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By B. Listerud, G. Zhan, M. A. Jones

Barrick Goldstrike Mines Inc. (BGMI) operates the Betze-Post openpit and the Meikle and Rodeo underground mines. Because the majority of the orebody is located below the water table, mining at BGMI requires a significant dewatering program. BGMI has a comprehensive dewatering and water management system that experienced a peak dewatering rate of 4,400 L/s in the mid 1990s. Changes to the hydrologic/hydrogeologic system caused by the mine dewatering have been monitored by an extensive network of groundwater monitoring wells and surface water monitoring stations, which cover about 1,550 km2. In addition to the monitoring program, a new tool, called Interferometric Synthetic Aperture Radar (InSAR), has also been used to enhance the evaluation of changes. Finally, a groundwater flow model has been developed that successfully simulates and predicts aquifer responses in the mine area and region. The well-calibrated flow model has served as a reliable tool to develop dewatering and mining plans, and project post-closure hydrologic conditions in the region. This paper introduces the BGMI dewatering and water management system and the means used by BGMI to evaluate and anticipate hydrologic responses in the region. The water management and analysis system has been and continues to be an integral part of managing ongoing operations, planning and pricing out future activities and evaluating the long-term effects of mine water handling.

Jan 1, 2011

By W. Roggenthen, Z. J. Hladysz, G. D. Callahan, W. G. Pariseau, W. Weinig, C. Randolph-Loar, R. Popielak

A Deep Underground Science and Engineering Laboratory (DUSEL) is being planned at the site of the former Homestake Gold Mine in Lead, SD, under the sponsorship of the U.S. National Science Foundation (NSF) in cooperation with the Department of Energy (DOE). This national facility will host a variety of multidisciplinary science and engineering experiments, including physics experiments that require shielding from cosmogenic radiation. Current plans include construction of large rooms (up to 55 m in width) at depths of 1.48 km (4,850 ft) and 2.25 km (7,400 ft) below the surface. Preparation of the preliminary design required the development of a geotechnical characterization program, including preliminary drilling and coring, core logging, drill hole mapping with a televiewer, drift mapping of the geology and rock structure, in situ stress measurements, and laboratory testing of the mechanical properties of the rocks and discontinuities. Overall rock quality is very good to excellent. Site investigations included geotechnical assessments for the construction of caverns and laboratory modules. The results are favorable and reaffirm selection of the Homestake site for establishment of a Deep Underground Engineering and Science Laboratory.

Jan 1, 2011

By Ashis Bhattacherjee, Bijay Mihir Kunar

A literature review on quantitative analysis of mine safety studies revealed that investigators use a wide range of statistical techniques for the analysis of mine injury data. Researchers have addressed the various issues of accident causation and prevention through analysis of mine injury data collected from mines. These studies are generally based on historical accident/injury data without considering the injured person/population at risk. In this paper, a public health approach, based on scientific methods of epidemiology, is presented to address mine safety issues. Epidemiology is the scientific study of disease and injury patterns among populations in time and space. Originally, epidemiology was concerned with epidemics of communicable diseases. Then it was extended to non-communicable diseases. Safety researchers found that epidemiologic methods are the best tools for injury research, because the occurrences of injury and the occurrences of disease are quite similar. As a result, some researchers started applying this concept to injury research. This paper presents some of the techniques used in epidemiologic studies and illustrates the application of a case-control study design to evaluate the role of some risk factors associated with injuries in underground coal mines. In this study, the injured persons were identified and, simultaneously, interviews were conducted to find the significant risk factors responsible for occupational injuries in coal mines.

Jan 1, 2011

By H. Askari-Nasab, B. Osei, K. Awuah-Offei

The U.S. coal mining industry consumes approximately 142 billion kWh/a of energy. The U.S. Department of Energy estimates that the industry’s annual energy consumption could be reduced by 49%. This constitutes nearly $3.7 billion of potential savings on coal production costs at 5.3¢/kWh of energy. Additionally, with climate change regulation on the horizon, any benefits from energy savings in the near future are compounded by associated reductions in CO2 emissions. Research indicates that operating conditions significantly affect energy efficiency. Modeling and simulation have been shown to be a cheap and reliable means of evaluating the effects of process interactions and operating conditions. The goal of this work was to apply stochastic process simulation to model the energy efficiency of a typical truck-and-shovel mining system and use the model to evaluate production strategies to improve energy efficiency. The research team conducted energy audits of truck-and-shovel overburden removal and used the results to develop regression models describing truck and shovel fuel consumption. The team then built a stochastic simulation model of the truck-and-shovel overburden removal operation and used it to assess a variety of improvement measures by simulation experimentation. Valid fuel consumption models for shovel loading and truck haulage have been formulated, based on the energy audit results. Valid stochastic process models of truck-and-shovel operations have been formulated to study energy efficiency. The following strategies, in decreasing order of impact, provide the most energy savings for truck-and-shovel overburden removal at the mine: (1) shorten haul roads, (2) increase shovel capacity and (3) increase shovel utilization through optimal truck matching. Additional data will be required to adequately describe operator effects on energy efficiency.

