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By Vladimir G. Kochnev

Crushing and grinding account for the major portion (60 to 80 percent) of the overall expenses for ore processing. Autogenous (AG) and semiautogenous grinding (SAG) have been considered a step forward in comparison to conventional grinding circuits with several stages of crushing and using ball (and/or rod) grinding mills (Bassarear, 1982, MacPherson, 1989, Pithois, Casalis, 1983, Maripuu et al., 1983). However, there remains room for improvement to existing AG and SAG technologies and both technologies have immense economic benefit potential. Experience gained by the Technics & Technologies of Disintegration Ltd. (TTD) in the research of grinding processes shows that grinding in AG and SAG mills can be performed in a more effective way. The company's approach comprises the following elements: ? Novel mill design. ? New liners and lifters. ? Novel discharge grid design. ? Technique of treating material of critical particle size. Comparative tests that demonstrated the usefulness of these innovations are described in this article. Currently, there are hundreds of AG and SAG mills in operation throughout the world. Application of new internal elements of the mills and reconsideration of the circuit design of the existing grinding equipment using present technological solutions would significantly increase the throughput rate and diminish power requirement.

Jan 1, 2008

By Joseph M. McCann

The Brightwater regional wastewater treatment facility, under construction in King County, WA, includes an extensive conveyance system that will feature deep, soft-ground tunnels and shafts. Excavation of the Ballinger Way Receiving Portal to 65.8 m (216 ft) below grade through challenging geology was accomplished by means of artificial ground freezing. This paper discusses freeze design development, system installation and monitoring, and the contractual and construction challenges that were overcome, including work sequencing and excavation means and methods, together with lessons learned.

By William Reininger

Microtunneling provides a necessary solution for multiple utility crossings associated with the New York Metropolitan Transportation Authority Capital Construction Company?s (MTACC) Eastside Access Project for the Long Island Rail Road. Construction of four TBM tunnels and their approach structures at the eastern end of the project in Sunnyside, Queens required significant modification and expansion of the railroad infrastructure at this location. Maintenance of railroad traffic during project construction is a principal requirement. As a consequence fourteen (14) utility crossing segments are being installed under active traffic by microtunneling methods. Microtunnels were installed in a variety of conditions including depths, types of soils and construction restraints.

By W. J. Miles

Many years ago, a relationship was established between dust inhalation and pneumoconiosis. Since then, various government agencies have regulated crystalline and amorphous forms of silica material in the workplace. In 1987, the International Agency for Research on Cancer (IARC) classified crystalline silica as a probable carcinogen. With this listing, crystalline silica became a regulated substance under the Hazard Communication Standard. The minerals and chemicals industries have responded in various ways. They have: • developed worker and user training programs and literature; • labeled products with appropriate warnings; • continued to implement dust reduction programs; and • developed meaningful epidemiological studies of workers. • begun development of reliable analytical methods for measuring crystalline silica at the 0.1 % threshold level; Background Silicosis historically has been the major health hazard resulting from exposure to crystalline silica. Silicosis is the scarring of the lung from excessive exposure to crystalline silica. It has been recognized as an occupational disease for more than 2000 years, since early Greek physicians noted the respiratory problems of miners, stonecutters, and quarrymen who were exposed to excessive quantities of mineral dust. During the industrial revolution, the incidence of the disease was greatly increased by the use of machinery that increased dust levels. Subsequently, the need for dust control was recognized and measures were instituted. Silicosis is characterized by progressive breathlessness on exertion and develops over the course of years. Xray images of the lungs show

