Search Documents

By Murali M. Gadde

Perimeter mining is a special form of very productive partial extraction method practiced at some mines in the United States. In the Illinois Basin mines where all major coal seams have weak underclay in the immediate floor, experience shows that any long-term ground control issues will arise due to floor failures rather than instability of the coal pillar itself. While there is a significant amount of work done on floor stability associated with regular pillars, no work has been done so far on the stability of perimeter pillars. This paper reports the results of a comprehensive study that was conducted for the first time on floor stability during perimeter mining in the Illinois Basin mines. A special plate template, which mimicked a common perimeter pillar configuration was created to conduct in-situ bearing capacity tests at five mines in three states of the Basin. Additionally, because of the complex shape of pillars created in perimeter mining that defies any closed-form solution, floor bearing capacity was studied using three-dimensional nonlinear numerical modeling. Based on these in-situ and numerical studies, some guidelines are provided for perimeter pillar stability analysis.

Jan 1, 2009

By T. G. Legare

It is now well documented that trace amounts of silver, gold, and platinum group metals occur in certain geothermal brine deposits. A significant body of literature has been generated over the last twenty years which describes attempts to quantify the frequency and levels of these precious metals in the brines. This literature is often confusing and contradictory. For example Barnea 1 states that the Salton Sea geothermal field carries 2 ppm gold, yet more recent data by workers at Lawrence Livermore National Laboratory2 (LLNL) concludes that the gold level in Salton Sea brine is <0.07 ppb. They report a platinum level in one well of 55 ppb. This apparent contradiction may be explained by sampling source and technique, but is most probably explained by difference in analytical technique. Analytical techniques and problems will be discussed in the next section.

Jan 1, 1985

By E. D. Thompson, Y. J. Zhang, K. F. Unrug

This paper presents the results of a recent study on the development of an in situ testing method for determining coal strength in mine pillars. The strength testing is performed in the horizontal holes drilled into the coal rib using a penetrometer, which is an hydraulically powered device that uses an indenter to press on the surface of the borehole until the load reaches the failure point of the coal. The pressure and the penetration of the loading pin are recorded by a data-acquisition unit. The results collected from several coal mines indicate that this testing method is ideally suited for the realistic coal strength measurements. The new testing system not only improves the accuracy of the pillar-strength determination, but it is more cost efficient than the conventional method.

Jan 1, 1997

By A. J. Hendron, G. Mesri, R. M. Semple

Squeezing ground conditions in hard-rock tunneling are associated with fault zones containing brecciated rock and gouge. Gouge is a stiff clay-like soil that exhibits a propensity to creep. The ground loads applied to tunnel supports in squeezing ground are known to be significantly time dependent. Accordingly, an experimental and analytical study is presented that deals with soil creep and its application to the prediction of tunnel support requirements in squeezing ground conditions. Relatively undisturbed samples of fault gouge obtained from Straight Creek tunnel in Colorado and Pacheco tunnel in California are classified as very stiff to hard clays of low plasticity. Constant-load undrained triaxial compression tests are performed on these materials. A simple, three-parameter creep equation is developed that adequately describes the observed deformation of fault gouge with respect to applied stress and time. The equation is shown to fit existing creep data of various soil types. The creep equation is used to modify an existing continuum-mechanics solution to the time-dependent behavior of unlined and lined cylindrical openings in a creepsensitive medium under a hydrostatic state of stress. Assuming properties for the medium that are representative of the fault gouge materials tested, parameter studies are performed for unsupported and supported tunnels in squeezing ground. The analyses permit estimates to be made of the steel set supports required for tunnels at different depths in various squeezing ground conditions.