Jan 1, 2011

By R. Krog, S. Schatzel, H. Dougherty

Longwall coal mine operators in the U.S. are required to ventilate multipanel longwall districts, but may have little or no knowledge about what happens to the ventilation air between the inlet evaluation points (IEPs), bleeder evaluation points (BEPs) and bleeder fans. The effectiveness of bleeder performance can directly influence the ability of a ventilation system to remove and dilute coal bed methane emissions. U.S. coal mining stakeholders have acknowledged their belief that the T-junction split at the longwall face tailgate corner is very important in controlling the distribution of ventilation air. To obtain direct measurements of bleeder performance, a tracer gas, sulfur hexafluoride (SF6), was released into the ventilation air stream on active and inactive longwall panels. Testing was performed on multiple longwall panels that included various phases of longwall development and variable path lengths of ventilation air transport to bleeder fan installations. Changes in the T-junction ventilation air distribution over the life of a longwall panel, and its variable effect on panel ventilation airflow are discussed. These findings will assess the effectiveness of commonly applied ventilation strategies for improving air distribution and ventilation controls to meet statutory requirements.

Jan 1, 2011

By D. S. Yantek, L. A. Alcorn, M. J. Lowe, H. E. Camargo

U.S. National Institute for Occupational Safety and Health (NIOSH) studies show that 43.5% of surveyed coal preparation plant workers had noise exposures exceeding the U.S. Mine Safety and Health Administration permissible exposure level of 90 dB(A). Sound levels around vibrating screens in these plants often exceed 90 dB(A). NIOSH is currently developing noise controls for horizontal vibrating screens. To characterize noise sources, NIOSH researchers performed sound pressure level (SPL) measurements on a vibrating screen at their Office of Mine Safety and Health Research laboratory in Pittsburgh. The results show that the entire screen contributes to noise below 1 kHz, and the vibration mechanism housings are most significant above 1 kHz. Constrained layer damping (CLD) treatments and an enclosure were used to reduce mechanism housing noise in this range from 1-10 kHz. These were evaluated using sound power level measurements according to ISO 3744. The CLD treatments reduced the A-weighted sound power level by 3.1 dB in the 1 to 10 kHz one-third-octave bands. A panel-on-frame vibration mechanism enclosure using various types of panels further reduced the A-weighted sound power level from the CLD configuration in the 1 to 10 kHz one-third-octave bands by 3.7, 4.0, and 3.9 dB for aluminum, steel, and Dynalam™ panels, respectively. The combination yielded a 7 dB reduction from baseline in A-weighted sound power for the same frequency range.

Jan 1, 2011

By A. C. Smith, J. H. Rowland III

The Mine Improvement and New Emergency Response Act of 2006 (MINER Act) established a Technical study panel (the Panel) to provide recommendations on the utilization of belt air and new technology that may be available for increasing the fire resistance properties of conveyor belt used in underground coal mines. The Panel Report recommended use of the belt evaluation laboratory test (BELT) as the method for testing and approval of flame resistant conveyor belts used in underground coal mines. The research conducted to establish the correlation of the BELT with large-scale belt fire flammability tests was done using 91 - 107 cm (36- to 42-in.) wide conveyor belt. Due to today’s coal haulage capacity, the mining industry is using 183 cm (72 in.) and wider conveyor belts. The U.S. National Institute for Occupational Safety and Health (NIOSH) conducted a study to determine if the BELT will also qualify wider belts as fire resistant for use in underground coal mines. This paper describes the results of recent experiments comparing results from using the BELT and the large-scale tests for six different belts.

