GPR and seismic imaging in a gypsum quarry

A combination of ground penetrating radar (GPR) and seismic imaging has been performed in a gypsum quarry in western Europe. The objective was to localize main cracks and damaged areas inside some of the pillars, which presented indications of having reached str ess limits. The GPR imaging was designed from classical profiles with GPR processes and a customized, PC-based image-processing software. The detection of energy reflection seems to be an efficient process for localizing damaged areas. Seismic tomographic images have been obtained from travel time measurements, which were inverted using a simultaneous iterative reconstruction technique (SIRT) technique in order to provide a map of seismic velocities. The imaging and techniques employed are compared herein. The two techniques are complementary; seismic tomography produces a map of Velocities related to the state of the pillar's internal stress, while radar data serve to localize the main cracks. Moreover, these imaging processes present similarities with respect to the damaged zone detection. (C) 2000 Elsevier Science B.V. All rights reserved.