Three dimensional fractures detection by geo-radar for sustainable production of ornamental stones

Fractures in rock mass threaten exploitability and productivity of ornamental stones quarries. Since propagation of fractures inside the rock mass is a random phenomenon, a non-destructive detection method of fractures shall be used. Between several fractures detection methods, Ground Penetrating Radar (GPR) was selected as data acquisition tool. GPR is fast, accurate and reliable method of fractures detection in rock masses. The in-situ survey, in a case study in a sandstone quarry in Firenzuola, Italy, was planned for achieving two main targets. The first one was focused on accurately modeling fractures as 3D surfaces from data obtained by a high frequency GPR antenna. The second main target was focused on surveying the rock mass to detect large aperture fractures surfaces as deep as possible by a low frequency GPR antenna. The proposed method was applied to two different benches using 400 MHz and 70 MHz antennas. A visualized 3D semi-deterministic model (as close as possible to reality) of sub-horizontal and sub-vertical fractures in a rock mass of 25 m length x 6m width x 2.5m depth was obtained from the high frequency GPR antenna survey. Whilst the low GPR frequency antenna survey allowed characterizing the extension, shape and orientation of the detected fractures surfaces in a rock mass of 12m length x 7m width x 14m depth. Moving from these results to further sustainable objectives, suggested exploitation and planning scenarios based on the presented fracture models are described in this paper in objectives to short term production optimization and long term production planning.