2D and 3D experiments to explore the potential benefit of GPR investigations in planning the mining activity of a limestone quarry

The reconstruction of the fracture distribution behind or below the accessible surface of the rock blocks in a quarry is fundlamental to plan the mining activity and to improve the profit. Some 2D GPR surveys were executed with 50 MHz unshielded antennas and with medium frequency antennas (around 250 MHz) produced by two different GPR suppliers. The target was to explore the potential of GPR to map the layers and to define the depth of the limestone in the quarry in order to evaluate the total volume of the limestone rock. The results of the GPR data were compared with the geological structures deduced from the outcrops and from the exposed layers within the quarry and finally with the results observed after the extraction of the blocks that were previously surveyed. A quite good penetration was observed: 70m at 5OMHz and about 13m at 250MHz. 3D GPFI surveys were also executed with both the medium frequency antennas on some areas where it was important to test the integrity of the rock by producing accurate 3D reconstructions of the main fractures. The encouraging results demonstrate that limestone quarries can represent a very favorable environment for the application of the GPR technique as a tool for guiding and impiroving the extraction activities.