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By W. E. Horst

In Part I of this paper we describe two techniques that were employed in the development of mathematical descriptions of the size reduction process which takes place in a ball mill. In Part II we show how the comminution model was imbedded in a process model to effect steady-state and dynamic simulation of a closed-circuit grinding operation. Increasing emphasis is being placed on development of approaches whereby the essential characteristics of a process can be succinctly represented in terms of a mathematical description of the relationships that exist among important process variables. This activity, commonly known as mathematical modeling, predates modern electronic computers: however, these computers with their tremendous computational capability have given new impetus to the whole field. Although the computer is quite helpful in the development of mathematical models, the real value to the engineer lies in the fact that computers represent such a powerful tool for simulating systems described by mathematical models. As a consequence, engineers may simulate and thereby study the behavior of complex. interacting, systems over a broad range of process variables and configurations once appropriate process models have been developed for the sequence of steps comprising the process.

Jan 1, 1970

By Richard L. Bullock

INTRODUCTION TO COAL MINE PRACTICES To illustrate the trends and the proportions of the various methods used to mine coal underground, Fig. 1 is useful. However, of all the underground coal mining practices in the US, room-and-pillar mining still accounts for 96.5%. This percentage is divided as follows: conventional, machine cut-33.0%; conventional, hand cut -1.7% : and continuous mining-61 .8%. As was stated in Sec. 1, Chap. 7, the term "development" means different things to a coal miner and a metal miner. Though some of the ideas and concepts presented in the first two chapters of this section are valid for all types of mines, they apply particularly to mines using noncoal methods. In coal mines (and many other mines using coal mining systems) development refers to that phase of the mining cycle which advances several entries through the virgin seam, forming pillars by cross- cutting between the parallel entries. Because in the past, coal seams (as well as seams of potash, trona, oil shales, gilsonite, salt, and some uranium) have been much more uniform in their thickness, continuity, and quality, and because they often cover large areas, it has been possible to develop the room-and-pillar mine completely from a preplanned, systematic approach with a minimum of surface drilling information. As the better coal seams of the midwest and east are being depleted (or eliminated because of high sulfur), seams of poor quality and continuity will have to be mined. Also, seams that are not nearly so well known at greater depth will have to be taken as well as some of the steeply pitching and folded seams of the west. The American coal miner is only now feeling the need to do a much more complete job of prospecting the geology of the coal seams than he has ever done before. This is the only way that the risk of unknown rock conditions can be minimized. In many ways, surprises in the rock or coal seams are much more of a disaster to the coal miner developing a room-and- pillar mine than to his metal mining counterpart. Be- cause of the multiple entries, the complex set of the Federal Coal Mine Health and Safety regulations, and the totally dedicated design of coal mining equipment, coal mining systems do not have the flexibility to easily overcome changes in the seams mined or the rocks around them. Thus, if a wide parting of rock shows up unexpectedly in the middle of a coal seam entry being milled away by a continuous miner, it will either have to slowly "chew" through it, convert to a conventional mining system, or stop that particular entry. Likewise, if suddenly the coal disappears completely and in its place are the remains of an old creek bed, the "want" or "wash out" as it's called will usually have to be mined right along with the coal, by the same methods and with the same soft rock equipment, or the entry will have to be abandoned. For reasons such as these, coal seams today should be drilled from the surface just as thoroughly as the ore bodies in metal mines. Having once determined a more precise location of where the coal seams are located and which are suitable for mining, the engineer must still take a systematic approach to planning the mine as completely as possible. The initial series of entries must be planned to be driven either from the side hill portal or from the bottom of the shaft or slope. In either case, they should usually intersect the area close to the midpoint of the mass to be mined.

Jan 1, 1982

By J. S. Murty

In this paper, a report is given of studies undertaken in a laboratory rod mill to obtain the optimum conditions for the desired particle size distribution for long-distance transportation of coal through slurry pipelines.

