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By G. T. Adel, J. D. Miller, C. L. Lin

In view of the success of recent laboratory studies using X-ray computed tomography (CT) to determine coal washability and with the availability of high-speed CT systems, it now seems possible to design an on-stream washability system for the control of coarse coal-cleaning circuits. Design features for such a system are examined and possible control strategies are discussed for different applications.

Jan 1, 1995

By R. Chen

Most tunnels built in Sydney encounter similar ground situations; they penetrate either the Hawkesbury Sandstone or the shales that lie beneath the city. Tunnels in these materials are generally sup-ported by rock bolts in combination with a shotcrete lining. A method of analysis is presented to improve our understanding of the long term behaviour of fiber reinforced shotcrete (FRS) materials and the tunnel support systems. A finite element method SAFEA (Semi-analytical FE Analysis) is developed to model the combined creep behaviour of a shotcrete lining and the Hawkesbury Sandstone. To model the time-dependent creep behaviour, the bulk modulus and shear modulus of the materials are represented by logarithmic functions in time. A Laplace transform is then applied to these functions of time and the solution of the problem found from a finite element analysis. Tablot?s method is then used to invert the transformed values and find the solution in real time. The time dependent creep deflection of the numerical tunnel models reflects the interaction of the shotcrete lining and rock which have different creep parameters.

Jan 1, 2008

By Ray E. Harris

Introduction A resource of more than 122 Gt (134 billion st) of minable trona and mixed trona and halite underlies an area of about 3400 km2 (1300 sq miles) west of Green River, WY (Culbertson, in preparation) (Fig. 1). In 1982, the total domestic consumption of soda ash (refined trona) was 6 Mt (6.7 million st) (Kostick, 1983). About 90% of this came from Wyoming trona. This enormous deposit occurs in the Wilkins Peak Member of the Green River Formation that is of Eocene age. This formation is derived from sediments deposited in a large lake named Gosiute. Lake Gosiute occupied the Green River Basin in southwestern Wyoming some 38 to 54 million years ago. The Wilkins Peak Member represents a restricted, evaporite-rich cycle of deposition when the trona deposits were formed. A total of 42 trona beds are known. Of these, 25 are of sufficient thickness and extent to be considered minable (Culbertson, in preparation). The production of sodium compounds from the trona deposits in the Wilkins Peak Member began in 1896 when wells were drilled within the present boundaries of the town of Green River. The purpose of the drilling was for extraction of sodium carbonate brines. Sodium carbonate (sal soda) was removed from these brines at a plant in Green River. Bedded trona was discovered in 1938 in a core from an oil well drilled south of Westvaco. In 1947, the underground mining of trona began. Production has continued from 1948 to date. Currently, five companies are mining trona and producing soda ash from the Wilkins Peak Member in Wyoming. Additionally, Allied Chemical Co. mines and processes trona for Church and Dwight's sodium bicarbonate (baking soda) operation in Green River. Competition in the soda ash industry depends primarily on the efficiency of mining and refining, allowing for lower-cost production. Newer plants and mine designs should increase efficiency. Solution mining holds promise as an even lower-cost method of mining. Employment in the soda ash industry is declining since the newer mining and refining methods are less labor intensive. Declines in employment, however, may be offset as production increases. Due to the large resource, the availability of minable trona should not be a problem for perhaps hundreds of years. Geology of Wyoming trona deposits Forty-two beds of trona or mixed trona and halite occur in the

Jan 10, 1985

By Y. Xi, T. M. Yegulalp

An availability approach for determining the capacity of a major Bucket Wheel Excavator (BWE) system to be used in the Yuabaoshan Surface Coal Mine in China is presented in this paper. Based on previous studies on other BWE systems for delay times due to internal and external causes and a four-level maintenance and repair schedule, a model was developed, taking into account all random failures, to present a fast and simple solution to this highly complex problem. A procedure employing the Markov renewal theory for determination of the distribution of random failure times and failure rate of the whole system, as well as some other factors useful for calculation of the overall system capacity, are discussed.

