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By S. J. Porter, M. T. McRae

The new tunnel at Genting Sempah is part of a privately funded infrastructure projectthat involves duplicating the existing highway extending from the Gombok Toll Plaza near Kuala Lumpur to Karak, in Malaysia. The 60 km long tollway includes an 800 m long, two-lane highway tunnel with excavated dimensions of 10.5 m wide by 8 m high. The majority of the tunnel extends through slightly to moderately weathered, moderately to highly jointed quartz porphyry. Excavation of the tunnel was performed using drill and blast methods and the primary tunnel support consists of rock dowels and shotcrete except for short sections adjacent to the portals where steel sets were utilized. A portion of the tunnel encountered sheared and altered material that was successfully supported using rock dowels and shotcrete. The final lining for the tunnel consists of mesh and fiber reinforced shotcrete. The flexible nature of the primary support and shotcrete final lining resulted in considerable cost savings and expedient construction methods.

Jan 1, 1997

By Jack W. Eloranta, Michael J. T. Orobona, Peter R. VanDelinder

Ore blending for process optimization is becoming an increasing factor for managing cost and productivity. Economic mining and processing a very low value ore in an extremely competitive market results in constant cost-cummng initiatives. The inherent conflict between the lowest possible mining cost and the lowest possible milling cost is reviewed here in the context of blasting for autogenous mills. Iron ore blending focuses on a number of properties-liberation values, weight recovery and concentrate silica being the most important. Other chemical and metallurgical factors are also commonly controlled. Recent research has fueled an emerging interest in blending on physical ore properties as well. Fully autogenous mills rely on the large, competent fraction of crushed feed to act as grinding media. Previous test work indicated that Hibtac mills require specific amounts of 6- to 10-inch ore. High recirculating loads require a steady influx of large rock fragments. Blast designs, therefore, are presently characterized by wide patterns and low powder factors. Current efforts are aimed at improving mill throughput while reducing overall energy costs. Based on research and published case studies and the advent of optical measuring devices, Hibbing Taconite Company has embarked on a blast optimization program to identify optimum mill feed and to design blast fragmentation goals for each geological unit and each mining area. This paper outlines the preliminary findings of an ongoing, broad-based team effort which requires close cooperation of geologists, mine engineers, crushing and milling personnel. Three specific areas of investigation are reviewed: I) Historical relationships between powder factor and mill performance, 2) Blast fragmentation modeling using the Kuz-Ram model, and 3) Drill

Jan 1, 2004

By M. Cambridge

The extractive industries are currently, and will continue to be, major contributors to the world economy, particularly in the developing world where economic growth is dependent upon a sound supply of primary materials. However, tailings dam and other mine failures have been very much a feature of recent anti-mining publicity, particularly in Europe, and thus instrumental in inhibiting new mine developments. Although, superficially, the record of dangerous incidents might support the anti-mining position, closer inspection suggests otherwise. This paper reviews the failures which have occurred over the last 50 years and demonstrates that, though poor practice is an ongoing problem for the industry, the record is one of improvement in both design and practice. Examples are provided of significant events which have led to dramatic advances in design and operation. The paper assesses the improvements made in technology and practice, and concludes that historic events must continue to form the underlying basis for design and operation of future mining projects.

Jan 1, 2005

By A. D. Davis

A ground-water flow model was developed to simulate the post-mining recharge rate at the Belle Ayr surface coal mine in the Powder River Basin near Gillette, Wyoming. State regulations of Wyoming require that reclaimed lands should provide a rate of recharge that approximates the pre-mining rate. Steady-state calibration and transient simulations showed that the post-mining recharge rate in backfill is at least five centimeters per year, exceeding the original infiltration rate of 0.4 centimeters per year to shallow, overburden aquifers. Major reasons for the increase include the flat topography of reclaimed areas and decreased spoil density. It is expected that the backfill will disaggregate and settle over time, eventually resulting in a nearly constant recharge rate less than five centimeters per year but somewhat greater than the pre-mining rate.

