In the study described above, the gold equivalent was used for calibration at Telfer and Ridgeway Deeps, as both mines produce copper and gold. The ability to change grade values is essential in order to maintain a profitable operation, but the changed value should be reflected in the draw control strategy by adjusting either the extraction ratio targets or production capacity. Mining-induced seismic events can be harmful to the infrastructure and buildings in the city near the mine; in some cases, they can pose a danger to the miners and the mine’s infrastructure. Each night, on average, five to six blasts are conducted. The authors acknowledge LKAB for its financial and infrastructural support. According to Booth et al. Concluding remarks The current draw control strategies at Kiirunavaara and Malmberget mines are guided by a bucket-weight-based drawpoint monitoring system.
An optimized draw control strategy is vital for improving ore recovery and reducing dilution in SLC. For example, the dilution entry method uses dilution behaviour Bull and Page, , but recent marker trials Brunton, ; Nordqvist and Wimmer, ; Power, ; Wimmer etal. A model for gravity flow of fragmented rock in block caving mines. Doctoral thesis, University of Queensland, Australia. However, both employ a draw control strategy that considers the production requirements and mining constraints and regulates the loading process through a continuous drawpoint monitoring system. Production and maintenance performance analysis:
According to Booth et al. The drawpoint monitoring method used in Kiirunavaara and Malmberget mines exploits the difference in the density between ore 4. The purpose is to provide information about the ore grade being loaded.
Qualitative comparison of current draw control strategies. Loading constraints The Kiirunavaara yhesis produced around A fixed target tonnage is decided for a ring based on drill pattern design and recovery targets. Loading thesia are a set of rules and guidelines that control the loading and closing of drawpoints in SLC.
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The mechanics and design of sublevel caving systems. These guidelines, along with the curves, provide the basis for draw control. The various draw control strategies used around the world are used to create a set of guidelines for a new draw control strategy.
The objective is not to simulate flow based on gravity flow lkb Cundall, Mukundakrishnan, and Lorig,but to predict the material grade extracted at the drawpoint for a given set of flow conditions Villa and Diering, The aim of a draw control strategy should be to provide information on when to close an active drawpoint, not to predict material flow.
Conducting a qualitative analysis of the information collected from personnel can yield useful results. If the operator is unable to handle the hang-up, water jets are used to release it. The orebody is first divided into cells.
The mine also has constraints based on vibration levels in the nearby city of Kiruna, but this is not a source of concern for the mine itself. In other cases, low hang-ups caused by boulders are drilled and blasted.
For the last drawpoint of a production drift, the second phase of loading, known as ‘restmalmslastning’ residual ore loadingis sometimes done by reopening the closed drawpoint to recover known ore remnants. However, there is an opportunity to create a new draw control strategy using the above guidelines.
The paper enumerates the loading criteria and loading constraints at the mines and outlines details of mine design, layout, and geology affecting the draw control. The non-uniform nature of material flow in SLC requires constant monitoring to control dilution while also recovering more ore thseis the drawpoint. The ore recovery for the first two sublevels was affected by the switch in the tgesis control system, but the ore recovery for the thezis and subsequent sublevels reached htesis same level as with a traditional draw control system, i.
The performance of drawpoints and the nature of material flow can vary from mine to mine.
In general, the cave front converges towards the entrance crosscut. Nonetheless, boulders are frequently encountered in the orepass and in the lower output of the orepass. Guidelines for designing a new draw control strategy. Similar arguments can be put forward about other methods. Loading from the muckpile should be stopped during the sampling period in order to ensure a representative sample.
Drawpoints near the hangingwalls have an open cavern at later stages of the draw; the hangingwalls have not yet caved or have just started to cave, creating an open cavern above the drawpoint. Based on the production details of the past month, the short-term plan is revised to meet future production targets. The model was calibrated against initial marker trial results at Ernest Henry mine, Australia.
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McMurray describes a visual inspection used on a shift basis for the grade control of asbestos ore at Shabanie mine in Zimbabwe. Tonnage-based draw control strategy Draw control strategies based on fixed tonnage and grade control at the drawpoint are collectively termed ‘tonnage-based draw control strategies’.
The mine is contemplating changing this practice, as it causes problems with reinforcement and caving. The method uses a series of Datamine macros to calculate the expected diluted grade for a series of rings Allman,in Jamieson, Sublevel caving at Craigmont Mines Ltd. Loading near ore boundaries: