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By E. Forssberg

Studies have been carried out with the High Pressure Roller Mill, HPRM, to produce calcium carbonate minus 10 micron. This paper presents the optimization of the specific grinding force of the HPRM system for a maximum energy utilization when limestone is ground. In addition, experimental tests of producing carbonate minerals using the HPRM as a pre-crusher are described in this paper.

Jan 1, 1996

By S. Tyson

The American Coal Ash Association, Inc. (ACAA) is an organization of producers and marketers of coal combustion byproducts. Since 1968, the goal of ACAA has been to gain recognition and acceptance of ccbs as an engineering material on par with competing virgin, processed and manufactured materials by advancing ccb uses that are technically sound, commercially competitive and environmentally safe. The use of ccbs is affected by local and regional factors including production rates, processing and handling costs, transportation costs, availability of competing materials, seasonal adjustments, and the experience of materials specifiers, design engineers, purchasing agents, contractors, legislators, regulators, and other professionals. An annual, survey of coal-burning electric utilities is conducted by ACAA to determine the quantities of ccbs produced and used in the USA. In 1993 approximately 88.5 million tons of ccbs were produced in the form of fly ash, bottom ash, boiler slag and byproduct from flue gas desulfurization (FGD). Approximately twenty-two percent of the combined production of these byproducts was used, while the remaining portion was deposited in disposal areas. The major markets for ccbs include cement and concrete products, structural fills, road-base layers, mineral filler in asphalt, grit for snow and ice control, blasting grit and roofing granules, grouting, coal mining applications, and waste solidification and stabilization.

Jan 1, 1995

By E. Westman

Geographic Information Systems (GIS) are becoming a more commonly used tool for resource estimation as they provide not only a database management platform, but also the graphical capabilities to visualize resource characteristics. Interpolation methods used commonly in these resource studies do not typically provide a quantitative answer to the question: "How accurate is the estimate?" By comparing localized measurements at several locations to the interpolated thickness distribution used in a resource estimate, a quantitative analysis of accuracy can be obtained. The technique is demonstrated with a case study from Central Appalachia.

Jan 1, 1999

By Wi11iam M. Leaders

Uranium Recovery Corporation was incorporated in the State of Florida in 1968 for the sole purpose of developing a method to economically recover uranium from Florida phosphoric acid. The preliminary laboratory work culminated in the demonstration of the process to United Nuclear Corporation in the spring of 1971. This was quickly followed by a pilot plant program to identify any unusual problems such as those arising from the day-to-day variation which occurs in a fertilizer phosphoric acid plant production system. After two years of pilot plant operation, United Nuclear Corporation purchased controlling interest in Uranium Recovery Corporation and committed several million dollars to the design and construction of the first commercial plant for this purpose in the State of Florida, or anywhere else in the United States, for that matter. After many start-up problems were resolved at the production plant located at the W. R. Grace fertilizer complex near Bartow, sustained production began March, 1971, and has continued to date. We still have some problems to solve but are currently producing sufficient uranium to make shipments to the UF6 converters for preparation of Florida uranium for use in nuclear power plant fuel materials.

Jan 1, 1978

By Wen L. Chen

The steam coal quality is less stringent than metallurgical coal quality. The steam coal is prepared either by cleaning full size range of raw coal or cleaning coarse coal only, leaving the fine coal raw. The latter scheme is more cost competitive. It is particularly applicable to U.S. eastern soft coal where low ash coal is concentrated in fine sizes. For raw coal size separation, a recently developed Rotating Probability Screen, developed by the British Coal Board, may be advantageously used for easy change of raw coal separating size and to avoid screen deck plugging when handling wet and clayey raw coals.

