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By R. L. Levens

The Underground Injection Control program was promulgated in 1981 by the U.S. Environmental Protection Agency under the provisions of the Safe Drinking Water Act. Placement of mine waste backfill underground is considered underground injection under the provisions of this program. A major issue is whether mine waste that is regulated as a contaminant source on the surface should be disposed of underground. The U.S. Bureau of Mines conducted research to investigate the impacts of mine waste sandfill on the quality of ground water. Analyses of water samples collected before and after contact with sandfill in a 10-year-old stope, as well as samples of the sandfill itself, were used to ascertain the influence of the sandfill after mine closure and subsequent flooding. Computer models supported the hypothesis that oxidation of pyrite by oxygen, accompanied by dissolution of carbonates, was the predominant reaction controlling the quality of the water being discharged from the stope. Concentrations of metals released as a result of acid production remained near or below detection limits. Metals release after mine flooding is expected to remain low as a result of the buffering by the sandfill and the reduced rate of oxidation.

Jan 1, 2010

By A. K. C. Chan

Recent hotel investment projects in China often involve very tight programmes for design and construction. An example given in this paper involves a 24-storey reinforced concrete hotel tower with 460 bedrooms and a 3-level podium commercial complex. The building is supported by relatively widely spaced columns and shear walls below which 88 number large diameter piers were excavated through fill, silty and bouldery clay on to dolerite and slate at depths between 15 to 3 0m below ground level. Whereas much experience has been accumulated in Hong Kong, hand-excavated pier foundation was only adopted for the first time in Dalian. This paper describes and discusses the various factors influencing the choice of the type and design of the foundation system. The criteria for determining appropriate founding levels are then explained. During installation, revisions to the acceptance procedure were made to cater for local conditions. Emphasis is placed on the role of the geotechnical engineer in making on-site decisions during construction. The advantage of the foundation system in accommodating on-site changes resulting from local complex ground conditions is demonstrated. The pier foundations were successfully completed ahead of programme.

Jan 1, 2010

By Valois R. Shea-Albin

An accurate assessment of the vertical stress on a coal seam at depth is important for mine design. Vertical stress calculation techniques presently available either are not sufficiently accurate or cannot handle complex surface topography. Therefore, the U.S. Bureau of Mines developed a computerized method to calculate vertical stress exerted on surfaces at depth that includes the effect of topography. Two input data sets are required: a digital elevation model containing topographic elevations and a coal seam file defining coal seam elevations at depth. Boussinesq's equation then quantifies the vertical stress resulting from topography. The computerized method was tested on a coal seam overlain by a complex topography where a vertical stress map encompassing several square miles was produced. Results show that depth mitigates the affects of surface topography, while the coal seam topography has a direct effect on the vertical stress. In comparison to the computerized method, the direct stress method overestimates stress under hills and underestimates stress under valleys. The largest difference between the two methods occurs under the steepest topographic relief. A limitation of the computerized method is that stresses cannot be accurately determined near an outcrop.

Jan 1, 2010

By W. P. Stroud

In this U.S. Bureau of Mines report, the conditions required for the direct reconstruction of a tomogram from observed line integrals are examined. Because of the limited access to the working faces in coal mines, the special case of access to only two opposite faces is emphasized. Classical matrix methods were used for small dimensional (2 by 2, 3 by 3, and 4 by 4) applications to determine the limitations and the requirements for a solution. The results for large (n by n) grids were then inferred and generalized from those of the smaller grids and matrices. Limited access tomography is found to be appropriate for in-seam hazard detection from seismic and microwave data, but it is shown that additional data must be added to obtain a direct solution.