Jan 1, 1987

By I. K. Kapageridis

Digital photography combined with three dimensional models of topography, mining operations and restoration plans can lead to extremely realistic images and animations of the current and future states of a mine or quarry. The amount of work and the time required for the successful modeling of a mine and its restoration plan are surprisingly low nowadays. All this means that the visual impact of mining and quarrying operations can be easily assessed using common computer hardware and some dedicated software packages. LAVA Mining and Quarrying SA is a company committed to strive continuously for the highest possible environment protection at the company?s quarries. The pozzolanic rock quarry located at Xylokeratia is one of the company?s quarries on the island of Milos and the subject of the study presented in this paper. A thorough restoration plan of the Xylokeratia quarry is being completed by the company. For its purposes, a complete visual impact assessment study was performed at the Department of Geotechnology and Environmental Engineering of the Technological Education Institute of Western Macedonia. The procedures used in this study and the produced visual results are presented in this paper.

Jan 1, 2006

By Robert D. Schmidt

The Bureau of Mines is conducting an investigation to develop remediation techniques for residential water wells whose yield has been affected in the long term, by underground mining. Initial work relating to this project was conducted in 1984-1987 at a room and pillar mine in Indiana County, Pennsylvania. Piezometer nest data from the room and pillar mine reveals that a downward gradient in piezometric head exists in shallow strata as a result of drainage into the underlying mine void. The vertical gradient in head in turn results in well bore leakage in open-hole water wells. The relative yield of valley wells is only slightly affected however because the high surficial recharge rate through fractures more than compensates for fracture leakage into the underlying mine. The relative affect of well bore leakage on well yield is greater in certain hillside and hilltop wells that have comparatively low inflow rates at shallow depths. The static water level of such wells is determined to a much greater extent by the chance interception of deep outflow fractures, than is the case for wells drilled in a more intensively fractured valley bottom. The lower static water level of wells that intercept deep fractures does not necessarily reflect the water table conditions outside of a small radius around the affected well. The results suggest that permanently isolating well bore outflow fractures may remediate certain open-hole residential wells that have been affected by high extraction underground mining.

Jan 1, 1986

By V. L. Magnus

The text of this chapter was not received in time for printing.

Jan 1, 1979

By Robert J. Auber, Thomas R. Scotese

The West Leg Interceptor is part of a new sanitary sewer system in the southwest suburbs of Cleveland. The first two construction contracts were excavated in glacial soils varying from hard tills to pressurized silts and flowing sands. These soil and groundwater conditions were locally problematic during shaft and tunnel excavations and final lining construction. A variety of solutions were developed primarily during construction. During the WLI-1R Contract, subgrade pressures, continued ground losses, and displacements necessitated extra eductor wells and modified inverts for stabilization of shafts. At the WLI-2Contract, one shaft excavation in similar ground required only one extra well. In the WLI-1R tunnel, localized inflows of groundwater, silt, and sand through the geotextile fabric were stopped by cement grouting. In one WLI-2 connector tunnel, damage to the TBM flood doors combined with wet, flowing silt and sand led to ground losses, surface settlements, plugging, patching, and chemical grouting. The concrete lining in the main WLI-2 tunnel required remedial work to improve watertightness at joints.

Jan 1, 1999

By Gordon L. Steele

Candelaria, a century old mining camp in western Nevada, was famous for its high-grade silver veins. Continuing demand for precious metals resulted in renewed interest in the mining camp and it is now being mined with modern open-pit methods and heap leaching of disseminated silver ore between mined-out veins. The Candelaria operation, in Mineral County, NV, handles 32.7 kt/d of material and was designed, built, and functioning within a year of corporate approval. Occidental Minerals Corp., an Occidental Petroleum Corp. wholly owned subsidiary, is the project's general partner and Congdon and Carey is the only limited partner.

