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By J. S. Miller

The Bureau of Mines conducted surface tests to determine the feasibility of using liquid explosives for underground rock fracturing. The effects of configuration, confinement, length, critical layer thickness, and fracture-propping sand on detonation and explosive propagation velocity of desensitized nitroglycerin were studied, using polymethyl methacrylate and glass-plate reservoirs through lengths from 3 to 12 ft, with explosive-layer thicknesses from 0.1875 to 0.0312 in and in aluminum tubes 8 ft long with diameters from 2.000 to 0.125 in. Interval and continuous detonation velocity data were obtained. Under the test conditions detonation velocity was dependent upon explosive confinement and fracture-propping sand. The detonation velocity of a confined nitroglycerin explosion in aluminum tubes can be reduced by as much as 85 percent, when the tube contains fracture-propping sand. The shape of the reservoir, whether triangular or rectangular, has little effect on the detonation velocity or explosive propagation. The critical or minimum explosive-layer thickness between glass plates, capable of supporting propagation, was 0.0312 in. The presence of a fracture-propping sand in the sheetlike layers increased the critical explosive layer thickness to 0.0625 in. In nitroglycerin-filled and nitroglycerin-sand filled tubes, the minimum tube diameters successfully tested were 0.125 in and 0.375 in, respectively.

Jan 1, 1969

By Gus Van Weert, Peter Kondos

"Ore sorting has been quite successful in providing a separation means in the rock size range of 1 to 6 inches; a range where mineral dressers do not have many options. The industrial minerals and recycling worlds have embraced this technology. However, ore sorting has not found wide application in the base or precious metals mining industry. One reason for this is thought to be the reliance of most sensors on rock surface characteristics, not very useful in case of sulphides, non-existing in case of gold. Microwave heating, however, is specific for sulphides and graphite (or carbonaceous matter) embedded in the rocks; washing or even drying does not appear necessary. Separation can be done afterwards by already existing ore sorting technology using infrared sensors. Test results on six Nevada gold ore samples are presented in detail. Some simple test procedures are also presented for those wishing to explore the microwave potential of sulphide sorting in their own operations.INTRODUCTIONMineral processing in the base metals industry most often involves upgrading of the ore, concentrating the valuable mineral fraction by classic methods, such as flotation. Since the liberation of minerals in the ore occurs mostly at or below the 100 micron level, the industry has been living with fault lines, so to speak, between blast hole spacing (10,000 mm), run-of-mine ore size (100 mm) and beneficiation size (0.1 – 0.01 mm). The acceptance of ore sorting will inevitably lead to the revisiting of the following questions: “Exactly how much below ore grade rock ends up in the mill because the geologists or the miners cannot define the resource boundaries more precisely? How can the economics of dilution be improved? How many ore grade rocks are lost with the overburden?”"

Jan 1, 2007

By R. J. Robbins

The mechanization of hard rock underground mines offers a large potential for reducing cost, improving efficiency, and increasing profitability. However, in spite of serious efforts by quite a number of equipment developers and mining company initiatives, the industry has achieved little real progress. The task is difficult and the blasting alternative to mechanical excavation is an effective and well-developed method, which continues to improve in spite of its inherent limitations. A large number of machines have been built and tried. Only a few developments have succeeded to make a major impact on underground hard rock mining. It is certain that hard rock mines would be laid out and designed quite differently if the mining engineers knew they had available continuous mechanical excavation machines. In the absence of the machines, mines will be designed for excavation by traditional methods. It is not easy to utilize mechanical excavation in a mine which is designed to operate with normal drill and blast excavation. This is certainly an impediment to machine development. But what if an ore body cannot be mined conventionally, simply because the mining company cannot get permits to satisfy the ever increasing strict EIS requirements of the general public and governmental agencies? This may provide the incentive necessary to develop the equipment that will be needed by a new mining method that will have almost no impact on the environment.

