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Conference Paper

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Publication Details

This conference paper was originally published as Payne, D & Ward, B, Strata Management in Weak Roof Conditions at Crinum Mine, in Aziz, N (ed), Coal 2002: Coal Operators' Conference, University of Wollongong & the Australasian Institute of Mining and Metallurgy, 2002, 126-134.


Crinum Mine is located in the Bowen Basin and is operated by BM Alliance Pty Ltd. Longwall extraction commenced in 1997 in the 3.4m thick Lilyvale Seam and seven panels have been mined to date in the current block. The roof strata are variable and include some of the weakest longwall mining conditions in Australia. The immediate roof is predominantly a 15 to 25 MPa thinly bedded sandstone but includes weaker siltstone layers, typically 1m to 2m thick, with an average strength of 10 MPa. In some parts of the mining area the whole of the immediate roof appears to change laterally to a laminated siltstone with a strength as low as 2.5 MPa. As the presence of these weaker horizons can influence the effectiveness of the primary and secondary support, as well as the roof stability on the longwall face, delineation of roof conditions forms a significant part of the strata management process. Strata are interpreted into geomechanical units from the sonic velocity logs to enable zones of similar conditions to be identified. More detailed interpretations are made along section lines for maingate development and panel hazard plans. Roof support and longwall management strategies are based on the delineated roof conditions. Roof performance is monitored by means of dual height telltales, mechanical, and three and four point electronic telltales, GEL extensometers. A substantial base of mining experience has been accrued, enabling support requirements to be matched with confidence to the predicted roof conditions.

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