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By Larry L. Snyder

A compact 4.87 m (16 ft) diameter tunnel boring machine (TBM) is capable of boring a 12.2 m (40 ft) radius curve while gripping horizontally, or vertically, as may be required for the excavation of turnouts. The machine's 5.0 m (16.5 ft) length and a patented machine structure allows steering while boring without causing harmful eccentric loads. An extremely stiff thrust system, rigid front and rear grippers, and the torsional stiffness of a front end electric cutterhead drive combine to create superior machine stability and boring efficiency. A 2.2 m (7.2 ft) diameter prototype, complete with a soft ground shield attachment, was used successfully on a tunnel project in Scotland.

Jan 1, 1989

By Barton Kelby Cross

In the early 1960's the feasibility of mathematical modeling was demonstrated in Northern Rhodesia and southwestern United States, where techniques were developed to use these models in a new approach to aid engineers in the estimation of ore reserves, mine designs, and financial evaluations. These rudimentary models closely followed the manual methods, producing ore reserves and production schedule estimates that were as accurate as the manual methods, yet were many times faster. Mines evaluated and designed using these new tools gradually came into operation during the 1970's and entered the phase at which production scheduling and ore-grade control became day-to-day problems. Management expected the number of operational engineers to be small because small planning engineering staffs had produced the original designs and operated the smaller high-grade pits. Unfortunately, the tools needed by the mine engineer to perform short-term production scheduling and ore-grade control were labor intensive; they had not yet been generally computerized. Several attempts to use the original or exploration model for these two functions were futile. While an exploration model based on data from exploration work proved sufficiently precise for overall mine design and long-term production scheduling, the model lacked the precision required for short-term scheduling and grade control.

Jan 1, 1979

By Adam Bedell, Jack Raymer, Brad Crenshaw

Tunnel contracts often include provisions for pre-excavation probing and grouting for areas ahead of the tunnel heading. If grouting triggers are met, tunneling stops, and grouting is performed. There is substantial variation within the underground industry on what criteria are applied to the grout verification hole that is drilled post-grouting and before excavation resumes. The criteria for determination of the effectiveness should be dependent on the geology and local hydrogeologic conditions. The purpose of this paper is to present specific criteria that can be used by a practitioner to determine whether tunneling can resume or if additional grouting is required.

Dec 1, 2022

By Hubert E. Sherer

The mining industry is presently one of the most heavily capitalized industries in the U.S. (U.S. - Statistical Abstracts, 1979). U.S. sales of new mining equipment (not including environmental, preparation, or long distance transportation equipment) are projected to reach approximately $5 billion/year in 1980 (Frost and Sullivan, 1979). Of these new equipment sales approximately 30 to 40 percent of this equipment will be used to replace old equipment. Therefore, an increase of efficiency in the use of equipment replacement capital could have substantially positive effects for the U.S. mining industry. This is very critical in these times of restricted capital availability, double digit inflation, burdensome governmental regulation, and rising foreign competition in the mining industry. This paper examines the numerous factors that constitute the typical mine equipment replacement problem. A computerized, mathematical model is formulated to utilize historic cost and production information to predict equipment cost versus age for the existing and potential replacement machines. Another part of this computerized model determines the best equipment replacement strategy that accomplishes estimated production goals at a minimum discounted cost. This computerized model is an easily used, consistent method of determining the optimum replacement age for any equipment unit or fleet of equipment at a mining operation.

Jan 1, 1982

By William Wargo

The basic reason for lining underground cavities is to keep the cavity open during its useful life by providing adequately for the support of the surrounding rock and for the necessary degree of water tightness. This covers the entire field of support methods from the simpliest timber support to reinforced concrete in all its variations as applied to tunnels, galleries or shafts. The problem involved in the design of more efficient and economical lining systems for even bigger cavities has been magnified by increased speed of advance made possible by better blasting tecniques, improved tunneling machines and more efficient material handling. Tunnel lining today requires a disproportionate amount of time and money compared to other operations mostly due to the manuel labor involved in its installation. One solution to this problem is the developement of an entirely new concept in tunnel lining designed notoonly to overcome this bottleneck but also to open up the field for further increases in speed of advance. This new lining system acts first as a fast protective armour then becomes the concrete metal form and ends up as reinforcement sheet inside the concrete lining. This system developed and manufactured by Bernold A. G. of Switzerland since October 1968 has been installed in 25 applications in Europe under all ground conditions from stable rock to unconsolidated ground.

