Mining through areas affected by abnormal stress conditions at Syferfontein Colliery

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Authors

Legote, C.

Journal Title

Journal ISSN

Volume Title

Publisher

Southern African Institute of Mining and Metallurgy

Abstract

This paper investigates the conditions leading to the indefinite termination of production in four critical primary panels at an underground coal mining operation, the observed shortcomings in the mining approach, and the proposed strategy to mine through the affected panels. Initial assessment of the abandoned panel conditions indicated time-dependent strata failure, (i.e. bolted roof failure overrunning intersections), which occurred from mere minutes to up to four weeks post-production, with and without prior warning of failure. This prompted the constant re-supporting of back areas, which raised safety and productivity concerns. Investigation of the initial mining conditions revealed that the failures were due to a critical combination of factors, the chief of which was isolated horizontal stress. Other factors that were initially overlooked by the mine (i.e. influence of hydraulic stress, misinterpretation of borehole data), resulted in the conditions being described as abnormal. Remedial actions were determined, and in so doing, a new strategic approach was formulated to thoroughly address all failure concerns. The four panels were explicitly planned to serve as the main intake and return airways for the recently commissioned secondary ventilation shaft, as well as providing access to millions of tons in proven coal reserves. It is thus imperative to mine the panels. A feasibility study showed that the proposed strategy set for implementation would be financially viable.

Description

Paper written as project work carried out in partial fulfilment for BEng (Mining Engineering) degree.

Keywords

Critical primary panels, Time-dependent strata failure, Horizontal stress, Proven reserves, Termination of production

Sustainable Development Goals

SDG-04: Quality education
SDG-08: Decent work and economic growth
SDG-09: Industry, innovation and infrastructure
SDG-12: Responsible consumption and production
SDG-13: Climate action

Citation

Legote, C 2015, 'Mining through areas affected by abnormal stress conditions at Syferfontein Colliery', Journal of the Southern African Institute of Mining and Metallurgy, vol. 115, pp. 265-269.