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By J. E. Matta

The methane gas emitted from coal samples collected from the conveyor belts dumping into silos was measured by the Bureau of Mines. Approximately 50 pct of the total gas desorbed into a sealed can within 1 week was released during the first 24 hours. No simple correlation between the gassiness of the coal stored and the methane concentration in the silo open space above the coal was found. This was probably because the gassier coals were stored in open-top Silos, which were better ventilated. Although the methane concentration in the open space above the coal pile was less than 1 pct for all 34 silos investigated, a methane measurement in the coal pile showed that high methane concentrations can exist. The methane released in the pile appears to accumulate and not liberate freely into the open space above the coal pile. Probably this gas is released during reclaiming operations, but further research is required to substantiate this claim.

Jan 1, 1978

By S. Borner Schweizer

An overview over SAM’s approach to assess corporate sustainability performance illustrates how sustainability challenges are linked to trends, assessment criteria and finally company performance. This process is exemplified with some general and industry specific criteria. Lastly, results of the Dow Jones Sustainability Assessment 2004 show a considerable gap between leading and average companies. Best practice examples demonstrate how lagging companies could improve their sustainability performance.

Jan 1, 2005

By T. Bernard, P. Dozolme

Electronic initiation devices appeared on the market more than 15 years ago and have definitely changed the rules of blasting. It becomes clear that this technology represents a powerful alternative to the traditional accessories. Electronic Delay Detonators (EDD) have attained solutions that were difficult and even impossible to achieve with the previous technology, thanks to the accuracy, usually inferior to one millisecond, and flexibility of the programmability range offering thousands of timing possibilities. Technological progress is long awaited to represent a step ahead compared with the last generation of products. In the case of electronic initiation, some limits nevertheless rapidly appeared, leading to the paradox of loosing operative and safety benefits, compared with the traditional technology it was supposed to outclass.

Jan 1, 2006

The New Technology of Enrichment of a Fine Low-Grade Tungsten from Complex Multi-Metallic Ore

Sep 13, 2010

By Ren G. Dong, Jay Kim, Daniel E. Welcome, Won Joon Song, Charles Hayden

Prolonged, extensive exposure to hand-transmitted vibration could cause a series of vibration-induced disorders in the vascular, sensorineural, and musculoskeletal structures of the human hand-arm system, which have been collectively called hand-arm vibration syndrome (HAVS).1 To assess the risk of HAVS the international standard ISO 5349-1 (2001)1 recommends using the root-mean-square (rms) acceleration of the measured vibration with a frequency weighting. While a few epidemiological studies have reported results consistent with the predictions made according to the recommendation, many other studies have reported results with large discrepancies.2 This may be partially attributed to the time-averaging effect involved in calculation of the frequency components, especially for impact type tools. Because the spectral characteristics of impact tools change dramatically with time, a time-frequency (T-F) analysis can provide better characterizations of such highly transient vibrations. The analytic wavelet transform (AWT) is an ideal T-F analysis tool because it possesses the advantages of both the Fourier transform and the wavelet transform.3 The objective of this study was to explore the application of the AWT method for characterizing the impact tool vibrations and assessing their exposure risk. Methods Five tools (two chipping hammers, two riveting hammers, and one concrete cutting saw) were used in this study. The saw vibration was measured when it was used to cut a section of road pavement during a repair. The vibrations on the other tools were measured by the procedure specified in ISO 8662-2 (1992).4 A sampling rate of 16,386 Hz was used in the measurement. The AWT and Fourier analysis were applied to these signals and to identify their characteristics. Results Figure 1 compares the T-F characteristics of the accelerations measured from the relatively steady concrete saw and a riveting hammer. The frequency weighting specified in ISO 5349-11 was applied in the calculations. The comparison clearly shows that the two tools have completely different T-F characteristics.

Jan 6, 2006

By E. L. Garton

[Analyses of may crude oils produced in Louisiana are included in reports that t have boon published by the Bureau of Mines. The first report, giving, analyse of 6 Louisiana crude oils, was 3 published in 1921 and this was followed a year later by Report of Investigations 2416,4/ giving 7 additional analyses. The eleven most important of these analyses were incorporated in Bulletin 291.5/ issued in 1928 In 1934 analyses of 26 crude oils produced in southern Louisiana were published.6/ The percent report presents analyses of 72 additional samples of crude oil from 45 fields in 23 parishes In Louisiana.]

