2D And 3D Gpr Imaging To Map The Fractures And To Evaluate The Integrity Of Limestone Ornamental Rocks

The reconstruction of the fracture distribution behind or below the accessible surface of the rock<br>blocks in a quarry is fundamental to plan the mining activity and to improve the profit. Some 2D GPR<br>surveys were executed with 50 MHz unshielded antennas and with a 250 MHz shielded antenna to map<br>the layers and to define the depth of the limestone in the quarry in order to evaluate the total volume of<br>the limestone rock. The results of the GPR data were compared with the geological structures deduced<br>from the outcrops and from the exposed layers within the quarry. A quite good penetration was<br>observed: 70m at 50MHz and about 13m at 250MHz. 3D GPR surveys were also executed on some<br>areas where it was important to test the integrity of the rock by producing accurate 3D reconstructions<br>of the main fractures. The data were processed with a 3D dedicated software developed by the authors.<br>The results are very encouraging showing that the penetration and the potential of the radar technique<br>to detect fractures and thin layer interfaces in this limestone are very high.