Jan 6, 1981

By William F. Lawrence

Within ten to fifteen years, coal-fired power generating stations will be producing over 40 million tons of coal-ash annually in the United States. The largest part of this ash will be emitted from the boilers, entrained in the off-gas stream and trapped as flyash. However, about 15 percent (six million tons) will he removed from furnace bottoms as bottom ash or molten coal-ash slag. In current practice, the molten coal-ash slap is generally water quenched and then transported either as a slurry or in granular form to storage or disposal areas. Although a small amount of this slag is marketed as abrasive grit or as roofing granules, most of it is considered a waste material which must be disposed of at considerable cost to the power companies and therefore to the public. The accom¬panying economic loss in terms of unused raw materials and displaced land is not as obvious but is just as real. The Coal Research Bureau at West Virginia University under the sponsorship of the U. S. Bureau of Mines has been examining the possible utilization of both coal-ash slag and flyash in the mineral wool industry as a method of partially alleviating the growing national problem of solid waste disposal. The potential marketing situation for mineral wool manufactured from coal-ash is illustrated in Figure 1. This bar graph depicts the growth in value of mineral wool shipments1 from 1949 through 1966. In this 17-year period, the value in¬creased by over 350 percent, more than 20 percent per year, despite a decrease in unit cost of mineral wool. It therefore appears likely that coal-ash could find a steady market as a supplement to existing sources of raw materials for mineral wool production.

Jan 1, 1970

By O. E. Etheridge Jr., R. A. Lowe, C. I. Basilio, J. M. Randolph, S. W. Sheppard

The low-shear viscosity of kaolin slurries is one of the principal characteristics that determine whether a clay can be utilized for paper and ceramic applications. In this work, the causes of high low-shear viscosity and methods for improving the rheological behavior of the slurries were investigated. The presence of fine-grained smectite impurities within the kaolin was shown to detrimentally affect the low-shear rheology of the slurries produced from these clays. It was also shown that mechanically working (i.e., pugging) a crude kaolin followed by desliming to remove these impurities can reduce the low-shear viscosity.

Jan 1, 2000

By Karl O. Toppel, Jim Flaherty

The desire to minimize gaseous effluent in smelting and maximize gold yields from refractory ore are driving the nonferrous and gold refining industries to demand more and more oxygen. This, coupled with an increasingly competitive marketplace, forces the investigation of alternate methods of oxygen supply. Current progress in both the non-cryogenic and cryogenic fields is making the use of low-purity oxygen much more attractive. The benefits of on-site production are now available to most oxygen users. Historically, these on-site advantages could only be achieved by relatively large plants using high-purity cryogenic technology. The evolution of low-purity cryogenic and non­cryogenic oxygen production has added a new method of delivering on-site production. Specifically, the advent of oxygen Vacuum Swing Adsorption (VSA) technology has brought these benefits to smaller-volume customers by cost-effectively supplying oxygen requirements as low as 20 tons per day, (tpd). Low-purity cryogenic plants have also made an impact on the market, yielding cost reductions for larger-volume customers with oygen requirements greater than 70 tpd. This paper reviews the advantages and disadvantages of current supply methods for users having varying volume, purity and other requirements.

Jan 1, 1993

By Thomas P. Kwiatkowski, John S. Anderson

The Massachusetts Bay Transportation Authority (MBTA) has undertaken an under-ground transit project to extend public transportation service from downtown Boston to the South Boston Piers area. This new system, known as the Transit way, will connect existing subway lines to this area which is comprised of approximately 300 acres, in light of the potential for 21 million square feet of development by 2010. This system includes construction of a concrete immersed tube tunnel crossing of Fort Point Channel. The crossing will be accomplished in the highly congested setting of down-town Boston and will be located just to the north of the famous Boston Tea Party ship exhibit and amid major Central Artery Construction activity. The most recent concrete tube constructed in the United States was in 1962. The Fort Point Channel Crossing will employ current design and construction methods commonly utilized in the Netherlands, Australia, Hong Kong and elsewhere. This paper will present the design philosophy, planning, and evaluation of alternative crossing methods which led to the selection of the concrete immersed tube tunnel and construction techniques envisioned for this particular application.