Jan 1, 1939

By Paul W. Mayne

Axial pile performance can be rationally evaluated within an elastic continuum framework using field results from seismic piezocone tests (SCPTu). Adopting a versatile Randolph-type elastic pile model, the approach can be applied to either traditional top down loading using an anchored reaction beam or the newer Osterberg cell that simultaneously pushes the base and shaft in opposite directions. The axial load distribution within the shaft is also evaluated. For site-specific data at a given site, the SCPTu is an optimal means for collection of subsurface information because it combines penetrometer readings and downhole geophysics in one sounding. The results obtained are at opposite ends of the stress-strain-strength curves, specifically the peak strength for capacity interpretations and the small-strain stiffness (Emax) for evaluating the initial deformations. Axial pile capacity can be analyzed using both direct and indirect CPT methods. As such, the approach allows for a complete representation of the axial load-displacement-capacity curve for pile response. Case studies are presented for deep foundations situated in stiff clays at two national geotechnical test sites located in Houston and College Station, Texas, using top down loading, as well as a third case study of a drilled shaft in clay till loaded by O-cell in Alberta.

Jan 1, 2009

By John Rusnak, Christopher Mark

Point load testing is used to determine rock strength indexes in geotechnical practice. The point load test apparatus and procedure enables economical testing of core or lump rock samples in either a field or laboratory setting. In order to estimate uniaxial compressive strength, index-to-strength conversion factors are used. These factors have been proposed by various researchers and are dependent upon rock type. This study involved the extensive load frame and point load testing of coal measure rocks in six states. More than 10,000individual test results, from 908 distinct rock units, were used in the study. Rock lithologies were classified into general categories and conversion factors were determined for each category. This allows for intact rock strength data to be made available through point load testing for numerical geotechnical analysis and empirical rock mass classification systems such as the Coal Mine Roof Rating (CMRR).

By D J. Black

Ventilation modelling is used to evaluate ventilation system performance. This paper describes modelling to assess potential changes to a single entry longwall ventilation circuit to improve ventilation and gas management. The longwall panel is extracting a 215 metre face in a 1.5 metre coal seam at a depth of 900 to 1000 metres below surface. The 1.5 metre B seam is located approximately 25 metres below the main 3.0 metre A seam and the gas content of both coal seams is approximately 20 to 25 m3/t. The B seam is extracted prior to the A seam and the mine relies on fracturing of the overlying strata to induce gas emission from the A seam to reduce the gas content prior to mining. Longwall operations in the B seam are constrained by limited ventilation and high gas emissions. Due in part to statutory limits on gas concentration and air velocity, the average longwall production rate is approximately 700 t per day.Gate roads in the B seam are single entry, developed using road headers and supported with steel arches. Additional timber cog support is installed to reduce roadway closure from abutment loading. Due to the slow advance of gate road development, mine management were reluctant to consider significant mine design changes, such as two heading gate roads; therefore, the investigation focused on determining the extent to which ventilation and gas emission impacted on longwall production performance, while recommending short-term, low-cost actions to improve ventilation and gas management to support increased longwall production.CITATION:Black, D J, 2017. Application of modelling to improve ventilation and gas management in a single-entry longwall panel, in Proceedings Australian Mine Vent Conference 2017, pp 239–244 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 28, 2017

By Alexander May

The Bureau of Mines, in cooperation with the Florida phosphate mining industry, investigated the dewatering of waste phosphatic slimes. Part of this investigation was to determine the electrophoretic mobilities and cation exchange capacities of the slimes. The mobilities and exchange capacities are reported for samples of slimes taken from 15 plants operating in the Florida land-pebble phosphate district that includes Polk,Hillsborough, Manatee, Hardee, and DeSoto Counties. The electrophoretic mobilities determined were all negative, ranging from -0.24 to -1.93 (micrometers per second) per (volt per centimeter). Also reported are frequency distributions of electrophoretic mobilities, electrophoretic mobilities of slime diluted with distilled water and electrophoretic mobilities of sand-slime mixtures. The cation exchange capacities ranged from 17 to 45 milliequivalents per 100 grams of slime solids.

