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By Guosheng Zhan

The Homestake Mine included the open cut and underground workings up to 2,484 m (8,150 ft) deep. The mine ceased mining activities in December 2001 after 125 years of operation. Pumping from the underground workings continued for 18 more months until June 10, 2003. Homestake had completed a comprehensive hydrologic evaluation on post-closure underground flooding prior to the shutdown of pumping. After closure, the mine was selected by the National Science Foundation as the site for the Deep Underground Science and Engineering Laboratory (DUSEL). An interim laboratory facility will be set at the 1478 m (4850 ft) Level. The final facility will be set at the 2256 m (7400 ft) Level or deeper. Pumping from the underground workings began on June 5, 2008 by the South Dakota Science and Technology Authority (SDSTA). During the period of June 2008 through March 2009, the pumping rate increased from 41 L/s (650 gpm) to 81 L/s (1,290 gpm) with an average rate of 60 L/s (950 gpm). As a result, the water level had been lowered more than 95 m (310 ft). It was found that the observed rebound and later decline to date is in close agreement with the model projections. Because of this, the authors of this paper reject claims of a lack of sufficient measurement devices in place and a lack of understanding of the hydrologic system at the Homestake Mine prior to shutdown of pumping in 2003 (Davis et al, 2009). Furthermore, it is believed that this validated model can serve as a useful tool for the SDSTA to manage future underground dewatering for the DUSEL operation. This paper evaluates the hydrologic conditions in the Homestake Mine area and projects the post-closure groundwater rebound and decline due to DUSEL pumping.

Jan 4, 2010

By M. Mankosa, G. Taylor, G. Luttrell, J. Yasalonis

Several industrial-scale HydroFloat separators have recently been installed at Mosaic’s South Fort Meade beneficiation plant for the purpose of improving phosphate recovery and throughput capacity. This technology was implemented after numerous laboratory, bench-scale, and on-site, pilot-scale test campaigns. The results from this detailed test work provided sufficient justification for the complete retrofit of the existing coarse and ultra-coarse flotation cells. Data indicate that the metallurgical results obtained with the full-scale separators are consistent with that obtained during both the bench- and pilot-scale evaluations. The apparent benefits, theory of operation, and commissioning of the equipment are also discussed.

Jan 1, 2007

By Jean J. Abiassi

The Boston Marine Industrial Park (BMIP) VENT 6 project is a cut and cover tunnel, part of the Central Artery / Tunnel (CA/T) in the city of Boston. The BMIP job will serve as the south approach to the Third Harbor Tunnel crossing. The alignment is approximately 2500 Ft long and is made up of four sections starting from west to east: 1. West Tunnel 2. Boat Section 3. East Tunnel 4. Tunnel inside Vent 6 Cofferdam and connection to the Third Harbor Tunnel. The support of excavation (SOE) system for the West Tunnel, Boat Section, and East Tunnel are all a part of this project whereas the SOE for Tunnel inside the Vent 6 Cofferdam was a part of the contract for the Third Harbor Tunnel.

Jan 1, 1994

By D. E. Pollock

Recent NIOSH published information has shown an increase of rapidly progressive coal workers? pneumoconiosis (CWP) in the southern Appalachian coal region (SAR) of the U.S., despite the fact that compliance data indicates that most coal miners have been exposed to coal mine dust concentrations below the statutory limit of 2.0 mg/m³. While the exact cause of these elevated CWP levels in the SAR has not been established, several factors may be contributing to the increase in occupational lung disease among coal miners. The mining of high rank coal is known to lead to higher CWP rates, and this type of coal is mined in a portion of this region. Also, a high percentage of the mines in the region are on reduced dust standards because of the high silica content of the airborne dust resulting in miners possibly being exposed to excessive amounts of respirable silica dust. Exposure to excessive amounts of respirable silica dust can lead to silicosis, a disabling and potentially fatal lung disease. NIOSH's Respiratory Hazards Control Branch has been investigating the possible causes that would account for the observed higher trends in disease progression through literature review, data analysis, and in-mine surveying. The investigation to date has revealed that underground mines are faced with cutting large amounts of rock in order to maintain haulage clearances. Cutting rock not only increases the potential for silica exposure, it increases the requirement for machine maintenance which was a concern observed during dust surveys conducted by NIOSH. Over half of the mines operating in the SAR are on reduced standards due to high silica content. Adequate face ventilation of the continuous miner and roof bolter and limited down-wind operations from the miner are also issues of concern and items which require the constant attention of miners operating in these conditions. Disclaimer: Mention of any company or product does not constitute endorsement by the National Institute for Occupational Safety and Health.

