In deep mining

there are a large number of local high confined water areas in floor aquifers which can easily induce floor water inrush disasters under strong mining disturbances have been confirmed by measured geological data and water control practices. Based on the theory of “lower three zone” and “the key strata”

the key aquiclude in the floor and the local high confined water area were simplified into a cylinder mechanical model

and the yield failure mechanism of the water-resisting key strata under the local high confined water was analysed. Four critical water pressure formulas for yielding in the water-resisting key strata were obtained. By dividing the critical water pressure values into sections and analysing the yielding state of the water-resisting key strata in different sections

the water pressure criterion balance equations for two stages of yielding and breaking of the water-resisting key strata caused by local high confined water were determined. The calculation expression of the remaining water-resisting capacity of the Ordovician top rock layer as water-resisting key strata was obtained. In addition

the formulas for the upper and lower limits of the mining depth were obtained by the inverse derivation. By combining with the deep mining practice of Jiulong mine

the mechanical model was validated and applied. Moreover

the relevant measures were proposed to prevent the local high confined water disaster

which has significant theoretical evidence for realising safe mining of deep coal seam.