Search Documents

By M. R. Shahan, W. R. Reed, S. Klima, T. W. Beck, Y. Zheng

Testing was conducted to determine the ability of foam to maintain roof coverage in a simulated longwall mining environment. Approximately 27 percent of respirable coal mine dust can be attributed to longwall shield movement, and developing controls for this dust source has been difficult. The application of foam is a possible dust control method for this source. Laboratory testing of two foam agents was conducted to determine the ability of the foam to adhere to a simulated longwall face roof surface. Two different foam generation methods were used: compressed air and blower air. Using a new imaging technology, image processing and analysis utilizing ImageJ software produced quantifiable results of foam roof coverage. For compressed air foam in 3.3 m/s (650 fpm) ventilation, 98 percent of agent A was intact while 95 percent of agent B was intact on the roof at three minutes after application. At 30 minutes after application, 94 percent of agent A was intact while only 20 percent of agent B remained. For blower air in 3.3 m/s (650 fpm) ventilation, the results were dependent upon nozzle type. Three different nozzles were tested. At 30 min after application, 74 to 92 percent of foam agent A remained, while 3 to 50 percent of foam agent B remained. Compressed air foam seems to remain intact for longer durations and is easier to apply than blower air foam. However, more water drained from the foam when using compressed air foam, which demonstrates that blower air foam retains more water at the roof surface. Agent A seemed to be the better performer as far as roof application is concerned. This testing demonstrates that roof application of foam is feasible and is able to withstand a typical face ventilation velocity, establishing this technique’s potential for longwall shield dust control.

Jan 1, 2017

By M. R. Shahan, W. R. Reed, S. Klima, T. W. Beck, Y. Zheng

Testing was conducted to determine the ability of foam to maintain roof coverage in a simulated longwall mining environment. Approximately 27 percent of respirable coal mine dust can be attributed to longwall shield movement, and developing controls for this dust source has been difficult. The application of foam is a possible dust control method for this source. Laboratory testing of two foam agents was conducted to determine the ability of the foam to adhere to a simulated longwall face roof surface. Two different foam generation methods were used: compressed air and blower air. Using a new imaging technology, image processing and analysis utilizing ImageJ software produced quantifiable results of foam roof coverage. For compressed air foam in 3.3 m/s (650 fpm) ventilation, 98 percent of agent A was intact while 95 percent of agent B was intact on the roof at three minutes after application. At 30 minutes after application, 94 percent of agent A was intact while only 20 percent of agent B remained. For blower air in 3.3 m/s (650 fpm) ventilation, the results were dependent upon nozzle type. Three different nozzles were tested. At 30 min after application, 74 to 92 percent of foam agent A remained, while 3 to 50 percent of foam agent B remained. Compressed air foam seems to remain intact for longer durations and is easier to apply than blower air foam. However, more water drained from the foam when using compressed air foam, which demonstrates that blower air foam retains more water at the roof surface. Agent A seemed to be the better performer as far as roof application is concerned. This testing demonstrates that roof application of foam is feasible and is able to withstand a typical face ventilation velocity, establishing this technique’s potential for longwall shield dust control.

Jan 1, 2018

By M. I. Brittan

Cyanide leaching of two West African gold ores was studied in multiple laboratories to provide process-engineering data for plant design purposes. Unusually slow leach extraction kinetics were observed using routine cyanide leach test procedures with pregnant solution monitoring. Carbon-in-leach testing, however, showed normal rapid kinetic behavior, with the same ultimate gold extractions being reached in much shorter elapsed times. Kinetic curves based on washed solids assays also exhibited more typical leaching characteristics. The results bore all the hallmarks of some equilibrium inhibition of the leaching. It was surmised that ore gangue components were responsible for weakly adsorbing gold-cyanide complex reaction product, thereby holding up soluble gold in the solid phase. The term ?preg-borrowing? was coined to describe the reversible phenomenon and distinguish it from irreversible preg-robbing. The two ores investigated may represent an extreme form of a more general effect that in most instances might pass unnoticed. The effect can lead to misinterpretation of kinetic leach curve data and underestimation of calculated ore head grades.

Jan 1, 2008

By A. Zeni, S. L. Bessinger, T. A. Palm

San Juan Coal Company (SJCC) operates an underground coal mine near Farmington, New Mexico. Continuous miners and a longwall produce 7-8 million tons per year. The coal seam at SJCC has tested to have a propensity for spontaneous combustion. As such, during feasibility for this project, it was elected to utilize a bleederless ventilation system on the longwall. Three-entry gateroads are developed, and the longwall gob is sealed as mining progresses. SJCC utilizes a nitrogen injection system to continuously inertize the gob. In 2004, the mine was nearing completion of its first longwall district. The next district would contain longer panels (up to 12,500 feet). Due to the liberation of methane, and to a lesser extent hydrogen sulfide, a typical wrap-around ventilation system would not be appropriate. Not only would gas concentrations likely be challenging, but the overall ventilating pressure in the mine would have to be increased beyond limits established to mitigate the potential for spontaneous combustion. Given the above-described operating constraints, SJCC determined a need for a small ventilation shaft in the back (longwall setup area) of the next district that would draw adequate air past the longwall seals to maintain low gas levels and permit the required regulatory inspections to occur. Extensive ventilation modeling and gas desorption testing indicated that the shaft would be required to handle a volume of air ranging from 40,000 cfm to as high as 185,000 cfm. This large range is driven by the position of the longwall face with respect to the shaft and the effectiveness of the SJCC degasification program (SJCC uses vertical gob vent boreholes and horizontal in-seam methods). Ventilation simulations determined an appropriate diameter for the 350-ft-deep shaft to be 5 feet. Having determined shaft size, the next decision related to the method of shaft construction. Conventional shaft sinking was ruled out, due to the small diameter. Raise boring was an attractive option but had two drawbacks: (1) development crews would reach the bottom of the shaft just a few weeks before longwall startup, leaving a compressed timeframe to install the shaft, and (2) raiseboring requires additional underground entries to be developed to stow the project’s cuttings. While raiseboring remained a viable option, the problems associated with it led SJCC to also investigate blind drilling.

Jan 1, 2006

By Jim Rozek, Robert A. Gee

The Epping to Chatswood Rail Line project is the largest publicly funded infrastructure project in New South Wales. Construction commenced in November2002 with opening scheduled for 2008. The work includes 13 route km of twin TBM driven 7.2 m diameter lined running tunnel, three cross-overs and three new underground stations. The new stations have platform caverns of 20m span with similarly proportioned concourse caverns alongside. The ground is bedded sand stone and shale with high horizontal stresses. Predicted stress-relief induced ground movements during staged excavation led to innovative use of rock anchors for permanent support.

Jan 1, 2005

By W. McMahon

Following the Sago Mine accident, the Mine Safety and Health Administration (MSHA) asked the U.S. Army Engineer Research and Development Center to study several possible methane explosion scenarios in the Sago coal mine. The study used a 1-ft resolution map of the mine to produce a 3-dimensional (3-D) model of a portion of the mine, including the sealed area where the explosion occurred. An advanced 3-D computational fluid dynamics (CFD) code was used to calculate the explosion pressures within the sealed area, on the mine seals, and in nearby regions of the mine. Based on the best available information on methane concentrations and assumptions on homogeneity and on layering and mix composition, three separate initial conditions of methane-air concentrations and location were studied. This paper discusses the CFD modeling technique, the results of the calculations, the challenges of conducting this type of modeling, and the advantages and limitations of CFD modeling of accident investigations of mine explosions.

Jan 1, 2009

By Alex Naudts

Pre-excavation grouting is a predictable and reliable technique performed to prevent or minimize settlement in advance of, or during the tunneling operation. It safeguards the infrastructure above the tunnel alignment. Cement based suspension grouts and sodium silicate based grouts are frequently injected to consolidate and strengthen the formation and create a reinforced canopy above the tunnel trajectory. Grouting is typically performed through permeation and permeation in conjunction with hydrofracturing. Multiple injection passes through steel sleeve pipes are ideal, since they create an effective forespiling system to facilitate tunneling without causing unacceptable settlement, even with minimal overburden thickness. Ten pre-excavation grouting projects performed in the North America are discussed in this paper.