Jan 1, 1970

By J. M. Mutmansky, A. Wang

This paper defines the elements of a basic economic model for decision making when considering a methane drainage system for an underground coal mine. A drainage system entails significant capital and operating expense; hence the decision to utilize drainage must be made carefully. The model outlines the basic structure of decision making and considers the costs and benefits when the methane is marketed and when the methane is vented to the atmosphere. The effects on mine safety and the dust levels in the mine are also considered, both in a general format and as economic variables. Sources of information for executing this decision making are provided for an actual mine decision.

Jan 1, 1999

By R. G. Swanton

The Bureau of Mines is investigating the leaching of phosphate values from Florida phosphatic clay wastes using sulfuric acid (H2SO4) as the leaching agent and methanol as the solvent. Acid-alcohol leaching studies were done using pure crystalline apatite to investigate potential causes for low extractions. It was found that a barrier layer formed on the surface of the apatite. Initial discovery of the barrier layer was made by analyzing pure apatite samples before and after leaching using an optical microscope. Subsequent Fourier Transform Infrared (FT-IR) analyses proved the coating was calcium sulfate hemihydrate (CaSO4-1/2H2O) and that unreacted apatite existed beneath the coating. Scanning electron microscope (SEM) photographs depict the CaSO4-1/2H2O morphology as long slender crystals adhering to the apatite surface. It was also shown that grinding the leached tailings and leaching again in the H2SO4-methanol system resulted in additional phosphate extraction.

Jan 1, 1991

By Gerald Zink

The work described in this paper is sponsored by the Bureau of Mines for the purpose of accelerating the drilling of roof bolt holes and reducing the quantity of materials needed to fill each hole. A high-speed small-hole drill has been fabricated and tested in the laboratory. High priority has been given to safety, reliability, and compatibility with underground coal mining practice. The combination of drag bits and erosion jets is designed for high penetration rate, long wear life, and uniform hole size in a variety of sedimentary strata. A reliable high-pressure high-speed swivel feeds water to the bit at about 4 1/min (1 gpm). The duplex hydraulic intensifier which drives the jets has a 40 kw capacity (30hhp) Results of recent full-scale laboratory testing are presented.

Jan 1, 1978

By John W. Welty

Volcanic activity occurred during six periods of Arizona's geologic history. Precambrian volcanism occurred in two pulses at 1.8-1.6 billion years (b.y.) ago and at 1.2-1.1 b.y. ago. Volcanism occurred again in mid-Jurassic and Laramide (Late Cretaceousearly Tertiary) time. Volcanic rocks from these times are not used commercially in any significant quantity. Middle and late Cenozoic magmatic activity covered large areas of Arizona with voluminous volcanic rocks. During the mid-Tertiary magmatic pulse, explosive silicic magmatism, with eruption of areally extensive ash-flow tufts, covered large areas in the Basin and Range Province, while the Colorado Plateau remained largely unaffected. Basalt eruption also occurred during and immediately after silicic volcanism, leading to compositionally diverse suites of volcanic rocks. Late Cenozoic volcanism occurred throughout Arizona and was dominated by wide-spread eruption of basalt flows with local cinder-cone clusters and siliceous volcanic deposits. Perlite deposits near Picketpost Mountain in northeastern Pinal County account for the bulk of the industrial uses of mid-Cenozoic volcanic rocks. Other perlites of presumed middle Tertiary age are present in central, southeastern, and western Arizona, but to date remain unexploited. Arizona Fire Agate is a valuable gem material and is associated with volcanic rocks of middle Tertiary age. Basaltic rock of this age also is utilized in the manufacture of rock wool for insulation. Late Cenozoic volcanism produced most of the industrial-quality volcanic rocks. Basalt, cinder cones, and materials of rhyolitic composition are commercially exploited by municipal and Federal agencies and private industry for aggregates, road conditioners and maintenance materials, asphaltic concretes, cinder block construction, pozzolans, and landscaping. These deposits are generally confined to the Flagstaff and Springerville areas. A famous peridot gem locality is associated with late Tertiary basalts at Peridot Mesa on the San Carlos Indian Reservation. Important products derived from altered volcanic materials of late Cenozoic age include clay and zeolite. Arizona's volcanic-rock sequences are still incompletely known, particularly in central and western Arizona. The potential for recognition and exploitation of important new deposits of useful volcanic materials is high.