Jan 1, 1983

By M. Ahmadiantehrani

The concept of hypochlorite treatment prior to cyanidation in the heap leaching of low grade carbonaceous gold ores is discussed. Laboratory column leach tests using a low grade carbonaceous ore were performed to investigate the effects of pH, concentration, hypochlorite consumption, and bed height on the total gold extraction. At high pH, the hypochlorite stability increases and thus, hypochlorite consumption is decreased. At room temperature, the total gold extraction is proportional to the hypochlorite consumption. However, at some point additional hypochlorite consumption does not increase gold extraction. Gold recoveries of 10 and 80 percent are obtained for 12 and 167 lbs/ton hypochlorite consumption, respectively. Increasing hypochlorite concentration increases the rate of extraction. For a given hypochlorite consumption gold extraction was increased by shortening the ore column height. Finally, calcium hypochlorite is more effective than sodium hypochlorite.

Jan 1, 1990

By Michael H. Vallez

On September 13, 1973 MAPCO Inc. leased from Pocahontas Land Corporation an 18,000 acre tract of coal lands in Eastern Kentucky's Martin County (See Figure 1.). In July, 1974 initial run of mine coal shipments commenced and in April, 1976 shipments of a 12,500 BTU, less than 1% sulphur, washed coal was being shipped. Results of exploration demonstrated that large quantities of overburden would have to be moved. MAPCO decided to invest in large surface mining equipment to tackle the job.

Jan 1, 1981

By Douglas N. Kendall

There are three definite steps in the making of a mining industry in any country. These are as follows: Step A - Geological Mapping This step covers the basic geological mapping of the country at scales of 1/250, 000 up to l/50, 000. This step eliminates territory and directs the exploration teams to the areas of potential interest. Step B Prospecting This step includes all phases from detailed geology through geophysics and drilling up to the point of proving that an economic ore body exists. Step C - Mine Development This is the expensive step, involving the creation of the mine, including shaft-sinking, ore treatment plant, etc.

Jan 1, 1963

By George J. Thompson

Almost all persons connected with mining industry have had an exasperating experience like the following: 'On a cold and frosty morning in mid-January, you find yourself quite happy with the world. Production is up and the mine has been running smoothly. All at once the radio cracks up your tranquility -- 'so and so' piece of equip¬ment has broken its 'whatzit'. Now the iron is in the fire, and things have to be fixed quick.!' This can be a major failure which will bring the whole operation to a grinding halt or just one of the numerous maintenance headaches on an auxiliary piece of equipment. After one has experienced a major or minor catastrophe, he has to wonder whether some other methods with respect to design and maintenance would help prevent these unexpected calamities. The objective of this paper is to gain an insight into the charac¬teristics of steel at cold temperatures so that better decisions can be made with respect to maintenance and repair of mining equipment. Most machinery and their structures are exposed to cold temperatures. Even in locations as far south as Alabama and Arizona, brief periods of cold in winter months can adversely affect the ability of mach¬ines to do their work. To understand the background of cold temperature brittle fracture, jet us examine its basic elements. First, when steel gets cold, it gets brittle. This is best described by Figure 1. This graph shows a typical stress/strain curve of a mild or medium grade steel at room temperature. Stress is defined simply as the amount of force acting on one square inch of

