Bulk Mining Methods Research Articles

Applying Receiver-Operating-Characteristic (ROC) to bulk ore sorting using XRF

As high grade deposits become depleted, the mining industry is challenged by mining lower grades that require the use of non-selective bulk mining methods. Bulk ore sorting can reduce the dilution of the mined ore thereby preventing costly processing of low grade waste while improving the quality of material reporting to the processing plant. X-Ray Fluorescence (XRF) is one of the sensing technologies used for bulk ore sorting. The grade of the bulk material is predicted based on XRF measurement that is correlated to a grade using a calibrated algorithm. The effectiveness of XRF bulk sorting depends on the accuracy of the grade classification of the scanned material. False classification is attributed to poor performance of the sorting algorithm to correlate the measurements with the assay grades.The paper presents an approach to analyze XRF measurements that reduce misclassification of material. Receiver Operating Characteristic (ROC) was applied as the tool in classification of bulk materials. The performance of this approach was compared to conventional sorting algorithm, namely, simple linear regression (SLR), where XRF responses was linearly correlated to the assay grades. The ROC approach was found to result in more accurate classification and enhanced economics performance of the bulk ore sorting system.

Development of an Underground Haulage System Evaluation Tool for Feasibility Studies

The mining industry faces many difficult challenges, for example, lower ore grades, smaller and deeper deposits, and longer transportation distances. In the past, there have been remarkable innovations in both equipment and the types of mining methods for which it is used, which have resulted in economies of scale. This has led to an increased use of bulk mining methods, like sublevel and block caving, which has increased productivity and reduced costs. Haulage alone plays a major role. Current haulage techniques are a significant cost driver, which account for between 15 and 30% of the overall capital investment (capex) in a mine and are an increasingly part of the operating costs (opex). The paper introduces a simulation tool of main haulage system in underground mining. Therefore, performances and the costs of the three most common underground main haulage systems, rail, truck, and conveyor, are calculated using a developed modeling tool. The tool was applied and validated in a case study carried out with the LKAB Kiruna Mine in northern Sweden.

Multifractal Modeling of Worldwide and Canadian Metal Size-Frequency Distributions

The Pareto-lognormal frequency distribution, which can result from multifractal cascade modeling, previously was shown to be useful to describe the worldwide size-frequency distributions of metals including copper, zinc, gold and silver in ore deposits. In this paper, it is shown that the model also can be used for the size-frequency distributions of these metals in Canada which covers 6.6% of the continental crust. Like their worldwide equivalents, these Canadian deposits show two significant departures from the Pareto-lognormal model: (1) there are too many small deposits, and (2) there are too few deposits in the transition zone between the central lognormal and the upper tail Pareto describing the size-frequency distribution of the largest deposits. Probable causes of these departures are: (1) historically, relatively many small ore deposits were mined before bulk mining methods became available in the twentieth century, and (2) economically, giant and supergiant deposits are preferred for mining and these have strongest geophysical and geochemical anomalies. It is shown that there probably exist many large deposits that have not been discovered or mined. Although overall the samples of the size-frequency distributions are very large, frequencies uncertainties associated with the largest deposits are relatively small and it remains difficult to estimate more precisely how many undiscovered mineral deposits there are in the upper tails of the size-frequency distributions of the metals considered.

Analysis of block stability for semi - level caving method with lateral loading

In the current conditions for global underground mining, with the new ore deposits lying deeper and deeper, with reduced ore grades, the bulk mining is a necessity. Only high production level provides chances for positive economic results of underground mining. The high productive mining methods enable significant reducing of costs per ton of excavated ore. Different variants of block methods belong to this group of bulk mining methods. One of them, named the semi - level caving, is present in this paper, with analysis of its block and drawbells stability.

Control of dilution using the modified creeping cone method at Selebi North Mine

Mining companies are adopting bulk mining methods in their operations because they are safe and can be easily mechanized and automated. The introduction of the creeping cone method at Selebi North Mine in Botswana reduced ore dilution by a half. However, the low grades of the mineable reserves in the deeper sections of the mine require further reductions in dilution to mine profitably. The modified creeping cone (MCC) method was designed to create stable stope wall conditions and give lower dilution levels. Voussoir arch and simple beam theory methods were used to design the MCC method. The results show that for stopes 50 m high and 4 – 22 m wide, 50 – 185 m of room span can be mined using cable bolt reinforced walls. With the MCC method, ore dilution can be reduced to 19.2% while ore grades will increase by 10.5%.

Vipiteno mine, Italy – underground mining for marble

There is increasing emphasis on the underground mining of industrial minerals in the UK and Europe. A recent example is Vipiteno mine in Northern Italy, whose products are crushed and powdered translucent white marble. The marble is in seams with minimal dark mineral impurities, about 20–30 m thick, dipping at about 45–50° extending about 1·5 km along strike and several hundred metres down dip. The mine is in mountainous terrain subject to heavy winter snowfalls. Production strategies have been developed using high and low elevation underground mines. A combination of large cross-section development and bulk mining methods has been adopted, notably open stoping with drawpoint extraction. Stopes excavated to date are up to 50 m high x 20 m true thickness x 80 m along strike. Higher stopes are planned. The rock mass is of good quality, with a GSI rating of up to 70 and a Q rating of up to 15. It is dominated by very continuous bedding, which controls hanging-wall stability. In some locations, faulting also exerts control on hanging-wall stability. The mass strength is about 24 MPa and the in situ stresses are estimated at 5–10 MPa. Pillars have been designed conservatively and the major design challenge is the hanging-wall stability. Extensometer instrumentation has been installed to monitor hanging-wall stability in some early stopes and these indicate stable behaviour to date. It is planned to modify current mining methods to minimise development costs by simplifying and eventually eliminating drawpoints.

