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By R. W. Waytulonis

New exhaust control techniques and devices may be necessary to meet future diesel particulate matter emission standards in underground coal mines. This paper reviews conventional work practices and devices used to control diesel exhaust emissions, and new techniques being tested by the US Bureau of Mines. Discussions will center on important work practices and on the function and efficiency of exhaust aftertreatment devices. An industry-government cooperative research project to develop and test an exhaust aftertreatment system for part 36 equipment is also discussed.

Jan 1, 1992

By Frederick W. Bauer

The potential worldwide "market" for metallurgical bauxite is about 94 million MT. The high degree of concentration of the alumina sector, combined with the high percentage of long-term contractual relationships, results in a small spot market with an illdefined price structure. Further segmentation occurs based on bauxite quality and alumina plant design. The potential 'free" market is estimated to be about 18 million MT that represent the requirements of nonintegrated alumina producers. It, too, is covered almost entirely by multi-year supply contracts.

Jan 1, 1984

By Simon T. Johnson, Robert J. Fowell

The application of roadheading and drag tool equipped machines requires an assessment of both cutting performance and tool consumption. Neither parameter can be assessed purely from compressive strength and tool consumption is often neglected, at a cost to the project. Results from in-situ monitoring show that a measurement of relative abrasivity using the Cercharscratch abrasivity test provides a basis for the assessment of tool consumption. This can be modified by also considering the effects of the machine specification and the rock mass quality.

Jan 1, 1986

By P. R. Hervey, J. W. Foise

Quartz is the second most widely used electronic material, with approximately 3,000 t (3,300 st) of single crystals used each year. Most of the quartz used in electronics is synthetic and is manufactured using a technique called hydrothermal growth. This paper reviews the basics of hydrothermal growth, the feedstocks used for these crystals and the challenges to improving the growth process. This paper also reviews the processing of these crystals, the markets and applications where they are used, and the global outlook for these markets.

Jan 1, 2002

By Donald W. Gentry

This article introduces mine planning as a complex process based on the quantitative and qualitative assessment of a myriad of independent and inter-or co- dependent variables. The interdependent variables of particular interest in this paper are those associated with mine planning activities that impact metallurgical processing plant performance and costs. These variables are identified and examples are provided to substantiate the argument that the magnitude and sensitivity of these variables must be formally assessed and analyzed to determine their potential impact on overall economics.

Jan 1, 1991

By Ruth A. Maurer, Steven L. Capt. Van Drew

Coal preparation for a company having several sources of coal and several contracts for sale of coal was modeled. The objective was to minimize wash loss by selecting the quantity of coal to be supplied from each source and the appropriate washbox specific gravity setting to yield contract quality for a given shipment. constraints inposed by silo and stockpile sizes, plant and rehandling capacities, and varying coal quality specifications were included in the model. Solution is by iterative linear programming on an Apple II.

Jan 1, 1987

By D. G. Fredlund, J. A. Wilson

Conventional disposal of waste rock results in the construction of benches with fine and coarse layers dipping at the angle of repose. This interbedded structure influences flow pathways within the waste rock. A numerical modeling program was conducted to study a four-layer system consisting of alternating fine and coarse waste rock. The system was inclined from the vertical to forty-five degrees with heights varying from one to twenty meters. The results show the effects of gravity as preferential flow developed under unsaturated flow conditions.

Jan 1, 2000

By Kadri Dagdelen

The definition and shortcomings of traditional cutoff grades are discussed. . The concept of optimum cutoff grade policy which maximizes the Net Present Value (NPV) of annual cash flows coming from a mining project is introduced within the basic framework outlined by K. F. Lane. Several examples are used to demonstrate the shortfalls of cutoff grade policies obtained by various heuristic optimization techniques. An algorithm to obtain an optimum cutoff grade policy which maximizes the NPV of a project is given and described in detail.