Jan 1, 2011

By D. Chakravarty, G. Samanta, B. Samanta

The present study highlights the planning and design aspects of a well-known openpit copper deposit in India. The mine has been operational since 1982 and presently reaches a depth of 168 m below the surface. The present planning effort has been given due consideration in view of the recent upsurge of copper prices in the global market. The prime focus of the study has been directed towards examining the possible extent of final pit beyond the current pit outline and generating an extraction sequence of future mining operations. To this end, an orebody model of the deposit has been developed and the optimized pit has been derived using L-G 3D algorithm. A sensitivity analysis has also been performed to scrutinize the possible effects of the changing economic scenarios on the ultimate pit configuration. It has been observed that with the current production rate, mine life can be extended another 40 years. With a five-year production plan, these materials can be extracted in eight push-back schemes. The extraction sequence of these push-backs has been outlined in this paper.

Jan 1, 2011

By C. Mark, D. M. Pappas

From 1999 through 2008, groundfall events resulted in 75 fatalities, 5,941 injuries and 13,774 noninjury roof falls in U.S. underground coal mines, according to the U.S. Mine Safety and Health Administration (MSHA). A comprehensive analysis of these events was conducted to better understand where and why these incidents occurred. The first segment of the study used the MSHA database to evaluate groundfall injury rate trends related to mining method, year, locality, seam thickness, mine size, coalbeds and seasonal effects. In the past decade, roof fall injury rates have dropped 50%, but rib fall injury rates have remained constant. Room-and-pillar mines had a roof fall injury rate that was nearly 2.5 times the longwall rate. High groundfall rates occurred in the Illinois Basin, a finding that correlates with other studies that have shown that roof rock in the Illinois Basin is weaker than that in the central Appalachian coalfields. Finally, noninjury roof fall rates in the eastern and central United States were found to be 50% higher from July through September, possibly because of the changes in humidity levels that may cause shale mine roofs to deteriorate. The second segment of the study evaluated the root causes of failure by reviewing all MSHA groundfall fatality reports for 1999-2008. Pillar recovery was the leading cause of groundfall fatalities (19%), followed by rib falls, roof skin falls and traveling under unsupported roof (16% each). Defining prominent ground control incident trends and hazards will identify areas where additional study is needed and where innovative solutions need to be developed to reduce these severe occupational hazards.

Jan 1, 2011

By L. Patts, J. Hummer

The use of diesel-powered equipment in underground coal mines has increased substantially during the last ten years in an effort to enhance mine safety and productivity. Pennsylvania and West Virginia are two of a number of states with regulations governing the use of such equipment. These states both developed and promulgated regulations before permitting diesel equipment in their underground coal mines because of concern for miners’ safety and health, especially with regard to the contamination of mine ventilation air with diesel exhaust emissions. The major components of diesel exhaust emissions are combustion gases and diesel particulate matter. The gaseous emissions consist of carbon monoxide, carbon dioxide, oxides of nitrogen, sulfur oxides and unburned hydrocarbons. The diesel particulate matter (DPM) is comprised of solid carbon particles, liquid and solid hydrocarbons, sulfates and moisture. The Federal Mine Safety and Health Administration (MSHA) also promulgated regulations in an effort to control diesel emissions in underground coal mines. MSHA has adopted threshold limit values (TLVs) for all gaseous components of diesel exhaust, which were established by the American Conference of Governmental Industrial Hygienists (ACGIH). MSHA (30 CFR Part 72 Subpart D) has established a tailpipe DPM emissions limit of 2.5 g/hr for diesel engines used in permissible equipment, heavy-duty non-permissible equipment, generators and compressors used in underground coal mines. A tailpipe DPM limit of 5.0 g/hr has been established for light-duty outby diesel-powered equipment. The rationale for the tailpipe emissions limit was that an ambient measurement of DPM in a coal mine was not feasible because there is no established sampling method able to distinguish between coal mine dust and DPM. The stringent tailpipe emissions limit mandates the use of exhaust aftertreatment devices for most diesel engines used in underground coal mines today. One method by which tailpipe DPM can be reduced to MSHA limits involves using an exhaust cooling device in conjunction with a high-temperature, disposable diesel particulate filter.

Jan 1, 2011

By J. C. Stankus, K. J. Ma, D. Faulkner

To protect mine personnel and moving equipment at underground roof fall areas, mine operators typically install steel sets, which are covered with wooden blocks and backfilled with an expanding-type cement material. In large roof falls, the cost of void backfilling becomes prohibitively high, causing some mines to leave the voids open. However, the durability of wood over time and the capability of the steel set and wood lagging to resist falling rock are unknown. This has caused concern for the U.S. Mine Safety and Health Administration (MSHA) and ground control engineers. During the last few years, Keystone Mining Services, LLC developed various impact-resistant steel set designs that were approved by MSHA and installed in various underground fall rehabilitations. This paper presents an impact-resistant steel set design methodology, including (1) steel set design per AISC national standard, (2) design, development and laboratory testing of a waterproof coated impact-resistant lagging panel and (3) impactresistant steel set design based on the law of conservation of energy. Two underground cases will be included detailing the application of the system.