Jan 1, 2001

By Carole L. B. Mitchell

The South 180th Street Grade Separation underpass in Tukwila and Renton, Washington, USA, permits vehicular traffic to pass beneath Burlington Northern Santa Fe and Union Pacific railroad tracks. The railroad tracks were temporarily relocated onto a shoofly crossing while the permanent bridges were constructed. The maximum underpass depth is approximately 25 feet (7.6 meters [m]). The majority of the sidewalls are supported using alternating reinforced and unreinforced secant pile walls. Temporary and permanent struts brace the top of the excavation. Because the groundwater is about 15 feet (4.6 m) above the base of the excavation and the subsurface materials are loose to medium dense fill, alluvium, and soft flood plain organics, the base of the excavation was strengthened and sealed using wet cement deep soil mixing (CDSM) methods. During construction, CDSM-treated ground temporarily acted as part of the railroad shoofly shoring while the remainder of the underpass was excavated on either side of active railroad tracks. The combination of secant pile sidewalls and CDSM bottom seal allowed for easy excavation, even during wet conditions. Using a 35-foot-thick (maximum) (10.7-m) CDSM layer both to act as a bottom seal and to resist uplift pressures is a unique, dual-purpose application of CDSM technology in the United States.

Jan 1, 2004

By M. Courchesne, C. Barbery, D. Hodouin, C. Carrier

"The carbon-in-pulp process for recovery of gold dissolved in dilute cyanide solutions, in the presence of solids, has now replaced the convedntional processes of pregnant liquid/barren solids separation followed by Merrill-Crowe precipitation. Most plants built over the past ten years incorporate a CIP section. The process is described as cheaper in capital and operating costs, and few major start-up or operational difficulties are reported. For the purpose of the present paper, the CIP process will be assumed to consist of the following sequence of operations (Figure 1):- the slurry stream coming out of the cyanidation circuit is first screened to remove any tramp oversize material. Gold dissolution is assumed to be complete before entering the CIP circuit.- the slurry is sent into a series of agitated tanks in which it is mixed with activated carbon. The carbon particles size is much coarser than the top size of the ground ore. The tanks are fitted with screens that allows the slurry to overflow continuously into the next tank, while retaining the carbon in the tank. Slurry dilution is adjusted to prevent carbon from settling in the tanks. Agitation intensity is kept low in order to minimize carbon abrasion.- carbon is transfered from tank to tank in a discontinuous manner. According to a specific schedule, the carbon from tank one is removed, then carbon from tank two is sent to tank one, and so on, till the last tank, which is filled with regenerated carbon corning from the elutionregeneration section. The amount of carbon removed, the transfer from tank to tank, the sequence of transfer, the carbon inventory in the various tanks are parameters which are, up to a point, at th2 discretion of the operators, as long as they remove, batch wise, an amount of loaded carbon containing a similar quantity of gold to the one that has entered the circuit since the last transfer."

Jan 1, 1987

By D. Craig Camp

conditions. The soils included 65 m of rock not exceeding an unconfined compressive strength (UCS) of 200 kgf/cm2, 130 meters of soft clay, silt, and sand not exceeding 30standard penetration test SPT blows per 300 mm, and 220 m of rock ranging between an UCS of 400-600 kgf/cm2. The river crossing, utilizing 1778 mm OD x 19 mm wall x600 mm steel casing pipe without intermediate jacking stations, was part of a seven kilometer liquefied natural gas (LNG) transmission line in South Korea. This 440-m, 1,442-ft, river crossing was microtunneled through three different ground conditions and completed in just over three months. The crossing was achieved with an average of 25 m of ground cover and 15 m of water cover. The Kwang Yang River Crossing was part of a 7 km liquefied natural gas pipeline project for POSCO, a Korean steel producer. The microtunneling machine was custom built for this project. The microtunneling machine selected for this project was tooled with 7 button bits and 2 roller bits. None of the cutter bits were replaced during the drive. Inside the machine, before the spoils laden slurry was pump back to the surface, it would pass through an independent cone crusher. The crusher is placed in the slurry flow to make sure that none of the spoils are so large as to stop the return flow of the slurry. An additional requirement was for the inclusion of a compressed air lock. The air lock was required in the event that the cutter tools required replacement. The cutters were back loaded so that the workers would have access to change the cutters in the event of cutter failure or wear out. No intermediate jacking stations were installed for the drive. The soils included 65 meters of rock not exceeding an unconfined compressive strength (UCS) of 200 kgf/cm2 with production averaging between 7 and 20 mm/minute. The second zone contained 130 meters of soft clay, silt, and sand not exceeding 30 standard penetration test (SPT) blows per 300 mm with production averaging between 80 and 180 mm/minute. The third zone contained 220 m of rock ranging between an UCS of 400-600 kgf/cm2 with production averaging between 7 and20 mm/minute. The steel casing pipe was 1778 mm OD x 19 mm wall x 6000 mm long. The project profile, see Figure 1, shows the soil conditions. The hand written numbers locate just above the pipeline are the production dates. The circled numbers are the 10 pipe joint increments. The project required 74 pieces of pipe to span the440 m drive. Figure 2 and Figure 3 are the jacking information. Figure 3 is a continuation of the information from Figure 2. The top section of the graph is the jacking force. The jacking

