Interpretation of Ground Penetrating Radar Attributes in Identifying the Risk of Mining Subsidence

Abstract

Sinkholes which occur in regions of old mine workings increase the risk to building and transport safety. Geophysical surveys, particularly with the use of ground penetrating radar (GPR), can help to locate underground voids which migrate towards the surface before they transform into sinkholes. The mining region in Upper Silesia, Poland was selected to test the method. The test was carried out on the profile at which sinkhole appeared few months after measurements. It can be assumed that the development of deformations in the ground was preceded by hydraulic and geomechanical processes, which directly caused this event. To identify the cause of the sinkhole formation exactly in this place in which it is located we carried out interpretation of GPR measurements through the calculation of GPR signals attributes such as instantaneous phase, instantaneous amplitude envelope, envelope derivative, envelope second derivative. The difference between two similar recorded data can be interpreted as a result of existence of hydraulic channels. On reflection, it appears that GPR signals attributes can be an important tool not only in the location of a cavity voids, but also can help in understanding the mechanisms of formation of the sinkholes.