Jan 1, 2008

By Andrea Koschinsky, Peter E. Halbach, Margret Halbach, Andreas Jahn

"Ferromanganese crusts contain hydrous Mn and Fe oxides as main metal compounds together with some economically interesting minor elements such as Co, Ni, Ti and Cu and trace metals such as Mo, W, Nb, Te, Ga, Pt, and REEs. Some of these metals or semimetals have a great future potential as innovative high-technology constituents. All of them are highly enriched in the crusts compared to seawater composition.The Mn in the crusts mainly originates from the O2 - minimum zone in the oceanic water column. The agent for Mn2+ oxidation is dissolved oxygen, transported upwards from colder deep water layers by turbulent eddy diffusion. The Mn itself descends from surface waters and is carried down to the O2-minimum zone by fecal pellet transport. In contrast, Fe is mainly supplied from carbonate dissolution of planktonic skeletons in the water column. These relationships result in the fact that the oceanic water depth strongly controls the metal composition of ferromanganese crusts: the Mn - group metals are more enriched in shallower water, whereas the concentration of the Fe - group metals increase with water depth. The REEs play a very important role with regard to the trace metal composition of the crusts: their concentrations increase with water depth mainly controlled by a decreasing Mn/Fe ratio.In seawater, REEs occur as carbonate complexes; preferably, the light rare earth elements (LREEs) form REECO3 +(aq) and the heavy Rare Earth Elements (HREEs) REE(CO3)2 (aq) complexes. The REEs are transition metals, their 6s orbital of the outermost shell is filled before the filling of lower 4f electron shells is completed, thus the configuration of the valence electrons is similar in all the REEs, and all REEs exhibit similar chemical behavior and exist, dominantly, as 3+ cations. The ionic radius decreases progressively from La3+ (1.18 Å) to Lu3+ (0.97 Å), this phenomenon is called "lanthanide contraction". Due to the fact that REEs in seawater form cationic and anionic carbonate complexes, the two main hydrogenetic constituents, hydrous !-MnO2 and Fe-oxyhydroxide, fractionate the group of REEs by surface absorption processes. According to the pHZPC-concept the ?- MnO2 phase has an electronegative surface, and Fe-oxyhydroxide a slightly positive surface charge at seawater pH. These relationships are the main reason for the observed REEs fractionation."

Sep 1, 2014

By S. M. Carpenter

In response to the FY2008 Consolidated Appropriations Act (H.R. 2764; Public Law 110?161), the United States Environmental Protection Agency (USEPA) issued the final Mandatory Reporting of Greenhouse Gases Rule (MRR). The rule, signed by the USEPA Administrator, Lisa Jackson, on September 22, 2009, requires reporting of greenhouse gas (GHG) emissions from large sources and suppliers in the United States, and is intended to collect accurate and timely emissions data to inform future policy decisions. The MRR will go into effect on January 1, 2010, and a report of the total emissions for calendar year 2010 will be due to the USEPA by March 31, 2011. Under the final MRR, suppliers of fossil fuels or industrial greenhouse gases, manufacturers of vehicles and engines, and certain facilities that emit 25,000 metric tons or more per year of GHG emissions are required to submit annual reports to the USEPA. The gases covered by the rule are carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFC), perfluorocarbons (PFC), sulfur hexafluoride (SF6), and other fluorinated gases as outlined in Table A-1 of Subpart A of the MRR, which is also provided in Appendix A of this report.

