Duration of the final phase of mining area deformation process in the conditions of Upper Silesia (Poland)

The ability to estimate the duration of mining impact on the surface is important for both active and decommissioned mines. It allows to plan rational land development and to assess the time of exploitation impact on buildings. The data concerns cases of exploitation with roof caving in 20 hard coal mines in Upper Silesia and cases of exploitation with hydraulic stowing in 4 mines. Based on the analysis of geological and mining documentation, the duration of the final stage of the subsidence process was established — from the end of mining operations to the final stage of the subsidence. It was assumed that the subsidence reached its final state when the increments between two consecutive measurements did not exceed 10 mm. Further analyses were carried out using the regression method using the Statistica program, looking for the relationship between the duration of the final phase of the subsidence process and the quantities characterizing the operating conditions. The obtained results indicate a significant impact of the depth of exploitation and the value of the parameter characterizing the rock mass strength properties on the duration of the final phase of the deformation process. As a result of statistical analyses, appropriate empirical formulas were proposed. In the case of performing exploitation with caving and when the variation in the value of tgβ parameter characterizing the rock mass is small, which currently occurs in the considered basin, one can use the proposed formula, linking the duration of the process with the depth of mining exploitation.