Jan 1, 1990

By Gerald C. Smith

Introduction Newmont Mining Corp.'s Carlin Gold Mining Co. mines gold ore and waste material from four open-pit mines in Northeastern Nevada. Combined production rate is 24.5 Mt/a (27 million stpy). The company is producing gold bullion from the 2.4 kt/d (2600 stpd) Carlin Mill No. 1. and the 2.3 kt/d (2600 stpd) Maggie Creek heap leaching plant. In August 1985, the 6.3 kt/d (7000 stpd) Carlin Mill No. 2 at Gold Quarry came on-line. The total combined throughput of 11.2 kt/d (12,000 stpd) will make Carlin Gold Mining one of the largest US gold producers. Feasibility studies are underway to increase the total gold out-put from Gold Quarry. This will be done by adding a continuous dump-leaching process that will recover gold from lower grade ore. History In 1961, Newmont exploration geologists located claims in the Lynn Creek mining district near Carlin, NV. An exploration drilling program revealed significant gold mineralization. A stepped-up drilling program revealed an ore body with an estimated 10 Mt (11 million st) of ore containing 109 t (3.5 million oz) of gold. Test results in 1963 allowed metallurgists to develop the flowsheet and design for a 1.8-kt/d (2000-stpd) countercurrent decantation (CCD) cyanide plant. Carlin Gold Mining Co. was formed to operate the property. Carlin purchased its first mining equipment in 1965. This consisted of two Bucyrus-Erie 2.7 m3 (3.5 cu yd) shovels and nine 27.2 t (30 st) Wabco Haulpak trucks, two Inger¬soll-Rand track-mounted drills, one Chicago Pneumatic T-650 rotary drill, one rubber tired Michigan 280 dozer, one Caterpillar D-8 36A track dozer, one Caterpillar 16 motor grader, and the necessary ancillary equipment. The fleet was capable of mining 3.2 Mt/a (3.5 mil¬lion stpy) working two eight-hour shifts, five days a week. In 1967, one P&H 1500 3.8 m3(5 cu yd) diesel electrical shovel and three 59 t (65 st) Dart trucks were added to the fleet, along with a Chicago Pneumatic rubber tire mounted rotary drill. This equipment addition increased the mining capabilities to 5.7 Mt/a (6.3 million stpy). Three separate pits, the Main, East, and West, within a 1.6-km (1-mile) radius of the Carlin mill were being mined. The crew consisted of 46 hourly men and three supervisors. This equals 497 t/ total hourly manshift (548 st) or 407 t/total manshift (515 st). Rising gold prices in the early 1970s allowed lower grade deposits to be mined at greater distances from the mill. The Boot-strap pit, 19.3 km (12 miles) north of Carlin, was started in 1973. Two Hough 45.4 t (50 st) front-end loaders, four Wabco Haulpak 45.4 t (50 st) trucks, and a second track type D-8H dozer were added. The higher grade ore was trucked to the Carlin mill using three

Jan 11, 1985

Minerals are fundamental to the U.S. economy, contributing to the real gross domestic product (GDP) at several levels?mining, processing and manufacturing finished products. The estimated growth rate for the real GDP of the United States was 2.1 percent and the nominal GDP was about $13.8 trillion in 2007 (Table 1). The prime interest rate decreased to 7.25 percent in December from 8.25 percent at the beginning of 2007, reflecting actions taken by the Federal Reserve Board to counter financial difficulties surrounding subprime mort-gages. Delinquencies on subprime mortgages increased throughout the year, affecting not only the delinquent home owners but also financial instruments invested in mortgage-backed securities. The average contract mortgage rate for the purchase of previously occupied homes in the United States was 6.35 percent in November; a slight decrease from 6.37 percent in January but still greater than 5.34 percent reported in July 2003, the lowest rate in the past five years. With the tightening of credit, the seasonally adjusted annualized rate for new privately owned housing starts declined 27 percent from December 2006 to November 2007. The loss in the residential market was balanced by a 9-percent increase in nonresidential construction between January and August 2007, during which slight increases occurred in nearly all

