Sinkhole Hazard Caused by Inactive Mining Shafts as Illustrated by a Selected Example

Abstract

Loss of stability of shafts liquidated in the past is a frequent cause of sinkhole creation on the surface. This manuscript presents such a case study. The sinkhole was created shortly after intense rainfall, so it can be assumed that displacement of the rock material in the shaft took place, i.e. the phenomenon of suffusion. One of the research aims was to confirm the assumption about the displacement of rock material filling the shaft on the basis of selected methods of sinking forecasting. Ex post forecast sinkhole creation was conducted using two methods (Bell and finite element method). It was assumed that the material filling the shaft lowered itself to a height determined on the basis of the sinkhole and shaft dimensions. Both methods gave the same results, consistent with the literature. The manuscript also presents a short overview of technologies used for decommissioning shafts and assesses their effectiveness in terms of preventing sinkhole creation. These methods have been used since the nineteenth century until present times. Considering the suffusion phenomenon, the paper proposes a way to drain rainwater from the shaft area, which was another purpose of the work. The necessity to find and verify the ways to secure decommissioned shafts from water is indicated as an important future direction of research.