Jan 1, 2010

By Tony Lipiec, Greg Gosson

"When it comes to new mines being developed, there is a general industry consensus that most low-hanging fruit has been picked. Many projects currently in the mine development pipeline have been around for decades, but were held back because of technical challenges. Future development of these deposits will likely require access to the public capital markets, and in Canada that means providing scientific and technical disclosure on these deposits in compliance with NI 43-101. As many of these “challenged” projects have metallurgical issues, the companies that own the projects need to ensure their metallurgical Qualified Persons provide transparent disclosure regarding proposed solutions to those issues.This paper provides an overview of the disclosure requirements under NI 43-101 that are pertinent to metallurgists, and other Qualified Persons who prepare technical disclosure regarding the metallurgical characteristics of a mineral project. It lists the triggers for a technical report under NI 43-101 and Canadian stock exchange policies, and identifies the sections of the report that should involve input from a metallurgist or process engineer. It briefly outlines new civil liabilities under Canadian securities laws that increase the possible consequences for not complying with the technical disclosure standards.These materials are provided for general information purposes only and do not constitute legal advice. Readers are advised to seek specific legal advice from their own legal counsel in relation to any decision or course of action contemplated."

Jan 1, 2010

By T. Eggenberg

Mechanization and automation of logistic equipment has become one of the main key factors in raising productivity and competitiveness especially for complex and larger mining or tunneling projects. The Lake Mead Intake Tunnel #3 shaft mucking installation is a good example to demonstrate the potential that is found in an overall optimized logistic. It starts with the planning and results in using customized installations which fulfill the specifically defined requirements for the project. Rowa developed a solution and supplied a shaft mucking system using a discontinuous double drum hoisting concept with shaft buckets, loading, and unloading devices. With this fully automated system a continuous muck flow of 437t/h can be achieved.

Jan 1, 2010

By Craig C. Hustwit

A pilot-scale treatment study was conducted on a copper-zinc bearing metal mine drainage using a pipeline treatment system called the In-Line System (ILS). The objective of this U.S. Bureau of Mines study was to determine whether the ILS could be extended from the treatment of coal mine drainages to the treatment of metal mine drainages. Hydrated lime (Ca(OH)2), quick lime (CaO), and caustic soda (NaOH) were used to neutralize the drainage. A novel reagent slurry of Ca(OH)2 and type C fly ash was also evaluated. Except for Ca(OH)2-fly ash slurry, treatment performance was evaluated for all reagents at pH values of 7,8,9, and 10. The Ca(OH)2-fly ash slurry was evaluated at a pH of 10. All reagents tested neutralized the metal mine drainage and substantially reduced the dissolved metal concentrations. It was concluded that the ILS could be useful in the treatment of metal mine drainages.

Jan 1, 2010

By Winton Gale

"The aim of this paper is to summarise the results and conclusions of Australian Coal Association Research Project (ACARP) Report Cl3013 which relate to water inflows into a mine which occur through the overburden above and adjacent to longwall panels. The study assessed available data of inflows into underground coal mines and utilised computer simulation of water flow through fracture networks. The study concluded that flow into mines is typically via an interconnected network of pre-existing and mining induced fractures. The height above the coal seam that mining induced fractures extend is typically related to the width of the panel. However the potential for those fractures to form a connected network which can facilitate flow, is related to the amount of subsidence and the depth of mining. The study compares model simulations with measured data and provides guidelines to estimate the average hydraulic conductivity of the overburden above extracted longwall panels in Australia.INTRODUCTIONWater inflow into coal mines has been a design issue for many years. Guidelines as to the potential for water inflow have been developed in many countries based on local experience and the form of mining being undertaken. In most instances, the guidelines relate to inflows which would endanger underground personnel and operations.In more recent times, water inflow criteria for mines has been widened to include lesser inflows which may not impact on mine safety or operations, but have the potential to reduce water flow within streams and surface aquifers. For the purpose of this paper the larger inflows which are readily measured in a mine or may impact on mining safety are defined as mine inflow and the lesser inflow relating to aquifer water loss as environmental inflow.The water losses referred to are those which enter the mine from the surface or from near surface aquifers.The empirical relationships developed as mine design guidelines or regulations typically relate to high flow (mine inflow) situations and in this paper, these have been reviewed as to their application to environmental inflow. In many cases environmental inflows were unlikely to have been noted or recorded in many mining operations in the past."