Jan 1, 2001

By R. R. Lowery

This project was proposed to provide information on the hazards associated with arc melting of thorium. A general air-sampling analysis was made to determine the separation, concentration, and distribution of thorium daughter (decay) products throughout arc melting, machining, and forging processes of a thorium handling facility. The value of well coordinated health physics program is stressed in connection with potential health hazards and personnel protection. Building, equipment, and exhaust ventilation requirements for such a facility are discussed. Special handling methods are described for thorium. INTRODUCTION The Bureau of Mines at the Albany Metallurgy Research Center has been involved in handling the naturally radioactive metals, uranium and thorium, for several years. Cooperative work for the Atomic Energy Commission has been carried out with thorium metal, and as a result the concerned laboratories of the Center have accumulated experience on the hazards associated with this metal. This report details the radioactive hazards arising from the arc melting, machining, and forging of thorium.

Jan 1, 1962

By R. Karl Zipf

Highwall mining is an important surface coal mining method, and it may account for approximately 4% of total U.S. coal production. Highwall stability is the major ground control related safety concern. Ground control plans for highwall mining should specify hole width, web pillar width, barrier pillar width and number of holes between barriers. This paper offers simple design charts for these parameters aimed at providing “ball park” checks. Web pillars containing pre-existing auger holes are analyzed and a design chart for estimating their minimum width is also presented. Finally, close proximity multiple seam highwall mining, which may have caused several serious highwall failures, is analyzed. Web and barrier pillar recommendations for this special situation are presented.

Jan 1, 2005

By Karl A. Bauer, Cornelis Bezemer

The deposition of calcium carbonate scale on surface and subsurface production equipment creates an operation problem in many oil fields. The formation water in which the carbonate-scale-forming components are initially dissolved becomes supersaturated with calcium carbonate as a result of the drop in pressure during production. The continuous flow of a supersaturated solution through the production equipment results in the growth of a dense layer of calcium-carbonate crystals. For a scale layer to be built up, the supersaturated formation water should contact the walls of the production equipment. The tendency for scale to be deposited, therefore, will be low, if the crude has a low water cut and if the water is finely dispersed in the oil. A scale problem will occur, if at a high water cut part of the water is present as free water. The rate of scale deposition will then be approximately proportional to the rate of free water production. Depending upon where the formation water becomes supersaturated, scale may be deposited in the flow line only, in both flow line and tubing, and in some cases even in the perforations and in the formation near the wellbore. In the South Sumatran fields (Indonesia) the main difficulties encountered due to the deposition of calcium-carbonate scale have been restriction of flow through tubings and flow lines, wear and abrasion of plungers and liners, and stuck plungers or wellhead valves. So far, the only methods of combating the *Presently associated with Brunei Shell Petroleum Co., Ltd.. Seria. scale problem have been routine acidizing and additional well pulling. As for the pumping wells, it was estimated that some 50 percent of the total well-pulling effort was directly attributable to scale deposition. The most promising alternative was to prevent the deposition of calcium carbonate scale by means of chemicals. Inorganic polyphosphates such as sodium hexametaphosphate and trisodium polyphosphate are known to retard the formation of scale by the "threshold action". They are adsorbed on specific faces of the crystal nuclei and thus prevent crystal growth, thereby stabilizing supersaturation. Polyphosphates are effective at very low concentrations ( a few ppm), and far less than stoichiometric quantities are required to keep the scaling ions in solution. Recent investigations on barium sulfate scale1 have confirmed this mechanism. The types of polyphosphate mentioned can be applied as concentrated aqueous solutions either squeezed into the formation, lubricated down the annulus or injected via macaroni string. Several squeeze jobs with polyphosphate solutions have been carried out in the South Sumatran fields, however, with disappointing results. Lubrication down the annulus and injection through a macaroni string were not considered attractive in this area because of the kind of equipment and the degree of supervision these techniques require. Polyphosphates are also available in a granular, glassy form, which, in contrast with the readily soluble types already mentioned, show an extremely low