Jan 1, 1992

By Frédéric Flament, Daniel Hodouin, Claude Bazin

A control strategy is proposed to meet the following specifications of flotation control: minimize the variations of concentrate and tails grades and recovery while limiting the amplitude of variations of the manipulated variables. The strategy consists of determining future control actions which optimize a performance criterion over a limited time horizon. The desired dynamic behaviour of the controlled flotation plant is specified using reference models. The strategy is tested on a 2-computer plant simulator working in an environment which emulates the industrial conditions.

Jan 1, 1993

By Andrew M. Garvie, William W. Plotnikoff, Eugenia Y. Kuo

Water infiltrating the surface of waste rock dumps transports pollutants into the environment. Lysimeters have been used to quantify the infiltration rate. To date their design has been guided by modeling under steady-state conditions. Recently a two-dimensional finite element code has been developed to model the response of lysimeters to time-dependent infiltration rates. It was used to investigate the response of lysimeters installed in a waste rock dump and subject to a monsoonal rainfall pattern. The results are presented and compared with field data.

Jan 1, 2000

By J-P Franzidis, M. C. Harris

Increasing costs, falling grades and a low gold price have caused severe problems for many of South Africa's gold mines. The need to maximise efficiency is extremely urgent. This paper describes the use of column flotation cell s to scavenge significant quantities of additional gold from flotation plant residues; in particular, very fine particles of free gold not recovered by conventional flotation. Experimental gold- specific collectors enhanced gold recovery significantly. The paper also reports the results of other plant trials, carried out on a variety of ores.

Jan 1, 1991

By Errol vanHuyssteen

Old tailings from Zn, Au, Cu, and Ni mining operations were characterized. Their mineralogical variation in depth is compared with matching pore water and solids chemistry. A geochemical model was used to predict minerals precipitating from pore water solutions. These are compared with actual secondary minerals occurring. The degree to which the precipitation of secondary minerals controls the sulfate and iron concentration of the pore water was also investigated. The results obtained are related to the selection of the most appropriate modes of tailings deposition.

Jan 1, 1998

By Samara Ali-Ahmad, Keith Hanks, Cindy Pham

The City of Los Angeles will rehabilitate approximately 9 miles of its North Outfall Sewer. This sewer was constructed in the 1920s as an unreinforced concrete semi-elliptical sewer. One of the methods for rehabilitation is to approach the sewer as a pre-excavated tunnel and install pre-cast segmental liners to provide a single pass corrosion resistant, structurally self sufficient project. The estimated cost for this project is $46 million. The project has completed the pre-design study, and the design is now underway.

Jan 1, 2003

By D. M. Jepsen

One of the first things we tell a potential new client is that they have only one chance to make a first impression with an Aboriginal community; all future communications and engagement will be predicated on that first impression. The key components of this most critical meeting are not your power point, your maps, or your draft plan for development ? they are instead a genuine, evident and clear demonstration of a sincere desire to develop a positive relationship that is based upon respect, and consideration and understanding of local communities and their interests, needs and desires. Relationship building is the foundation of proactive and positive consultation and accommodation with Aboriginal communities and the tone is set with the first meeting. C3 has refused more clients than we have accepted due most often to the fact that relationships between the company and the Aboriginal community have already devolved into a tense and toxic scenario. Land access and tenure certainty for exploration and mine development is critical to the foundation of a healthy, sustainable and environmentally and economically sound mineral exploration and mining sector. Without certainty confidence to invest in mineral exploration will be severely eroded. We all understand that substantive investments in exploration are required to increase the possibility of discovering, defining and developing new mines. The development of positive relationships based on a shared commitment of understanding, mutual respect and trust by Aboriginal Peoples and the mineral sector can provide the required business certainty and deliver social and economic benefits for local Aboriginal communities.