Jan 1, 2010

By Louis E. Dalverny

U.S. Bureau of Mines research to develop diagnostic methods to locate and evaluate fires in abandoned mines and waste banks and techniques to extinguish such fires was applied to an abandoned 60-acre underground bituminous coal mine (Renton, Allegheny County, PA) to locate and extinguish three separated fire zones. Mine fire diagnostics interpret changes from baseline values in subsurface pressures, temperatures, and mine gas composition under imposed pressure gradients induced by a borehole exhaust fan. The effective gas sampling area surrounding each borehole is greatly enlarged. Sampling iterations, using a "communicating" boreholes set, provide "fire signature" information for locating both heated and cold areas. Time-dependent monitoring differentiates heating and cooling periods resulting from combustion front movement and/or fire extinguishment activities. A water injection with fume exhaustion extinguishment effort involved injecting water through boreholes to quench the heated zones while exhaust fans actively removed heated gases from the mine. The technique was ineffective as implemented, primarily because of inadequate spreading of water from the injection points. The Bureau's diagnostic method determined the fire locations and the effectiveness of the water injection with fume exhaustion extinguishment technique.

Jan 1, 2010

By Qing-Xun Low

Ni current collector has excellent electronic conductivity and mechanica, properties. However, nicke, cannot be used in H2S-containing syngas SOFCs due to sulfur poisoning and coking. Copper coated nicke, is prepared by electrochemica, deposition. XRD, SEM, and EDX techniques are used to characterize the samples. After high temperature treatment in syngas containing, the coated samples exhibit high resistance of coke formation and sulfur corrosion compared to pure nickel. Therefore, copper coated nicke, is a promising anode current collector for H2S-containing syngas SOFCs.

Jan 1, 2010

By Charles D. Litton

This U.S. Bureau of Mines report details the results of a series of large-scale experiments where small coal fires were used to ignite the conveyor belt at air velocities ranging from 0.76 to 6.1 m/s. In the tests, electrical strip heaters imbedded within a pile of coal were used to heat the coal to a point of flaming ignition. The flaming coal subsequently ignited the conveyor belt located approximately 5 to 10 cm above the coal pile. During the tests, temperature, CO, and smoke levels were continuously measured in order to determine both alarm time and level as the fire intensity progressed through the stages of smoldering coal, flaming coal, and flaming coal plus flaming belt. Analysis of the data leads to certain conditions of air velocity and sensor alarm levels that are required for early detection of conveyor belt entry fires. Two nomographs are presented, which define sensor alarm levels and sensor spacings as a function of belt entry cross-sectional area and belt entry air velocity.

Jan 1, 2010

By P. A. Roberts

A proposal for a modified in situ leaching method for extracting gold from oxidized gold ores using a non-cyanide lixiviant is described. A non-cyanide lixiviant is suggested because of the obvious concerns posed by injecting cyanide-bearing solutions into the subsurface. Oxidized gold ores were chosen as a focus because earlier research on the use of sodium thiosulfate as a lixiviant under anaerobic conditions indicated that the presence of pyrite led to rapid thiosulfate breakdown. A reconnaissance research program involving ore characterization and hydrometallurgical test work on samples from four Australian ore deposits and preliminary reactive transport modeling studies was carried out. This work showed that lixiviant-oxidant combinations of sodium thiosulfate and ferric EDTA and iodide and iodine are both capable of extracting high percentages of accessible gold from the selected samples in bottle roll tests under anaerobic conditions. The ore characterization and reactive transport studies suggested that both physical and chemical methods of permeability enhancement may be required to lift bulk permeability and the availability of gold for dissolution to sufficiently high levels to obtain adequate gold recoveries. Assuming that such methods prove to be both necessary and economically viable, the mining method would no longer be regarded as simple in situ leaching. Therefore, the term ?in-place leaching? has been adopted for the proposed gold extraction system.