Jan 1, 1987

By J. C. Yingling, V. Badaker, R. J. Sweigard, P. W. Conrad, J. M. Ringe, D. H. Graves

The University of Kentucky has developed reclamation cells at a surface mine in southeastern Kentucky to evaluate the impact of spoil handling (reclamation methods) and compaction alleviation methods on the physical properties of replaced growing media and on tree survival rate. From 1997 through 2001, penetration depth, penetration resistance, bulk density, and tree survival data have been collected at the reclamation cells and correlated to determine the relationships that exist between the soil physical properties at the site and tree survival. Regression models have been developed for each reclamation method evaluated using the collected data to predict tree survival rates on reclaimed surface mined lands as a function of the soil physical properties of the replaced growing media. Procedures have been developed for handling soil/spoil during reclamation that can minimize compaction in the replaced growing media. Procedures have also been developed for alleviating compaction in growing media on reclaimed and orphaned surface mined sites. These procedures, if implemented, will increase the potential for reforestation success. Finally, procedures have been developed for collecting soil physical property data for use in evaluating the suitability of spoil conditions for reforestation.

Jan 1, 2003

By Richard Seal

Nabarlek is situated in the Arnhem Land Aboriginal Reserve about 270 km due east of Darwin in the Northern Territory of Australia. During the dry season (May to November) Nabarlek is accessible from Darwin over the Arnhem Highway-- a distance of 330 km. Throughout the wet season (December to April), except for a few days, access is provided by aircraft from Darwin to the Nabarlek airstrip. Because of the limited access during the wet season, reagents and supplies have to be stock- piled for six months on the site to maintain operations. With the mine and plant being remotely located on private Arnhem land with very limited access outside the site fence, operating personnel are flown to Darwin every six days for their days off.

Jan 1, 1980

By S. Bentley

"Everyone has a general idea what mixing means, but describing the mixing process is not so simple. The objective of any mixing process is to distribute and blend the materials with different characteristics, different quantities as evenly as possible resulting in a homogenous mixture. Introducing proportional movement with the optimal intensity into the materials achieves effective homogeneous mixing results. A simple one directional movement with inadequate acceleration of the materials would obviously not achieve the same mixing results. This would be more like stirring than mixing. The amount of relative movement that is introduced is a decisive factor. Circumstances for successful mixing involve distribution of all materials, and achieving the highest probability that all recipe particles located in a specific position at the beginning can be found at any random location in the mixing chamber at the end of the process. This is the only way to ensure that a consistent result is achieved every time mixing is repeated.THREE-PART CYCLE The mixing cycle occurs in three phases; charging the mixer, the mixing process, and discharging. The sequence in which the individual materials to be mixed are filled into the mixer can have a huge impact on the efficiency of the mixing cycle. The mixing cycle overlaps the charging process and the discharge cycle follows the mixing cycle. To achieve optimum results, effective discharging methods should be taken into consideration to avoid risks of segregation. Costs for energy and wear should be as low as possible and finally, it is very important that the mixing cycle takes place as quickly as possible. In concrete or paste backfill production, selecting the best mixing technology is crucial for both the quality of the final product to be blended and the efficiency of the production process. The optimum mixing system is one that rapidly disperses all ingredients evenly throughout the mixing trough and completely surrounds all the course or fine aggregate particles with the slurry cement particles. Specific for paste production it’s the mixers job to also break-down unconditioned tailings to achieve consistent paste viscosity or measured spread. Many paste and concrete formulas also involve small quantities of chemical additives which also must be evenly distributed effectively. The time required per mixing cycle as well as the costs of energy, wear and maintenance will determine the economy of the concrete production."