Jan 1, 2009

By J. Chilton

The fact that methane ignitions continue to occur at the mining face indicates that monitoring with machine-mounted methanometers does not always indicate the presence of high methane concentrations. Methane concentrations at the face change quickly due to changes in airflow. By measuring these changes in airflow, it may be possible to predict changes in face methane levels more quickly. Currently there are no techniques or instruments to accurately measure airflow in by the mouth of the ventilation curtain or tubing. Tests conducted in the NIOSH ventilation test gallery compare the data provided by one-, two-, and three-axis ultrasonic anemometers. The effects of changes in airflow direction and turbulence on instrument readings are discussed, and guidelines are given for selecting the type of instruments to be used for monitoring airflow near the mining face.

By I. R. Firth, D. L. Taylor

Metal mining operations, in particular gold mining operations, use intensive ore control procedures in order to manage the extraction of ore zones from benches containing both ore and waste material. Typical grade control procedures rely on blast hole samples to indicate ore grade. Statistical techniques and geological controls are then used to create two-dimensional polygons, which indicate zones of material designated as ore. These ore-polygons are calculated using pre-blast material locations and are generally not corrected for rock movement caused by blasting. This lack of correction appears to exacerbate the material mischaracterization problem of sending ore to the waste dump and/or waste to the mill. One Nevada gold mining company has estimated that this could be a $10 million per year problem for their operations. Using a simplified vector field algorithm, a method of taking point movement data and interpolating post-blast positions for all nodes in a polygon has been developed. Currently working in 2-dimentions (X-Y), this algorithm utilizes the movement vectors calculated from pre-and post-blast positions of targets placed in a blast, to generate a spatial transformation function for any point on the bench. This transformation is then applied to the nodes of the ore-polygons to produce modified dig lines ore polygons reflecting distortion and movement resulting from the blast. The method as implemented uses common mine planning routines and is performed using the Surpac software suite. The method may be adapted to use any pre-and post-blast point movement data available, and most mine planning suites include the simple interpolation algorithms used. Keywords: Blast movement; Ore control; Open pit blasting; Grade control

Jan 1, 2003

Most statistical and geostatistical methods of re-source and reserve estimation work extremely well for Normal (Gaussian) well-behaved information. However, most interesting mineral deposits exhibit far from this idealistic distribution of values. It seems that the more valuable the mineral, the less likely the data are to have a Normal distribution. Values tend to be "positively skewed" with a long tail into the high values. Using averaging techniques, such as inverse distance or ordinary kriging may result in consider-able overestimation of grades and tonnages unless such values are cut or otherwise modified. This paper presents some real case studies where distributions are (a) highly skewed and (b) the product of multiple phases of mineralisation. Practical methods are presented for solving such problems including combinations of indicator and log normal kriging methods. The emphasis of the presentation is on developing operational methods which can be used on project evaluation or grade control in producing mines.

Jan 1, 2000

By Ellisworth R. Spencer, Lynn A. Alcorn, Peter G. Kovalchik, Adam K. Smith

Noise induced hearing loss (NIHL) is the most common occupational disease among workers in the mining industry. Previous studies conducted by the National Institute for Occupational Safety and Health (NIOSH) have shown that approximately 90% of coal miners and 49% of metal/non-metal miners have a hearing impairment by age 50. The Mine Safety and Health Administration (MSHA) has determined that continuous mining machines rank first among all equipment in underground coal mining whose operators exceed 100% noise dosage. The conveying system is one of the principal noise sources on continuous mining machines, due to metal on metal impacts that occur between chain flights and the conveyor deck. A highly durable polyurethane coating has been developed for the chain flights to decrease noise generated by these impacts. A continuous mining machine retro-fitted with coated flight bars has achieved overall sound level reductions of 5-7 dB in a laboratory setting. This paper evaluates the effectiveness of this engineering noise control in reducing the noise exposure of continuous mining machine operators in an underground coal mine environment. The results show that the operator of a continuous mining machine utilizing the coated flights receives a predicted 35% reduction in total work shift noise dose.

By Matthew A. Baumann

Tooth-wear on mining shovels requires continuous monitoring. Worn teeth impede excavation performance, increase energy usage, and increase the risk of lost or broken teeth and adapters. A machine-vision-based automated tooth-wear monitoring system is presented. The system employs a rugged boom or stick-mounted camera to capture images of the shovel teeth. An onboard computer processes the images in real-time to determine the length of each tooth. The current wear state is available via a network-accessible log for on-demand status updates. By continuously recording tooth length changes over time, the logs can be used to estimate wear rates and patterns, permitting comparisons between different G.E.T. configurations, operator behaviour patterns, or material types. This detailed, quantitative data permits site-specific optimizations to wear packages and maintenance scheduling. Automating wear monitoring offers the crucial wear information necessary to minimize maintenance costs and reduce unscheduled downtime. A 37-day field trial in a copper-gold mine demonstrated the ability of the system to measure tooth lengths, compute wear rates, and detect differences in tooth wear based on their position on the bucket.