Jan 1, 2012

By B. S. Pierce

The National Coal Resource Assessment – 2000 project was a multi-year effort by the U.S. Geological Survey to identify, characterize, and assess the coal resources that will supply a major part of the Nation’s energy needs during the 21st century. The purpose of the USGS National Coal Resource Assessment (NCRA) was to (1) digitally assess selected coal beds and zones that will be the most important in the next few decades, (2) create publically available stratigraphic, geochemical, and geographic information system (GIS) databases to answer a variety of questions of importance to government, industry and public decision makers, and (3) provide interpretive geologic and geochemical information for the primary coal resources of the Nation. Five priority regions were assessed: the Appalachian Basin, Illinois Basin, Gulf Coast, Illinois Basin, and Northern Rocky Mountains and Great Plains. The NCRA was a cooperative effort between the USGS and a number of State geological surveys in these coal-bearing regions. A study of coal resources on Federal lands was also conducted. Adequate energy supplies and the efficient use of those supplies are critical to the economic well being of a country. Affordable and reliable coal supplies are essential to the interests of our national and local policymakers. Policy makers require a range of information on the energy supply, as well as the economic and environmental issues associated with that energy source and its use. Formulation of an effective national energy policy and development of energy resources requires that we understand the geology, distribution, quality, and size of the national energy endowment.

Jan 1, 2001

By Gregg Sherry, Bob Gordan

INTRODUCTION This paper report presents the general case history for the construction of the North Outfall Replacement Sewer (NORS) project. A 1982 City of Los Angeles Wastewater Facilities Plan recognized that a 19.3 km (12¬mile) section of the North Outfall Sewer (NOS), from Culver City to the Hyperion Treatment Plant, was deteriorating and had insufficient capacity. Built in the 1920s of unreinforced concrete and lined with vitreous clay tiles, the originally unventilated NOS suffered considerable corrosion by H2S gas. This caused roof tile and concrete to fall to the bottom of the pipe, which, over the years, reduced the 11.9 M3/S (420 cubic feet per second (cfs)) design capacity of the NOS to a current level of approximately 8.5 M3/S (300 cfs). This worsening condition, thereby contributing to the polluting of Santa Monica Bay. This situation culminated in the State of California Regional Water Quality Control Board, Los Angeles Region, issuing a Cease and Desist Order on January 27, 1986, which required the City of Los Angeles to eliminate such dry weather overflows through a number of prescribed actions. One of these was to construct the North Outfall Replacement Sewer (NORS) by April 1, 1993. PROJECT DESCRIPTION The NORS Project involved the construction of over eight miles of tunnel and related structures. It consisted of a main tunnel conduit to convey sewage to the Hyperion Treatment Plant and four diversion lines connecting the main tunnel to major existing

Jan 1, 1993

By Vernon R. Shorter, Wayne N. Clark

Introduction Coal is the US's largest indigenous fossil fuel resource and is used to power 57% of this country's electrical generation (NCA, 1986). Congress, however, is focusing its attention on the acid rain issue and public sentiment is leaning toward further curtailments of SO2, NO, and particulates from utility and industrial coal-burning facilities. The Cool Water plant has proven that integrated-gasification-combined-cycle (IGCC) technology can reliably produce economical electrical power while limiting SO2, NOx, and particulates to a rate of only one-tenth of the federal New Source Performance Standards for coal-fired plants. Process water requirements at Cool Water are 40% less than those of a conventional coal-fired utility plant equipped with flue-gas desulfurization units for stack gas scrubbing, thus reducing waste water treatment requirements (Clark and Shorter, 1985). The IGCC technology employed at Cool Water has now been demonstrated to efficiently convert coal to electricity in an environmentally superior fashion. The Cool Water Coal Gasification Program is an unincorporated California association of six partners whose commitment is proving that the integration of gasification with combined cycle power production (IGCC) is commercially viable and environmentally safe. The 120 MW Cool Water plant began commercial production on June 24, 1984. The Program is operating it for a five-year commercial demonstration period. The Program is about halfway through this period. Much of that which was intended to be proven is now fact. In this mid-term assessment, the authors report that the com-