Jan 1, 1974

By David B. Campbell

INTRODUCTION This submission was made to the Royal Commission of Inquiry into uranium mining in British Columbia. It discusses the stability of waste rock piles that might be developed in conjunction with uranium mining and the control of leachates that might be generated within these waste rock piles over the short and the long term. Short term refers to the interval during which a waste rock pile undergoes either continuous, or alternatively intermittent development, and in general can be considered to extend over the operating life of the mine. Long term refers to the postmining period, i.e. after the ore-body has been exhausted, and mining operations have ceased. Two major classes of waste material are generated in the course of mining and milling operations. Tails, which are the solid waste materials produced by the milling operations commonly exit the mill in slurry form and are stored in tailing retention ponds. Management and control of these slurried wastes are the subject of other papers to the Commission and this conference. In the course of the mining operations, it may be necessary to remove rock materials that are below cut-off grade. That is, ore concentrations within some of the mined rock may be lower than the concentrations which on the basis of economic considerations justifies milling the material. Rock which is removed in the course of the mining operations, but which is below cut-off grade is referred to as waste rock. This waste rock is commonly consigned to a specific area for disposal where it is placed in a mound or pile, i.e. a waste rock pile. Ore concentrations within the waste rock may vary from zero to just below cut-off grade. Since an increase in the market value of uranium could at some time in future result in reduction of the cut-off grade, it follows that waste rock containing ore concentrations slightly below today&apos;s cut-off grade could become ore grade rock at some time in future. For this reason, the mine operators may deem it advisable to separate waste rock according to grade, and to consign the waste rock to two or more individual waste rock piles. For purposes of clarity and simplicity, this submission treats the stability of waste rock piles and leachate control in a manner which assumes that these potential problems are isolated and separate from other aspects of the mining and milling operations. For many site specific cases, the problem of potential leachate control might be integrated with the tailings management aspect of the project, thereby realizing economic benefits while at the same time reducing the potential for adverse environmental impact.

Jan 1, 1980

The Mining Foundation of the Southwest will hold its 15th annual American Mining Hall of Fame Awards banquet on Saturday, Dec. 6,1997 in Tucson, AZ, preceeding the Arizona Conference of SME. The Mining Foundation&apos;s Hall of Fame, located in Tucson, recognizes outstanding contributions to the mining industry by individuals and industry partners. A permanent display of honoree vitae is located at the Arizona Historical Society at 949 E. Second St. in Tucson. Each year, one living award recipient and up to two honorees from mining history are chosen by the Hall of Fame committee and the board of governors of the Mining Foundation. In 1989, the Mining Foundation also initiated a Medal of Merit to recognize outstanding individual technical and professional contributions to the mineral industry. And in 1995, an award was instituted to recognize contributions made by companies and organizations in partnership with the mining industry. This year&apos;s inductee is James R. Moffett, chairman and chief executive officer of Freeport-McMoRan Copper and Gold Inc. He will be present as guest of honor and featured speaker. The Hall of Fame will induct John V. Dorr, metallurgist and chemical engineer. Also inducted will be Frederick L. Ransome, a geologist. Medals of Merit will be awarded to Hugo T. Dummett, senior vice president, Exploration BHP Minerals, and Spencer R. Titley, professor in the Department of Geosciences at the University of Arizona. An Industry Partnership Award will be presented to the Colorado School of Mines for its continued support to the mining industry through education and research. The banquet will be held at the The Westin LaPaloma in Tucson beginning with cocktails at 6:30 p.m. Tickets are available from Clare A. Roscoe, manager, Mining Foundation of the Southwest, telephone 520-577-7519, fax 520-577-7073.

Jan 1, 1997

By Carl E. Schubert

The application of geophysical technology relative to the exploration, planning, and operation of coal mines is expanding. This is due to the trend of the industry to increase the size of operations, use of mechanized equipment and mining of more difficult coals, where unforeseen conditions can affect mine profitability. Coal is a good geophysical target because of its lower density, higher electrical resistivity, lower seismic wave velocity, and lower magnetic susceptibility in comparison to typical country rock. The more important techniques are well logging, high resolution seismic reflection, seam wave velocity, and radar. These methods can be used to map coal horizons, determine the physical properties of the coal, and identify mining hazards. The methods are not a pancrea however. Their use should be based on a careful assessment of their expected success and cost benefit analysis in comparison with conventional technology, primarily drilling, which none of the techniques presented should entirely replace. In general, the level of technology developed for geophysics surpasses their current level of application to coal problems. In some cases, identifying hazards in advance of mining using seam wave seismic in particular, the state of the art has been developed in Europe and is awaiting fruitful application in the United States.

Jan 1, 1982

By Ora H. Rostad

Veins containing silver and gold values, with some associated values in copper, lead, and zinc, were discovered in 1890 by Will Kirwin in what was later designated the Kirwin mining district situated on the North Fork of the Wood River, about 56 km (35 miles) west of Meeteetse. (See Fig. I.) After considerable prospecting activity, including the driving of several short adits on veins, most of theclaims in the district were consolidated into two ownerships. One was held by the Galena Ridge Mining Co. which was organized on Nov. 18, 1902. The other was held by the Shoshone Mountain Mining Co. which was organized on Mar. 23, 1903. During the period from 1903 to 1907 inclusive, the two companies continued exploration on veins in their respective areas. The major exploration-development activity for the Galena Ridge Mining Co. was the driving of the Galena Ridge crosscut adit for 709 m (2327 ft), to cut veins at depth which had been explored by short adits high on Galena Ridge. Shoshone Mountain Mining Co. concentrated their work on the Bryan and Pickwick veins. Neither of the companies found ore that was rich enough to sustain profitable operations in that remote locality. Most of the major exploration and development activities were stopped in late 1907. A major snowslide in February 1907 killed three people and destroyed several buildings and may have contributed to discouragement in the area. From 1908 to the early 1920s, only minor exploration work was done. Galena Ridge Mining Co. was dissolved Aug. 5, 1922, and Shoshone Mountain Mining Co. was dissolved on Mar. 23, 1923.

Jan 1, 1991

By T. C. Eisele

The use of column flotation was considered for the ?reverse flotation? of iron ore, where the gangue (quartz) was recovered in the froth product. This use of the froth for carrying the gangue mineral rather than carrying the valuable concentrate significantly changes the operational requirements of the column. The objective of this work was to determine which of several column flotation technologies would be most suitable for this type of flotation operation. Studies were carried out using both the Jameson column and the Deister column. Comparative results are presented that show the capabilities of both column types in this application relative to conventional Wemco flotation cells. Columns were demonstrated to have grade-recovery performance superior to what could be achieved with conventional cells. Two-stage flotation with the columns could produce a concentrate that was up to 70.2% Fe at 87.5% iron recovery, compared to 70.4% Fe at only 77.7% iron recovery for four stages of flotation in conventional cells. It was shown to be particularly important to operate the columns to recover a maximum of the quartz gangue into the froth. It was noted that there are often problems in scale-up of laboratory columns to plant scale, because the increase in height and the decrease in the ratio of height to diameter at the larger scale allows more axial mixing and bubble coalescence, both of which degrade the column performance. Horizontal baffling was shown to improve column performance by reducing axial mixing and breaking up large bubbles, and so the use of such baffles in the reverse flotation application was investigated.

Jan 1, 2007

By J. Yianatos

The collection zone residence time distribution (RTD) of mechanical self-aerated flotation cells was characterized for liquid and solid per size class (-45 mm, +45-150 mm and +150 mm). It was found that a single large industrial cell with a volume of 130 to 250 m3, now used in plant operations, can be well represented by an LTST (large and small tank-in-series) model plus dead time. From a scale-up point of view, results showed a similar mixing behavior for industrial cells ranging from 130 to 250 m3. Also, single mechanical cells showed a similar mixing pattern (RTD) when compared to large pneumatic flotation columns. It was confirmed that for practical purposes, the mixing condition in a flotation bank of three or more cells in series can be well described by the classical N tanks-in-series model.