Jan 1, 2008

By Kevin Andrews, Terry Hamric, Scott Nelson

"Mining conditions in underground coal mines are dictated by the environment in which the coal seams were geologically deposited. Depositional features can change rapidly, significantly affecting mining conditions. Mine geologists understand factors affecting mining conditions, predict future conditions, and provide guidance to mine management. A case study demonstrates how a mine in Appalachia merged an understanding of depositional environments with mining conditions and drilling data to make informed decisions as the mine encountered geologic anomalies. The assessment included drilling, mapping of geologic hazards and mine productivity, and creation of a conceptual depositional model. Metallurgical coal quality and clean tons per foot served as incentives for continued advance. Mining in the south was historically favorable, with good production and advance rates. As mining advanced north, changing geologic conditions caused the upper seam split to abruptly disappear. The mine ramped down into the lower seam split. Mining in the north area encountered unfavorable conditions, including transition roof, “horsebacks,” sandstone intrusions, roof rolls, and bony floor, resulting in low rates of mining advance. The mine geologist characterized the features and created a predictive model for future mining. Most of the adverse conditions were attributed to the coal in the north being part of an incised, transgressive valley fill environment, as compared to the favorable conditions in the south resulting from a floodplain depositional environment. Geologic conditions, low productivity, and unfavorable future predicted conditions in the north ultimately resulted in mine closure and reallocation of resources to a new mine with better forecasted conditions.INTRODUCTIONThe role of a geologist in assisting coal mining operations to understand and predict the impact of varying geological factors on mining productivity is a critical one, especially when management decisions must be made about the future prospects of a mine operating in difficult conditions. Chase, Newman, and Rusnak (2006) provide a very thorough discussion of the evolution of the role of the coal mine geologist and emphasizes the importance of understanding geology with regard to mine management decisions. Using actual mining performance data to determine which geologic factors are the most critical for mining is a powerful tool for making informed mine management decisions. For example, Nelson, Mullennex, and Miller (1988) provide a case study of analyzing the geologic factors impacting productivity of a Kentucky longwall mine to predict future mining conditions for the operation. In that case, the difficult geologic factors for longwall mining were prevalent across much of the remaining permit area and, in response, mine management converted the operation from a longwall operation to a continuous miner (CM) operation to better adapt to the geology. In another example, Keim and Miller (1999) evaluated geologic conditions impacting a West Virginia longwall mine. In both examples, significant geotechnical and geological information was available, including the opportunity to compare predicted mining conditions against actual conditions as mining progressed. Numerous examples of advanced Geologic Hazard Mapping (GHM) methodologies have come from government agencies and academia. For example, development of the Coal Mine Roof Rating (CMRR) system (Molinda and Mark, 1994) provided a standard means for geologists and engineers to communicate quantitatively with regard to mine roof conditions, and the introduction of the Stability Mapping System (SMS) provided an efficient means for analyzing numerous factors affecting coal mine stability (Wang and Heasley, 2005)."

Jan 1, 2019

By P. Rosten

US mine production of iron ore in 1984 showed some improvements compared to 1983. But reduced demand from the iron and steel industry caused temporary shutdowns of many iron ore mines and pelletizing plants. US raw steel production in 1984 was slightly above 1983, but still at a depressed level. Production was 83 Mt (92 million st), compared with 77 Mt (85 million st) in 1983 and 68 Mt (75 million st) in 1982. Two major production trends continued in 1984. They were the increased production from electric furnaces and the growing use of continuous casters. Electric furnace production included 33.2% of the steel poured in 1984, compared with 31.5% in 1983. Continuous casting was used for 39% of 1984 steel production, compared with 32.1% in 1983. Statistical Process Control Statistical Process Control (SPC) has taken on new proportions in the iron ore and steelmaking industries within the last year. This mathematical technique is used to monitor, control, evaluate, and analyze a manufacturing process. The technique charts variability of important quality parameters. Training and adaptation of SPC techniaues for process control have been initiated at Inland, Steel's Minorca, Pickands-Mather's Hibtac, Cleveland-Cliff's Empire and Sherman operations, and at Reserve Mining. One of these operations has requested its bentonite supplier provide SPC charts on quality specifications. Some of the steelmaking operations (Inland Steel, Bethlehem Steel, Dofasco, LTV Steel, National Steel, Stelco, Weirton Steel, and Wheeling-Pittsburgh) have set up SPC programs within their operations. And they also have insisted that some of their suppliers use SPC. Plant Shutdowns The permanent closure of Stelco's Griffith mine at Red Lake, Ontario, has been delayed by one year. This gives employees more time to adjust. The mine is now set to close in April 1986, instead of April 1985. Sidbec (Canadian government) and its other partners (including British Steel Corp., Quebec Cartier Mining, and US Steel) closed its iron mining operations at Gagnon, Quebec. The pellet plant has been leased to Quebec Cartier. New Iron Ore Operations The massive Carajas iron ore project in Brazil is scheduled to come onstream in Jan. 1986. It is to achieve full-scale commercial shipments by July of that year. The 66% iron crude ore requires only crushing and screening before shipment. The product consists of 83% sinter feed and 17% coarse ore. Annual production capacity will be 32 Mt (35 million st) when the project is completed. Principal customer for the ore is Nippon Carajas Iron Ore Co., a consortium of Japanese steel mills. The Arab Iron & Steel Co. (AISCO) has started up a $US300 million, 3.6 Mt/a (4 million stpy) iron ore pelletizing plant built by Kobe Steel Ltd., at Al Hidd-hide in Bahrain. By 1986, this grate-kiln-cooler plant will supply high quality iron ore pellets to feed direct reduction plants in the immediate Gulf area and Far East markets. Iron ore supplied from Brazil, Peru, India, and Mauritania provides the feed to the pellet plant. Hydrated lime (2%) is used as a burden.

