Abstract

The paper examines methods of assessing the critical fractures and quality of an ornamental stone deposit. Fracture status was evaluated by an in-situ Ground Penetrating Radar (GPR) test. The resulting 3D GPR model allowed exploration of the extension, shape, and orientation of the detected fractures surfaces. It also identified a rock stratum with a noticeably lower load of critical fractures compared to the other strata. Physico-mechanical properties were investigated by laboratory tests allowing classification of the deposit into quality categories, which provided a promising correlation with the GPR survey results.

1. Introduction

Research on ornamental stone evaluation, production, and processing have witnessed sustainable trends in recent years. Ornamental stone products have a wide range of uses for construction and prestigious purposes. Evaluation of ornamental stone deposits is a decision making tool not only for quarrying, but also for classifying deposit quality. The aesthetical appearance of ornamental stones and the commercial size of ornamental stone blocks are very significant marketing factors [1]. Rock mass fractures hamper the cutting of commercially viable ornamental stone blocks. Fractures are also the main cause of production waste. For this reason, fracture status evaluation is a critical assessment factor during the exploration stage.

Since ornamental stones are non-renewable resources of considerable economic value, a non-destructive noninvasive fracture detection tool is recommended. We have selected Ground Penetrating Radar (GPR) [2] from among several fracture detection methods (Fig. 1) as a geophysical electromagnetic data acquisition tool for this research. GPR has been widely used to detect fractures in rock mass in quarries [3–8]. In this paper, we investigate the use of a low frequency GPR antenna to detect critical (large aperture) fractures inside a discontinuous heterogeneous rock mass in a sandstone quarry. The objective of using low frequency antenna is to obtain as deep a subsurface image as possible, since penetration depth is inversely proportional to wave frequency.

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