Ground surface uplift during subsidence trough formation due to longwall mining in the shaft protection pillar of the CSM Mine

Abstract

Ground surface uplift was detected at the start of longwall mining, a significant part of which is situated in the shaft protection pillar Sever of the CSM Mine in the Czech Republic. The largest uplift was found to be 23 mm, by the levelling method of surface points with height connections to non-mined areas. Due to the length of the connection to the non-influenced area, precise levelling was chosen to observe the vertical displacements and prove the displacement values using a confidence interval with 5% risk. This article aims to clarify the cause of ground surface uplift during longwall mining. Therefore, the height changes of the given area were extracted also from satellite radar interferometry (InSAR). The changes of the observed ground surface were compared with the empirical subsidence. The largest difference between the measured and empirical surface subsidence was 85 mm and occurred in the period before the ground surface uplift. Spatiotemporal evaluation of the data was used to determine the presumed cause of the occurrence of surface uplift in the overburdened strata, due to previous mining activity and the subsequent unburdening of the rock mass.