Characterisation of Fine Particles Generated at Draw points During Sub-Level Cave Mining for Assessment of Mud Inrush Hazard

Abstract

The inundation of mud, known in the industry as ‘mud inrush’ is a hazard associated with caving mining methods. Ineffective inrush management strategies can result in sections of the mine lost, or in some cases, fatalities. Previous studies have focused on water and various percentages of fines (particles <2mm - <5cm) in draw points as risk indicators for the hazard. Standardised material tests were conducted on samples collected from a sub-level caving operation in Australia. Concrete slump tests were carried out on two in-situ mud samples based on their observed mobility. The immobile sample had 6% more material below 300μm and required a 2% higher moisture content to begin slumping and turn from plastic to soft flow. Shear strength tests reflected the higher plasticity of the immobile sample with a cohesive strength of 23.08 kPa compared to the second mobile sample of 9.16 kPa. The elemental assay revealed the mobile sample had lower iron oxide, and higher silicon oxide content than the immobile sample. The work presented in this paper indicates that fine fractions <0.6mm noticeably affect laboratory test results that are hypothesised to relate mud flowability and potential hazard.