Jan 1, 1995

By Yoshihiro Kawarabata

INTRODUCTION The shield-driven method in Japan has been adopted widely in soft ground tunneling, namely, subway, water supply, sewer and utility tunnels, and recently this is an indispensable method in urban area. Since this method was started to adopt on a full scale from the beginning of 1960, construction achievements in length were about 830 km for 15 years until 1974 (1). According to the recent informations of the Japan Tunneling Association, the achievement in length under construction as of December, 1977, was about 350 km (2) and the extention of increase in shield-driven method can be guessed (Tab. 1). Tab. 1 - Achievement in Length by Shield-driven Method (As of December, 1977, Unit: m) (---): Achievement by Okumura Corporation [ ]

Jan 1, 1979

By Anthony G. Fonseca

About 45% to 50% of the coal mined in the United States passes through coal preparation plants. East of the Mississippi River, this number increases to about 75% to 80%. Although the cost for coal preparation is worthwhile to some, the coal industry faces the challenges of continuing downward pressure on the price of coal and the impact of new environmental regulations. Coal preparation is an effective process that achieves 75% to 80% ash reduction, 15% to 80% trace element reduction and 85% to 90% Btu recovery. It is less effective for pyrite reduction (35% to 70%) and on-line operating time (40% to 60%). It also suffers from obsolete control systems. In coal preparation, raw coal is modified to a more preferred form to enable its use. The methods used to achieve this modification must be cost-effective and appropriate to the raw coal, the scale of production and the end-user requirements.

Jan 1, 1995

By John Jonkman

During the decade of the eighties, the mining industry was able to take advantage of numerous advancements in computing technology. The development of the desktop workstation and the tremendous increase in power of minicomputers have cause many of the technical computing applications to be taken out of the "glass house", or central computing facility, and distributed to where the work is actually performed. This trend, combined with the significant price/performance improvement being experienced, has resulted in computers becoming more readily available at a reasonable cost for research and development activities, thus increasing the amount of new development taking place. The papers in this session discuss research and development work which has resulted in advancements in mining technology applications in the following areas: - Technical Parameterization - Linear Programming - Dynamic Programming - Computer Aided Design

Jan 1, 1989

By James D. Reilly

The time-worn adage "an ounce of prevention is worth a pound of cure" was never more applicable than when used in reference to coal mine safety. Many individuals have dedicated many hours to developing effective accident prevention programs, and much has been accomplished. Each production escalation, however, creates new hazards and safety problems which need special study and research. It is a never ending cyle. To study the progress of coal-mine safety is to raise memories of many individuals who have been dedicated to removing the hazards that have developed with increased productivity and deeper penetration into the earth for coal. Some vivid examples of this dedication are the works of the men who pioneered the use of the safety lamp and the use of rock dust in mining.

Jan 1, 1968

By John H. White

As production of ground limestone increased our Company found it had an enviromental problem with limestone dust from our hammer mills. With the quarry and processing plant situated within 1 klm of a small township of 5000 people dust collection became essential. Regulations under the Clean Air Act 1972 also had to be complied with. Prior to this any demand for lime flour had been met by the use of a small drier and ball mill. Both expensive to operate. Dust emitting from the mills would amount to over 4000 tonnes per year. The cost savings were obvious. We had a better product which was essentially a by-product. Faced with a surplus of a very useful, but difficult product to handle we considered the possibility of disposing of it on the agricultural market.

Jan 1, 1982

By E. M. Williams

The U.S. Bureau of Mines recently conducted a limited-scope study on the use of lineament analysis and electromagnetic geophysics to better identify the surface expressions of faults at the Cimmaron Mine near Raton, NM, an operating longwall mine in the York Canyon mine complex. Two normal faults were encountered by the mine, one during gate road development and drilling and another only through drilling. The potential ground control problems and offsets associated with these faults will severely impact long-range development plans, so it is essential to know the lateral extent of these faults within the coal reserves. The surface topography at the site is fairly rugged, yet outcrop exposure is poor. There is no obvious visible geologic evidence to indicate that the faults identified at depth extend to the surface. Both the geophysical and remote sensing techniques provided information on the presence and extent of important geologic structures which could not be gained just from drilling and surface outcrops. The geophysical surveys also were invaluable in confirming the presence of subsurface geologic structures in the vicinity of the lineaments assumed to be associated with the faulting.

