Search Documents

By K. F. Bailey

Naturally occurring asbestos in aggregate and other mineral deposits, and the release of asbestos fibers into the ambient environment, is a public health concern. Determining the presence of asbestos in an ore body also presents a considerable sampling and analytical challenge. Improper and inaccurate identification of asbestos can result in unwarranted public and worker panic leading to significant costs to mine operators both in terms of dollars and company image. Some companies have been forced out of business simply because they had the non-asbestiform, prismatic variety of one of the six asbestos minerals. In the late 70’s, asbestos was found as a contaminate in a trap rock quarry in Rockville, Maryland. This discovery led to a massive overreaction by federal, state and local governments. In 1986, the Occupational Safety and Health Administration (OSHA) promulgated a final rule that regulated the common non-asbestiform mineral habits of actinolite, tremolite, and anthophyllite as if they were asbestos. The rule was reversed after a six-year struggle. Recently, the Libby, Montana, W. R. Grace vermiculite - asbestos, as well as the California chrysotile in serpentinite, and the New Jersey Southdown quarry – asbestos events have rekindled the entire issue of naturally occurring asbestos. It is time to get this concern addressed with sound science so that real asbestos is properly identified and controlled.

Jan 1, 2002

By S. Frimpong

Shovel excavation constitutes a significant component of production costs in any surface mining operation. This makes shovel loading an important cost center that needs to be improved to lower production costs. Optimization of tool design will improve energy efficiency in earthmoving operations. However, modeling the soil-tool interaction is a complex process due to the fact that forces for excavating particulate material are functions of many variables. The magnitude of this resisting force depends not only on the type of soil but on the size, shape and orientation of the cutting element. Moreover, part of this complexity is attributed to the fact that the behavior of the material during excavation is not yet well understood. For the past five decades, researchers have mostly used the passive earth pressure theory to study the soil failure patterns around a cutting tool and to develop force prediction models for design optimization with some success. Although the force models developed from the passive pressure theory have been successful to some extent, they can hardly be extended to a general case because of the underlying assumptions and simplification of tool shapes. This paper aims at reviewing some of the existing empirical and analytical methods of cutting and excavation tool modeling with a focus on their merits and limitations. The paper also explores the use of numerical methods, specifically the discrete element method, for dealing with the unresolved aspects of soil dynamics in excavation.

Jan 1, 2011

By S. Gaillard, E. Cauda

"Diesel particulate matter (DPM) is an occupational health hazard in underground mines. It generally occurs in the submicrometer size range and is often present in the mine atmosphere with significant concentrations of dust particles that tend to occur in the supramicrometer size range. As dust can interfere with analytical methods to measure DPM, it is often removed from a sample stream using an impactor-type size selector such as the DPM impactor (DPMI). Because the DPMI physically removes oversized particles from the stream, its performance may be gradually reduced with aging. Sharp-cut cyclones (SCCs) are an alternative size selector for DPM sampling applications, with a major advantage that, by design, they should not be susceptible to rapid aging. This paper presents the results of a field study designed to compare the performance of aged versus new/clean DPMIs and SCCs in an underground mine. DPMI aging resulted in clogging of the device and, eventually, a reduction of its effective particle cut size, but when sample flow rate was maintained, DPM sample mass collection was not affected until significant aging had occurred. Under the conditions of this study, the effects of SCC aging were observed to be minimal at the end of the study period. IntroductionSubmicrometer-sized particles are increasingly recognized as significant respiratory health hazards (Cantrell and Watts, 1997; Kenny, Gussman and Meyer, 2000; Ristovski et al., 2012). Diesel particulate matter (DPM) represents a major source of submicrometer particles in both public and occupational environments (Kittelson, 1998; Abdul-Khalek et al., 1998). Relative to other occupational groups, underground miners can have some of the highest DPM exposures due to their work in confined spaces where large diesel equipment is used (U.S. Environmental Protection Agency, 2002; Grau et al., 2004). DPM largely consists of solid elemental carbon (EC), commonly known as soot, and organic carbon (OC) that may be sorbed to EC particles (Kittleson, 1998; Abdul-Khalek et al., 1998). EC and OC can be measured by thermal-optical methods such as the U.S. National Institute for Occupational Safety and Health (NIOSH) 5040 standard method (Birch, 2016), and their sum is referred to as total carbon (TC). While the complex nature of DPM does not allow for its direct measurement, both TC and EC have been accepted as suitable surrogates for monitoring occupational exposures to DPM (Noll et al., 2007; Birch, 2016)."

