Open Cut » Overburden Removal
This report presents a method for measuring the in‐place bulk density through comparisons of digital terrain models and machine monitor data. For the context of this report in-place refers to the original place of blasted material after the blast and before being handled by the dragline. This bulk density is determined by the performance of blasting and provides a key indicator on the digging context in relation to dragline performance. This research takes the next step towards incorporating in-‐place bulk density measurements into mine planning, scheduling and blasting feedback to advance context aware production monitoring and improve energy efficiency across the mine.
The proof‐of‐concept prototype developed by CRCMining was installed on a production BE1370W dragline located at Anglo American's Drayton Mine in NSW. This system continuously collected laser scans of the terrain, navigation data of the boom and machine monitor data over the months of May and June 2012. This data provides the inputs for the developed terrain profiling and in‐place bulk density measurement by mapping the bulk density to the in ‐place dig location.
The system works by geo-‐referencing the laser data using navigation data from a GPS/INS sensor to continuously update the state of the terrain. A snapshot of the terrain profile is taken between each dragline cycle where the height change caused by the dig is used to measure the volume extracted and when fused with the payload weight the in‐place bulk density can be calculated. The location of the volume extracted from the blast is then labelled with the measured bulk density.
The system is able to map bulk density variations across the blast and data collected shows a correlation between high bulk densities and blast fragmentation results. Furthermore in-efficiencies of the material entering the bucket can be monitored and are linked to the bulk density variation. This characteristic has shown that areas of lower bulk density enable better utilisation of the bucket moving more tonnes per cycle. A comparative analysis of different blast areas in the data collected during trial indicates that poor blasting can result in up‐to 6% less payload per cycle on average and greater variation per cycle.
It should be noted that after reviewing the results of the extensive field trial, a number of limitations have been discovered within the approach used during this project. Some of these stem from the chosen hardware configuration, some from the nature of the task, and some from the analysis methodology itself. Some approaches to correct these limitations are presented.