Nickel Laterites: A Review

ABSTRACT Nickel laterite deposits are formed by the prolonged and pervasive weathering of Ni silicate-bearing ultramafıc rocks, generally in tropical to subtropical climates. The deposits can be further classifıed as hydrous silicate deposits (e.g., SLN Operations, New Caledonia), clay silicate deposits (e.g., Murrin Murrin, Australia), and oxide deposits (e.g., Moa Bay, Cuba; Cawse, Australia) on the basis of the ore mineralogy. The physical and chemical nature of a nickel laterite deposit is a function of many factors, including the composition of the parent rock, the tectonic setting, climate, topography (specifıcally, laterite morphology), and drainage. Nickel laterite ore is extracted using both selective and bulk mining methods in open cast mining operations. The mined ore has traditionally been processed either by hydrometallurgical leaching technology (pressure acid leach or Caron processes) to produce oxides of nickel and cobalt or mixed Ni-Co sulfıdes for market, or by pyrometallurgical smelting to produce ferronickel granules or nickel matte. However, recent advances in high-pressure acid leaching and continued testing of atmospheric leach technology should lead to a reduction in overall operating costs and increased exploitation of Ni laterite resources in the future.

Rock mechanics aspects of mechanised and bulk mining methods at Western Areas Gold Mine : James, T V; Leih, D L Proc ISRM International Symposium on Static and Dynamic Considerations in Rock Engineering, Swaziland, 10–12 September 1990 P147–156. Publ Rotterdam: A A Balkema, 1990

Rock mechanics aspects of mechanised and bulk mining methods at Western Areas Gold Mine : James, T V; Leih, D L Proc ISRM International Symposium on Static and Dynamic Considerations in Rock Engineering, Swaziland, 10–12 September 1990 P147–156. Publ Rotterdam: A A Balkema, 1990

Geology of the DeLamar silver mine, Idaho; a volcanic dome complex and genetically associated hydrothermal system

The DeLamar silver mine, located in southwest Idaho, produced over 17 million ounces of silver and 230 thousand ounces of gold by bulk mining methods between 1977 and late 1987. The mine occurs within the Silver City rhyolite--an extensive and complex sequence of middle Miocene silicic volcanic flows and domes that unconformably overlie a thick pile of Miocene alkali olivine basalt. The basalt overlies Late Cretaceous granite which is correlative with the Idaho batholith. All three major rock types contain epithermal silver-gold veins, although rhyolites such as those at DeLamar, are the only hosts for low-grade, large tonnage mineralization.The DeLamar mine occurs within a sequence of six pervasively altered silicic volcanic units. From oldest to youngest these units have the following informal designations: (1) porphyritic latite, (2) quartz latite, (3) tuff breccia, (4) porphyritic rhyolite, (5) banded rhyolite, and (6) millsite rhyolite. The porphyritic rhyolite unit is spatially, temporally, and genetically related to silver-gold mineralization and is the principal host rock at DeLamar. This unit was emplaced as coalescing and overlapping lava domes and was preceded by cogenetic eruption of tuff breccia in the form of tuff rings. The emplacement of tuff rings and lava domes was controlled by structures related to a shallow level magma body and regional basin-and-range faulting. Onlap of banded rhyolite preceded hydrothermal activity and served as an important control on localizing ore deposition. The mineralogic character of ore and alteration at DeLamar is similar to adularia-sericite-type volcanic-hosted epithermal deposits, but the geologic setting is more like that of acid-sulfate deposits.

Microprocessor-Controlled Down-The-Hole Drill for Enhancing Productivity and Accuracy in Underground Hardrock Bulk Mining Methods

Underground bulk mining methods are being used increasingly where geology and ground conditions permit. Relative to alternative methods, they are more productive and safe. Down-the-hole drills are commonly used in bulk mining to drill blast holes. Although present performance is satisfactory, further improvement is possible from more accurate initial drill setting and the availability of on-line drill azimuth and deviation reports. Microprocessor-controlled accessories developed to achieve these goals are described.

The Future of Large, Low Grade, Hard‐rock Tin Deposits

The price of tin is at historically low levels and tin is in oversupply. Present production is largely from alluvial deposits worked mainly by small‐ and medium‐sized producers. These producers, often undercaptilized and working deposits of declining grade, are faced with rising production costs. It is expected that many will cease production in the future. Interest is therefore beginning to focus on the viability of exploiting large hard‐rock tin deposits amenable to low‐cost bulk mining methods. Among the countries which appear to have very large reserves of hard‐rock tin deposits is China, and it is anticipated that in the future China will be a major supplier of tin.