Jan 1, 1995

By G. P. Hand

Graphite usage in the United States during 1994 was fairly strong. The hearty showing of the domestic economy, along with sound performances from the major industries that use graphite, helped make 1994 a solid year for the graphite industry. Supply Virtually all natural graphite is imported into the United States, as there is no domestic production. The primary producers are Brazil, Canada, China, Madagascar, Mexico, Mozambique, Sri Lanka and Zimbabwe. Mozambique is a new producer. It is now supplying a high-carbon, large-crystallite flake in large quantities. Sri Lanka continues to experience problems with one of its two mines, closing operations in December 1994. The synthetic graphite used domestically was produced primarily in the United States as a byproduct of electrode production. Synthetic graphite was also imported from Switzerland for specialized applications. The purified graphites/carbons, such as Desulco and ThermoPURE materials, were also produced domestically. There was a sufficient supply of all types of graphite to meet domestic demand.

Jan 1, 1995

By A. D. Agate

In developing nations, novel mineral processing methods like bacterial leaching are gaining prominence. The principles and practices for isolation and preservation of cultures used in bacterial leaching are discussed with special reference to cultures used in leaching copper from Indian ores. In all, 145 potentially useful microorganisms such as iron- and sulfur-oxidizing bacteria were isolated from various ecosystems of the copper mining areas in the country. The major organisms isolated by enrichment culture technique belonged to T. ferrooxidans and T. thiooxidans species. In addition, thermophilic cultures like Sulfolobus sp. and thermophilic thiobacilli were also isolated. The process of copper leaching was scaled up to the 300-kg level in PVC columns. Since the preservation of efficient cultures in active state was vitally important, a new method was devised that preserved the activity of thiobacilli for a period of more than two years. The novel method of storage in sterile chalcopyrite ore at 8°C can be considered an important advance.

Jan 1, 1987

By J. L. Chakravatti

The movement of air from the surface, through the workings and then back to the surface, is the most important consideration in the ventilation design. The purpose of mine ventilation is seen as the maintenance of acceptable atmospheric environments wherever men work or travel underground; and acceptability is related to the risk of harmful biological responses associated with exposure to atmospheric environments in mines. In mine ventilation, a design engineer often has to contend with a number of problems not experienced to the same degree in other industrial situations; i.e. the vast extent of many workings - offering continuously moving work locations; the difficulty of predicting. inflows of contaminants to the airways which contain the micro-environment; and especially, the effect of mining activity within the duct system (e.g. mine roadways) carrying the airflow. Mining of uranium does not differ, in many respects, from the mining of other metals; the ore must be drilled, blasted and transported from the mine. Underground mining proceeds by the continous development and advancement of a network of passages and rooms or stopes from which ore is excavated. As in most mines, rock conditions and ore grades in uranium deposits very from area to area and between different mines. 1 In uranium mining, in addition to eliminating noxious gases from blasting, diesel equipment exhaust, and the control of dust, it is also necessary to dilute and remove radon, the gaseous element in the uranium chain and its decay products. Long term epidemiologic studies of United States uranium miners and that of miners in Czechoslovakia have confirmed that there is an association between excessive ex¬posure to radon daughters and an increased risk of lung cancer. The common practices for controlling these airborne contaminants are: (1) the circulation of large volumes of fresh air from surface to dilute these contaminants to a permissible concentration, and (2) the sealing of worked-out areas to prevent ingress of radon into ventilating air. 2 The sealing of worked-out areas can be easily and effectively accomplished, but the contaminants intro¬duced from the workings may raise the concentrations in the airways despite a good ventilation system and use of the maximum available amount of fresh air. The ventilating air can be strategically filtered to reduce dust and radon daughters to acceptable levels, and reused prior to final discharge. This strategy properly applied, will decrease the air colume requirements in certain marginal areas of the mine and thereby avoid an overall increase in the mine airflow. This is particularly advantageous in the cold climates of Canada, where the incoming fresh air must be heated in the winter months to a comfortable temperature, Thus, an economical and technically feasible air filtration system, strategically placed, can improve the underground mining environment and reduce the overall cost of ventilating the mines. In addition to affording flexibilty to the venti¬lation system, a potential saving of $1,500/m3/s/year would be realized if air is successfully cleaned and reused when compared with the conventional methods of generating an air current. 3 Denison is justly proud of its achievements in the air filtration technology development. This paper limits itself to an examination of the radiation control aspect of the air filtration strategy.