Jan 1, 1972

By W. M. Ma, Daniel W. H. Su, K. Centofanti, Yi Luo, W. L. Zhong, Syd S. Peng

9.1 INTRODUCTION There are approximately 70,000 abandoned coal mines nation¬wide, which is about 35 times the number of underground coal mines presently operating. The US Bureau of Mines estimates that there are over 8 million acres of undermined land due to the extraction of coal, metals, and nonmetals. Subsidence has affected more than 2 million acres, and more than 99% of the subsidence is related to underground coal mining. There is reason to believe that some of the remaining 6 million acres of the undermined land have a high potential to subside. The expansion of housing, highways, commercial structures, and other facilities has required the use of many areas that are underlain by abandoned coal mines, and this growth will continue. Many subsidence problems are derived from the collapse of aban¬doned underground coal mines. There are numerous abandoned mine workings in the anthracite fields of northeastern Pennsylva¬nia, in the Appalachian bituminous fields, the Illinois Basin, the Rock Springs, Wyoming area, and other areas of the United States (Gray et al., 1976). Various room and pillar patterns of mining have been used in the dipping anthracite seams and the nearly flat-lying bituminous seams with considerable variation in the per¬centage of coal extracted. The progressive deterioration of pillars, mine floors, and mine roofs after long exposure to air and water may later result in the collapse of strata over the mine entries, the crushing of the remaining coal pillars, or the bearing failure of the mine floor beneath the coal pillars. Subsidence then results as the collapse reaches the ground surface in the form of differential strains, depressions, cracking of the ground, and sinkhole devel¬opment. Subsidence over active longwall mines, which occurs concurrently with mining or is completed within a short period following coal extraction, has been studied extensively over the past decade. On the other hand, subsidence over abandoned coal mines receives little attention by the researchers, mainly because it is difficult to predict and takes place decades after mining has ceased. The techniques of investigating the subsidence events over abandoned coal mines are similar to those employed for active mines except that at the outset, it is necessary to determine whether or not the subsidence events are mining-related (Chugh et al., 1986; Cummings and Singh, 1986; Peng and Hsiung, 1986). This calls for the identification and confirmation of abandoned mine workings under or near the affected surface structures. Gen¬erally old mine maps, if available, are acquired, the surface bore¬holes are drilled for confirmation of the accuracy of the mine maps and determination of the potential for continued subsidence. Sub¬sidence monuments are established and periodic surveys con¬ducted to determine the amount and trends of surface movement in and around the affected surface structures; surface boreholes are used to investigate the integrity of the underground structures (i.e., roof, coal pillars, and floor) by TV camera. They are also used for monitoring the vertical and horizontal movements of the subsur¬face strata by Sondex (FPBX) and inclinometer (PFBI), respec¬tively, for determining the continuity of the subsidence events. Tape extensometers, crackmeters, etc., are used to monitor the development trends of major cracks in the structures or on the ground. These data are used to identify the causes of the subsidence events. Finally, abatement methods are selected to stabilize the structures. It must be noted that most subsidence events over abandoned coal mines are reported after the fact, and investiga¬tions are begun some time after reporting, that the subsequent measured movements are generally much smaller than that at¬tained in the active mines, and that due to lack of knowledge about the damage conditions and the exact location of the abandoned mine workings with respect to the affected surface structures, the precise causes of surface subsidence or surface structural damages are in most cases very difficult to identify. 9.2 TYPES OF SURFACE SUBSIDENCE According to Gray et al. (1977), after examining 354 incidents of subsidence above abandoned mines in the Pittsburgh metropol¬itan area, the subsidence features have a mean diameter (i.e. the average of long and short dimensions) from less than 1 ft to 1600 ft, with 84% less than or equal to 15 ft; the subsidence features have a depth ranging from less than 1 ft to 48 ft, with 89% less than 25 ft; 66% of the subsidence features are deeper than they are broad. Nearly 59% of the subsidence features occur with overbur¬den less than 50 ft thick and 81% less than 100 ft thick. No subsidence features occur with overburden thicker than 450 ft (Fig. 9.1). Occurrence of subsidence incidents varies from imme¬diately to more than 100 years after mining (Fig. 9.2). In analyzing the characteristics of approximately 3000 chim¬ney subsidence features along the Colorado Front Range, Matheson and Eckert-Clift (1986) examined historical aerial photographs on 4- to 14-year intervals between 1937 and 1967 and found that the majority of observable surface subsidence features occurred within 30 to 40 years after mining. According to Gray et al. (1977), the most prevalent subsi¬dence features over abandoned mined land are sinkholes, with depths of more than 3 ft, and troughs or sags, usually less than 3 ft deep. Sinkholes are steep-sided pits, while troughs are shallow depressions much wider in area than sinkholes. A. SINKHOLE SUBSIDENCE A sinkhole is caused by the collapse of a mine roof that works its way upward. If it is not arrested during the process it will eventually reach the surface and emerge as a sinkhole. The process is governed by the thickness and character of the overburden, the width and height of the mine openings. Sinkholes are usually 3 to 20 ft deep and may be 2 to 40 ft in diameter, although most are fewer than 16 ft across (Gray et al., 1977; DuMontelle and Bauer, 1983). Newly formed sinkholes have steep sides with straight or bell-shaped walls. At times, they appear to be conical in profile with the apex upward. If the topsoil collapses, the top portion will widen to form an hour-glass shape. Sinkhole subsidence usually occurs over abandoned mines less than 165 ft deep (Hunt, 1979). Matheson and Eckert-Clift (1986) found that chimney sink¬holes are likely to occur when the ratio of overburden thickness to mining height (h/m) is less than 4 to 5. When h/m is between 5 and 10 to 11, the potential occurrence of chimney sinkholes decreases rapidly. When h/m is more than 10 to 11, less than 10% of the mine openings that collapse will induce sinkholes on the surface.

