Underground » Ventilation, Gas Drainage and Monitoring
The potential expulsion of methane from the goaf during wind blasts and its possible incursion into the working place has been of concern to the Australian underground coal mining industry for many years. For example, the explosions at Moura No. 4 Mine in Queensland in 1986 and at Endeavour (formerly Newvale No. 2) Colliery in NSW in 1995 are believed to have involved such an occurrence.
The principal objective of the project described in this report, the development, construction and testing of a new 'tool' with which to study and quantify the phenomenon-the Wind Blast and Methane Expulsion Monitoring System (WBMEMS)-has been achieved.
Development of the WBMEMS was funded by ACARP with additional financial support provided by Coal Operations Australia Limited and Oceanic Coal Australia Limited. ACARP's contribution formed part of its broader funding for the project described in this report and for Project No. C8017 'Reducing the hazard of wind blast in underground coal mines'. The WBMEMS is capable of detecting and recording transient methane levels, air velocities and overpressures during wind blasts.
Field monitoring of wind blasts in 'non?gassy' longwall mines has demonstrated that air which is expelled from the goaf may penetrate up to 200 metres into the working place. Consequently, it is recommended that in 'gassy' wind blast prone mines, the assessment of risk associated with the potential for wind blast should consider the hazards which may arise from the expulsion of methane from the goaf. A potential control to manage this hazard would be the extension of the 'hazardous zone' to 200 metres on the intake side of the longwall face and the exclusion of non explosion protected electrical apparatus from this extended 'hazardous zone'.
It remains to be proven by direct measurement whether or not methane in explosive concentrations is expelled from the goaf during wind blasts in 'gassy' coal mines. Unfortunately, no suitable site was available during the current project after substantial completion of the WBMEMS. It is anticipated, however, that such a site may become available in 2002. Consequently, the resolution of this issue has been 'carried forward' as one of the objectives of ACARP project C10024 'Wind blast and methane expulsion: extension of field monitoring to generalise the results of projects C7031 and C8017. It is anticipated that such measurements will facilitate the drawing up of further guidance for the industry regarding safe working practices in mines subject to the potential expulsion of methane from the goaf during wind blasts and its possible incursion into the working place.