Jan 1, 1980

By J. J. K. Daemen, C. Fairhurst

Two aspects of tunnel support design are considered, and for both particular attention is paid to the influence of rock failure around the tunnel on the loads developed on the supports. 1) In general it has not been possible to extend analytical methods for the study of rock failure around tunnels to three dimensions. As a consequence it was not possible to calculate either the influence of the face or the actual sequence of support loading as the face advanced. The finite element method made this extension possible. A simplified analysis of the influence of the face and of the sequence of support installation has been made. The influence of the original stress field and of the rock behaviour on the length of tunnel which can be left unsupported (related to the stand-up time) is shown. The degree to which a 2-dimensional analysis can be used to approximate the final support load is shown to be dependent upon the post-failure behaviour of the rock. 2) Tunnel support design requires a knowledge of the forces and of the -rock displacements which cause stressing and deformation of the support system. A 2-dimensional model incorporating a detailed representation of several support systems, of the rock behaviour in the broken zone and of the interaction between rock and support is given. The model allows the calculation of the stress distribution in the support. The significance of the relative stiffness of support and rock on the stresses developed in the support is shown.

Jan 1, 1997

By Cyril W. Draffin

Introduction Americans have long been proud of their ability to recognize a need, define it, and then develop workable solutions. The U.S. underground coal conversion (UCC) program is a good example. In 1974, the need to utilize coal resources that could not be mined was recognized, and Congress gave the Bureau of Mines $1.7 million to gain a better understanding of the UCC technology and its potential applications. Since 1977 when the U.S. Dept. of Energy (DOE) was formed, workable technologies have been tested, the market for underground coal conversion has been recognized, and extensive industrial interest has developed. Perspective The U.S. is blessed with extensive coal resources. Coal supplies about 19% of our national energy needs, yet recently promulgated environmental standards and increasing mining costs have limited direct coal use. UCC potentially can use coal that is economically or technically infeasible to mine because the coal is too thick, deep, dirty, high-ash, and wet; has an excessive angle of dip; or has unpredictable and poor over-burden characteristics that make mining unsafe. Coal can be gasified underground or perhaps liquefied below the earth's surface. Underground coal gasification (UCG) is the prime element of the underground coal conversion program. It enables coal to be converted to gas underground. UCC Coal Resource Recent data show a total U.S. coal resource base of about 6.4 trillion tons. Of this, 1.8 trillion tons might be accessed by UCC, including some minable coal. A commercial UCC process could quadruple roughly the 450 billion tons of U.S. coal reserves, which presently are recoverable by mining. The U.S. coal resources are divided into five sectors. The two most eastern sectors contain relatively thin, swelling bituminous coals that are difficult to gasify. Of the two, the bituminous coal in the Eastern Province is the most difficult because it is deeper than in the Interior Province and the terrain is more rugged. The sector along the Rocky Mountains contains huge amounts of thick low-rank coals that are the most promising for early development by UCC. The coal has good continuity and the terrain is suitable. Low-rank coals such as subbituminous and lignite are highly reactive and tend to shrink and disaggregate when heated. Most of the coal in the Pacific