Jan 1, 1970

By Christopher C. Woomer

Cyprus Shoshone Mine uses the longwall method to extract a deep, thick, pitching coal seam in the Hanna Basin of South Central Wyoming. The immediate, and main roof rock consists of weak, thinly-bedded, silty mudstones with weak, interbedded fine-to medium-grained sandstone. Tailgate ground control has been a critical factor impacting productivity at the mine. A gateroad condition mapping program for the 11 left longwall gateroads indicated potentially severe ground control problems for the tailgate. It was predicted that the existing, secondary support pattern of wood cribs would not provide adequate support capacity. As predicted, severe deterioration of the tailgate occurred in the form of a roof cutter, sloughing ribs, and failing wood cribs. Productivity was affected and additional support was required. Shoshone personnel evaluated several options for providing the additional support needed in the tailgate. The additional support system and placement method had to satisfy several requirements with respect to access, materials handling, placement method, set-up time and support capacity. Approximately 6,000-ft. of deteriorating tailgate had to be supported. The initial wood crib support system left a 6-ft. walkway for access and construction of the additional support. This access was further reduced as the roof loaded the wood cribs. This eliminated the possibility of mechanized material handling to the construction locations. All materials would have to be transported by hand. The additional support system had to be placed quickly to stay ahead of, and keep pace with, the required longwall advance rate. It had to incorporate the existing wood cribs and provide at least 500 tons of extra support capacity. And most critically, the system could not affect longwall ventilation. Longwall coordinators and engineers made the decision to use a low density, pumpable cement known to the industry as TeksealTM, to provide the system required. A 200 psi ultimate strength mix was decided on to provide the required load capacity. The existing cribs were formed with 1-in. by 6-in. boards and brattice cloth to provide the containment. To overcome the access limitations, three boreholes were drilled from the surface to the tailgate on 2,000-ft centers. A mobile pumping station was established on the surface and the TeksealTM was pumped 900-ft. down the boreholes through a 1.5-in. steel pipe, then as much as 1,800- ft. along the tailgate entry through 1.25-in. miner spray hose. The materials required for the TeksealTM supports could all be carried into the construction locations by hand. As a direct result of incorporating relatively new methods of pumping high yield, low density, cementitious grouts, the Shoshone Mine reduced downtime due to tailgate ground control problems by approximately 70% in comparison with previous Longwall panels. The longwall set three monthly production records while mining the 11 left longwall under the deepest cover, steepest pitch, and most extreme ground control conditions ever encountered at the mine.

Jan 1, 1995

By H. L. Burmeister

This is one of a series of publications by the Bureau of Mines dealing with mining methods and costs at representative operations in the United States. The report describes all phases of the mining methods for the open-pit operation and milling practices employed at the Vermont Asbestos Mines in Lamoille and Orleans counties, Vermont. A brief history of discovery and development of these asbestos deposits is given, and the ore deposits are described. Methods employed in exploration, sampling, and estimation of tonnage and grade are outlined. A breakdown of available cost figures is summarized in the last section. All asbestos ore produced in this area has been won by the use of surface-mining methods. Two quarries, the Lowell and the "C" Area, are in operation. The quarries combined are producing and the mill is processing approximately 3,500 tons of ore per 3-shift day The average 40,000 tons of crysotile asbestos fiber produced at this plant annually accounted for 96 to 98 percent of the total fiber produced in the United States in 1958. The mine is located (fig. 1) approximately 4 miles north of Eden Mills village on the southeastern flank of Belvidere Mountain (fig. 2).