Jan 1, 2011

By C. Özgen Karacan

The formation of the gas emission zone in longwall mining and the potential amount of gas in this zone are factors of local geology and spatial variability within this geology. Therefore, geostatistical methods can be used for modeling and prediction of gas amounts and for assessing its uncertainty in the gas emission zone of longwall mines. This study used core data obtained from 64 exploration boreholes drilled from the surface to the bottom of the Pittsburgh coal seam in a mining district in the Northern Appalachian basin. After identifying important coal layers for the gas emission zone, semivariogram modeling was conducted for different coal seams to define the distribution and continuity of various attributes. Sequential simulations were performed for stochastic assessment of these attributes to calculate gas-in-place (GIP) in each coal seam. GIP calculations for coals of various gas emissions zones were combined and ranked for their cumulative distribution function to find GIP in the caved zone and in the fractured zone at the 5%, 50%, and 95% quantiles. Fifty percent quantile results were later used to isolate a panel from the whole area and create a mosaic representation corresponding to the daily advance rate of the longwall face. This approach helped to estimate the daily emissions of this panel from the caved zone and from the fractured zone. Results showed that gas-in-place in the Pittsburgh coal seam, in the caved zone, and in the fractured zone showed spatial correlations that could be modeled and estimated using geostatistical methods. This study showed that gas-in- place volumes in the study area may be as high as 12.3 Bscf and as much as 3.5 MMscf per acre of mining.

Jan 1, 2012

By Daniel Connor, O&apos

The Cal-Sag Relief Sewer is a 2.6 m (8 ft 6 in.) diameter 9.1 km (5.7 mile) rock tunnel bored in dolomite for the Metropolitan Sanitary District of Greater Chicago. Included in the project are 18 shafts varying in depth free 70 m (230 ft) to 41 m (135 ft). This paper discusses how Healy/Vanessa reduced costs by eliminating conventional hand excavation by hoisting muck from a high production Robbins TBM (Tunnel Boring Machine) through small diameter drilled shafts and using a trailing rail-utility backup system.

Jan 1, 1985

Since the beginning of the computing age, technical software packages have not been developed to address only programming specialists but have been dedicated to process engineers. For process analysis, BRGM is developing and commercializing three packages: ? sampling software: ECHANT 2.0 for Windows ? material balance calculation: BILCO 2.0 for Windows ? steady-state simulator for plant design, adaptation and optimization: USIM PAC 2.1 for Windows This paper deals in a first part with the main features of these three packages. In a second part, advanced models are presented for SAG/ AG mills and flotation columns. An industrial case of application is shown for each of them.

Jan 1, 1997

By Daryl E. Radcliffe, Raymond M. Stateham

The Bureau of Mines, under a Cooperative Agreement with the Bear Coal Company, Somerset, Colorado, conducted a large scale evaluation of the effect of time lapse on roof stability. Time lapse in this study is the interval between exposure and permanent support of the mine roof. The study indicates that time lapse is not a critical factor in roof stability provided permanent support is installed before catastrophic failure begins. Concurrently with the time lapse study, investigations were made of stress distribution around resin-grouted bolts, the regional stress field, and anomalous geologic conditions. The behavior of the resin-grouted bolts, at least in the Bear mine, appears to fit the Coulomb-Navier Theory. Geologic conditions are primary factors in trends of roof stability that extend across the mine.

Jan 1, 1982

By Edward DeLilla

For the past 30 years, surface mines have moved toward more highly mechanized, automatic systems that continuously mine overburden and ore to increase productivity, lower operating costs and minimize manpower needs. To achieve these goals, mine operators must be involved in every step of the machine procurement process. Several factors are involved in making the machines operate economically and efficiently: -Prudent engineering. -Proper planning. -Realistic feasibility studies. -Effective specification. -Thorough training of the mine personnel.

Jan 1, 1994

By Franziska Günther, Helmut Mischo

The calculation of costs for an underground mine, as well as the planning of the equipment and materials to be used, is a complex and time-consuming process. The estimation depends on a multitude of parameters, and all mining processes are interconnected. A novel tool has been developed that enables automated calculation of underground mines and allows for the comparison of the effects of changing individual parameters. Previously, changing individual planning parameters often necessitated a complete recalculation of the mine. The newly developed calculation tool provides an innovative planning aid that allows for more efficient and accurate mine planning and cost estimation. The tool enables the user to implement continuously up-to-data costs and prices. This allows for more accurate planning data and results. The underlying concept of the calculation tool, its implementation at a planned quartz porphyry mine in Germany, and the verification of the tool at an existing underground mine will be presented.

