The particle size distribution of fragmented rock in mines significantly affects operational performance of loading equipment, materials handling and crushing systems. A number of methods to measure rock fragmentation exist at present, however these systems have a number of shortcomings in an underground environment. This paper outlines the first implementation of high resolution 3D laser scanning for fragmentation measurement in an underground mine. The system is now used routinely for fragmentation measurement at the Ernest Henry sublevel-cave mine following extensive testing and calibration. The system is being used to study the effects of blasting parameters on rock fragmentation to optimise blast design. Results from 125 three dimensional scans measured the average P50 and P80 to be 230mm and 400mm respectively. The equipment, methodology and analysis techniques are described in detail to enable application of the measurement system at other mines.
The use of automatic load-haul-dump (LHD) machines in underground metal mines is a promising way to overcome some of the challenges now facing mining companies. They offer several potential benefits over man-operated units, mostly in terms of safety and health of the workers, but also in terms of higher availability, increased productivity, and reduced mining cost. That said, using such systems at their full capacity is a challenging and complex task. In this context, after describing some commercially available equipment and systems, the paper examines factors affecting reliability, availability and productivity of automatic LHDs and notes several technical and operational concerns.
The current trend in Australian longwall mines is to increase panel dimensions and production rate, and mining in gassy regions. However, this trend poses a challenge to provide adequate ventilation to manage gas emissions. While the traditional two heading gateroad bleederless U ventilation circuit, which is the most commonly used circuit in Australia, is no longer suitable due to its low volumetric capacity, a few mines manage to overcome this problem by employing a three heading gateroad ventilation circuit. However, this circuit requires significant additional development, which makes it not popular in Australian coal mines. The aim of this paper is to review the suitability of two heading and three heading gateroad traditional bleederless U ventilation circuits for a large longwall panel mining in gassy conditions. It was found that significant predrainage of the thickest roof seam is required in order to make the two heading gateroad circuit feasible in large and gassy longwall panels.
There remains a debate within the literature and among practitioners of caving methods as to the effect on draw zone geometry for the concurrent drawing of multiple drawpoints. Concurrent draw refers to an extraction schedule where a limited amount of material is drawn from each drawpoint before moving to the next drawpoint to draw the same amount. One hypothesis concludes that the flow geometries of a single drawpoint increase while another assumes no change from that of isolated draw. The largest 3D physicalmodel constructed using gravel as themodelmedia has been used to further investigate interactive draw of extraction zones as part of an International Caving Study (ICS) and Mass Mining Technology Project supported by major international companies with interest in caving methods. All extraction zones were measured in 3D. To date a maximum of 10 drawpoints have been modelled. Model results so far indicate no growth in the horizontal width of extraction zones using concurrent draw. Experiments conducted with multiple drawpoints that were spaced less than the width of isolated extraction zones showed that the combined horizontal area of draw appears to reduce with the increasing overlap of isolated extraction zones. The horizontal widths of extraction zones continued to increase within the height of the draw tested.
Image analysis as a technique for fragmentation measurement of rock piles has been the subject of research since the 1980’s and to date, run of mine (ROM) fragmentation optimisation studies have primarily relied on particle size measurement using photographic based 2D imaging systems. Disadvantages of 2D imaging systems include particle delineation errors due to variable lighting and material colour and texture variation; no direct measure of scale & perspective distortion; and inability to distinguish overlapped particles, non-overlapped particles and areas-of-fines. With the development of 3D imaging technologies, there is an opportunity to develop techniques that could improve data collection and overcome the limitations of existing 2D image based systems. This paper describes the first attempt to use 3D high resolution laser scanning techniques to quantify “whole of muckpile” fragmentation from full scale production blasting. During two monitoring campaigns in 2013, high resolution laser scanning data was collected from production blasts at Esperanza Mine (Antofagasta Minerals Group). Fully automated analysis of the 3D data was possible in all cases where the data was of sufficiently high resolution. Manual pre-processing was required when the data was of low resolution to specify the region of fines. Overall results indicated that run of mine fragmentation requirements were meeting specified targets despite the marked differences in powder factors. This was particularly the case for those blasts conducted in similar geological domains. This work has demonstrated that high resolution laser scanning can be used as an alternative technique to measure “whole of muckpile” fragmentation in production blasting.