The curves are used to complement mine planning and scheduling. Several samples are taken at the drawpoint and then prepared and analysed underground Cokayne, This technique is used when no visual differences can be seen between ore and waste Cokayne, The last rings drilled in the production drifts have their drill collars in the footwall, resulting in internal dilution. Grade control is guided by the overall average run-of-mine grade and the shut-off grade for material loading at the drawpoint. Analysis of rock fragmentation and its effect on gravity flow at the Kiruna sublevel caving mine.
Historical data on drawpoint abandonment and other performance-related information can provide a baseline for assessing loading issues. 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. Large scale field test of gravity flow at the Kiruna mine. Thereafter, the selected cells’ weight contribution is assigned to the closest suitable production ring Salinas, Careful assessment of dilution behaviour: A study of isolated draw zones in block caving mines by means of a large 3D physical model. Analysis of rock fragmentation and its effect on gravity flow at the Kiruna sublevel caving mine.
Similarly, Bull and Page define an effective draw control strategy as one that maximizes ore recovery while minimizing dilution and delaying dilution entry in the drawpoint by deploying ‘corrective methods’.
However, certain assumptions, for example assuming low extraction ratios in upper levels will translate into more ore at levels below, should not be made because of the chaotic nature of the material flow.
Other control strategies lack a robust drawpoint monitoring system and rely on mill grade madter assess drawpoint performance. Qualitative comparison of current draw control strategies.
A consistent issue in sublevel caving SLC operations is the regulation of loading at the drawpoints, especially as the decision to stop loading from a particular drawpoint and blast the next ring is irreversible.
Laboratories were set up close to the centres of production, returning assay results within half an hour of sampling using standard sample preparation equipment and a portable isotope fluorescent X-ray analyser Hancock and Mattson, Loading criteria are a set of rules and guidelines that control the loading and closing of drawpoints in SLC.
Smith and Rahal state that draw control incorporates the sequencing and scheduling of development, production, and the material handling system, with the dual and contradictory objectives of minimizing mining costs and dilution. English pdf Article in xml format Article references How to cite this article Automatic translation. Tonnage-based draw control strategy Draw control strategies based on fixed tonnage and grade control at the drawpoint theais collectively termed ‘tonnage-based draw control strategies’.
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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. A suitable parameter to measure the ore potential from above levels needs to be defined and used in correlational analysis to understand the effects of secondary and tertiary recovery on drawpoint performance. The material can be loaded from the adjacent drift to try to loosen and release low hang-ups, while lkwb production ring can be blasted in the adjacent drift to release high hangups.
Low hang-ups caused by big boulders are sometimes drilled and blasted by a special crew. In these situations, LHDs can load directly onto trucks but this reduces productivity. It took only hours to completely analyse more than 2 million draw strategies over the SLC footprint Jamieson, The paper presents the findings of a thesiss baseline mapping study performed on the two largest underground iron ore operations, Malmberget and Kiirunavaara mines.
Mining constraints for draw control In the initial mining sequence in a mining level at Kiirunavaara, the cave front is kept flat; i. Cut-off grades are calculated based on mine economics, and shut-off grades are re-estimated using marginal cost information to analyse the feasibility of the shut-off grade with respect to depreciation and repayment Bull and Page, If the loading at drawpoints in active seismic areas is not safe, the mining sequence is changed by halting the loading mawter in these areas or postponing blasting until the situation is stabilized.
In field tests performed in test areas at Jing Tie iron ore mine, China Zhigui and Xingguo,the method was mastter with a shut-off grade of The mining area stretches 5 km in the E-W direction and 2. The loading process and draw control near the hangingwall are guided by safety concerns.
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The mining sequence at Malmberget varies for different orebodies and mining levels but is primarily guided by the development situation of the level below. Cited by Google Msster in Google. Systems can provide ore grade measurements continuously Quinteiro, Larsson, and Hustrulid, or periodically [e.
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Several samples are taken at the drawpoint and then prepared and analysed underground Cokayne, The operator can see information related to ring location 1last bucket weight 2ring design 3extraction ratio ratio of the total tonnage of material loaded from the drawpoint to the estimated tonnage of the ring 4system status 5report status 6loading graph 7nearby charged holes 8ring information 9and extraction ratio of proximate rings As a result, loading is stopped when an opening is encountered at the drawpoint because of a gap between the muckpile and the drift roof.
In general, loading is stopped when all three loading criteria are fulfilled, but closing the drawpoints is a subjective decision and depends on the assessment of the loading personnel. Loading near ore boundaries: PFC3D modelling of flow behaviour in sublevel caving. Qualitative comparison of current draw control strategies Detailed descriptions of draw control strategies used at sublevel caving mines around the world are normally not published in the open literature, making it difficult for researchers to objectively assess their quality.
Drawpoint monitoring systems can be divided into three types based on the technique used.