Jan 5, 1985

By Clement K. Chase

Since the dawn of cyanidation leaching techniques for precious metals, certain manganese-bearing silver ores have been a problem due to low silver extraction. Since simultaneous occurrence of silver and manganese is common in nature, this situation has made many otherwise attractive silver deposits uneconomic in the past. Several older techniques have been useful but at $1.29 per ounce of silver, the economics were unfavorable. With the new look in silver prices and some improvements in processing technology, neglected silver districts offer new promise.

Jan 1, 1981

By Anthony B. Szwilski, Dalip Sarin, Richard D. Begley

This paper will present the results of an analysis of several abandoned coal mine projects and includes field data for over a dozen different reclamation projects recently completed in the state of West Virginia. The analysis was performed with the objective of summarizing and or classification of the environmental consequences with reference to the characteristics of the mining facilities (surface, underground, etc.). The analysis also addressed the itemized cost of remediation with respect to procedures, environmental concerns and time. The results of the analysis are that each abandoned coal mine site in West Virginia have/had many unique features and in most cases include a combination of environmental concerns that complicate comparisons. The study also revealed that the abandoned mine land program for mines abandoned prior to 1977, that is being financed by a tax on the production of coal, has produced many benefits for the state of West Virginia. This grant program administered by the Office of Surface Mining, has resulted in a high quality methodology of remediation that has been successful for many years in greatly minimizing and/or eliminating environmental concerns from abandoned coal mines.

Feb 24, 1997

By Paul C. Schmall, Lucian P. Spiteri, Arthur B. Corwin

Moving groundwater is generally recognized as the most adversarial condition for ground freezing. Moving groundwater can occur due to natural or man-induced groundwater flow, but either way may result in freeze formation difficulties. History has shown that if the condition goes undetected, catastrophic failure of the frozen shaft or excavation can occur. The success of ground freezing under potentially flowing groundwater conditions depends on an evaluation of the likelihood for this condition; an accurate and early diagnosis, with a careful evaluation of freeze pipe temperatures and piezometer water levels; and timely reaction to mitigate the possible delays. Successful remedial measures have included the reduction of ground permeability by modifying the soil properties between the freeze pipes with various kinds of grouting, or increasing the freezing effect by adding freeze pipes and/or the use of liquid nitrogen as the freezing agent.

Jan 1, 2007

By Y. Q. Zhang, S. S. Peng

Numerical modeling was used to design the pillars and bolting plan for a mine with weak roof and multi-seam stress condition. Previous mining experience, pillar/roof yielding and in-situ horizontal stress were considered in the models. By modeling the upper seam yielding and vertical stress transfer, a multi-seam influence zone was obtained. Appropriate pillar sizes were designed for conditions with and without upper seam stress influences. Roof support for the track and belt entries, using fully-grouted resin bolts and cable bolts, was proposed and implemented in the model. The bolting plan was evaluated under the weak roof condition.