Jan 1, 1975

By Barry D. Simmons

"A well-defined approach is essential to ensure the long-term success of a regional exploration program. Teck's approach in eastern Canada is designed to fulfill corporate objectives while recognizing certain unique parameters for exploration in the area. The elements of this approach include clearly defined objectives, technical considerations and personnel policies, all of which are equally important. The goal is a significant discovery before the mid-l990s and the company is confident that this target will be achieved.IntroductionAs one of Canada's oldest continuously operating mining companies, Teck Corporation traces its roots to Kirkland Lake, Ontario, with the development of the Teck-Hughes gold mine in 1913, later supplemented by production from the Lamaque gold mine in Val d'Or, Quebec. Control of the company was acquired by Temagami Mining Company, part of the Keevil Mining Group, in 1959. Credited as one of the first discoveries made using airborne geophysics, the Keevil Group had recently found the small but very high-grade copper deposits at Temagami, Ontario. These developments in eastern Canada formed a foundation for remarkable growth and Teck's present status as one of Canada's most successful and respected mining companies.Teck currently operates successful mining ventures across Canada and has international exposure through its association with Cominco Ltd., M.I.M. Holdings Limited and Metallgesellschaft AG. Operations in eastern Canada, however, remain an important component of Teck's ongoing success. The David Bell and Williams mines at Hernlo, Ontario, are Canada's lowest cost and largest gold operations, respectively. The Niobec Mine at Chicoutimi, Quebec, is North America's only significant producer of niobium. Teck maintains a 45070 interest in Golden Knight Resources Inc., part owner of the successful gold mining operation in the Casa Berardi area of northwestern Quebec. As a significant shareholder in Aur Resources Inc. and as a part owner, Teck is participating in the development of the Louvicourt deposit, a major base metal discovery at Val d'Or, Quebec."

Jan 1, 1992

By Maísa Villela Freire

Refratários MgO-C encontram-se entre os mais adequados para o uso na linha de escória de panelas para aço líquido. Seu comportamento, nesta aplicação, depende de fatores termodinâmicos e cinéticos. Métodos de cálculo termodinâmico para avaliar o potencial de degradação de refratários MgO-C por escórias e pela atmosfera são revistos brevemente. Tais métodos envolvem, em geral, premissas importantes sobre a quantidade de materiais envolvidos. Para avaliar um método mais simples, foram escolhidos dois tijolos MgO-C e duas escórias típicas do processo da CSN. Estes tijolos e escórias foram caraterizados, neste trabalho. O método apresentado consiste na realização de cálculos de equilíbrio em que a principal variável é a fração de escória em uma mistura hipotética com o refratário. Para a composição do refratário foram empregadas (a) composição média e (b) composição da matriz do tijolo. Os resultados indicam que é possível realizar previsões iniciais quanto à reatividade do refratário e determinada escória de forma simples. Os cálculos, evidentemente, não substituem testes cinéticos e testes em escala industrial, em vista da complexidade dos sistemas em questão.

Aug 17, 2017

Many of the world?s largest existing mines are considering substantial step changes in production volumes, compensating for declining ore grades while trying to address increases in world demand for resources. The natural configuration of coal deposits allows for many mine development openings along the strike to access the ore body and thus increase volume. Similarly, with iron ore the nature of the deposits means that additional capacity can easily be added by opening up new mesas and providing extensions to infrastructure. On the other hand most of the non-ferrous metaliferous deposits form vertically and additional extraction volume comes from increasing depth. Underground mining from the base of the strata allows for large extraction rates, but block or panel caving operations develop at rates dictated by the geophysics of the overlying strata and the need for massive tunnelling developments to establish sufficient extraction points for high volumes. For really big mine production capacity, open cast mining still allows the easiest development of more massive mining techniques. But there remains the question of whether there are limits to how large an open cut mine can become in terms of throughput?