Jan 8, 2018

By M. Hancer, J. D. Miller

The sign of the surface charge of selected potassium soluble salt minerals namely KClO4 , K2SO4 , KNO3, and KCl was determined from nonequilibrium electrophoresis measurements and found to be negative for each of the salt. Dodecylamine flotation of these salts revealed that the concentration of amine required for flotation increases in the order KClO4< K2SO4< KNO3<KCl. Precipitationof the amine collector colloid was not required for flotation of the oxyanion salts and in this case it appears that adsorption of the dodecylamine cation is sufficient to create the hydrophobic surface state. The order for flotation is explained in terms of surface hydration of these respective potassium salts based on contact angle measurements and FT Raman spectroscopic characterization of water structure.

Jan 1, 1999

By David A. Milligan

This paper describes the Darwin Silver Recovery project, located 66 km (40 miles) outside of Lone Pine, near Darwin, Inyo County, California. A lead-zinc mine and a flotation concentrator were operated there from 1945 to 1957. By the time the mine was shut down, 1.53 Tg (1.69 million short tons) of tailings had been stored in ponds. An average silver assay of 47 mg/kg (1.38 troy oz/st) of tailings stimulated interest for commercial silver recovery. A heap leach process was developed in 1981 at the Tucson Research Center of Anaconda Minerals Company, a division of Atlantic Richfield Company. Agglomeration techniques were used on the ore since the fine grind did not allow direct heap leaching. Lime and cement were required as binders, Early laboratory tests showed that recoveries equal to those from an agitated leach could be achieved at lower capital and operating costs. Laboratory tests determined cyanide requirements, lime and cement usages, and percolation or leach rates, as well as confirming that a zinc precipitation step could recover the silver from the leach solution.

Jan 1, 1983

By R. L. Braun

In situ chemical mining of primary sulfide ore requires distribution of injected oxygen in a large underground flooded region of broken ore. Although the maximum oxygen content of the leach solution will be dictated by the operating temperature and hydrostatic pressure, the actual oxygen content will be limited by the geometric dispersion of the injected oxygen, the rate of dissolution of oxygen, and the rate of convective circulation of oxygenated solution within the flooded bed of ore fragments. These factors are examined by a detailed theoretical analysis supported by laboratory experimental data. Typical results of the study illustrate that adequate dissolution of oxygen and circulation of oxygenated solution can be obtained in a column of 4 million metric tons of broken ore by using three gas injection lines and an oxygen injection to consumption ratio of 1.84.

Jan 1, 1974

By E. Arioglu

Discussion by E. Arioglu Y. Luo and S.S. Peng are to be congratulated for their outstanding paper providing new results from surface subsidence monitoring over longwall panels under different conditions. This writer found the authors&apos; paper very interesting. In reference to this paper, the following contributions are offered: • In the paper, the maximum possible subsidence [(ASmax)] induced by chain pillar convergence has been related to a parameter (h/1- p) by linear regression. (Notations are expressed in this discussion&apos;s Fig. 1 (b).) It is a well-known fact that in a goaf the roof lowers onto broken material that gradually compacts. Then the physical behavior of goat may closely follow the compaction characteristics of broken materials. In light of this assumption, a mathematical means (Fig. 1(a)) of defining the expected compaction (i.e. surface subsidence) represents an exponential expression between [ASmax/m vs. h/1-p]. This is based on Luo and Peng&apos;s field observations from the Appalachian, Illinois and Alabama coal fields. (The coefficient of regression "r" under consideration was computed to be 0.883). • According to Wardell&apos;s (1969) findings for board and pillar mining, the maximum possible subsidence can be expressed in terms of maximum pillar loading (depth, ratio of extraction) and the height-to-width ratio of the pillars left. Using Luo and Peng&apos;s 1991 results, this writer discovered a regression equation between the above-mentioned factors. As displayed in Fig. 1(b), the functional expression approximates as closely as possible the observed subsidence data. It may be noted here that Wardell&apos;s approach (1969) can be successfully utilized for longwall panels having chain pillars. Reference Wardell, K., 1969, "Ground surface and control," Mining Congress Journal, January, pp. 1-7.

Jan 1, 1993

By Ray Brainard, Adriana Ventimiglia, Amanda Kerr

Preliminary design is underway for a new Southern Nevada Water Authority (SNWA) project that will ensure one of America’s most reliable water systems by providing continued, reliable water service to existing and future customers. The Horizon Lateral is a $1.6 billion water transmission pipeline that includes 7–10 miles of 108-inch finished diameter rock and soft-ground tunnels. The tunnels will traverse volcanic rock in or around the McCullough Mountain Range and the surrounding alluvial basin. The tunneling community will find relevance in hearing about this critical infrastructure project from a leading wholesale water utility owner with a proven track record for on-time, collaborative projects.