Nov 1, 2011

By Claude Cunningham

Ths oonoept of precise. eooursts timing with Elsotronic Delay Detonators (EDD’s) was first ssriously sddresssd in ths mid 80’s end much wss made of the cheapness end profusion of digital wstohes in terms of the likelihood of EDD’s also being cheap and essyto produce. Ten years Iater. with every major explosives group end many elsotronios groups having instituted projects to capitalize on the promise of these devices, production devices are still to come into asneral use.

Jan 1, 1994

By Victor C. Bryan

One of the most sought after answers in any consideration of blasting activities relative to mines and quarries is how to safely and efficiently use explosives. While that discussion might be relatively straightfonvard in a “site specific” situation. it becomes more complex when viewed from a broad geographic perspective. Such is the case in considering the operations of one United States producer of crushed stone with surface and underground mines spread over a thirteen state area. Differing geologic environments set conditions that dictate to the blaster as now specifically to get optimum results from the blast hole. This treatise is a discussion of the various methods, materials, and principles used in conducting such blasting operations.

Jan 1, 1991

By G. F. Friel, J. C. Edwards

A series of seven underground-coal-mine fire experiments was conducted in the Safety Re-search Coal Mine at the National Institute for Occupational Safety and Health, Pittsburgh Research Laboratory. Coal and styrene-butadiene-rubber conveyor belting were burned upwind of two sensor stations, 18 m and 148 m from the fire source. Exhaust from a diesel locomotive flowed over the fire sources in six of the tests. Metal-oxide-semiconductor (MOS), CO, and optical-path-smoke sensors were positioned at both stations and found to be an optimum set of sensors for the fire discriminations. A representative set of 7,679 samples of CO data and data from the smoke and diesel-exhaust MOS sensors were used as inputs to train a neural network (NN). By testing 42,538 data samples from the seven experiments, all fires were detected by the NN within 9.67 min from the onset of significant changes in the MOS voltages without any false alarms.

By Murat Baydogan

Effect of retrogression and reaging treatment on hardness and stress corrosion cracking resistance of 7075 aluminum alloy was investigated. As received 7075 alloys in T6 temper condition were retrogressed at 170, 220, 240 and 380°C for different durations between 15 s and 60 min. Subsequent reaging was made at the T6 aging condition. Treated materials exhibited higher hardness and better stress corrosion cracking resistance than T6 temper in a wide range of retrogression temperature and time. The highest hardness was obtained after retrogression at 170°C for 210 s followed by reaging, corresponding to 20% hardness improvement. Improvement in stress corrosion cracking resistance of the alloy by as much as 85% was also observed. In this paper, improvements in hardness and stress corrosion cracking resistance are discussed on the basis of the microstructural changes during retrogression and reaging treatment.

Jan 1, 2006

By R. Dillinger

In the environmentally conscious social atmosphere today, reclamation in surface mines has become a main issue to the public and the regulatory committees. In response to this increased attention, many regulatory committees have begun to enact more stringent regulations on surface mining operations. Operations across all spectrums of the industry have seen changes. Recently and most visibly the mountain top removal mines have seen several new regulations focusing on environmental protection. Specifically regulatory committees have emphasized a focus on the methods of reclamation and recovery of layers suitable for vegetation. These layers are the most visible once the operation has concluded. Also, these layers have the most human interaction (farming, hunting, and house development). Often times the new regulations enacted are shifting from a performance base to a standards base. The key differentiator being a performance base dictates the final result while a standards base dictates the method to achieve the result. The very nature of many regulations (especially those that are standards based) not only challenges the physical limitations of the equipment used today, they come with a financial impact. For the purpose of this paper, the model will be a surface coal operation, utilizing draglines as primary overburden movers. The coal seam is ten feet thick, the overburden ninety five feet thick, the pits are 150 feet wide, and the dragline is a Bucyrus Erie 1570.