Jan 1, 2008

By Anders Sellgren, K. Hansson, A. Jedborn

In the mining industry, conversion of fine particles into a slurry is often part of the normal processing of the ore. Therefore. from a system&apos;s point of view, slurry transportation would be considered as a natural alternative, all the way from the working face to the final processing. In underground mines, there is sometimes a considerable inflow of ground water that has to be pumped out. When the mine dewatering installations are integrated with a hydraulic hoisting system, the cost of power needed to pump out the ground water can be excluded from the cost of hoisting, compared with other modes of transporting the solids to the surface. The chief advantage of hydraulic hoisting is that the hoisting capacity can be increased at comparatively low total cost without necessitating the sinking of new shafts. Alternative examples include deepening of the existing mechanical hoisting system, truck, or conveyor belts transport in ramps to the present level. These often become very expensive. The economic effectiveness of hydraulic hoisting and hydraulic design considerations have been discussed by Kostuik (1965) and Sellgren (1985, 1986) for both small shallow mines and large deep underground mines. Objective and scope The objective of this study was to demonstrate the feasibiliy of hydraulic hoisting in hypothetical examples of mine deepening. Underground grinding to a maximum particle size of about 700 um (about 25 mesh) is considered. The pumping of ground ore products with positive displacement plunger or membrane type of pumps at working pressures of up to 15 MPa (2200 psi) is a thoroughly tested technique (Venton, 1986). Hydraulic hoisting system A hydraulic hoisting system is described schematically in Fig. 1. The ore is mined, handled, and crushed conventionally. It is then ground wet underground. The slurry is then temporarily stored in an agitated tank and pumped to an agitated receiving tank on the surface. The ore is then further processed in the concentrator. The capacity of a pipeline is very high. For example, an annual production of 500 Kt (550,000 st) of ore can be handled in a 100-mm-diam (4-in.-diam) pipeline. Systems layout - economic effectiveness Schematic mine layouts are presented that represent situations where hydraulic hoisting often is the most economical alternative. A situation where the ore is trucked to the level of the existing hoisting system is shown in Fig. 2 (following page). With hydraulic hoisting, only a shaft for ventilation, pipe- line, and personnel are needed. In a first phase (Fig. 2). a hydraulic hoisting installation with crushing and grinding units, storage facilities, and pumps has been located at a level of about 400 to 600 m (1310 to 1970 ft) below the surface. With further development of the mine, the hydraulic hoisting

Jan 1, 1990

Where space is limited, as it is throughout most of the northeastern United States, new construction either takes place high above street level, or below it. In Lower Manhattan, NY both kinds of expansion can be found in abundance. That is good news for the nearly 200 attendees at the George A. Fox Conference, presented by the Underground Construction Association (UCA) of SME at the Graduate Center, City University of New York, on Jan. 30. Among the many projects taking place in Lower Manhattan?s massive trans-formation process, are expansions to the city?s vast underground network of subways and other tunnels. ?New Yorkers either live on the ground or below it,? said keynote speaker Charles J. Maikish while explaining how an attempt to build above street level walkways never caught on in the city. Maikish is the executive director of the Lower Manhattan Construction Command Center. His job is to oversee the $22 billion project that will transform the island by 2010. From the construction of Freedom Tower at the site of the fallen World Trade Center buildings, to the expansion of the Second Avenue Subway, the extension of the East Side Access, No. 7 line, the new trans-Hudson line and numerous waterway tunnel expansions, including City Water Tunnel No. 3, the task Maikish is charged with is a huge one. He is primarily responsible for coordinating the scheduling and staging of the overall rebuilding plan, along with the day-to-day coordination of construction work down-town. He places particular focus on mitigating impacts on the environment and mobility, maintaining and improving access and alleviating congestion of any kind related to construction. At the time of the Fox Conference, there were 59 projects under way in Manhattan. All of those projects need things like concrete and steel delivered to sites in very tight working environments. And some need the equipment in even tighter spaces. ?This is not just about the recovery of Lower Manhat-tan (from the 2001 terrorist attacks) but this is a plan to restore it and to maintain its integrity,? said Maikish. ?I think that is the appropriate response to the terrorist attacks.? When Freedom Tower is completed, it will stand 541 m (1,776 ft) about the skyline. That will be a strong statement to the world about America?s strength. But it is the work that takes place much lower that was of interest to the conference attendees. On this respect, Maikish said Manhattan?s efforts below ground aim to provide relief to the city?s street level congestion and to make sure Manhattan ? already essential to the economy of the United States and the world ? stays current by upgrading the existing telecommunications and technological network while also allowing room for growth in that area.