Jan 1, 1997

By Jorgen Elbrond

The mineral industry shares a particularity- heterogeneity-with the other primary industries exploiting nature such as agriculture, fisheries, and forestry, which may not be found in the secondary industries, In the mineral industry heterogeneity is evident both in the raw material, the ore in situ, and in the working conditions. Mining engineering, which encompasses the tools for designing mine production systems, is mostly an assembly of the other branches of engineering and applied science. The assemblage's goal is to arrive at an optimal production system. As such, mining engineering is similar to systems engineering. The technique for the development of systems-mine production systems or mining operations -is operations research with its succession of activities: observations, modeling, experimentation, and verification. Comparisons among alternative systems are highly desirable during the development phase of a mining operation as well as during later phases where modifications, ameliorations, and expansions are carried out on the existing system. The role of the independent consultant in systems design and development lies in the collection and breadth of experiences from modeling and model verification in other operations, which he can add to a new system's development and thus in- crease its credibility with management.

Jan 1, 1979

By David M. Mchaina, Steve Hardcastle, Michel Grenier

An overview of the process employed to assess arsenic exposure levels at a gold mine is provided together with the recommended control measures. Arsenic and its compounds are regulated in Ontario as designated substances in all workplaces except mines and concentrators. There is a proposal to remove the exemption for mine and concentrators. If the exemption is removed, the mining industry will be required to adopt the proposed exposure Limit of 0.01 mg/m over 40 hours. There are many mines in Ontario which will be affected by this new regulation. To determine the extent of which workers are exposed to Levels exceeding 0.01 mg/m , an assessment program was initiated at the mine. The main objective of the program was to determine the effect of the proposed regulation on underground and surface operations in term of compliance if it becomes Law. The data obtained from the assessment program shared that only 1ML of the workplaces monitored for arsenic indicated levels above the proposed limit of 0.01 ,/yard all workplace levels were below the present Limit of 0.2 mg/m .

Jan 1, 1992

By James E. Monsees, Richard J. Proctor

INTRODUCTION Los Angeles is one of the world's largest cities in area with a span of 70 km between its north and south limits. The population in the Los Angeles Basin exceeds 11 million people. Los Angeles is second only to New York City in density of U.S. urban population and it operates one of the largest city bus fleets in the world, 2,500 buses. After many years of planning and many consultants' reports, it is planned to initiate a 30 km (18.5 miles) starter line subway -- the "Wilshire Corridor" (Figure 1). Construction is to start in 1985. In several locations, subway routes ultimately will skirt or cross old oil fields, which may cause gassy tunneling. Of particular note are the La Brea Tar Pits, which overlie a part of the old Salt Lake oil field. Tunneling through tar sands for about 3 km will be unique for subway construction and will occur on the starter line. Experience with previous gassy tunnels in the greater Los Angeles area shows that tunnels can be completed safely if precautions are taken. Abundant ventilation is the main solution, although other precautions are discussed herein.

Jan 1, 1985

By H. Bernatowicz

The Nucoalyzer (On-Line Nuclear Analyzer) is a new method recently made comercially available for monitoring the elemental composition of a process stream. Applications for the Nucoalyzer include grading ore on a conveyor belt before or after it has gone through primary crushing, monitoring the slurry being transported in a pipe to the concentrator, and monitoring the stream of concentrate or the tailings from the concentrator. The Nucoalyzer may also be used at the smelter to monitor elements in the feed that include copper, sulfur, iron and silicon where a uniform feed is desired. The advantage of the Nucoalyzer over most other techniques are (a) it performs the measurement directly on the process with no sampling necessary, (b) the analysis can be performed on streams of particulate and slurries, and (c) the system does not have to make contact with the material it measures. These Nucoalyzers are operating at coal fired power plants and several more are about to be placed in service. This paper discusses the principles of operation of the Nucoalyzer, our experience in the field, application of minicomputers to data reduction, and potential applications in the ferrous and non-ferrous industries.