Jan 1, 2010

By W. W. Hartley

Following a Major underground coal mine incident there followed a review of the role of mines rescue ? the Queensland Mines Rescue Brigade. It wasn?t until 2002 that the real change started to happen. The issue of geographical distance was addressed by mines rescue sub stations being located on the mines sites with parent rescue stations in a central location. The funding was by means of a levy on the mining industry with legislative standards and performance included. The previous Rescue Brigades were not well organised (central districts) and the application of recognised quality management practices within local management was lacking. The structure was based on other nations models and miners managing miners was an issue for the organisation. The reform was some what painful and the QMRS organisation will still evolve with continuous improvement. Queensland has the National Champion mines rescue team for the eighth year. QMRS is participating at the level in the industry of influencing emergency systems and training senior mine management in ?Emergency Mine Management? coaching the industry in emergency response systems. We have come a long way. We have had some success and there is always the challenge of setting the standards, those we should aspire to and the courage to influence the industry to higher goals of a safer future.

Jan 1, 2010

By K. J. Maggs

The U.S. Bureau of Mines has investigated the chemical vapor deposition of diamond films on tungsten substrates. The effects of deposition parameters on the adhesion of the films was determined. The films were produced using a hot filament chemical vapor deposition system. Parameters investigated were substrate temperature and methane concentration in the feed gas. Film quality, morphology, and composition were characterized by scanning electron microscopy and Raman spectroscopy. Adhesion testing was performed using an indentation technique, and the results were quantified by relating adhesion to interface fracture toughness. Diamond films with well-faceted crystalline morphology with grain size greater than 1 µm had poor adhesion properties regardless of substrate temperature or methane concentration. Diamond films with smooth morphologies consisting of rounded clusters of small (<0.2 µm) diamond crystallites and amorphous carbon phases displayed much higher adhesion, although the conditions that led to the growth of these films are not understood.

Jan 1, 2010

By Walter K. Utt

The U.S. Bureau of Mines conducted research to develop an accurate, real-time, position monitoring and warning system for the vehicles used in surface mining. The product of this research will be technology to reduce accidents and injuries associated with the operation of surface mining haulage equipment. The position monitoring system should reduce accidents related to vehicle position and also increase the efficiency of haulage operations. This research was conducted in preparation for development of an accurate, real-time position monitoring and warning system, which notifies equipment operators when they deviate from a known safe course and are approaching a fixed hazard. A radar positioning system designed for marine applications was evaluated and a series of tests was run to determine the accuracy of the radar positioning system when used in a land vehicle. The radar position determination was compared to surveyed values. Both static and dynamic (moving vehicle) tests were conducted. The static test results were marginal and the dynamic test results were not accurate enough for the position monitoring and warning system. Although a promising technology, the system tested needs to be modified to meet the accuracy requirements of mobile mine equipment.

Jan 1, 2010

By Nadia C. Miller

In situ metals research to characterize the hydrology of a fractured crystalline rock mass in under-ground mine stopes is discussed. The objective of this study was to find the potential direction, velocity, and concentrations of a lixiviant plume, should leaching solvents (lixiviants) escape from a test stope. The study was conducted by the U.S. Bureau of Mines at the Colorado School of Mines Experimental Mine in Idaho Springs, CO. Since this was a method evaluation site, the lixiviant was simulated using water and acceptable tracers. The site is located in moderately fractured Precambrian migmatite-biotite gneisses of the Idaho Springs Formation. The data required for the characterization were obtained from geologic maps and reports, core logs, and air and water permeability tests. The acquired data were analyzed and applied to a computer model that calculated&apos; the characteristics of a lixiviant plume originating at the stope. A sensitivity analysis showed that dispersivity, ground water velocity, fracture porosity, and fracture spacing had notable effects on the concentration of the plume. Assuming a saturated rock mass, the lixiviant plume would disperse to undetectable levels in a very short time because of a high fracture density at the mine site.