Feb 27, 2013

By R. D. Begley, A. W. Khair

Introduction The technique being investigated here uses a physical mine model which consists of a plexiglass room-and-pillar model 11.4 x 11.4 cm (4.5 x 4.5 in.). It is placed at the bottom of a larger plexiglass box 25.4 x 30.5cm (10 x 12 in.). The box is then filled with a model material representing geologic overburden. Sand has been selected because of its deformability under gravitational forces. The mine model is capable of creating a cavity and induces movement on the surface of the model material. This surface disturbance can be measured using a photographic technique called holographic interferometry. This paper discusses results of an investigation of the possibility of generating subsidence criteria using physical mine models and laser holographic interferometry. Problem Statement Subsidence appears to be widespread in two states - Pennsylvania and Illinois - although serious subsidence is found in localized areas of numerous other states (HRB Singer Inc., 1977). The US Bureau of Mines estimates that more than 1618 km2 (400,000 acres) of urban areas are threatened by subsidence. Pennsylvania and West Virginia contain 57% of these threatened areas, with the remainder being spread out over 16 states (Johnson and Miller, 1979). Events of subsidence have been reported in urban areas, including Pennsylvania (Gray et al., 1977) and Illinois (Mahar and Marino, 1981). One location has observed three episodes of subsidence beginning in 1950 (Bruhn et al., 1981). These subsidence events all occurred over abandoned room-and-pillar mines. Some mines have been abandoned more than 50 years (Bauer and Hunt,1981) . Available research does not offer much on the problem related to time dependent subsidence, especially those associated with the failure of remnant coal pillars. The physical modeling technique developed at West Virginia University is capable of measuring both instantaneous and time delayed subsidence. Laser Holographic Interferometry Laser holographic interferometry, or holometry, uses the interference properties of laser light to measure small movements of objects. The object requires only optical access and no surface instrumentation. This technique is closely related to photoelasticity. Both techniques rely on the uniqueness of the light reflected off or through an object in any given state of stress. The entire measurement process is done remotely without any surface instrumentation and without using a camera. The interferogram is constructed and visual observation will yield fringes on all areas that yielded or moved. The displacement represented by one fringe was determined by Wilson et al. (1977) and is given by the relationship: [d ='1(1) 2 cos 8 where d = displacement of one fringe 6 = incident angle of laser light A = wavelength of light (632.8 x 10-9 meters for Helium-Neon lasers)] In summary, holometry is capable of detecting very small movements of objects under study. It is a very sensitive process that requires laser light and vibration free experiments. Experimental Program Lab Facilities The primary components of the facilities were the laser and the optical table. The light source was 50 milli-watt, Helium-Neon laser. The optical table was a granite slab weighing nearly one ton. All experiments were performed on the optical table. It consists of a large table sitting on air cells similar to car innertubes. Six air cells were placed on top of two layers of wood and Styrofoam. Figure 1 is a schematic diagram of the vibration free table. Even with these precautions, the experiments still had to be performed at night to reduce potential traffic related vibrations. Room-and-pillar mine models consisting of three different pillar sizes were constructed out of plexiglass. The models were designed to represent three different extraction ratios. Figure 2 shows the models. The extraction ratios were determined by the tributary loading concept (Peng, 1978). These models were the primary component of a seam extraction simulator. A schematic of this simulation device is shown in Fig. 3.

Jan 1, 1986

By Greg Rasmussen

"Huckleberry Mines Ltd is an open pit porphyry copper-molybdenum mining operation located 120 km south of Houston, British Columbia with a 18,000 tpd milling facility. Huckleberry Mines is owned 60% by Princeton Mining Corporation, the operator, and 40% by Japanese partners.The Huckleberry deposit is one of several porphyry systems located in the Tahts a district of the intermontane belt of British Columbia. The principal economic minerals are chalcopyrite and molybdenite. The ore deposit is split into two ore deposits, the Main Zone, consisting of24,241,000 tonnes of mineable reserves grading 0.484 %Cu and 0.013 %Mo, and the East Zone, consisting of 66, 131,500 tonnes of mineable reserves grading 0.523 %Cu and 0.014 %Mo.The milling begins with gyratory crushing. This sizes the product down to 100% passing 6 inches. This product is discharged onto a stockpile by a stationary conveyor. The stockpile was designed for a capacity of 144,000 tonnes with a live capacity of 20,000 tonnes. Two apron feeders draw the ore from the bottom of the stockpile and discharge onto a SAG mill feed conveyor which in turn feeds a grinding circuit consisting of one 32' x 15' SAG mill and two 30' x 16.5' ball mills. The grinding cyclone overflow feeds bulk flotation at 55 -65% minus 200 mesh.The bulk flotation uses conventional rougher and column flotation methods to float a bulk concentrate recovering 92.6% copper on the East Zone and 95% copper on the Main Zone with 75% recovery molybdenum on both zones. The bulk concentrate feeds the bulk thickener which produces a density of 60 %solids. This in turn feeds the molybdenum circuit, which separates the copper and molybdenum, by depressing the copper then using conventional rougher and column flotation produces a copper concentrate of 27 %Cu and 0.02 %Mo, and a molybdenum concentrate containing 1.5 %Cu and 54 %Mo at 67% recovery. These concentrates are separately thickened, filtered, dried, and shipped to the smelter for processing."