Dec 1, 2022

By K. G. Correia

The replacement of the dry mining method at Guajú Mine by the dredging method was a means of ensuring its feasibility by maintaining the production levels. Dry mining increased the cost of the deposit with the distance and presented a limited mined volume, while the decreasing grade of the deposit led to a production drop. With the new methodology, there was a considerable reduction in unit cost of the mine and an increase in the production level of a deposit with low heavy minerals content.

Jan 1, 2005

By P. G. Corser

A gold and silver open-pit mine located in northwestern Chile contracted ACZ in 1991-92 to assess the stability of their spent ore pile and to determine the cause and magnitude of cyanide contamination associated with leaching operations. The mine is a conventional open-pit located at an elevation of approximately 4,800 meters (m.) (15,744 feet). A spent ore pile is located approximately 2,000 m. southwest of the mine and approximately 1,000 m. northeast of the active pad and plant facilities. The pile was constructed on a gentle northwest slope dipping 12 to 13 degrees. The pile is bordered by a small river to the northwest and by a larger river to the northeast. Both rivers eventually flow into Bolivia. Heap leaching and processing commenced at the mine in 1988. Since 1988, nearly 6.0 million tons of ore at an average grade of 1.96 grams/ton (0.07 ounces/ton) of gold and 52 grams/ton (1.83 ounces/ton) of silver have been treated by cyanide heap leach methods with zinc (Merrill Crowe) precipitation. In approximately three years of operation, the mine has yielded more than 225,000 ounces of gold and over 1.5 million ounces of silver. Currently ore is agglomerated and hauled to the leach pad by truck and is top loaded to produce a 5-meter lift height. Four contiguous reusable (on/off) leaching pads were constructed with an asphalt layer above a carefully compacted sub-base of High Density Polyethylene (HDPE) liner and screened fines. Leach solution of pH 10-11 containing 1.2 to 1.5 gram/liter of cyanide is applied to the heap at a rate of 10 liter/hour/square meter for a total active application period of 30 days. Leached (spent) ore is transferred to the spent ore pile located approximately 1,000 meters to the northeast. The pile currently contains approximately 6 million tons of spent ore. The pile liner, which has been constructed over a prepared sub-grade consists of three geosynthetic layers (geotextile/flexible membrane liner/geotextile). Long term objectives include washing the pile to recover an additional 3 to 4 percent gold and silver.

Jan 1, 1993

By C. Ford, R. E. Salas Rojas, J. P. Contreras Rodriquez, S. A. Pierce

Heightened environmental consciousness has resulted in the development of various international accords dealing with natural resource management. This international awareness is now being translated into regional and local initiatives that proactively implement collaborative environmental management programs. One such program was recently initiated in northern Chile in recognition of the interconnection of Andean salars. Cooperative efforts between industry, governmental agencies and academic professionals have resulted in the implementation of simultaneous environmental monitoring of flora and fauna in the salars of northern Chile. This coordinated effort is leading to an improved understanding of the migratory patterns of South American fauna, as well as improved access to an expanded database for the multiple user groups associated with the Andean salars. The El Abra Mine is actively participating in these coordinated monitoring efforts.

Jan 1, 1999

By Vladimir Nikolić, Alex Doll

The Bond ball mill grindability test is one of the most common metrics used in the mining industry for ore hardness measurements. The test is an important part of the Bond work index methodology for designing and measuring the efficiency of mineral grinding circuits. In spite of being called “Bond’s Law,” the work index equations are not a law of nature; but rather an empirically measured regression of a large data set collected by the Allis- Chalmers corporation in the period between 1930 and 1952. As a regression, it is valid within a specific “calibration space,” and great care is required when deviating the test procedures or observing results that are outside of that calibration space. This paper is a collected summary of other works by the Authors that describe feed sizes, product sizes, quality control checks, and other information about interpreting the test and using its results. Examples of adjustments that are sometimes required when using the test are: changing the test product (P80), and coping with a feed that is too fine to apply the “proper” feed preparation steps (such as is sometimes observed from HPGR or SAGDesign product testing). Related metrics, like the Morrell Mib value and Levin B value will be discussed, along with recommendations for their use on design projects. The intended audience is any user of laboratory work index test data.

Feb 1, 2024

By D. Brunner, G. R. Baiden, H. J. Yazici

System simulation is an increasingly popular technique for analyzing and improving existing as well as newly designed underground mining operations. An engineering firm that specializes in simulation helped a major metals producer build a long-range planning model of an existing underground mine. Subsequently the team adapted this model to assess technology alternatives in the design of a new mine. The two models differ in the level of detail used for modeling the development process. This paper discusses the differences in approach between the models along with the experiences gained and challenges faced during the construction and use of the models.

