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Production rings with a very high percentage of waste intrusion visualized in the WOLIS system are not drilled but left intact. Malmberget mine produced around The bucket weight reading is used to estimate the percentages of ore and waste in the bucket visualized in Figure 1 Gustafson et al. Draw control strategies based on fixed tonnage and grade control at the drawpoint are collectively termed ‘tonnage-based draw control strategies’. Table II shows eight draw control strategies used in various mines; in-depth descriptions of these strategies follow.

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. The information is used by the operator to decide if loading should be continued or discontinued at a particular drawpoint Shekhar, Gustafson, and Schunnesson, Annual and sustainability report, The system used to monitor the ore grade depends on the ore type and mine requirements. Recent marker trials highlight the chaotic and random nature of material flow in SLC.

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 thezis, creating an open cavern above the drawpoint. Clearly defined production demands and grade controls: Draw control strategy at Malmberget mine Malmberget mine consists of about 20 orebodies, 12 of which are currently being mined.

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The Kiirunavaara mine produced around The performance of the drawpoints above a blasted ring has an influence on the ore grade that will be extracted from thesks drawpoint. Detailed work on gravity thewis and flow simulation techniques, along with software developments, has produced several types of flow-based software and modules for simulating flow behaviour that can forecast drawpoint performance Cundall, Mukundakrishnan, and Lorig, ; Diering, ; Pierce, The Malmberget and Kiirunavaara mines are the two largest underground iron ore operations in the world.

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Influence of proximate drawpoint: In the study described above, the gold equivalent was used for calibration at Telfer and Ridgeway Deeps, as both mines produce copper and gold. Sublevel caving at Craigmont Mines Ltd.

Careful assessment of dilution behaviour: McMurray describes a visual inspection used on a shift basis for the grade control of asbestos ore at Shabanie mine in Zimbabwe. The authors acknowledge LKAB for its financial and infrastructural support. A load cell placed on the hydraulic cylinder of the load haul dump LHD bucket reads the hydraulic pressure in the cylinder and converts it into tonnage. However, in the present scenario of fluctuating metal prices and increasing thesid costs a new draw control strategy is mastwr which is probabilistic in nature and can handle the uncertainties associated with caving operations.

Monitoring the drawpoint in SLC The monitoring ghesis the ore grade at the drawpoint is termed ‘grade control’ Booth et al. Cited by Google Similars in Google.

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In other cases, low hang-ups caused by boulders are drilled and blasted. However, there is an opportunity to create a new draw control strategy using the above guidelines. Dilution is given a grade which is an average of the top cave material grade and the grade of unrecovered material from the above levels Bull and Page, The weight is directly proportional to the distance from the main cell to the sampling point of the neighbouring cell Salinas, Visual grade control techniques and sub-level cave draw optimisation – Perseverance Nickel Mine, Leinster, Western Australia.

Instead, boulders are transported to a separate drift where they are broken by drilling and blasting. A study of isolated draw zones in block caving mines by means of a large 3D physical model.

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The assessment shows that traditional draw control strategy, dilution entry method, and non-dilution methods are not recommended for draw control masher. Power geotechnical cellular automata PGCA. Because of this, the loading procedure for these rings is different. Loab of Mining Engineers of Turkey, Ankara.

Other methods discussed would benefit significantly from either model improvement or improvement in drawpoint monitoring technologies. The current loading procedure dictates that no loading can be performed in an open cavern situation.

The production data includes bucket weights, estimated bucket grades, and final extraction ratio for all the production rings blasted at the mines.

A drawpoint monitoring system that can provide a reasonably accurate estimate of the material grade loaded is a requirement for an efficient draw control strategy. The lkwb main principles guiding the growth of IMZ are porosity, collapse, and erosion Pierce, A model for gravity flow of fragmented rock in block caving mines.

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The V-shaped cave front can change depending on the mining sequence in nearby mining blocks, seismicity, and structural stability of the drifts in the block. Drawpoint monitoring systems can be divided into three types based on the technique used.

The model uses a layer concept, whereby an IMZ is comprised of a number of disk-shaped layers, and its growth is based on incremental laws applied at layer levels Pierce, ; Sellden and Pierce,