Jan 1, 2015

By J. F. McDonald

On December 8th of last year, the new St. Clair River tunnel was holed-through to Port Huron, Michigan. The tunnel, commissioned by the Canadian National Railway, was needed to replace an existing tunnel that had been built between 1889 and 1890, and had remained in continuous operation until the new tunnel was opened to traffic in April of this year. The original tunnel, after more than 100 years of service, was still structurally sound, but was too small to accommodate the double stacked container cars and other advances in the railroad's equipment that had developed over the years. Prior to the construction of the first tunnel, all freight was barged across the river. It was a slow, expensive process, which in winter was sometimes impossible. The nineteenth century tunnel was built in twenty months, utilizing two shields that mined to the middle from each end. The lining, which is still in excellent condition, consisted of bolted, cast iron segments, with an O.D. of 6.4 meters. It was the first sub-aqueous tunnel built in North American, and it's use of compressed air under the river and hydraulic power on the shields may also have been firsts. The digging was done by hand, and the muck hauled out by mule drawn wagons. Boulders and methane gas were reported to be a constant problem during the drive, and compressed air sickness was common, but when the two shields came together in August of 1890, it was reported that the alignment was within 6 mm. The new St. Clair River Tunnel was constructed for basically the same reason as the original. The larger equipment which the railroad is using today would not fit through the old tunnel, and once more they were forced to ferry the cars across the river.

Jan 1, 1995

By H. M. Conger

I'm really very pleased to be talking with you today about the environmental impacts of gold ore processing as part of this symposium on emerging process technologies for a cleaner environment. But before I talk about some of the newer developments that are coming, I would like to set the stage by reviewing some of the recent past. Over the last decade or so the U.S. gold mining industry has experienced remarkable growth, primarily in heap leaching operations, and not surprisingly there has been parallel growth of environmental regulations. At Homestake, we have had the excitement of bringing on-line a new mine embodying state-of-the-art technology and environmental planning, and during the same period the flagship of our company, the Homestake mine, has been brought into modern day compliance through the application of innovative environmental technology. This has been a learning process; in both cases we found that we had to develop new ways to meet our objectives. At our McLaughlin mine in California a major achievement was pioneering the use of pressure oxidation, or autoclaves, for refractory gold ores, and at the Homestake it was the development of a unique bio-treatment plant for wastewater. These projects were developed balancing operational goals, environmental concerns and costs, and I would submit that being cost-effective is our greatest challenge in the development of new, environmentally sound, process technology. In meeting that challenge, our job has not been made any easier by the myriad environmental laws and regulations that directly affect the design and operation of our facilities. Most of these constraints have evolved through the political process more or less independently, but in their application there often are over-lapping provisions. Adding to this complexity is the fact that action takes place in both state and federal arenas. As a result, state and federal roles sometimes become intertwined, and a good case in point is provided by various cyanide issues faced by gold producers. The vast majority of U.S. gold mining takes place in the so-called "mineral States," the western States that come under the Mining Law of 1872 as amended. This is the basic statute that provides for access and tenure to develop mineral resources on federal lands in those states. There is gold mining outside the defined mineral States, and there is also gold mining in the mineral States on private lands. Our own Homestake mine in South Dakota is one of the best examples of the latter category: located entirely on private land, it is nevertheless subject to at least 13 federal environmental statutes and some 29 federal regulatory requirements. There are also nine significant state statutory and regulatory requirements that apply. On federal lands in the mineral States there are numerous federal statutes and regulations which affect mining, over and above the current Mining Law. These, which are in addition to the laws applying to private land, include the National Environmental Protection Act and the Federal Land Policy and Management Act, among others. Still, those who advocate radical changes in the basic Mining Law would have us believe that sweeping environmental protection and reclamation provisions, not to mention new land use restrictions, are needed. Such changes could effectively prohibit mining on the federal public lands. Strict enforcement of our current Mining Law would have presented most of the abuses cited by the critics but if the Law is to be changed at all, I believe that, at a minimum, the principles of self-initiation and security of tenure embodied in the present statute should be maintained. These are critically important concepts, but there are other statutory and regulatory issues constantly before us as gold miners. Let me cite a few examples: Reauthorization of RCRA There are several bills being considered by Congress to amend the Resource Conservation and Recovery Act (RCRA) that have as their theme