Jan 1, 2011

By X. Li, J. C. Stankus, J. Ma, H. Chen

Accurate evaluation of stress and geological conditions is critical to ground control design in underground openings. For a slope entry, the problem is more difficult, because a slope will transverse through many types of strata. Over the last few years, Keystone Mining Services LLC, an affiliate company of the Jennmar Corporation, has developed a new methodology designated the “Stress, geologic and support design system (SGS).” The method analyzes the stress, geology and support design for a mine slope. The method has been successfully applied in various new slopes across the United States, and ground control plans developed using SGS methodology has helped coal companies successfully pass review and/or hearings by state and federal regulatory agencies. With a case application in the U.S. Midwest, this paper details and demonstrates the main concepts of the methodology, including (1) analysis of stress and geology and identification of strong, fair and weak zones along the slope; (2) primary and supplemental support design; (3) long-term support design in the form of steel square sets or arches and (4) validation of the support design utilizing advanced finite element computer modeling.

Jan 1, 2011

By P. H. S. W. Kulatilake, T. Hudaverdi, C. Kuzu

Prediction of blast fragmentation plays a key role for overall productivity of mines. In this study, a new multivariate analysis procedure for prediction of blast fragmentation is presented. Several blasts performed in various mines and rock formations worldwide were brought together and evaluated. An extensive blast database was created. Blast design parameters, the modulus of elasticity and in-situ block size were considered to perform multivariate analysis. A complete multivariate analysis procedure was applied in three steps. First, a hierarchical cluster analysis was used to separate the blast data into different groups of similarity. Two different groups were formed based on the elasticity modulus values. In the second step, group memberships were checked by discriminant analysis. The dominant parameters of the occurrence of the groups were determined. Also, discriminant analysis was used to determine the group membership of the respective blasts. As the last step, the multivariate regression analysis was applied to develop prediction equations for estimation of the mean particle size of muckpiles. Two different prediction equations were developed based on the rock stiffness. Validation of the proposed equations on various mines was performed. Prediction capability of the proposed models was found to be strong. The models are not complex and are suitable for practical use at mines.

Jan 1, 2011

By S. Chatterjee, S. Bandopadhyay

A spatial modeling technique based on the Bayesian neural network (BNN) is proposed. Incorporation of the Bayesian method for posterior probability of the output parameter helps calculate the uncertainty associated with the estimate. Parameters of the BNN model were selected using a grid search algorithm. The expected value and the variance of block support were calculated by Markov chain Monte Carlo sampling of the posterior distribution at discretized points within the block. The BNN model was validated by applying it to the Walker Lake data set and comparing the results with ordinary kriging results. The comparison revealed that the proposed BNN method performs marginally better than ordinary kriging. The variance map is less smooth than with ordinary kriging, and the proportional effect is less in the BNN-based model than in the ordinary kriging model. The developed BNN model was applied to the Coho block of a placer gold deposit in Nome, AK. Results reveal that the BNN model is globally biased for the Coho block and underestimates the sample mean. The grade volume curve was developed by calculating the block mean and block variance after discretizing the block into a number of points and applying the BNN model to each discretized point.

Jan 1, 2011

By J. Kemeny, K. M. Kim

A site-specific blasting model has been developed for the Asarco Mission mine. The main inputs to the model are the in situ block size (F80), the post-blast fragmentation (P80) and the intact tensile strength (To). The output from the model is the specific blast energy (ESE). Modern techniques are being used to obtain the input parameters for the site-specific blast fragmentation model. In particular, image processing software is used to obtain both the in situ block size and the post-blast fragmentation, and the Schmidt hammer is used to obtain the tensile strength at numerous locations throughout the rock mass. An initial model was developed using five test shots in an area of the mine that contains argillite and is relatively homogeneous. This process also included calibrating Schmidt hammer readings against actual Brazilian tensile measurements. The model for argillite will be updated as more tests are conducted, and the model will be extended to the four other primary rock types at the Asarco Mission mine.

