Abstract
Rock mass is typically characterized by inherent fractures that cause natural blocks of rocks. Unplanned cutting of stone deposits in quarries may lead to over-producing waste (rock debris) or extracting unfi t (fractured) stone blocks. This paper presents two case studies through the use of low and high frequency Ground Penetrating Radar (GPR) antennas to detect fractures in two benches of a quarry. In the fi rst case study, a high frequency GPR antenna was used aiming to: (i) compare the GPR results with a map of the out-cropping fracture intensity in the bench surface, developed using the data of the GPR survey marks and interpolated by the Ordinary Kriging technique, and (ii) present how sub-vertical fractures can be numerically modelled in three dimensions from the GPR results. The second case study was focused on using a low frequency antenna to detect large aperture size of fracture surfaces as deep as possible in order to evaluate a deposit stratum before quarrying. This could be done through studying the refl ections from a 3D cross-sectional GPR model anda 3D transparent GPR model. In the discussion section, an exploitation planning approach, based on modelling fractures as 3D surfaces, is theoretically and graphically proposed to optimize the stone production recovery. The two case studies showed that GPR is a successful tool for the assessment of ornamental stone deposits and a promising tool for recovery optimization.
Highlights
Ornamental stones are raw materials with potential economic value that are used in various applications for construction or prestigious purposes (Ashmole and Motloung, 2008)
This paper presents two case studies through the use of low and high frequency Ground Penetrating Radar (GPR) antennas to detect fractures in two benches of a quarry
In the Ƥrst case study, a high frequency GPR antenna was used aiming to: (i) compare the GPR results with a map of the out-cropping fracture intensity in the bench surface, developed using the data of the GPR survey marks and interpolated by the Ordinary Kriging technique, and (ii) present how sub-vertical fractures can be numerically modelled in three dimensions from the GPR results
Summary
Ornamental stones are raw materials with potential economic value that are used in various applications for construction or prestigious purposes (Ashmole and Motloung, 2008). A leading factor that gives a pro¿table value to the stones is the block size, since small sizes of the extracted blocks limit the dimensions required for processing the stone pieces, and a narrow range of applications will be available. Most quarrying operators consider the extracted stones sizes less than the required commercial block size as waste. The standard dimensions range of commercial block sizes is between 2.0 m x 1.0 m x 0.5 m and 3.0 m x 2.0 m x 1.0 m (Report of United Nations, 1976). Rock mass fractures control the feasible exploitation and stability of benches.
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