In situ measurement and physical analogue on water inrush from coal floor induced by progressive intrusion of artesian water into protective aquiclude

The water injections into both fracturing and intact coal floor strata reveal that water drain in the lower part takes place earlier than in the upper part, and the break of rocks in deeper part of coal floor occurs before mining. The physical analogues on these two kinds of floor reveal the same phenomenon. In the in situ measurement it is found that the artesian water intrudes into the coal floor before mining. The paper considers that the secondary stress creates conditions for the development of the instruction of the artesian water. The progressive intrusion is one sort of mechanism for water inrush.