Jan 2, 1987

By Trevor A. Moss

Installation of equipment and structures at mines often requires mine planners to evaluate unique loading and operating conditions. Consideration of these unusual features is required throughout design and construction and into operation. Most planners understand the necessity of employing sound civil, structural and mechanical engineering techniques to design these structures and equipment. However, the influence of geotechnical factors on the overall progress of construction and operation is less appreciated. Mine operators routinely perform exploratory drilling to define ore deposits. These exploration activities can be extensive and often include provisions for assessment of subsurface conditions as they relate to the mining operation - requirements for ground support. All of these factors are important to the economics of the mine and are well justified. Surface facilities are provided to access and service the mine, and they play an important role in the successful development and operation of a project. Headframes, hoist foundations and shaft collars, in particular, are examples of unique installations encountered at underground mine sites. The design and above-surface behavior of these facilities can be analyzed with the usual fundamental engineering practices employed throughout the engineering professions. However, near surface exploration for the purposes of assessing soil and rock conditions for foundations is often given a reduced priority and less consideration. This article provides an outline of the benefits and importance of performing such exploration. References here relate particularly to shaft headframes, hoists and shaft collars. But the issues raised apply equally to other installations of a similar nature, including milling equipment.

Jan 1, 1992

By Joginder S. Bhore, Francis M. Keville, David E. Puza, Roger C. Borggaard

A portion of the Massachusetts Bay Transportation Authority's Red Line Extension through Somerville, Massachusetts consists of 1,553cm (5,092 LF) of hard rock tunneling 6.7m (22 ft.) diameter horeshoe, 148m (485 LF) of mixed face tunneling, 7.2m (23 ft.) diameter circular, beneath an active railroad in a heavily commercialized business district. This paper will deal with the excavation of the mixed face area without the use of a shield. It will address the special excavation and support problems encountered during tunneling operations using the floating crown bar and modified spiling methods. Topics covered will include excavation and support methods, cement grouting, compaction grouting, and instrumentation. PROJECT DESCRIPTION The Davis Square to Porter Square Tunnels and Shafts Somerville/ Cambridge, Massachusetts is part of the Massachusetts Bay Transportation Authority's (MBTA) 5.1km (17,000 ft.) Red Line Extension. This extension runs from Harvard Square, Cambridge, to Alewife Brook Parkway, Cambridge through Somerville. This portion (MBTA Contract #091-106) required the excavation and concreting of 1,701m (5,580 LF) of single track twin tunnels consisting of 1,553m (5,092 LF) of conventional hard rock tunneling under 56 residential properties and 148m (485 LF) of mixed face tunneling beneath an active railroad in a heavily commercialized business district. The mined diameter of the mixed face tunnel is 7.16m (23.5 ft.) Access to the tunnel was via the Summer Street vent shaft, and the two Grove Street access shafts where all tunnel excavated materials were removed.

Jan 1, 1981

By Steve Kral

When discussing stock market investments, a company's performance is important. But so is the financial community's perception of that performance. To be sure, a good product or service, coupled with sound manage¬ment, remains important but is no longer enough. How stock analysts view a company's performance has become equally important. A major task of a mining company's investor relations officer, then, is to build and maintain a positive perception of the company to mining analysts throughout the world. That's a tough assignment in any market. The subject here, though, is gold. And, with its weakened price, gold companies must work harder to convince analysts their company is still a good investment. The analyst, on the other hand, must see through the corporate hype and decide whether it's worth recommending to clients as an investment. No simple task, either. Annual reports, 10-K forms, and quarterly reports only tell part of the mining company's story. Site visits, complete with discussions (sometimes interrogations) with a mine's principals, oftentimes tell an analyst more about a company's investment potential than the annual or quarterly report. So it was that three of the nation's major gold companies arranged a three-day tour of their gold operations in Nevada for a group of 22 analysts and a pair of mining industry scribes. The analysts represented investment houses the US, Canada, and England. The host companies and mines visited included FMC Gold's Paradise Peak mine, Amax Gold's Sleeper and Wind Mountain mines, and Battle Mountain Gold's Surprise and Fortitude mines.

Jan 1, 1989