LABYRINTH® has been used to quantify blast damage pre-conditioning.
Pre-conditioning (damage/weakening) of rock through blasting has the potential to improve cave productivity (cave propagation and fragmentation), whilst also potentially improving mill throughput. A full-scale experiment was conducted to evaluate the effect of blasting upon both rock mass and intact rock strength. Blast damage was quantified at both macro (visible) and micro (x-ray microCT) scales. From a cave mining perspective, the objectives of the experiment were to; quantify the effect of confined blasting on rock mass characteristics relevant to enhanced caving, and to provide calibration data for the purpose of numerically modelling alternative blast pre-conditioning designs. The experiment was located approximately 360 m below surface, and consisted of two 165 mm blast holes (60 m vertical holes) and eight HQ diamond drill holes (35 m horizontal holes). The diamond drill holes were used to sample the rock mass before and after the blast at varying distances from the blast holes. Rock mass blast damage was quantified both visually using core logging, and on a micro-scale using LABYRINTH® statistical analysis of x-ray microtomography data. On the visible macro-scale, the experiment indicated no change in geotechnical logging rock mass attributes, apart from a 78% increase in the number of hairline cracks within five metres (p value = 0.015). Micro-scale tomography results indicate significant localised intact rock damage up to 4 metres from the blast hole (p=0.0073). Calibrated numerical blast modelling has enabled alternative blast pre-conditioning designs to be evaluated for the purpose of enhanced caving.