Jan 1, 1992

By M. P. Fahey

A significant amount of silca is recovered in the rougher stage of anionic flotation of Florida apatite. This recovery, in the past, has been attributed to both entrainment and cation activated flotation. This study shows that by using a transport factor, it is possible to determine the contribution of each mechanism towards silica recovery. Further, it is shown that the concentration of cations in the conditioning water significantly affects both the amount of silica recovered due to entrainment and true flotation. Further confirmation of this phenomenon was obtained by Ca++ doping of the conditioning water and by using a sodium silicate depressant.

Jan 1, 1996

By Burton E. Gilpin, Dr. George W. Annadale

A two level risk analysis procedure which is specially designed for use in river environments, is presented. The first level risk assessment (Level I) is often adequate for purposes of most projects, and entails hazard assessment, exposure identification, consequence estimation, and risk characterization. Two unique features of the method are the Composite Hazard Rating system, which is used in hazard assessment, and a formalized decision model for risk characterization. The risk characterization procedure provides information on the acceptability of risks, can be used to distinguish between the relative severity of risks, and to evaluate whether more advanced risk assessment would be required.

Jan 1, 1992

By Eric W. Johnson

In the late 1950's a low-grade copper ore zone was outlined at the fifty-year-old McIntyre Porcupine Mine in Northern Ontario. Following this an independent copper circuit was installed in the existing gold mill. The nature of the operation decreed that capital expenditure be a minimum. To this end, in order to resolve the problem of storing and grinding two separate ores, it was decided to install a divider in the existing 4000 ton capacity fine ore storage bin and to replace ten conventional feeders with sixteen Mexican feeders. The article describes a successful application of the Mexican type feeder.

Jan 1, 1968

By Gene Mattila

Each installed rock bolt costs in excess of 520.00. High cost in conjunction with the primary purpose of safety makes it only logical to install the highest quality anchors possible. Each bolt has designed support capabilities in axial, shear and fluctuating ground condition, if installed to manufacturers recommendations. The quality of anchor is not; however, only affected by material specifications, but by transportation, handling storage, installation procedure, machine performance and geology. The quality is not only affected by many variables, but reliability should be assured. Non-destructive methods of testing reliability are only available for several types of bolts.

Jan 1, 1985

By R. Wu, R. Howell, J. Dase

Turquoise Ridge is an underground gold mine located in the Potosi Mining District, approximately 64 km northeast of Winnemucca, Nevada. Turquoise Ridge Underground is accessed via two shafts and a system of internal ramps and utilizes underhand drift and fill mining methods with cemented rockfill. The mine also employs mechanical mining as well as sill benching as mining methods. Ground conditions at Turquoise Ridge Underground are poor, and the Rock Mass Rating (RMR) may be less than 20, or very poor, in ore headings. Current production rate is 2,700 tonnes of ore per day. Key challenges in increasing production levels and reducing costs are the development of sufficient stoping areas and the transition from top-cut development to undercut stoping. Completion of the infrastructure development in the North Zone is necessary to achieve and optimize higher production levels. The #3 Shaft project is well underway and is expected to be commissioned in mid. 2022. The shaft will drastically decrease the haulage requirements in the North Zone

Mar 2, 2022

By M. Liu

In-situ soil washing using surfactants shows great potential to remove hydrophobic organics from subsurface environment. Lab scale soil washing experiment were performed using Sodium Dodecylsulfate (SDS), an anionic surfactant, and anthracene, a highly hydrophobic compound. The results of this research show that solubility of anthracene increases linearly with an increase in SDS concentration above the critical micelle concentration. Furthermore, SDS can be effective in removing anthracene from contaminated sand.