Feb 1, 2025

By Susan L. Bednarz

Recent advances in digital cameras and image processing allow photographers to produce excellent high-resolution action shots in low light and high contrast conditions commonly encountered underground. Digital photography is often used for construction and inspection documentation for underground structures. Designers, owners, and contractors benefit from quality photographs that document incremental progress and project milestones. Documentation photos serve as a lasting record of as-built conditions, are an important marketing tool, and help the owner build public support for expensive public works projects. When the project is complete, the only mementos that the participants will hold onto are the photographs.

Jan 1, 2008

By Stephen A. Orr

Underground mining is a dynamic art and science with a diverse set of design, production, and economic criteria that must be considered before selecting an optimal method to extract the ore. While all methods can be technically classified as either self-supported, supported, or caving, the multitude of subsystems and existing variations bear witness to the fact that each orebody is unique and, as such, justifies an individual approach to optimize mineral extraction. In this sense, underground mining is an art. The ability to evaluate the unique characteristics of each ore body and utilize sound engineering principles to design the optimal system constitutes effective method selection. The task by no means ends at this juncture, however. Subsequent implementation requires an ability for modification. Very rarely are all the facts available to make a concrete decision prior to development of the resource. As a result, the risk of a wrong decision can never be eliminated. This requires a significant degree of flexibility with each method. Each unit of exploration, development, or exploitation work contributed to a deposit enhances knowledge of the ore body. The best mining methods are those that correctly account for the known parameters but provide an allowance for change at minimal cost and adapt to unanticipated conditions.

Jan 1, 2008

By Melvin W. Jackson

The study of the excavation of large spherical cavities in salt formations first became of interest in 1958 when it was recognized that a large cavity could be of value in the study of the detection or concealment of underground nuclear explosions. Previously unpublished studies are reported in this paper and other studies reviewed relating to the excavation of large cavities in salt by mining ad by solution. Special emphasis is placed on the utilization of the Tatum salt dome (about 22 miles southwest of Hattiesburg, Mississippi) for the proposed site of a large excavated cavity. The U. S. Atomic Energy Commission has recently been studying such a cavity as Project Payette, but no details have yet been published. If Project Payette is determined feasible and work funded, it would eventually involve the firing of a nuclear explosive at the center of a large cavity.

Jan 1, 1969

By George K. Schenck

INTRODUCTION Recent advances in high-pressure water jet technology can be effectively employed in mining and tunneling. The new equipment is based on available industrial hardware such as pumps, nozzles, and rotary swivels and seals, and is compatible with present mining and tunneling techniques. Principal advantages of water-jet assisted cutting relative to standard cutting are higher production rates, lower dust levels, and reduced fines. When used on rock and coal miners, water jets mean that relatively smaller and cheaper machines can be purchased. If properly applied, the combined effect is lower cost and significantly improved health and safety. While commercial use of high-pressure water blast cutting and extraction of rock (and concrete) already has a firm foothold in Europe, application of this new technique is just beginning in America. This paper begins with current American applications of high-pressure water jets for drills, for slotting and channeling machines, and then discusses the emerging technology for initiating rock failure in conjunction with drag bits on coal plows, continuous miners and boom-type miners (roadheaders). The focus of this paper is use of high-pressure water jets for cutting rock. High-pressure water jet cutting utilizes water above 70 MPa and currently reaches to 300 MPa and above. Some informatfon is included on low pressure "wethead" coal shearers and boom miners with water pressure to about 15 MPa.

Jan 1, 1983

By Daniel Journeaux

Introduction Daniel Journeaux is President of Janod Incorporated. Janod is a family owned and operated company that has been working in the field of slope stabilization since 1970. Daniel has worked in the rock stabilization industry for 25 years and has been President of Janod since 1992. Daniel has been an invited speaker for the Federal Highways Administration for the Northwest and Southwest divisions, Queens University in Kingston Ontario, The University of Laval, Vulcan Materials Company, CSX annual meeting for the Northeast Division. Daniel has written several articles and has been published in Pit and Quarry, World Tunneling, and American Shotcrete Association magazines. What is Required to Remediate Highwalls There are several techniques available to stabilize highwalls or temporary rock walls to allow for safe mining practices. The following are some of the techniques that can economically be used.

Jan 1, 2005