Jan 1, 2011

By Yi Luo

Subsidence events occurring above inactive room-and-pillar (R&P) mines, including abandoned mines or sealed portions of active mines, are classified as unplanned subsidence, because of their timing and distribution are unpredictable. When investigating such subsidence cases, many uncertainties exist and disputes often focused on whether the observed structural damages are caused by mine subsidence or other natural or artificial causes. However, solid evidence to identify the cause is often lacking. In order to conduct a complete and impartial investigation, thorough knowledge of subsidence theories and other ground control topics, as well as broad experience, are required.

Jan 1, 2011

By J. F. Colinet, W. R. Reed, J. D. Potts

Dust surveys were conducted at six underground coal mines to determine if deep-cutting practices expose face workers to higher levels of respirable dust. The surveyed mines were able to successfully mine deep cuts without significantly increasing the dust exposures of face workers. In general, all of the selected mines exercised good dust control practices by maintaining water sprays, scrubber airflows, proper curtain setback distances and providing sufficient airflow to the active faces. For exhausting face ventilation, field data indicate that scrubber airflow is the most important factor for controlling dust. Data collected for this study indicate that 20-mesh screens should be cleaned for every 12.2 m (40 ft) of advance, because 22% of the deep cuts surveyed for this study experienced a 20% to 35% decrease in scrubber airflow over the course of the cut. For blowing face ventilation, field data and past research indicate that dust control is aided by maintaining a proper curtain-to-scrubber airflow ratio of 1.0 (measured before scrubber activation), as well as a curtain setback distance that allows the miner operator to stand at the mouth of the curtain for the entire cut. Dust levels on the bolting faces did not appear to be affected by the longer cycles associated with deep-cut mining when good ventilation practices were used.

Jan 1, 2011

By H. S. Duzgun, N. Demirel

Estimating productivity of a walking dragline is of paramount concern to mining engineers and mine planners. Risk based evaluation of the dragline productivity is a valuable tool to estimate the dragline’s long-term availability, to develop preventive maintenance plans and to make future projections about the dragline’s performance. This paper aims to provide mining professionals with an overview of risk assessment methodology for productivity of two walking draglines, Page 736 and Marion 7820, which have been operating in the Tunçbilek openpit coal mine of Turkish Coal Enterprises (TKI) in Turkey. The study encompasses three main stages: (i) acquiring of monthly maintenance records, operating hours, mechanical and electrical failure hours between 1998 and 2009; (ii) reliability modeling using mean time between failure data and (iii) determining hazard rate and consequences to compute risk associated with dragline productivity. The results showed that that Page 736 (15.29 m3) seemed to be more reliable and less likely to fail when compared with Marion 7820 (30.58 m3). The operating hours without failure range from 41 to 51 hours with 50% reliability.

Jan 1, 2011

By S. Kenzap, V. Kazakidis

Risk assessment is an essential component of mine feasibility studies. However, it is often challenging to identify the appropriate analysis and derive the required input data. The uniqueness of a mining project and the associated technical issues require customization of the risk assessment approach to meet both requirements and characteristics. The uncertainty driving the operating risk in mine feasibility studies and its assessment through Monte Carlo simulation as a component of a cash flow analysis are discussed in this paper. The paper introduces the use of the analytic hierarchy process for derivation of qualitative input and conducts quantification of the three main sources of operating performance delays, equipment, ground and schedule problems, in a cash flow simulation. A methodology for the assessment of operating risk in mine feasibility studies is presented.

Jan 1, 2011

By C. D. Taylor, A. L. Mazzella, A. L. Martikainen

In fluctuating airflow, continuous air velocity recording is the most reliable method of air velocity measurement. It allows for fast recognition of changes and the calculation of long-term averages. Also, it enables the mine operator to identify when the airflow has decreased to a point requiring action. Using ultrasonic anemometers provides an accurate option for continuous air velocity monitoring. This paper provides information about the effect of common obstructions in underground mining on air velocity readings. Stationary and moving obstructions are used to represent workers and equipment that would cause discrepancies in measured airflow. Also, it is important to know how large of a sample size is required to ensure reasonable accuracy of results. Statistical analysis is used to evaluate the required sample size. The sampling procedure is further studied by comparing two different sample rates. The results show that obstructions provide noticeable differences in air velocity measurements. Also, movement of obstructions can be recognized from changes in results. Surprisingly small sample sizes provide reliable air velocity information. Standard sample rates are found to be suitable for the underground environment.

Jan 1, 2011