Jan 1, 2004

By J. D. Morgan

Demand for nonfuel minerals depends on the overall state of the economy, which steadily improved each quarter in 1984. New housing starts rose to 1.8 million units. Automakers turned out about 15% more cars (7.8 million) and 30% more trucks (3.1 million) than in 1983. Nevertheless, many domestic mineral operations experienced difficulties in 1984. This resulted from import competition greater use of newer engineered materials, emphasis on multi-unit housing and downsizing of motor vehicles. About 15% of our energy was imported. This in cluded $36 billion worth of crude oil and $22 billion in refined products This added significantly to the overall merchandise trade deficit of $12; billion. On the bright side for mining, coal production rose 14% to 810 Mt (890 mil lion st). Three-fourths o: the coal was burned to generate electricity and more than half of our electricity was derived from coal-burning plants. With the exception of a few large-bulk, low-value raw minerals, most minerals move relatively freely in world trade. The strong dollar encouraged imports and made exporting more difficult. Consequently, our nonfuel minerals trade deficit rose 60% to $19 billion, reflecting imports of $39 billion and exports of $20 billion. There were increased pressures from some major segments of the minerals industry for some form of import protection. But President Reagan said, "Our goal is a system of free and fair trade in goods, services, and capital. We will work toward this goal through both bilateral and multilateral trading agreements." The US minerals industry consists of domestic mines, concentrators, smelters, refineries, mineral manufacturing plants, and recyclers. It also includes many wholly- or partially-owned operations in many parts of the world, providing employment and income for US citizens and others as well. Compared with 1983, the value of US raw nonfuel mineral output rose 8%, to $23 billion. The $253 billion worth of goods processed from this crude mineral output was a 14% increase. Major Metals Raw steel production - a major indicator of both material use and mineral production-rose 10%, to 84 Mt (93 million st). This stimulated a 36% rise in domestic iron ore production, to 52 Mt (57 million st), about 98% pelletized. Iron ore imports rose 44%, to 14 Mt (15 million st). Despite the increase of steel production, output remained well below levels of just a few years ago. For example, 1984 production was still 23% less than in 1981. Raw steelmaking capacity remained steady at 122 Mt (135 million st). The industry continued to cite steel imports as a major reason for low domestic capacity. In December, pacts with seven leading steel exporting nations were announced. This is an effort to reduce import penetration to about 18.5% of the domestic market. Domestic producers of bulk ferroalloys of chromium, manganese, and silicon operated at about 50% capacity. The US mined no manganese or chromium. Only a small quantity of ferronickel was produced from domestic laterite mining in Oregon. Molybdenum production, at 45 kt (49,500 st), rose threefold. Mine shipments of tungsten, another mineral tied to steel

Jan 5, 1985

The prediction and control of ground deformations due to underground mining are important considerations in the permitting, planning, and monitoring of coal mining operations. The prediction of mining-induced ground movements using the influence function method is a mature technology and is widely used in many coal basins around the world. Such movements mainly include subsidence, horizontal displacement, and horizontal and/or ground strain. Predictions can be accomplished using regional subsidence parameters and site-specific data.

Jan 7, 2020

By F. Djahanguiri

The U.S. Bureau of Mines is conducting research on underground stope leaching of metalliferous ores to minimize the environmental impact of ore processing on the surface and to maximize minable reserves. An aspect of this research is to minimize pregnant solution losses and/or groundwater contamination by leach solutions. Bulkhead design and construction are important issues for solution control and stope leaching economics. A reinforced concrete bulkhead was designed, constructed, and tested for solution control in an underground mine near Idaho Springs, CO. This paper presents the bulkhead design methodology and construction procedure.

