Published in the May 2008 Coal USA Magazine

A joint Queensland-based project funded by the Australian Coal Association Research Program is investigating the science behind the new US regulations to determine their suitability for Australian conditions.

The joint project is between the Queensland Department of Mines and Energy’s mine safety research organisation Simtars, within the Department of Mines and Energy, and mining engineering consultants Gillies Wu Mining Technology. Working together on the project are Simtars’ Dr Jan Oberholzer and Gillies Wu Mining Technology ‘s Dr Stewart Gillies.

The information gathered by the 18-month-long project will be used by the mining industry and legislators to assist in understanding the strength requirements for local seals. It will form the basis for a decision to maintain the present level of strength requirements or to propose different levels.

“The aim of the project is to recommend approaches that Australia can take to maintain world best practice in seal design,” Gillies said.

NIOSH investigations into the required strengths of seals have indicated a significantly higher strength level requirement to what is presently used in Australia.

Recommendations have been made for a three-tiered explosion pressure design criteria for seals in coal mines, the lowest of which requires a seal to withstand 345kPa overpressure and the highest which requires a seal to withstand a possible 4.4MPa.

The basis of these higher strength requirements lies in the assumption of a high likelihood of a methane detonation occurring as well as the higher chance of a fully contained or constant volume explosion occurring in the underground environment.

One question the researchers have to work out is the likelihood of a detonation in the Australian mining environment.

“The project is based on the premise that risk should be robustly and actively managed and not ignored or passed on to someone else through unrealistic regulations,” Gillies said.

As part of the project Gillies will carry out a comprehensive survey of about 14 major mines in Queensland and New South Wales that all have different approaches, and some of which are more likely to experience gas issues. The survey, which began in April this year, will include a visit to each mine and underground assessment, comprehensive discussions with management and an examination of the mine’s history.

“We want a definitive survey on what are the real issues that need to be taken into account to determine safe design, construction and the ability to maintain seals throughout their life,” Gillies said.

Through this survey the researchers will be able to establish the differences between normal US mine layout practice (particularly in longwall extraction) and Australian practice. Other relevant differences will be identified and the effects on seal explosion pressure wave development reviewed.

Whilst Gillies is visiting the mines, Oberholzer will review international literature on the topic. He will also use Simtars’ explosion propagation tube laboratory to undertake some fundamental experimental tests to further understand the nature of pressure generation.

The principal aim of the project will be to study the theoretical basis for a detonation or significantly higher pressures occurring, and the conditions under which they would occur in Australia. The likelihood of higher overpressure occurring will be determined by examining the chance of such conditions developing in the existing geometry of Australian coal mines.

“Many Australian mines have a history of good monitoring and inerting practices particularly when goaf atmospheres pass through the Explosibility Triangle,” Gillies said.

“The project will compare the implications for explosion pressure build-up of three or more heading gateroads, as practiced in the US, compared to the normal two headings in most mines in Australia.”

At the end of the project the research team hopes to present its recommendations based on solid science and facts specific to Australian operations.

“We want to be able to apply NIOSH’s findings to the results of the survey and come to a conclusion where our Australian approach can stand up when lined up to science,” Gillies said.