The current global economic conditions have caused businesses to relook at streamlining their operations to achieve a profitable outcome. Analysis of the operations resulted in new technologies and methods being implemented to define the efficiency. With these concerns being at the forefront of the day-to-day business, the mining sector has embraced the concept of utilising technology to improve their operations. Blasting forms one of the major contributors to improving the downstream benefits in mining.
The control of muckpile distribution, uniformity in fragmentation and increased digging rates are but a few of the factors that dictate the efficiency of the beneficiation process. The correct application of the equipment and expertise during blasting will result in a very efficient process. Software used for delay designs and blast simulations have recently become very prevalent and a crucial part of blasting. This article focuses on the use of software known as ViewShot™ being used at a trial site.
The inception of ViewShot™ was based on the primary requirement to interface a blast delay design to the electronic initiation systems, which is found in the ShotTM product range. The intention of this software was to eliminate delays caused by manually inputting the blast design and introducing human input errors during blasting. ViewShot™ is developed and maintained along with the control equipment in DetNet, a joint venture partner with AEL Mining Services.
ViewShot™ contains multiple features that allow the user to design timing before blasting time. The user is able to either free style a blast design or import the blast design coordinates in a comma delimited (CSV) format. A “helicopter” view of the blast is then presented to the user to create a delay design with the tools provided in the ViewShot™ suite.
The blast is then visually simulated and once corrections are made, the tagging plan may be generated. Thereafter, this plan is provided to the blaster in charge to commence with tagging according to the blast design in ViewShot™. This ensures that the tagging pattern on the bench correlates to the designed pattern on ViewShot™. The file will be downloaded into the respective Shot™ control equipment in preparation for blasting.
ViewShot™ is primarily used to do blast delay designs. Due to the flexibility of the electronic initiating systems, it was inevitable that there would be a request from a customer who required us to stretch this particular software beyond its conventional operating limits. This particular customer is an open cast platinum operation situated in the North West province of South Africa.
The customer provided six perimeter hole coordinates that defined the perimeter of the blast area. The instruction was that a blast design had to be generated from the information provided in Figure 1.
This request presented an interesting opportunity to explore the capabilities of the ViewShot™ design tools. The customer required control of the spill over material while minimising the backbreak on the High wall.
The ruler tool found in ViewShot™ was used to measure the bench to determine the dimensions of the intended blast area. A staggered hole design was created for this blast using the customer’s design requirement. Once the dimension of the blast was determined, it became a simple task of calculating the number of holes required based on the calculated burden and spacing measurement. The mine accepted and approved the design shown in Figure 2 allowing for the blast pattern to be drilled and completed 7 days later.
A comparison of the designed and actual drilled patterns revealed that there were two rows of drilled holes missing. The perimeter holes were picked up by the survey department when the material in front of the new blast bench was not cleaned out. On completion of the loading process and subsequent inspection it was determined that there were two rows missing from the intended design as a result of excessive back break, thus allowing for additional material excavation from the previous blast.
This did not delay the drilling process as bench preparations had commenced. The charging was done over a three day period with no delays. The pre-split was shifted into the main bench by 1.5 m while the last line on the blast was squared off as per requirement by the mine.
Due to missing holes and a ragged free face the customer decided to drill additional holes on the first row to ensure proper burden relief shown in Figure 3 above. The ViewShot™ programme enables the user to allocate the different channels of the Control Equipment which are represented by the different hole group colours on the design above. This technique assists in harnessing and in possible fault diagnostics if required. It also assists the designer to ensure that the allocation of the number of holes and surface wire length falls within the system parameters.
To reduce the spillage of material, two diamond cut chevrons, as seen in Figure 4, were proposed to obtain the required results by confining the cast. In this particular blast the two chevrons also generated a secondary pulverisation of the material resulting in the uniformity of material distribution through the muckpile which improves digging and loading rates. The blast delay design was optimised by the responsible AEL representative according to scientific calculations and their pre-knowledge of the ground behaviour and environmental conditions.
The AEL support team on site had highlighted the benefits of electronic initiation systems, blended emulsion and accurate blast design while also reducing the powder factor from previous designs of 1.1 to 0.9 for the AEL blast.