Deterministic Three-dimensional Rock Mass Fracture Modeling from Geo-radar Survey: A Case Study in a Sandstone Quarry in Italy

Rock mass fractures adversely affect the production of ornamental stone quarries. Fractures cause natural rock blocks which threaten extracting the required commercial block size of ornamental stones. An accurate subsurface detection and modeling of fractures is required for pre-exploitation evaluation and planning. This paper introduces a new three-dimensional deterministic fractures modeling approach using Ground Penetrating Radar (GPR) as a data acquisition tool. A case study was performed in a fractured bench of a sandstone quarry in Firenzuola, Italy, using a 400 MHz GPR antenna. To accurately detect fractures at true depth, an in-situ calibration based on knowing the depth of a subsurface reflector, as a reference, allowed to estimate a bulk dielectric constant of the rock mass in the time of data acquisition. A data interpretation tracing technique was developed to model fractures as 3D surfaces in two forms, either irregular or planes. The modeled fractures were visualized through a multiplatform visualization software package (ParaView). A comparison between the orientations of the fractures measured through the traditional manual survey and the orientations of the modeled fractures is presented as a possible geologic validation for the detection and interpretation of fractures. For the objective of pre-exploitation evaluation, a distribution analysis study of fractures allowed to obtain an evaluation-based fracture index for the bench of the case study.