This paper discusses the wind blast / air blast phenomenon, how it is managed in coal mines and how it might best be managed in other underground mines. L'article qui suit a pour objets de decrire le phenomène de tir a l'air comprime et les methodes de moderation de celui-ci dans les mines de houille, et d'indiquer de quelle manière il pourrait être surmonte dans d'autres mines souterraines. Dieses Seminararbeit diskutiert die Windexplosion / Luftexplosion Phanomen, wie es in Kohlenbergwerken geleitet wird, und wie es am besten in anderen untertage Bergwerken geleitet werden könnte.
Caving is a fundamental part of many modern underground mining operations. On occasion, however, caving does not occur readily, resulting in an extensive mass of unsupported rock spanning a large void. Such a 'hang up' may collapse, suddenly and often without warning, compressing the air beneath and forcing it out of the void through surrounding openings giving rise to a phenomenon generally known as air blast but referred to by Australian coal miners as wind blast. In this paper, the latter term is applied to the phenomenon when it occurs in coal mines while the term 'air blast' is reserved for non-coal mines.
Wind blasts / air blasts are characterised by significant overpressures and air velocities either of which may result in injury to mine personnel, damage to equipment or disruption to mine infrastructure. An additional hazard, particular to coal mines, is that a wind blast may give rise to an explosion by expelling a mixture of methane and air from the goaf (void) and mixing it with raised coal dust. Explosions at two Australian coal mines, Moura No. 4 Mine, Queensland, on 16 July 1986 (SIMTARS 1990) and at Newvale No. 2 Colliery, New South Wales, on 28 June 1995 (Anderson 1997) were both preceded by wind blasts.
The issue of wind blast / air blast has affected caving operations in both coal and non-coal mines. Operations exploiting metalliferous ores have been affected as have those working kimberlite and even those mining evaporites. Wind blast in coal mines is mainly of concern in longwall and pillar extraction panels. However, some of the most severe wind blasts in coal mines, such as that associated with the tragic event at Coalbrook North Colliery in South Africa on 21 January 1960 (McPherson 1980), have resulted from violent pillar failure. In non-coal mines, air blast is principally an issue in block or panel caving and sublevel caving, although, on occasion, air blast has resulted from crown pillar failure in open stopes, one such example being the event at Epoch Mine, Zimbabwe (Stacey, Diering & Rigby 1991). In these cases, the issue is one of pillar design and such events lie outside the scope of this paper, which is confined to those wind blasts / air blasts associated with intentional, albeit delayed, caving.