Assessment of structural conditions of rocks behind lining in vertical mine openings based on attribute analysis of GPR data

The article discusses the use of the attribute analysis of GPR data in diagnostics of concrete lining and space behind it in mine shaft no. 6 in the Taimyrsky Mine in intervals of diagonal fracturing. Mine shafts in the Talnakh ore province feature high interference load (metal structures, high-rate water inflow), high level of signal attenuation and weak contrast at interfaces. The goal of the research was the localization of presumable damages behind lining in shafts—softening zones and possible loss of adhesion at the concrete lining—rock mass contact, for the further substantiation of design decisions on rehabilitation of the space behind lining and improvement of long-term stability of concrete lining. Considering a priori information (position of fault no. 4, data from investigation well), surveying was carried out in the depth interval of 55–65 m using georadar OKO (400 MHz) with the subsequent data processing using the automated analysis method of Back-Scattering Electromagnetic Field in software system GEORADAR–Expert. The use of this method essentially improves information content of GPR data, and provides a more impersonal and reliable framework for the sound decision making on repair and rehabilitation of mine shafts. Application of BSEF requires optimizing a scanning pitch along a survey profile. If the pitch exceeds an allowable value (defined by the directivity diagram and central frequency of the antenna), diffraction hyperbolas are insufficiently frequently sampled: the vertexes often appear between the traces, and the shapes and curvatures are distorted (spatial aliasing).