Jan 1, 1999

By Gerald H. Luttrell, Seyed Hassan Amini, Aaron Noble

One of the most important processing engineering tools for designing mineral processing facilities is linear circuit analysis. This technique, originally conceived and developed by Meloy, Williams, and Fuerstenau nearly four decades ago, provides fundamental insights regarding how unit operations interact and respond when arranged in multi-stage processing circuits. Researchers have successfully utilized this tool to improve the operating performance of industrial processing circuits incorporating coal spirals, magnetic separators, mineral spirals, and eddy current separators. More recently, advanced versions of this tool have also been developed to provide a standardized framework for circuit mass balance calculations, to output exact analytical solutions to mass yield and value-based efficiency expressions, and to estimate uncertainty propagation in separation circuits. This article reviews the historical development of linear circuit analysis, describes how the technique has evolved to address more complex circuit design problems, and presents industrial case studies that highlight the importance of this process engineering tool.

By K. Whiting, R. Huffsmith, R. Olsen, D. Adams

Long-term closure alternative selection for heap leach pad effluent is a daunting task. Passive water treatment, if designed with enough long-term capacity, can minimize long term O&M while meeting water quality objectives. Leach pad effluent from a 30-acre leach pad at Basin Creek Mine, Basin, Montana was targeted for long-term water treatment using a passive water treatment system. The objectives and results of design and construction are: 1. Design a long-term passive system utilizing existing infrastructure. 2. Construct a field scale pilot test at the mine site.

Jan 1, 2002

By Hongwei Wang, PEIPEI CAO, Yongping Wu, JIANQIANG JIAO

In the fully mechanized top caving mining of steeply inclined, extra-thick seams with variable angles, the mechanisms of roof rock movement, failure, caving and filling are highly complex. This is due to the varying angle of coal seam in different areas, which makes rock–equipment stability control challenging. In this paper, the surrounding rock deformation and failure mechanisms, bearing structure of the overburden, and working characteristics of the supports are elucidated. The principle and key technologies of rock–equipment stability control are presented and applied to control the overburden of the regional failure and realize safe and efficient mining of the working face.

By G. Daws, N. Woodward, A. Oxley

Many mines around the world have been seeking ways to achieve sustainable developments and reduce operating costs. Rockbolting is a technology that needs to be considered as it provides a means of reducing operating costs and improving safety whilst allowing improved production to be achieved. The problem is how to introduce this technology in the knowledge that a successful outcome will be achieved. Rockbolting is a complete package and not only includes the consumable materials but also training, production of Codes of Practice, Monitoring Schemes, Refinement of Design and long term management of the systems. This paper explains the methods that have been applied for its successful introduction and discusses several case studies. It does not give fine detail but is intended to allow decision makers to gain a basic understanding of the method used to successfully introduce rockbolting to a mine.

Jan 1, 2011

By A. D. MacPhail

The Highland Valley Copper partnership was formed in July 1986 and was the logical result of a mine with a large ore reserve but no adequate mill, and a mine with a large, modem mill but dwindling ore reserves. The original partners -Cominco and Lornex -were joined in January 1988 by Highmont Mining Co. which contributed a two-line concentrator. During 1988/1989, the Highmont mill was moved 7.5 km to adjoin the Lornex mill, forming what is now called the Highland mill, with a current nominal capacity of 130 000 tonnes per day. The mine is located 220 km northeast of Vancouver, British Columbia and is close to four communities in which personnel make their home: Logan Lake, Merritt, Ashcroft, and Kamloops. The map in Figure 1 2.2 shows the general area. Kamloops is a major service centre and is serviced by two railways, two major roads and a regional airport.

Jan 1, 1993

By R. S. Shoemaker

Environmental and regulatory authorities are increasingly requiring that precious metals heap leach piles be contoured before they are abandoned so they may present a more "natural" look to the eye. Depending on the ore type, many of these contoured heaps will be subject to substantial erosion by precipitation events, native plants will have difficulty in establishing themselves and slimes be washed onto surrounding areas or into watercourses. This paper presents the argument that the results of contouring heaps are counter to good environmental practice. Calculations which have been made demonstrate that leveling and berming the heap tops as well as berming the edge of each lift or setback will effectively prevent water erosion and promote the growth of native plant species.

Jan 1, 1993

By T. R. Ellis

Australia’s mineral valuation code continues to evolve, while mineral valuation standards are also being written for Canada and Southern Africa. The author is leading a task force for writing the extractive industries addition to the International Valuation Standards. Meanwhile, the International Accounting Standards Board is continuing the development of an extractive industries addition to its International Financial Reporting Standards, with an emphasis on valuation reporting. This paper analyzes the need, content and ownership for a U.S. minerals appraisal standard in the context of both these developing international standards and also existing U.S. regulations and appraisal standards. The author provides many questions for research and debate.

Jan 1, 2003