Jan 1, 2007

By J. Owens

The methodology of quarrying changed significantly in the Indiana Limestone industry in the sixty years between September 11, 1941, the date of the Pentagon groundbreaking ceremony and September 11, 2001 when the building was damaged by American Airlines Flight 77. So too, though to a lesser degree, did the machinery and methods used to fabricate the stone. The rededication ceremony on September 11, 2002 marked the end of the Phoenix Project, as the rebuilding effort was named. The story of this remarkable project illustrates what the American construction (and Indiana Limestone) industry can accomplish when working toward a common goal.

Jan 1, 2004

By Thomas Schultheis, William Heron, Paul Watson, Colin Warren

This paper describes the geology and geotechnics associated with construction of the Thames Tunnel, part of the UK’s Channel Tunnel Rail Link (CTRL). The 2.5km long twin tunnels run beneath the river Thames at depths of up to 40m and are currently under construction. They pass through varying geology comprising alluvium, terrace gravels and chalk with flints and are currently being bored using Herrenknecht mixshield slurry tunnel boring machines (TBM’s). This paper outlines the lithology and engineering properties of each geological formation and describes the geotechnical processes, potential hazards and difficulties experienced in the works. A summary is given into the extent of the investigative work in terms of route selection, tunnel design, TBM optimisation and further details are provided on the geotechnical aspects associated with the construction of the tunnel approach structures and the tunnels.

Jan 1, 2003

By Kurt Egger, Emily A. Baker

Rehabilitation work at the Cameron Run Tunnels entailed the restoration of seven heavily deformed, approximately 69 m long, steel liner plate supported culverts through a CSX Railroad embankment near Alexandria, Virginia. A custom fabricated expander, equipped with four 200-ton hydraulic jacks on two expansion arms was used to push back the liner plates encroaching into the proposed tunnel profile and install the steel set support. In a second phase the tunnels were then lined with 16 cm of fiber reinforced shotcrete. Geotechnical instruments both in the tunnels and on the railroad embankment were used to monitor the effects of the rehabilitation work on the two CSX Railroad tracks above the tunnels. Freight and passenger trains were required to run uninterrupted and at maximum speeds throughout construction.

Jan 1, 2003

By R. K. Paramguru, K. Srinivasa Rao

This paper describes a new approach for examining the kinetics and mechanism of zinc dissolution from sphalerite concentrate in acidic ferric sulfate solution in the presence of manganese dioxide. A literature search was performed to access the possible action of the two oxidizing agents, i.e., ferric ion and manganese dioxide. The possibility of galvanic coupling between ZnS and MnO2 and the cyclic action of the redox couple, Fe2+/Fe3+, on these two minerals were theoretically examined based on corrosion principles. Expressions for the mixed potential (Em) and the mixed current (im) were derived for the relevant corrosion and galvanic couples. Leaching experiments were conducted to establish which of the above phenomena is operative during leaching. The results indicated that the dissolution mostly occurs by the action of ferric ion on ins producing ferrous ions. The presence of MnO2 enables a quick conversion of ferrous to ferric, which maintains the rate of in dissolution. The process has promising features for commercial exploitation.

Jan 1, 1999

By John M. Marek, David E. Nicholas

INTRODUCTION The purpose of this article is to outline the data requirements for selecting a proper underground mining method and to discuss the general steps taken in selecting that method. Determining the appropriate mining method is an iterative process that continues throughout the life of a mineral deposit. We will discuss the subject from the standpoint of a feasibility study, where a realistic assessment is necessary in order to determine investment merit. The feasibility stage of a project is that point where the drilling program has defined sufficient geologic reserves to consider mining the deposit but little or no underground development has been done. Primary parameters for consideration in choosing a mining method are 1) geometry of the deposit; 2) distribution of grade; 3) rock mass strength for the deposit, as well as the hanging wall and footwall; 4) mining cost and capitalization requirements; 5) mining rate; 6) type and availability of labor; 7) environmental considerations; and 8) other site-specific conditions. Of these parameters, the first four have the most impact on determining the general mining method to be employed.

