A Parametric Study of Blast Damage on Hard Rock Pillar Strength

Abstract

Pillar stability is an important factor for safe working and from an economic standpoint in underground mines. This paper discusses the effect of blast damage on the strength of hard rock pillars using numerical models through a parametric study. The results indicate that blast damage has a significant impact on the strength of pillars with larger width-to-height (W/H) ratios. The blast damage causes softening of the rock at the pillar boundaries leading to the yielding of the pillars in brittle fashion beyond the blast damage zones. The models show that the decrease in pillar strength as a consequence of blasting is inversely correlated with increasing pillar height at a constant W/H ratio. Inclined pillars are less susceptible to blast damage, and the damage on the inclined sides has a greater impact on pillar strength than on the normal sides. A methodology to analyze the blast damage on hard rock pillars using FLAC 3D is presented herein.

Estimation of Damage Induced by Single-Hole Rock Blasting: A Review on Analytical, Numerical, and Experimental Solutions

“…When a rock is idealized as a continuous medium, continuum-based approaches such as FEM [75][76][77][78][79][80][81] or FDM [82][83][84][85][86][87] are usually employed to simulate the model. However, the rock is modeled as a set of structural units (such as springs, beams, etc.)…”

An improved pillar design methodology

“…The dip of the discontinuity has a dominant effect on the pillar bearing capacity, specifically when the dip is between 30° and 60°. Jessu, Spearing, and Sharifzadeh (2018) researched the influence of discontinuities in horizontal and inclined pillars. The results show that a discontinuity has a minimal effect on pillars with a larger width-to-height ratio in horizontal pillars.…”

“…A linear relationship developed between the average strength factors due to blasting (RF B ) and width-to-height ratio of the pillars can be written as: [16] This reduction factor is based on the maximum blast damage that can occur on the pillar, which can be quite conservative. A table (Appendix B) has been developed by Jessu, Spearing and Sharifzadeh (2018) to evaluate the reduction factors for different blast damage factors and blast damage thickness. One of the main limitations is the specific range of the width-to-height ratio (between 0.5 and 2.5).…”

“…A flow chart was developed to apply the blast correction for the improved pillar design methodology as shown in Figure 14 (Jessu, Spearing, and Sharifzadeh, 2018).…”

A case study of the periodic fracture control of a thick-hard roof based on deep-hole pre-splitting blasting

“…To avoid the problem of calculation interruption and reduced simulation accuracy induced by the severe distortion of the Lagrange element meshing during the blasting process, the partition of the rock mass and explosive in the modelling was meshed using Euler elements, and the multi-material ALE algorithm was used, which allows element deformation and explosive detonation product diffusion. According to related research results, the numerical model and field application adopted the Class-2 coal mine permissible emulsion explosive (Gorgulu et al, 2015; Jessu et al, 2018). The kinematic hardening plastic model (MAT_PLASTIC_KINEMATIC) was employed to characterise the rock breakage and fracture process with the Cowper–Symonds high strain rate model. where σ 0 is the initial yield stress; c and p are the Cowper–Symonds strain rates and ξ p eff is the effective plastic strain.…”