Jan 1, 1992

By C. E. Jordan

Under its program of advancing minerals technology, the Federal Bureau of Mines has developed a laboratory apparatus for continuous separation of minerals according to their dielectric properties. The unit consists of a rotating wire grid drum electrode and a fixed curved wire screen electrode positioned 3 mm apart. By applying high voltage across the electrodes, which are immersed in a dielectric fluid medium, a high-gradient electric field is produced. The high-dielectric-constant minerals are attracted and conveyed through the separator by the rotating drum electrode, whereas the low-dielectric-constant minerals settle through the fixed electrode. In typical tests, a sample of Montana chromite ore containing 43 percent chromite was concentrated to 72 percent chromite with 90 percent recovery.

Jan 1, 1977

By Charles G. Weakly, Alan M. Lander, Pamela B. Zohar, Robert W. Leonardson

The cluster of gold deposits at the Goldstrike property is located in the Northern Carlin Trend in northeastern Nevada (Fig. 1). At many mature mining camps like Goldstrike, exploration innovation and success may wane with time. In this regard, sufficient exploration drilling was conducted in the area immediately north of the ultimate pit crest and under the final planned pit wall to test for a major deposit. No indications of large deposits were found, however, the majority of drill holes did intercept mineralization. Mining along the northern pit wall exposed significant structurally controlled ore-grade mineralization that had been missed by exploration drilling. In 2002 and early 2003, the mine geology group added reserves to the pit and improved the definition of underground resources by targeting specific ore-controlling structures within favorable stratigraphic units by utilizing relatively inexpensive horizontal RC drilling from the pit wall. The widespread occurrence of mineralization to the north of the pit was re-interpreted to be an indication of continuity of these mineralized zones. In January 2003, 70 feet of 0.332 opt Au at a depth of 710 to 780 feet was intercepted in a dewatering well. This intercept was significantly thicker and higher-grade than average for the area, which confirmed the existence of high-grade structural continuity, and helped secure management support for additional exploration. A timely and cost effective solution was needed to confirm the potential of the area. Immediate follow-up drilling on tighter grid spacing was rejected in favor of improving the geology model. Exploration across the property would benefit from an improved geology model, but to provide results in a timely manner, the area to the north of the Betze pit was chosen as a starting point (Fig. 2).

Jan 1, 2005

By Gerhardt A. Bennewitz

The mechanism shown here (Fig. 1) may not be all that it appears to be. To many of you it may look like a hopper car, a thing of mobility, in which you would ship coal, ores, limestone, or other bulk materials. It is approximately 50 feet long, 12 feet high, and can be placed on tracks which are on approximate 14 foot centers. But far too often in the past, and all too often today, this mechanism has been made to serve as an immobile storage box, with its primary role -- the transportation of products, seemingly incidental to the storage function. Our engineering training teaches us to conserve resources, despite some of the popular and misconceived philosophies being advanced these days. Those of you who work for companies with traffic departments know that they are always striving to reduce the price which is paid to move your mine products. Today, let's consider and analyze the ways in which the cost of transporting your mine products might be reduced, based on particular reference to coal. Bear in mind that in this context, cost and price are not necessarily synonymous. Until a few years ago, most coal and other bulk materials handled by railroads moved under standard tariff rules. These rules, which still exist today, provided transportation vehicles (railroad cars) for extended periods at no added price to the shipper or receiver. "Normal" free time rules would permit a car to be held for a maximum of 48 hours without charge; however, in the case of coal, there is a rule which, subject to liberal rules as to the

Jan 1, 1972

By H. J. H. Pieterse

This paper highlights the mineralogy of the Barrick Goldstrike Mines Inc. area. The mine is located at the north end of the Tuscarora Spur and is part of the Bluestar/Goldstrike subdistrict of the Carlin Trend. The Betze, Post, and Meikle Mine are major deposits located in the area. The deportment of gold, its leachability, and various process options are also evaluated. Particular emphasis is given to the practical and economic considerations of ore control, and routing of ore to a process option.

Jan 1, 1993