Water inflows and weightings above longwall workings

A micro-computer database, incorporating historical data from British Coal mines, to study the factors affecting inflows from proximate aquifers into longwall workings, showed that the most important factor affecting mine water inflows was the cover strata lithology, particularly within the 30m of roof strata. When this comprised principally stronger sandstones, there was a tendency for periodic inrushes associated with face weighting. This phenomenon is explained by the collection of water in bed separation cavities, where free water connected to a high pressure head aquifer source may be trapped. This finding attributes the difficulty in predicting mine water inflows to the changeable nature of cover strata lithology.