Jan 1, 1994

By James Giulianelli

Personnel at the Jet Propulsion Laboratory (JPL) are studying the technology and applications of salt-gradient solar ponds (see below) for both electrical and thermal energy generation. The brine extraction and processing site operated by the Kerr-McGee Corporation at Searles Lake, California, offers ideal conditions for economic construction of solar ponds. Furthermore, since rising conventional energy costs adversely affect the economic recovery of brine by the present process, this site was selected for a study on the feasibility of integrating the solution mining of trona (Na2CO3?NaHCO3?2H20) in the lower salt with solar ponds for heating. The major emphasis of this study was to determine whether inexpensive thermal energy available at the brine extraction site would be useful in extracting increased mineral value from the resource. The present operation, which involves the simple extraction of the complex brine and its processing at the adjacent plant, is sometimes referred to as solution mining. Since the concept discussed in this paper involves injecting a heated sodium sulfate brine to dissolve carbonate underground, the proposed scheme is referred to as "enhanced" solution mining. The subject is discussed in greater detail in a recent JPL report. (1)

Jan 1, 1981

By Steven Norris, William Moler, Michael Cole, Patrick Doig, Debi Lewis, Craig Pyle, Matthew Crow

The recently completed Lower Northwest Interceptor Program (LNWI) in Sacramento, California comprises, ten pairs of micro tunnels totaling 4,369 m (14,417 ft),three horizontal directionally drilled bores totaling 956 m (3,154 ft), and two large diameter tunnels under the Sacramento River totaling 1,198 m (3,953 ft). This paper briefly summarizes surface and subsurface conditions, and planning and design considerations. It then goes on to describe problems encounterd with each trenchless crossing, as well as lessons learned with respect to shaft construction, ground control at shafts during tunnel break-in and break-out, frac-out and heave, settlement, obstructions, coordination with permitting agencies, and application of geotechnical baseline reports.

Jan 1, 2007

By Will Foreman, Douglas D. McLearie, Edwin K. H. Tong, William H. Hansmire

Hong Kong’s Strategic Sewage Disposal Scheme (SSDS) Stage I involves the provision of a system of deep tunnels for transporting to a central treatment works wastewater collected from a number of catchments around Victoria Harbour. For the SSDS Stage I works, about 24 km of tunnels have been excavated in hard rock at depths ranging from about 80 to 150 m below Victoria Harbour and the surrounding heavily developed areas of Kowloon and Hong Kong. Five tunnel boring machines(TBMs) with diameters ranging from 3.2 m to 4.3 m were used to excavate the tunnels. Tunnel excavation has been completed and tunnel linings are in progress. Major tunnelling issues such as ground stabilisation and water control encountered in the project are summarised. An overview of one of the possible future tunnel systems that might be adopted in subsequent stages of SSDS is also presented.

Jan 1, 2001

By C. D. Wittreich

The results of an engineering study of fiber-reinforced cemented tailings are presented. These tests were conducted to evaluate the potential for using fibers to increase the strength of cemented tailings used as backfill for ground support in the undercut -and - fill mining method in a mine subject to high horizontal stresses and rock bursts. Stress-strain measurements indicate that fibers not only increase the peak compressive tensile and flexural strengths of cemented tailings, but limit reductions in residual strength following failure. Results also show the effect of water content, fiber type, fiber density, and curing time on strength.

Jan 1, 1987

By W. D. Monaghan, G. L. Mowrey, C. W. Ganoe

In addition to developing various types of coal-interface detection systems, the US Bureau of Mines is actively involved in developing a coal rib-thickness monitoring system for high wall mining applications. One particular system that shows promise uses a ground-penetrating radar system to detect the coal-air boundaries of coal ribs. Based on preliminary laboratory and field tests, results indicate that this method can be applied successfully in highwall mines to maintain a constant rib thickness. The coal seam should be relatively clean in the vicinity of the antenna (e.g., have minimal partings or dirt bands) for best results.

Jan 1, 1996

In this paper, uniaxial compression tests were conducted on intact rocks and broken rocks that were reinforced by grouting, and the effects of grouting on the strength of broken rocks were analyzed. The results show that after grouting reinforcement, the bearing capacity of broken rocks with different lithologies increased, and their uniaxial compressive strength recovered by approximately 6%–16%. The results indicated that the stronger the rock, the smaller the strength recovery of the consolidated body formed after grouting. At the same time, using borehole camera observation and deep overburden strata separations, the fracture development characteristics of surrounding rocks of the gob-side retained entry were analyzed and divided into different regions. On this basis, a guided grouting method was proposed; that is, shallow hole grouting was first used in the plastic zone of the broken surrounding rocks to form the isolation layer, and then deep grouting holes were arranged in the elastic-plastic zone of the transition zone to guide the slurry flow to the shallow unfilled zone. Therefore, the broken surrounding rocks were reinforced into an integrated body and selfbearing capacity improved.

Jul 28, 2020

By R. G. Dalbke

An increasing number of water pollution control systems are certain to be installed by many industries in the future because of new federal, state, and local government regulations, and because of the rising general concern about the deterioration of our water resources. Extensive engineering, some of it based on methods not yet developed, will be required if these new systems are to provide optimum pollution control. Capital cost, operating cost, and present and future regulatory requirements will be primary factors to be considered by engineers. This paper outlines procedures and gives examples of advanced engineering practices that have achieved efficient pollution control systems in the steel and nonferrous industries.