Jan 1, 1998

By Rolf Katzenbach

The principle questions related to the design of deep foundations especially in soft soils are the stability and the cost optimised settlement reduction to prevent possible damages and to minimise the deformations of the adjacent infrastructure. The present develop­ments in the design of deep foundations lead to the design approach of the Combined Pile-Raft Foundation (CPRF) which offers a lot of new possibilities, e.g. the utilisation of the CPRF for horizontal loading or the use of the subsoil as a geothermal storage system.

Jan 1, 2006

By F. J. N. Bruwer, T. R. Stacey

The research described considers whether the variability in coal material strength, as derived through a series of uniaxial compressive strength (UCS) tests, could be used to indicate the variability in coal pillar strength. The aim is to be able to use a distribution of UCS tests as input into the coal pillar strength calculation. This will allow the pillar design to be expressed in terms of a probability of failure rather than as the commonly used safety factor. To achieve this, the bulk strength factor associated with commonly used pillar strength formulae was replaced with a distribution of UCS results divided by an adjustment factor. The factor was determined so as to ensure that the resulting bulk strength does not deviate from the statistically determined bulk strength published in the original formulae. This approach enabled pillar strength distributions to be obtained using industry-accepted strength formulae, subsequently allowing for a probability of failure to be calculated for a specific pillar design. Using a regional coal material strength curve as a baseline, coalfields in which the coal is stronger than the regional mean can be identified and the pillar designs optimized. This is based on the stronger coals achieving lower probabilities of failure at similar safety factors. The research has considered actual UCS data from multiple mines in the Mpumalanga coalfields of South Africa, and has proved that the variability in material strength between coalfields could allow for some optimization using the proposed approach. Based on the data used in the study, a 2.78% increase in extraction could be achieved. However, further research will be required to validate the results of the study in an underground environment.

May 3, 2023

By R Simcock

Why Rehabilitate? Legislative Requirement Land rehabilitation is a condition of resource consents for mining. Clause 17 (1) of the Resource Management Act 1991 (duty to avoid, remedy, or mitigate adverse effects) provides the legislative basis for local authorities to impose resource consent conditions requiring land to be rehabilitated to approved uses during and after mining.

Jan 1, 1997

By Steve Dillingham

Whenever misfired holes or portions of misfired holes remain after a blast is fired, a hazardous situation exists until the unfired explosive materials have been disposed of properly. Yet, there are so many factors that can contribute to misfires that it is impossible to give blanket instructions on how to handle them. To complicate matters, misfires today are rare due to reliable blasting products. As such, it isn’t very surprising that many blasters have never had to deal with a misf i re condition. While the likelihood of a misfire occurrence is minimal, you should always be pre p a red to handle a misfire should you be involved in such an event. To begin, every blaster and blasting org a n i z a t i o n should develop a misfire policy which contains the company’s safe operating pro c e d u res, emergency contact list, as well as any regulatory compliance re q u i re m e n t s . Tailgate and/or company-wide safety meetings should communicate the company’s contingent misfire pro c ed u res and any special site-specific precautions BEFORE the start of any project.

Jan 1, 2004

By R. L. Blake

The crystal structure of hematite, a-Fe203, has been refined as part of a continuing study of the behavior of phases in the Fe-O system during reduction and oxidation. Three-dimensional diffraction intensities were collected on two spherical single crystals of hematite with a semiautomated Buerger single-crystal diffractometer. The first crystal refined was a natural Elba hematite with minor impurities. The other, a synthetic crystal, was refined at the request of Mossbauer spectroscopy investigators concerned with impurities in the natural crystal. The structure has been refined with a least-squares program and the final structure for the natural crystal irradiated with CuKa-radiation gave a discrepancy factor (R) of 3.65 percent using 49 unrejected reflections of the 51 measured. For the synthetic crystal, using MoKa-radiation, the discrepancy factor converged to 2.8 percent using 95 unrejected reflections and was 3.3 percent for all 109 reflections. The structure model of Pauling and Hendricks has been confirmed with essentially no change in the iron coordinates and approximately a 5-percent change in the oxygen coordinates. Selected interatomic distances and angles were calculated as were anisotropic temperature factors.

Jan 1, 1970