Jan 9, 1980

By David A. Lindsey

In this paper, we present a physiographic classification of gravel deposits, identify some field measures of aggregate quality, and describe sampling strategies for mapping aggregate quality in the Front Range Urban Corridor of Colorado. Gravel occurs in four types of deposits along the Front Range of Colorado: (1) piedmont alluvial fans, (2) high dissected terraces, (3) high (continuous) terraces, and (4) floodplains and low terraces. The four deposit types are the basis for definition of gravel-deposit models, which differ in geologic environment, deposit characteristics, deposit size, environmental impacts of mining, and post-mining use. Of the four types, floodplains and low-terrace deposits have been exploited most for gravel. High terraces also have been mined. Deposits of high dissected terraces and dissected alluvial fans have produced minor amounts of gravel, mostly for use as local fill. Studies to identify useful field measures of aggregate quality and to determine the appropriate scale for sampling were conducted on gravel deposits beneath the flood-plain and low terraces of the South Platte River north of Denver and the Cache la Poudre River between Ft. Collins and Greeley. Gravel deposits of the South Platte were selected for study because they represent the last major resource of gravel for aggregate in the Denver metropolitan area. The Cache la Poudre valley is the primary source of gravel aggregate for rapidly urbanizing areas around Ft. Collins and Greeley. Of all the field measures of gravel quality, the most important is particle size. Various parameters that measure particle size were investigated, but the easiest to determine, and the most useful to the aggregate industry, are measures of the proportion of coarse sizes. Particle size varies widely in gravels of the urban corridor. Gravel lithology, particularly the presence of deleterious particles such as reactive volcanic rocks and decomposed rocks, must be determined to assess aggregate quality. Studies of South Platte and Cache la Poudre gravels have not revealed large proportions of deleterious lithologies. Studies of particle shape revealed only small numbers of physically weak shapes in both the South Platte and Cache la Poudre gravels. Particle shape does not appear to vary from place to place in the gravels. Rounding, or the ab¬sence of angular corners, may play a role in the tendency of loose gravel to yield under load. South Platte and Cache la Poudre gravels are rounded, and rounding tends to increase upstream. Before the quality of gravel in a valley can be assessed, the stratigraphy of the gravel must be known because it affects sample design. If only a single gravel layer is to be studied, only the thickness of the gravel must be known before sampling. If, however, more than one layer of gravel-distinguished by particle size, sorting, or lithology-is present, sampling must take into account the thickness and distribution of each layer. For example, three gravel layers of different particle size underlie the floodplain and low terraces of the South Platte. The tributary Cache la Poudre, on the other hand, contains gravel layers that can be distinguished only locally and vary slightly in particle size. Sampling experiments were conducted on gravel bars in the South Platte River and in gravel pits on the floodplain and low terraces of the South Platte and Cache la Poudre Rivers. Experimental results indicate that, even where sample error is large, regional and stratigraphic variation may be measured if it is large relative to sample error. Using vertical trench samples weighing an average of 40-90 pounds, down-stream decrease in coarse particle size was mapped for Cache la Poudre gravel, and differences among superposed gravel beds were measured for South Platte gravel.

Jan 1, 1999

By David R. Quigley, Patrick R. Dugan

First reports of microbial coal solubilization appeared in the early 1980's (Fakoussa, 1981; Fakoussa and Truper, 1983; Cohen and Gabriele, 1982). These degradations, which occurred at ambient temperature and pressure, resulted in a dark brown to black viscous liquid and required days to weeks to occur. Rates and degrees of coal biodegradation varied from coal to coal. Hard coals were not extensively degraded (5-7%) while low-rank coals such as Leonardite, a sublignite, were completely solubilized. A correlation between degree of weathering or oxidation of coal and the coals susceptibility to biological attack was observed. This led to oxidative pretreatments as a method to enhance microbial degradation of coal (Strandberg and Lewis, 1986). Products of microbial degradation of coal are water soluble solids that do not have significant solubilities in organic solvents (Wilson, et. al., 1987; Quigley, et. al., 1987; Quigley, et. al., 1988a). Solutions of solubilized coal did not separate or form precipitates which suggested that they were true solutions and not colloidal suspensions. Biosolubilized coal contained more oxygen than starting material suggesting that microbial attack of coals involved oxidative cleavage of carbon-carbon bonds. This small change in oxygen content was the only change observed in coal structure during the biosolubilization process. Many coal solubilizing microorganisms have been isolated. Some are lignin degrading organisms such as Phanerochaete chrysosporium and various Streptomyces species (Gupta, et. al., 1988; Wilson, et. al., 1987). This was not unexpected since the structures of lignin and low-rank coals are similar. These organisms produce an enzyme complex, ligninase, that utilizes hydrogen peroxide to oxidatively cleave the bond between a and ß carbons of an aliphatic chain bound to an aromatic nucleus. Another important organism is Trametes versacolor (syn. Coriolus versacolor, Polyporus versacolor). Even though this organism produces a ligninase (Dodson, et.al., 1987), coal solubilization has been attributed to the enzyme laccase (Pyne, et. al., 1987). Laccase utilizes molecular oxygen to oxidatively cleave a - ß bonds using a mechanism similar to that observed for ligninases (Kawai, et. al., 1988). Other coal solubilizing microorganisms have been isolated from coal outcrops (Ward, 1985; Ward, 1988), but enzyme activities responsible for coal solubilization have not been identified. Research at the Idaho National Engineering Laboratory has focused on those mechanisms involved in coal biosolubilization. An

