum modeling tools for simulating large displacements and accounting for the influence of rock support. This study employed a bonded block modeling approach in 3DEC to simulate pillar deformation and support behavior under monotonic loading conditions for three different width-to-height ratios (0.5, 1, and 2). These models were calibrated against large-scale laboratory compression test data for a porous limestone with a cross-section of 0.5 × 0.5 m2. The objective was to evaluate the ability of a model calibrated against unsupported pillar test results to reproduce observed ground-support interaction trends for supported pillar tests. The supports, such as grouted rock bolts, face plates, and wire mesh, were explicitly represented using built-in structural elements to resemble the laboratory tests, and their properties were calibrated using a trial-and-error approach until the simulation reasonably matched the laboratory results. The effects of the support systems on the peak strength, residual strength, and deformational behavior of the pillar were evaluated for all three width-to-height ratios. 1. INTRODUCTION Underground mine pillars play a crucial role in providing natural stability to the roof and ensuring safe working conditions for both workers and machinery. Despite engineering design efforts, the challenges of ground falls and pillar failures persist and continue to be concerns in the field. Consequently, support systems such as rockbolts, wire mesh, face plates, and shotcrete are frequently employed to stabilize pillars, limiting the progression of spalling and pillar degradation, and mitigating the associated risks of sudden or violent pillar failure (Kaiser et al., 1996; Mohamed et al., 2016). Therefore, pillar design should consider rock-support interaction in addition to common geological and loading considerations.