Jan 1, 1968

By M. G. Karfakis, K. P. Chong

Determination of fracture toughness using the semi-circular specimen, the chevron edge notch round specimen, the short rod specimen and the cylindrical burst specimen, are critically reviewed. These methods, among all, are the most applicable for fracture toughness determination of rocks. They require minimum machining. Samples are small, and testing procedures are simple. They have a sound analytical basis and allow the fracture toughness to be determined without measurement of fracture length.

Jan 1, 1986

By K. R. McGinnis

A major cost to a mining company is funding of an exploration program. It is a necessary cost to insure the company's future. But if the exploration effort does not discover an economic are body, there is no return on investment and the days of the company are numbered. However, if you are aware of what exploration geologists are saying, it places the exploration process in a different light. Basically they are saying that ore bodies exist that contain 250,000 tons or less of gold and silver bearing ore that is cyanide amenable utilizing heap leach technology.

Jan 1, 1988

By J. C. Stankus, S. Guo, S. S. Peng

In this paper, a model is developed for a resin anchor bolt system in which the smooth bar is modeled by using one-dimensional truss elements, and the resin annulus is modeled by using axisymmetric elements. These two submodels are combined and then incorporated into an existing computer code called Roofbolt. After this development, all of the components in the resin anchor bolt system, including smooth bar, bearing plate and resin annulus, can be correctly modeled.

Jan 1, 1997

The Mine Safety and Health Administration (MSHA) conducted a respirable dust survey to evaluate the effectiveness of a water curtain utilized for dust control on continuous miner sections. The purpose of this survey was to determine if the water curtain was effective in reducing respirable dust concentrations, since several mines currently use water curtains to control miners? respirable dust exposures. The survey was conducted on a supersection of an underground coal mine, which utilized two continuous miners on the same split of air. Each continuous miner alternated taking a cut so that both continuous miners would not operate at the same time. The underground coal mine is located in Knox County, Indiana. The water curtain evaluated in this survey was located in the last open crosscut between the intake side continuous miner and the return side continuous miner. When the intake side continuous miner cuts coal, its exhaust air would be used to ventilate the return side of the section. The intent of the water curtain was to reduce the intake air respirable dust concentration (generated by the intake side continuous miner) before the air stream ventilated the return side of the section. To determine the effectiveness of the water curtain in reducing respirable dust concentrations, respirable dust sampling pumps were placed on both the intake side and the return side of the water curtain. Additional respirable dust sampling pumps were placed farther downstream from the water curtain to monitor dust levels downstream of the water curtain, but in an area where respirable dust would not be created by anything other than the intake side continuous miner or additional section air. The water curtain and the respirable dust sampling pumps were operated only when the intake side continuous miner was cutting coal. The samples were analyzed for respirable dust and quartz content. The water curtain showed minimal effect in controlling respirable dust and respirable quartz dust, but the reduction was so negligible that this survey could not quantify the reduction. The measured reductions are within the accuracy of the sampling equipment.

Jan 1, 2009

By Joseph W. Leonard

By combining statistical methods with specialized coal technology, novel and widely applicable procedures are developed which are useful for making important decisions based on coal seam structure. By analyzing such properties as ash in visual coal types of seam cross sections and by processing the ash data to 100 gram increments of coal ranging from the top to the bottom of the seam, intraseam comparisons between data populations of samples from a given seam and a reference seam can be made. Moreover, illustrations are presented for estimating the number of drill cores required to purchase a specified level of sampling accuracy together with procedures for determining the probability that different coal scan cross sections are not unlike and by inference are therefore comparable. Such comparisons can be valuable when making important, costly and long prevaling decisions involving coal exploration, mining, preparation and utilization.