Jan 1, 1962

By Tom Szynakiewicz

Micropiles are routinely used in the United States for foundation support and underpinning applications. The high capacities achievable with the use of micropiles, combined with specialty rigs for easy installation in low headroom and difficult access areas makes them a good choice for situations often encountered on existing commercial projects. The bond zone of the pile is typically drilled into a competent stratum such as sands, gravels or bedrock. In this paper, the authors will discuss a project where the lack of a shallow ?competent stratum? led the geotechnical contractor to create their own bond zone for the micropiles using jet grouting. Due to problematic clay (CH) soils, the original foundation of a six story office building in west Houston had experienced up to five inches of differential movement in-between the shallow under-reamed shafts. The owner desired a permanent solution to the problem without disturbing the majority of the tenants. The structure was underpinned with a hybrid system of jet grouted micropiles as well as jet grouting alone and the structure was re-leveled using hydraulic equipment to within a 0.25? tolerance. Design, construction and sequencing of the project are discussed in the paper. QA/QC methods are also discussed, including coring for verification of jet grout column diameter as well as a full-scale micropile compressive load test. The structure was successfully re-leveled and the entire project was completed without disturbing any tenants on the floors two through six.

Jan 1, 2008

By Larissa Koroznikova, Steve Durkin, Patrick Bouwmeester, Michael Tuck

In currently used mining methods, blasting techniques often causes dilution of valuable ore and results in costly processing requirements. In the context of narrow vein mining of thin and highly concentrated orebodies there is a need of a mining method that can reduce dilution in order to remain economically viable. This research project explored the viability of a new mining technology, thermal fragmentation, in narrow vein mining. Thermal fragmentation technology uses a flame jet to produce extreme heat that spalls the surrounding rock to a strategically located drill hole, as an alternative to traditional blasting. This paper creates a net present value (NPV) model of a mining method using thermal fragmentation, as well as for an existing method used for narrow vein mining; comparisons and evaluations were made regarding the feasibility of the new technology. It was found that while overall costs for thermal fragmentation were relatively high, reductions in wages, haulage and processing costs, as well as increased productivity and ore recovery, meant that the new method would improve the financial performance of any operation. These results identify that there is an opportunity to introduce the thermal fragmentation technology to narrow vein mines within Australia, in order to lower costs and increase profit.

By Jim Richards, Eli Choueiry, Brett Robinson, Amanda Elioff

The Los Angeles Metro Gold Line Eastside Extension (MGLEE) extends Metro’s light rail system to the densely populated and growing East Los Angeles communities. Much of the 6 mile alignment consists of at-grade track, but the project also features a1.7 mile underground segment in cut-and-cover and twin-bored tunnel structures. In light of past experiences with open shield construction, The Metropolitan Transportation Authority (Metro) specified, for the first time, use of Pressure Face Tunnel Boring Machines (TBM’s) to advance tunnels through soft ground. This paper describes the history of the tunnel design, construction management, and construction methods adopted that resulted in successfully completing the tunneling segment.

Jan 1, 2007

By W. H. Tomlinson

This publication presents the basic text for a 20-hour accident-prevention training course developed for supervisors by the Federal Bureau of Mines. During the past 2 years, the course has been used by the Bureau in teaching more than 300 groups of coal-mine supervisors-men whose responsibility is twofold: To manage in production and maintenance phases of coal mining and to guide their men along paths of safety. This is a handbook for teaching teachers. In this handbook will be found references to safety practices followed by companies that consistently have low accident records. These companies credit their outstanding performance to the adoption and faithful observance of accident prevention by supervisors and workers alike on a wholesome, cooperative basis. Teaching safety to workers involves both on-the-job and classroom-type instruction. If such training is to be permanently effective, it must be reinforced consistently on the job by the immediate supervisor of the worker. This publication is intended to provide such a supervisor with the motivation to provide such follow-up and shows how he can accomplish it effectively.