Jan 1, 2010

By E. Bakhtavar

It is considered that the most economical method for the exploitation of Gol-e-Gohar Area 3 iron ore mine is to combine open-pit and underground methods. In this regard, the most critical problem is the determination of optimal final pit depth. In this paper, a method which was recently introduced on the basis of economical block models of open-pit and underground is used to determine optimal final open-pit depth of Gol-e-Gohar Area 3 mine with due regards to the future underground mining option. Considering a low cost and productive underground method as a feasible alternative for extraction of the lower part of this deposit, room and pillar was selected. It is concluded that after the assessment and comparison of different values for depth, optimal final open-pit depth was determined to be equal to 285 m.

Jan 1, 2010

By Richard O. Kneisley

An empirical method, based on U. S. Bureau of Mines field studies in several Western U.S. coal mines, is presented for sizing gate road yield pillars. Discriminant analysis was used to generate functions separating successful from unsuccessful case studies. These functions relate the pillar width-height and extraction ratios and a pillar development factor to the Coal Mine Roof Rating System (CMRR), and are assumed to establish three criteria that other entry systems, under similar conditions, must satisfy. A program, Pillar Sizer, from user-provided inputs, generates a range of pillar sizes that meets the proposed criteria. Although the analysis is based on a sample consisting primarily of two-entry systems, the derived expressions generate pillar sizes closely agreeing with observed, two-entry and three-entry in situ pillars. It is concluded that the proposed approach should assist mine operators estimate entry system yield pillar dimensions.

Jan 1, 2010

Blast vibrations induce sounds within neighboring residences. A house wide vibration and sound monitoring system was installed in a West Virginia home which was subjected to blasts at varied distances and direction. Eighty-nine blast events were monitored and analyzed for this case study. Fifteen channels of data were collected including three triaxial geophones, one airblast microphone, one uniaxial geophone mounted to the wall of the house (response channel), and four microphones that recorded CD quality sound waves inside the house. Each of these channels was recorded on the same time reference and scale allowing for direct comparison of the waveforms. The response channel signal was easily separated into ground vibration induced and airblast induced movement due to the differences in their times of arrival. This response channel was then compared to the sounds recorded inside the home to determine which component of blast vibration induced the maximum sound response inside the home. Blasts at distances less than 762 meters (2,500 feet) had maximum sound responses from both ground vibration and airblast. While for blasts beyond 762 meters (2,500 feet), the maximum sound response inside the home was caused by ground vibration without exception. When airblast was identified as the dominant sound generator in the house, the peak amplitude of the sound was directly related to the amplitude of airblast. When ground vibration was identified as the dominant sound generator in the house, the peak amplitude of sound was not related to the amplitude of ground vibration. In these cases, sound amplitude was driven by the conditions present in the house such as loose items, doors, and windows creating sudden peaks from falling or slamming. In the same respect, sound amplitudes varied depending on where the sound was recorded. Different rooms generated very different sounds based on the contents of the room. Findings from frequency analysis showed that the frequency content of sounds inside the house were not related to frequency content of airblast or ground vibration regardless of source suggesting that residents would have difficulty determining the source of blast induced noise in their homes.

Jan 1, 2010

By William P. Diamond

This report presents results of a cooperative research project between the U.S. Bureau of Mines and BethEnergy Mines, Inc. Four coreholes (two before mining and two after mining) were drilled at a longwall mine operating in the Lower Kittanning Coalbed to obtain coal and rock samples from over-lying strata to determine their gas content at various times in the mining cycle. The results of those tests indicate that 91 pct of the gas removed from the overlying strata came from coalbeds. Material balance calculations were made to compare the volume of gas produced both from gob gas vent holes drilled on the panel and gas removed by the mine&apos;s ventilation system with the volume of gas removed from strata directly overlying the panel to a height of 275 ft. This analysis indicates that only 40 pct of the total gas produced from the panel actually came from the strata directly overlying the panel. The remaining volume of gas production probably migrated to the longwall gob from overlying, and perhaps underlying, strata immediately adjacent to the panel and perhaps from greater distances downdip because of the establishment of a long-term pressure gradient in the study area.

Jan 1, 2010