Jan 1, 1989

By B. A. Wills

Much research effort has been spent in attempting to reduce the high energy costs in grinding, but relatively little in developing methods to enhance the liberation of the minerals from each other. This paper presents some ideas on the nature and role of grain boundaries in mineral assemblies, and their influence on the propagation of cracks through the rock. It is argued that if the mechanisms of fracture are more clearly understood, crack propagation may be controlled in such a way that intergranular fracture dominates breakage, producing less fines and a higher degree of liberation.

Jan 1, 1995

By Carl P. Venzke

Mining lignite in the Gulf Coast often requires some interaction with shallow ground water system. Suggestions for determining ground water data and analysis requirements for regulatory compliance are given. Simple methods for estimating mine inflow seepage, ground water level declines, and changes in ground water chemistry, which may result from mining, are discussed. The mining of lignite often results in interaction with shallow ground water systems. An evaluation of the interaction is required as input to mine permitting and engineering. Your evaluation will proceed more smoothly and produce more meaningful results with some planning prior to performing your evaluation. The following are tips to consider in planning and carrying out a successful study.

Jan 1, 1982

By Cyril W. Draffin

Introduction Americans have long been proud of their ability to recognize a need, define it, and then develop workable solutions. The U.S. underground coal conversion (UCC) program is a good example. In 1974, the need to utilize coal resources that could not be mined was recognized, and Congress gave the Bureau of Mines $1.7 million to gain a better understanding of the UCC technology and its potential applications. Since 1977 when the U.S. Dept. of Energy (DOE) was formed, workable technologies have been tested, the market for underground coal conversion has been recognized, and extensive industrial interest has developed. Perspective The U.S. is blessed with extensive coal resources. Coal supplies about 19% of our national energy needs, yet recently promulgated environmental standards and increasing mining costs have limited direct coal use. UCC potentially can use coal that is economically or technically infeasible to mine because the coal is too thick, deep, dirty, high-ash, and wet; has an excessive angle of dip; or has unpredictable and poor overburden characteristics that make mining unsafe. Coal can be gasified underground or perhaps liquefied below the earth’s surface. Underground coal gasification (UCG) is the prime element of the underground coal conversion program. It enables coal to be converted to gas underground. UCC Coal Resource Recent data show a total U.S. coal resource base of about 6.4 trillion tons. Of this, 1.8 trillion tons might be accessed by UCC, including some minable coal. A commercial UCC process could quadruple roughly the 450 billion tons of U.S. coal reserves, which presently are recoverable by mining. The U.S. coal resources are divided into five sectors. The two most eastern sectors contain relatively thin, swelling bituminous coals that are difficult to gasify. Of the two, the bituminous coal in the Eastern Province is the most difficult because it is deeper than , in the Interior Province and the terrain is more rugged. The sector along the Rocky Mountains contains huge amounts of thick low-rank coals that are the most promising for early development by UCC. The coal has good continuity and the terrain is suitable. Low-rank coals such as subbituminous and lignite are highly reactive and tend to shrink and disaggregate when heated. Most of the coal in the Pacific

Jan 1, 1980