Jan 1, 1969

By Karl W. Mote, R. K. "Ivan" Urnovitz

One of the Northwest Mining Association's guide-lines is: "If you always do what you've always done, you'll always get what you've always gotten." Another way of saying this is, simply, "when the road curves, don't refuse to turn." Our industry has been roundly criticized for living in the old political world, and, I believe, justifiably so. Until about 20 years ago, members of both houses of Congress deferred to specialists among their members for mining legislation. This was true for all public lands and natural resource issues, and were referred to as the mining bloc, or the timber bloc, or the ranching bloc. We felt safe, and to a large degree, were safe in the sense that western members of the US House of Representatives and of the US Senate understood the need for multiple use of public lands, and the need for the natural resources they supply. They also knew what it takes to stay in business and how to create the economic atmosphere that encourages private industry to find and provide the natural resources. Almost daily, members of our industry bemoan the destructive effects that current regulations, let alone new proposals, are having on American industry. And, there are some intriguing aspects for us to ponder. First, the specific complaint about the government is not regulation per se, but rather that the rules or policies don't make sense. We recognize that few understand our industry, but we have assumed that the government will rely on people experienced and knowledgeable in the area being brought under government controls. There was a time that this assumption was valid, but it is no longer true since we have entered the era of the professional regulator. Much like the MBA who believes that a professional manager can manage anywhere, the new breed of regulator sincerely believes that process is the key to developing effective regulations or programs. They reason the process virtually assures that all the pertinent facts will inevitably come to light and, after receiving appropriate considerations, will result in the proper decision being reached and implemented. Unfortunately, following the process also allows politics to play a new and greater role than ever before, since information based on what can only be called weird-science can now be presented to the professional regulator and accepted as fact. Regulators do not have the background to question the basic tenets of the conclusion being presented to them. To add insult to injury, testimony from people in the industry involved, intended to set the record straight, is too easily discounted as being merely self-serving. A second aspect is that the question of why the associations aren't doing more to stop poorly conceived legislative and regulatory proposals, or to counter the ever-increasing influence of the selfappointed public interest groups is being increasingly discussed. This is occurring despite the fact that there is a higher level of involvement and closer cooperation between the various associations than ever before. This raises a most important question: where are we going wrong? In the last 20 years or so, major changes have taken place. A new philosophy, taking advantage of the public's recognition of need to protect our environment, has swept through the nation, resulting in a whole new body of law enacted to assure environmental protection. We all acknowledge the need to prevent undue degradation during the course of mineral development, and we all consider ourselves to be responsible stewards of the land, because we live and work in the outdoors and know the importance of environmental protection. The changes in the federal statutes apply now to every aspect of mineral discovery, development, and production, and assure adequate reclamation of lands when we are done. Along with the positive changes, are a constant barrage of attempts to stop public land use, or stop mining, or stop any new economic development, ostensibly to "protect the environment," but often reflecting a hidden agenda of social reform. These types of extreme, irrational, and just plain impossible proposals are everyday occurrences, but we have not geared up to challenge all the proposals which could end mining. Instead, we did what we always had done. The road turned, but we didn't. And we wondered why those who had always protected mining weren't doing their job, and why we were having such limited success in reining in the regulators. The Congress had changed, the public demands had changed, the recognition of importance of natural resources had

Jan 1, 1991

By Verya Nasri

The use of a single tunnel boring machine (TBM) tunnel of approximately 12 to 13 m (40 ft to 43 ft) diameter for transit systems to house both light rail or subway tracks in a stacked configuration is an advanced concept that allows significant savings in construction cost and time while reducing, to a large extent, the negative effects on the environment. This solution, similar to the recently completed Barcelona Metro Line 9, integrates station platforms, train storages, crossovers, bypass tracks, ancillary areas and utility corridors inside a single tunnel. Each of the underground stations consist of a cut-and-cover entrance structure and ventilation shafts, that also serve as emergency exits. The excavations for the station structures and shafts can be done on one side of the street with nominal impact on traffic and utilities.

Jan 1, 2010

By Turan Uysal, Thierno Saidou Barry, MURAT ERDEMOGLU, Mustafa Birinci

Nonbauxite ores such as aluminum silicate clays and coal fly ashes have been widely considered as potential resources of alumina (Al2O3). The interest focused on these ores is due to their high alumina content. Over the years, in countries where there are little or no bauxite reserves or where the recovery of existing bauxite ores to produce alumina with the Bayer process is not economical, alternative processes have been explored. Among these processes, acid leaching is seen as the most attractive process. In the acid leaching process, heat treatment for thermal activation to destruct the refractory structure of the minerals in the ores is generally recommended as a pretreatment method. Recently, the applicability of high energy ball mills, which are useful for mechanical activation as a pretreatment method before leaching, has attracted much attention. This is a short summary of our previous review [1], giving the details of alumina manufacturing from thermally and mechanically activated clays and coal fly ashes by acid leaching.

By M. Rezaee

Push backs used in the production planning of open pit mines play an integral role in generating annual cash flow. Although several algorithms for push back designs have been proposed, none have studied the optimum number of push backs. In this paper, different algorithms have been implemented for the push back design of a cross section of a copper deposit and the results discussed. Moreover, the optimum number of push backs has been determined using analytical and multiple attribute decision making (MADM) methods based on minimizing the risk associated with grade uncertainty, and minimizing stripping ratio, while maximizing net present value (NPV). According to the findings, the optimum number of push backs has been proposed to be between three and six, as lower quantities of push backs are more likely to achieve the calculated net present value, and have smoother stripping ratios for different pushbacks. This approach was examined in an operating mine and the optimum number of push backs determined to be four.

Jan 1, 2012