Jan 1, 1982

By J. A. Frew, R. M. Glen

Recovery of galena and sphalerite from fine grained lead-zinc ores by flotation normally requires re-grinding to achieve economic recoveries at acceptable concentrate grades. Re-grinding aims to reduce the coarse valuable mineral particles to a size where they float more readily and to liberate the composite valuable particles so that the gangue in these composites does not dilute the concentrate. Besides changing particle size and liberation, re-grinding changes the surfaces of the minerals and thus may alter the rate that mineral particles of a given size and liberation float. A method was developed to apportion the total change in recovery after re-grinding between changes in size and liberation and changes in flotation rates. The flotation behaviour of minerals, before and after re-grinding, was measured by floating samples of plant streams under controlled conditions in a laboratory cell. Results from several industrial lead-zinc circuits indicated that the change in behaviour observed fell into three different categories. It is concluded that the method will indicate whether the focus for optimization of existing plant should be on comminution or flotation, and it will help determine the path for laboratory testing in designing new regrind circuits.

Jan 1, 1995

By W. Addy Majewski, Kenneth L. Bickel

The U.S. Bureau of Mines (USBM) and Diesel Controls Limited evaluated a new diesel emission control system on an underground mine vehicle. The system was a catalyzed ceramic wall-flow diesel particulate filter (CDPF) combined with an catalytic converter, or diesel oxidation catalyst (DOC). This paper describes the design and installation of the system on a load-haul-dump (LHD). The results of screening tests conducted by the USBM are also given. The screening tests were conducted to determine if the device's particulate collection efficiency, regeneration temperature, and effect on gaseous hydrocarbon (HC) and carbon monoxide (CO) emissions changed over the period it was being used. The system was removed from the LHD and evaluated in the laboratory after operating for 308 and 1200 hours. After 308 hours of operation, laboratory testing revealed its particulate collection efficiency varied from 41.0 to 93.5 percent, depending on engine operating conditions. Its regeneration temperature was about 415° C. It reduced HC emissions by up to 97.6 percent, and CO by up to 95.0 percent. When tested in the laboratory after operating for 1200 hours on the vehicle, no significant change in performance was observed.

Jan 1, 1995

By T. J. Cox

The Red River is located within the Sangre De Cristo Mountain Range in northern New Mexico. An approximate 12-mile segment of the river from the town of Red River to the village of Questa (Questa) includes several hydrothermal alteration zones. Alteration ?scars? formed as a result of rapid chemical weathering and physical erosion of pyrite-rich hydrothermally altered rocks. Storm water runoff from the scar drainages contributes metal-laden, acidic water to the river and creates a visible plume of discolored water in the river. Acidic runoff reduces the river pH from 7 to the mid 3s for at least 2 hours during large storms and the low pH water continues downstream. Runoff from scar drainages increases some metal concentrations in the river from below chronic ecological criteria to as much as two orders of magnitude greater than acute ecological criteria, and results in acutely toxic conditions for macro-invertebrates. A general improvement in the river?s water quality occurs downstream due to dilution from tributary inflow from non-mineralized watersheds, the natural buffering capacity of the river, and storm water controls at the Chevron Mining Inc. Questa mine.

Jan 1, 2011

By W. Blake, J. K. Whyatt, B. G. White

In situ stress on the scale of a tunnel or mine may be distorted by geologic structures. The resulting variations in in situ stress have a direct bearing on the potential for mining-induced seismicity. New evidence collected from the Lucky Friday mine by US Bureau of Mines researchers, as well as a review of previous case studies, demonstrated that in situ stress variations affect the [spatial] distribution of mining-induced seismicity. Although overcore stress measurements have been useful in these studies. they are too expensive and, depending, on conditions, may be too difficult to collect. However, information on borehole and raise breakouts: deformation of mine openings: and patterns of seismicity, ground-control problems and rock-burst damage can be used to build a stress database. In conjunction with maps of mine structure and geology and models of rockmass behavior, this database can then be used to build a map of in situ stress variations. Such a map could provide a means of anticipating patterns of mining-induced seismicity and. Thus, could be the basis for planning appropriate measures to ameliorate rock-burst hazards.

Jan 1, 1997