Oversized fragments appearing at the drawpoint pose a major problem to all block cave mines. If an oversized fragment is not identified by the extraction vehicle operator, it has the potential to block the Materials Handling System (MHS), preventing subsequent loads from being processed and reducing overall efficiency in the mine. Existing techniques for automated rock fragment detection at the drawpoint use optical cameras to identify individual fragments, but these methods are limited to detecting surface fragments only.This thesis presents a method to identify oversized fragments below the surface of a rock pile using Ground Penetrating Radar (GPR). The radar response to the rock characteristics was determined from experimentation in the laboratory. Different antenna arrangements were tested and a method for auto-calibration of zero-time at a remote antenna developed. Two approaches were taken in this thesis to identify oversized fragments below the surface of a rock pile. Firstly, 2D imaging of the individual fragments within the rock pile was tested. A new method to improve the contrast of radar images of the internal structure of the rock pile using the physical motion of the antenna was developed. Secondly, a volumetric measuring approach was developed. This method measures various radar signal properties from the rock pile volume rather than mapping individual rock pile constituents. One benefit of this approach is the speed of acquisition and determination, allowing the presence of an oversized fragment in a rock pile to be inferred from signal properties.Results from laboratory experiments are presented which demonstrate volumetric analysis is capable of detecting oversized fragments in a rock pile, and that this method could be used to identify oversized fragments at a mine drawpoint. Identifying oversized fragments at the drawpoint will assist in the reduction in crusher blockages and reduce unnecessary vehicle movements, improving the efficiency of ore extraction and metal recovery.
|Qualification||Doctor of Philosophy|
|Award date||01 Oct 2014|
|Place of Publication||Australia|
|Publication status||Published - 2014|