Jan 1, 2011

By B. J. Vorster

AngloGold South Africa region currently consists of twelve gold plants. These plants use a combined total of $20 million of cyanide per annum. Of this, the major portion (60%) is consumed at two Ergo dump retreatment plants. Historically the primary motivation for cyanide control at Ergo has been one of leach/cost optimization. However, more recently, with the increased public awareness of cyanide in the environment, a secondary but increasingly important motivation for control has been to ensure that only the minimum amount of cyanide is added to the process whilst not compromising leach performance. Following a brief overview of the Ergo process, the methodology in determining the amount of cyanide to be added is described. The paper then traces the developments in cyanide control from very basic manual systems to the current automated control system. In line with the increasingly sophisticated control systems, developments also took place in regards to the method of cyanide analysis. The development of these analysers is also discussed. Whilst cyanide is one of the major drivers, if not the major driver of gold dissolution, it cannot be viewed in isolation particularly with respect to the relationship between cyanide and oxygen as ascertained from the Elsner?s well-known equation. Consequently, in order to control cyanide addition, knowledge of the relative cyanide/oxygen profiles is necessary. Various means investigated at Ergo for pulp oxygenation have therefore been included for the sake of completeness. Finally a comparison is made of the control achieved from the current system compared to the original manual system. The knowledge and experience gained at Ergo is now being used to draw up guidelines for the installation and optimization work at the other AngloGold plants. The net effect of this will be reduced cyanide consumption for the region, which also, apart from the obvious economic benefit, translates into a reduced environ-mental risk.

Jan 1, 2001

The recovery of coarse particles has been widely recognized as being limited by the froth in mineral flotation. In response to this, FLSmidth has developed the Selective Froth Recovery (SFR) System. The SFR System is an extraction system that vacuums material from select locations within the froth and separates the recovered solids into coarse and fine fractions with a hydrocyclone. The SFR is supported and located by an actuator connected to the cell?s level control so that the suction heads are maintained at an offset distance from the slurry level. This can increase the recovery of coarse material by selectively recovering the material close to the bottom of the froth where drop-back of coarse particles typically takes place. The SFR System has been tested at two separate mine sites, and has been proven to increase the copper recovery in both trials. TEST RESULTS The SFR prototype was installed in a copper recovery circuit, on a rougher scavenger 160-m3 flotation cell. Figure 1, shows the SFR System, which consists of four conical skimmer heads that are plumbed together and share a common actuator. The SFR System, raised out of the froth prior to a test, can be seen in Figure 2. The SFR prototype was able to maintain a variety of set points using the level control to determine the slurry height.

Feb 27, 2013

By M. A. W. Bryson

It is well documented that a significant amount of the new PGM (Platinum Group Minerals) production that is coming on stream now, and over the next few years, is to come from the UG-2 reef. Clearly the reservations, or perhaps the perceived reservations, attached to the processing of this ore are no longer there. What were the metallurgical issues that delayed the exploitation of the PGM values from this reef? Traditional furnaces treating Merensky concentrates were not able to accept the concentrate produced from a UG-2 plant due to the relatively high chromite content of this product. The chromite reports to an insoluble spinel phase that accretes in the furnace, resulting in the necessity to shutdown and dig the furnace out periodically. This was clearly not an attractive economic option, so producers stayed away from it in the early days. The Merensky ore had all higher base metal credits anyway, and you needed them to get a matte fall, so there was no driving force to look seriously at the UG-2 reef. Platinum demand at this time could be easily met from the Merensky ore, so the motivation to tackle more complex ores was not there. The low price of PGMs meant that these operations were not particularly profitable and there was little effort directed at improving the operations. Concentrators were generally not run very efficiently and the emphasis was on cost reduction through increasing milling rates.

Jan 1, 2004

Jan 1, 1969

By J. Winterton

Estimating the residual metal inventory of large heap leaching operations is desirable for many reasons. Several methods have been tried with limited success. Drilling data from the Valley Leach Facility at AngloGold Ashanti's Cripple Creek and Victor Gold Mine has been used to develop a robust inventory estimation technique. The technique is presented along with discussion of the particular inventory components and evaluation methodologies.

Feb 27, 2013

By W C. Burton, J S. Kuszma, T O. Aspinall

The environmental impact of mining and evolving environmentallegislation has received increased attention worldwide in the last two decades (Bradfield, Shultz and Stone, 1996). The potential impacts associated with unstable spoil dumps from mine operations is the focus of concern both by the mining industry, environmental regulatory agencies and members of the public. Engineered slopes of mine spoils may be stable at the end of construction, but they can deteriorate over time. There is thus the need to increase the base of knowledge on the existing practices of spoil dump design and rehabilitation. Efficient engineering design and systematic economic evaluation of spoil dump reshaping techniques for mine rehabilitation assists in maintaining the expected standards of environmental compliance. As part of the overall approach for effective engineering design ofspoil dumps, a comprehensive, computational and efficient tool isrequired for assessing the economics and productivity of existing spoil dump reshaping practices for efficient mine rehabilitation. Such a design tool is useful in linking current spoil dump environmental management practices with engineering design planning and economic impact evaluation. This paper identifies the processes for the economic impact evaluation for existing spoil dump reshaping practices and proposed final site dump designs. Selection of an efficient spoil dump design at optimum costs will ensure operational efficiency. A case study is presented identifying economic impact evaluation in earthmoving equipment selection and the costs involved for the reshaping of spoil dumps to that of varying final site designs.

Jan 1, 2000