Dynamics of Wind Blasts in Underground Coal Mines

In some underground coal mines where the roof comprises strong and massive rock, the roof strata do not cave regularly as extraction progresses but 'hang up', leading to extensive areas of unsupported roof. These areas can collapse, suddenly and often without warning, compressing the air beneath and forcing it out of the goaf through surrounding openings giving rise to a phenomenon known as wind blast. The force of the wind can, and sometimes does, cause injury to mine personnel, disruption to the ventilation system and damage to plant and equipment. It may also increase the hazard of explosion if methane in explosive concentrations is expelled from the goaf and mixed with raised coal dust.

The aim of the program of wind blast research currently being undertaken by the School of Mining Engineering at The University of New South Wales is to develop a fundamental understanding of the wind blast phenomenon resulting from massive roof failure and provide a basis to mitigate the hazard.

Building upon earlier work, where a 'world first' - the successful instrumental 'capture' of wind blasts and the elucidation of their characteristics - had been achieved, the extensive program of field monitoring, enabled the fluid mechanics involved in the compression and distribution of air during wind blasts to be defined for the first time.

The primary objective of the project as described in this report has been met in full. Monitoring work is continuing as an element of ACARP project C8017 Reducing the Hazard of Wind blast in Underground Coal Mines. It may well be that the results will be generalised in order to produce a set of empirical wind blast 'laws'. However, this is dependent upon the availability of monitoring sites in geological and geometric environments that differ from those of the project panels.

Secondary objectives, the provision of improved, practical design 'tools' with which to optimise panel design, in order to minimise the hazards associated with wind blasts, and of management 'tools' to assist in reducing the wind blast hazard are likely to be completed within the current project C8017 Reducing the Hazard of Wind blast in Underground Coal Mines.

This final report documents recent advances made in understanding the wind blast phenomenon.