Jan 1, 1981

By Richard Adsero

The Australian Bureau of Statistics and the United States Bureau of Labor Statistics publish data for a range of industries, allowing a measure of performance to be quantified, called multifactor productivity (MFP), and allowing performance between industries to be compared on a consistent basis. At the time of writing, the last released data was for 2011-2012. For Australia, the plot of mining industry productivity and a basket of the 12 most significant industries in Australia?s economy (including mining) are shown in Fig. 1. For the United States, mining and petroleum and all manufacturing productivity are also displayed in Fig. 1. The trends are as follows: ? The MFP in the Australian mining sector rose 36 percent from 1986-1987 to 2000-2001. There was a 47-percent decline in MFP from 2000-2001 to 2011-2012 (Australian Bureau of Statistics, 2011). ? The MFP in the United States mining sector rose 17 percent from 1986-1987 to 2004-2005. There was a 7-percent decline in MFP 2004-2005 to 2010-2011, (Topp et al., 2008).

Sep 1, 2013

By Ellis Brien, O&apos

The fine coal fraction of a coal stream is that fraction which contains particles essentially in the -28 mesh size range. This fraction will normally first appear, in a coal preparation process, as a result of classification to segregate raw coal into various size components for beneficiation. More specifically, it could appear in desliming screen underfiow, classifying cyclone overflow, and in other process circuit components. It&apos;s recognized that the top size of this fraction has been determined more by secondary reasons, such as desliming screen area for the heavy medium cyclone circuit, the dewatering equipment for the fine clean coal, or even the stability of the refuse thickener circuit. Benefits, both economic and environmental, gained by beneficiating the fine coal fraction of a raw coal stream are increasing in number, until today, fine coal beneficiation is a necessity in most coal operations requiring any degree of preparation. This is due to some of the following reasons: • In the past it was frequently more economical to discard -28 mesh raw coal sizes than to recover the coal values from them. Today, mining costs have escalated to the point where all coal values leaving the mine should report to the finished product if possible. • Today&apos;s mining methods are producing run-of-mine coals containing higher percentages of -28 mesh sizes. This heavily weighs the economic balance in favor of beneficiating this fraction. As much as 25% of the run-of-mine coal from some mines is in the fine coal fraction. Beneficiation is recommended so that clean coal contained in the fraction can be recovered to reduce the loss of coal values. • Existing and pending environmental regulations mandate that solid fuels now consumed in power station boilers contain almost no pyritic sulfur. This form of sulfur appears in raw coal in the fine coal fraction, but can be removed by coal beneficiation. Environmental considerations dictate that every year, more of the fine coal produced for steam generating purposes in the US be beneficiated. To deliberately discard any portion of the fine coal can only add to this cost, not only in the sense that fewer tons will be recovered but, more importantly, additional tonnage will be diverted to the most capital- and labor-intensive section of the entire preparation plant-the fine refuse dewatering section. It is apparent to preparation engineers that dewatering and ultimate disposal of the fine refuse derived from this beneficiation step is certainly the most difficult technical problem presented in the entire plant design. Therefore, any beneficiation procedure which increases the fine coal recovery, or in any manner decreases the tonnage of fine refuse to be dewatered, is going to be cost effective. Since the -28 mesh fraction contains both coal and refuse particles in their finest particle sizes and thus presents the greatest degree of liberation, one would immediately infer that the highest degree of beneficiation would be achieved. This is not the case-the opposite is more likely true. Conventional coal cleaning devices based on specific gravity (such as

Jan 8, 1980

By Richard L. Patterson, Alan P. Finch

Twenty years ago, when tunnel projects in the UK were generally procured by the public sector, many were completed late and over budget. Now a significant proportion of new infrastructure is developed by the private sector. Seeking more certainty in cost and programme, promoters have tried new and radically different methods of procurement and contract forms. The paper will review these developments, then examine the approach adopted for some of the largest current UK tunnelling projects (both in the public and private sectors) including the Channel Tunnel Rail Link, the Heathrow Terminal 5 Development and new highway tunnels.

Jan 1, 2003