Jan 1, 1992

By Rex T. Ellington

The fluidized bed is an effective method for investigating retorting phenomena and possibly a commercial means of retorting oil shale. Both were examined by Sinclair Oil Corp. (now part of Atlantic Richfield Co.) in the period 1.965 to 1968. The results of the work show that presence of an oxidizing environment during retorting results in loss of oil yield which indicates that vapor phase oil burns in preference to combustion of coke on spent shale. This has implications for several types of retorts. Correlation of the results of this work with that of other investigators shows that the partial pressure of retorting products in contact with oil shale during retorting has an effect on yield. Consideration of hardware indicates that there are several possibilities for commercial embodiment. As a companion to shaft-type retorts the fluidized bed could have good potential. Realistic assessment of costs suggests that further development may have to await commercialization of another process. The existence of a plant in which to test prototype size would markedly reduce such development costs. Results Preliminary development work with the apparatus was carried out using a fluidized bed of sand, as explained later, with the entire system brought up to temperature and flows stabilized. The shale was injected rapidly in a slug (batch) which had small mass compared to that of the high temperature system to make the reaction approach isothermality with reasonable approximation of instantaneous preheating. Typically, the temperature in the center of the bed dropped from 900°F to 600°F one minute after batch addition. It returned to 750' within three minutes and 900° within seven minutes. Obviously, the bed was quenched but it recovered rapidly. Average bed temperatures of 700' to 1020°F were examined to compare the effect of temperature with published results. Yields In the 700°F range were only 10 to 15%, of Fischer Assay (FA). Above about 950'F, oil yields decreased and gas yields increased. Nitrogen was used first as the fluidizing gas to provide a chemically inert medium. Incept for an insignificant dip at 895"F, Figure 1, oil yield was not affected by retorting temperature in the 800° to 900' range as long as residence time was adequate (16 minutes). At 925°F, the oil yield was some 103% FA. With further increase in temperature, the yield decreased to 86% FA at 1015°F. There is no increase in carbon on spent shale, the lost oil goes to Increased gas make.

Jan 1, 1972

By Thomas R. Kuesel

Just south of the L'Enfant Station in Seventh Street, the WMATA system splits into two branches, each comprising twin single-track soft ground tunnels. Immediately at the beginning of the section, Interstate Route 95 crosses transversely over the alignment in open cut, removing most of the cover over the tunnels. Seventh Street spans I-95 on a bridge whose abutments and pier also cross transversely over the four tunnels, with their footings as little as 7 feet above the tunnel crown (Figure 1). Soil investigations revealed that the tunnels would have to be driven through mixed face, with a clay invert and a waterlogged sand crown. Thus, there was a good chance that the roof would fall in, leaving 1-95 and the Seventh Street Bridge in a crater. Since there was no roof that could be counted on, these were figuratively (and potentially truly) Washington Metro's Topless Tunnels (Figures 2 and 3). DESIGN ALTERNATIVES Faced with this situation, the designers considered several options, including temporary detours that would permit demolition of the bridge and building tunnels under the 1-95 Freeway by cut-and-cover methods. They also investigated structural underpinning of the bridge and freeway pavement, and strengthening the bridge abutments and center pier by post-tensioning to enable them to span over any subsidence trough.

Jan 1, 1976

By M. P. Adamson, Bryson D. Trexler, R. V. Ramani, Mark L. Koenig, V. Rajaram, Alan Burton, C. S. Crocker, Kim. Y. C., A. G. Law, William C. Larson

