Verification of forecasts of subsidences, inclinations and curvatures of area caused by multideposit mining conducted by including mining margin – case analysis

Nowadays surveying – geological departments of Polish coal mines conduct forecasts of leverages of underground mining on area and construction works based on J. Bialek’s formulas including, among others, distant leverages, reactivation of old workings and mining margin. The objective of this article is the adequacy study of the conducted forecasts of area deformation in this way with relation to real values of deformation indicators confirmed by surveys. For this purpose, an example of a really terminated exploitation of hard coal, run in three deposits by a longwall system with a fall of roof rocks by a certain mine located with the territory of Upper Silesian Coal Basin, was used. The forecasts of subsidences, inclinations and curvatures of mining area were conducted in measurement points with the use of EDN-OPN computer programme and J. Bialek’s formulas. Typical values of parameters of these formulas were used in the forecasts, namely, mining coefficient equal to 0.8; tangent of scope angle of main leverages amounting to 2.3; mining margin parameter equal to 0.15. The forecasts were conducted for each exploitation stage, namely, leverages deriving from the exploitation of one, two and three deposits were calculated. Subsequently, such conducted forecasts were compared with values of subsidences, inclinations and curvatures calculated from altitude and distance surveys of stabilised points in the ground over an exploitation field, forming a parallel line to face runs. The values of R correlation coefficients were provided between theoretical and measured courses of deformation indicators, their extreme values were compared and their standard deviations were calculated.