Jan 1, 1962

By Armando Gallegos Monteagudo

El presente texto señala las experiencias realizadas en GERENS, empresa de consultoría y capacitación en gestión del sector minero, formulación, implementación y control de planes estratégicos que utiliza herramientas con un alto nivel ambiental en la creación de valor económica, ambiental para las empresas mineras el Balanced Scorecard (BSC) y el análisis de la cadena de valor de la empresa. El Balanced Scorecard es una herramienta gerencial que apoya la implementación del plan estratégico y permite su monitoreo y control. Para ello, el BSC requiere que el plan estratégico de la empresa se traduzca en objetivos claros y medibles, indicadores, líneas de base, metas, y programas de acción estratégicos y tácticos.

Sep 12, 2005

The largest investment in mining equipment in Caterpillar?s history ? The F series mechanical and electrical drive trucks ? is rapidly advancing. Caterpillar showcased the 793F and 797F mechanical drive trucks and the 795F ac electric drive truck at MinExpo in 2008 and have continued testing since then. The 793F and the 797F have accumulated more than 75,000 hours of field testing and have proven their performance capabilities and their durability. The new Cat C175 engine that powers them has racked up 130,000 hours of field testing in mining trucks and more than 120,000 hours in power systems. Because of the success of these field-follow programs, the 793F is targeted to go into full production within a few months and the 797F late this year. Caterpillar engineers have been testing two 795F ac prototypes at the Tucson Proving Grounds in Arizona. The development program has provided input for the construction of a new 795F ac in Decatur, IL. The new truck recently shipped to a copper mine in North America where it will serve as the first field-follow 795F ac as it works at the mine. The 313-t- (345-st-) capacity 795F ac will enter a new size class for Caterpillar, and, as a result, the primary focus of the Caterpillar ac electric program has been on the 795F ac. The commercial launch date will be defined as the field-follow program progresses. ?It?s fitting that soon after producing the 50,000th Cat off-highway truck, we are now shipping our first ultra-class ac electric drive truck to a mine,? said Chris Curfman, president of Caterpillar Global Mining. ?Our new trucks further solidify our position as the one manufacturer to provide unparalleled options and unmatched customer support.?

Jan 1, 2009

By V. B. Teffo

The aim of the project was to experimentally determine the coefficient of restitution, and static and rolling friction of Eskom-grade coal for discrete element modelling (DEM). These parameters will be used in further DEM studies to simulate the flow and behaviour of coal during conveyance. For the simulation to yield realistic results, the parameters for the different coal shapes identified in the samples were determined. DEM uses spherical particles, and it was found that the difference between the DEM default parameters and those measured is significantly different, by as much as 97%, which illustrates the importance of experimentally determining these parameters. The spherical particles in DEM can be used to construct the various coal shapes identified, and the parameters measured can be used to simulate realistic results. The conveyance system can then be optimized accordingly.

Jan 1, 2013

By A Bax, G Wardell-Johnson, A Giblett, W Staunton

This paper presents a number of key considerations for process development testwork as a reliable basis for the inclusion of gravity separation in gold recovery flowsheets. Operating data, experiences and numerous case studies are also discussed in support of identifying best practice principles for gravity circuit design.CITATION:Giblett, A, Bax, A, Wardell-Johnson, G and Staunton, W, 2013. A review of best practice in gravity circuit design and operation, in Proceedings MetPlant 2013 , pp 272-284 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 15, 2013

By J. M. Mitchell

Kuala Lumpur, Malaysia is underlain by karstic limestone. Firm clays, mudstones and siltstoncs of the Kenny Hill Formation overlie the limestone for about two thirds of the city. The remaining third has deep deposits of very soft alluvium, or tin mining slimes, overlying the limestone. It is only recently that large buildings have been constructed in the area. Arup Jururunding have been concerned with several projects located on the limestone, although space here only permits the description of four sites in detail. The experience has allowed the development of a design approach for the foundations. The aim is to make the architectural scheme compatible with the geology. This is not always possible, and examples are given of both situations. The case histories give examples of compensated foundations, and piled foundations include steel H-piles, precast concrete piles, micropiles, bored piles with rock sockets, and barrettes up to 90m deep.

Jan 1, 2010