Document Type

Conference Paper

Publication Date


Publication Details

This conference paper was originally published as Black, D, Aziz, N, Jurak, M & Florentin, R, Outburst Threshold Limits - Are They Appropriate?, in Aziz, N (ed), Coal 2009: Coal Operators' Conference, University of Wollongong & the Australasian Institute of Mining and Metallurgy, 2009, 185-192.


The 1994 outburst threshold limits imposed on coal mines operating in the Bulli seam were lower than the conservative value proposed by Lama in 1991. Equally conservative is the DRI900 method for outburst threshold limit determination. A number of mines have encountered areas where it has been difficult, if not impossible, to reduce the seam gas to below the prescribed threshold limit prior to the arrival of roadway development machinery, despite extensive inseam gas drainage. In such situations these mines can experience lengthy production delays or even loss of reserves. Several Bulli seam mines have completed reviews of their outburst risk management which led to increasing their threshold limits. These mines have been operating safely, without outburst, for some four years. The method of determining the outburst threshold limits applicable to non-Bulli seam coal mines also hold a high degree of conservatism which is discussed. The need for re-appraisal of the threshold limits undertaken is reported, based on the further data analysis. The process of gas desorption methodology and the optimum gas content is one particular aspect of this study as it has a clear influence on the established values of the recognised threshold limits. The study has demonstrated that there is justification to increase the operating threshold limits to values of 12 m3/t for 100% CH4 and 8 m3/t for 100% CO2. Research is continuing to include sample analysis from other Australian mines.