Another record year vas experienced by the mining industry as the value of nonfuel minerals production soared to $23.5 billion-up 15% from the previous year. Based on preliminary estimates by the Bureau of Mines, US mine output was the basis for about $225 billion worth of minerals-derived materials. Metal mining accounted for $8.5 billion, or 36%, of the total. Of the 22 metals produced in the US, 11 showed quantity increases, while 16 had value increases. Business Week's survey of 1200 companies (Mar. 17, 1980, pg. 81) revealed that 21 metals and mining companies had sales increases of 30% with earnings up 104%. Higher prices and increased demand for metals were primary factors behind the improved performance. The steel sector reported a 30% decrease in earnings for the year, but the slump was primarily the result of a $383-million loss for US Steel coupled with a 17% decrease in earnings at Inland Steel. Other firms did well in 1979, with earnings up 279% at Interlake and 269% at Kaiser Steel. Major obstacles facing the steel industry included substantial tonnages of dumped and subsidized imports, environmental expenditures, runaway inflation, and price controls. Turning to nonmetallic production, of the 49 commodities reported by the US Bureau of Mines, 29 had higher outputs and 39 had increased values. While production statistics may seem encouraging, government regulations continued to stifle industry efforts to develop needed new capacity. A case in point may be publication of the Environmental Protection Agency's simplified procedure to streamline five permit programs by consolidating them into one. The five included: hazardous waste management, national pollution discharge elimination, dredge and fill, underground injection control, and prevention of significant deterioration. The new procedure, published by EPA in the Federal Register, took 149 pages. AMC's J.A. Overton, Jr., noted that (MCJ, Nov. 1979, p. 39) to visually depict the complexity of the proposed regulations, Sell Oil Co. developed a flow chart mapping a path through one section. The chart required 10 days to map and two weeks for two draftsmen, using computerized drafting techniques, to plot the results. Overton said, "Perhaps the greatest service EPA has performed in preparing its proposal is to demonstrate again that federal regulations have become a complexity compounded by confu¬sion that culminates in a conundrum." While regulatory agencies promulgate new regulations, the lack of a cohesive government minerals policy remained a matter of significant importance to mine management. A non-fuel minerals study to provide input to the Administration for a national minerals policy program was a dismal shock, according to Rep. Jim D. Santini (D-NV). He said the first phase of the program, which was to identify industry problems, failed to come to grips with the hard decisions necessary regarding these problems, their impact, and their interrelationship. Santini said the report failed to acknowledge government's role in the process and absolved the government of any adverse influence on the domestic minerals industry. In response to the phase one report, eight senior mining executives testified before Santini's House Subcommittee on Mines and Mining concerning mineral supply, access to foreign sources, environmental protection, conservation and recycling, national security, and capital formation. By year's end, Rep. Santini promised to prepare a hard-hitting committee report on problems affecting the non-fuel minerals industry to provide a better base for subsequent policy recommendations (MCJ, Jan. 1980, p. 34). On the technological front, interest again centered on mechanization, automation, and scaleup to improve and expand production. Computer use increased for calculation of ore reserves, mine planning, operations research, and mineral processing.

Jan 5, 1980

By Ulrich Benatzky

Rheinbraun AG, Germany, is the management company of the mining and raw materials division of RWE AG. Rheinbraun's core business and major functional area is opencast lignite mining in the Rhineland. The characteristic feature of opencast mining is continuous operation using bucket-wheel excavators, belt conveyors, and spreaders. The report gives a survey of the conveyor systems used. In addition to the general performance data of these belt conveyors, this report will deal in particular with major components, such as drive stations and individual mechanical components (e.g., conveyor belts, pulleys, gears, couplings, brakes, scrapers), as well as monitoring systems. Finally, an assessment of the conveyor systems, together with future developments, will be given.

Jan 1, 2000

By Z. J. Hladysz

The Hladysz Rock Tester was developed at the South Dakota School of Mines as a portable rock strength tester. The hand held device is placed against a rock surface and struck by a hammer. The impacted force causes a steel ball in the device nose piece to indent the rock and simultaneously indent a standard steel bar also contained in the nose piece. By comparing the two indented diameters the compressive strength of the rock can be calculated using laboratory determined correlation coefficients.

Jan 1, 1984

By L. V. Wade

The use of longwall/shortwall mining systems is under increasing scrutiny by the U. S, coal industry as a means to reverse the decline in productivity. The success of these mining systems depends to a great extent upon designing the system hardware to best suit local conditions. Of particular importance in this regard is designing the various elements of the total ground support system, including face, face end, and gate road supports, to accommodate local geologic conditions. This presentation centers on the problem of selecting the face support system. The existing geologic situation can influence the selection of the face support hardware in a variety' of ways. In general terms, these influences can be grouped into the following four areas: 1. The capacities required of the support unit; 2. The roof, coverage supplied by the support units; 3. The flexibility required of the support unit to meet changing geologic conditions; and 4. The required stiffness characteristics of the individual support units both vertically and horizontally. The following will center on the first area, i.e., the required d capacities of the support unit, in particular, the maximum required load density for a particular geologic situation.

Jan 1, 1976