Jan 1, 1995

By J. Garretson

When mining accidents occur, workers often become trapped and/or incapacitated. Current rescue operations can be dangerous and too slow to produce favorable outcomes. Currently, no method exists for rescue crews to scout ahead at critical times to assess the situation. Sandia National Laboratories (SNL), through a National Institute for Occupational Safety and Health (NIOSH) sponsored program has developed the Gemini-Scout mine rescue platform. The Gemini-Scout was created to assist in underground mine rescue missions. It has been designed to go into potentially hazardous environments to assess the conditions (structural, air quality, temperature). In addition, it will enable two-way communications with potential survivors prior to human rescue teams being able to enter the area. The Gemini platform is a dual tracked-chassis design, which gives the robot excellent mobility in unstructured environments. The design includes a passive 2-degree of freedom joint between two identical bodies allowing for ±30deg of pitch and roll. In addition to the base mobility platform, the Gemini-Scout incorporates many other features to help it succeed in its underground mission. The electronics are mounted in explosion proof housings to ensure safe operations in hazardous gas environments. The platform is also able to operate in up to 18in of standing water with its elevated pan/tilt cameras for navigation. A four-channel video link and Two-way audio on the vehicle help to ensure located survivors can communicate with the robot operators. The platform also incorporates a Mine Safety and Health Administration (MSHA) approved multi-gas sensor to monitor air quality. SNL believes that this technology is broad enough to be appealing to other first responders, such as police, firefighters and medical personnel. Gemini could easily be fitted to handle earthquake and fire scenarios, and it could provide relief in currently inaccessible situations.

Jan 1, 2012

By Andrew K. Simpson

What will this deal do to the company’s stock price? This question arises when a publicly traded mining company is presented with a new mine project, or business combination. The standard tool for addressing this question is to use discounted cash flow analysis, or net asset value(NAV), which is discounted cash flow net of liabilities. Cash flow-based analysis is invaluable for assessing project costs and other impacts on debt service capacity and internal rates of return. But cash flow analysis and NAV do not work very well for stock price analysis.

Jan 1, 2000

By M. Karmis, S. K. Weisiger

The traditional method for training personnel in the mining and other heavy industries has been face-to-face, either via a lecturer in a classroom or through an apprenticeship. With the advent of applications tools such as video, computers, and the Internet, however, a much broader range of training delivery methods is available. Especially exciting are the broad capabilities of multimedia packages that combine the best features of numerous delivery methods. Applying multimedia environments in training holds great potential, especially when there is considerable difficulty in reconstructing real training environments. The authors discuss various delivery methods currently used in training employees, including perceived advantages and disadvantages of those methods. The authors then discuss and evaluate current computer-based training efforts of the mining industry and present an example of a multimedia training tool.

Jan 1, 2001

By James J. Gusek

Passive-treatment systems that mitigate acid-rock drainage (ARD) from coal mines have operating since the mid-1980s. Large systems at metal mines are being contemplated. A 95L/sec (1500-gpm) capacity system is planned this year at an underground lead mine in Missouri. Mine, process and environmental managers need to understand how and why passive-treatment systems work. They must understand what operational limitations to expect, as well as the economics of construction and operation compared to the alternatives, like lime precipitation. Wetlands have been recognized as nature's method of improving water quality. Contaminant reductions can occur through the precipitation of metal hydroxides, sulfides and carbonates and pH adjustments. Local conditions, oxidation state and water and soil chemistries dictate whether these natural reactions will occur under oxidizing (aerobic) or reducing (anaerobic) conditions.

Jan 1, 1995

By M. H. Pelkki, R. J. Sweigard, P. W. Conrad, J. M. Ringe, D. H. Graves

Research has shown that excessive soil compaction is detrimental to the establishment of trees in reclaimed soils. Dry bulk density and penetration resistance are two soil parameters that can be used to indicate the level of compaction in reclaimed soils. It is believed that reclamation practices which minimize soil compaction will produce better results when forestland is the intended post-mining use. The University of Kentucky has developed reforestation test cells on reclaimed soils at a surface mine in eastern Kentucky to test this hypothesis. Each test cell has been planted with various species of trees, and since 1997, data have been collected at these test cells for soil average dry bulk density, average penetration resistance, average depth to refusal, and average survival rate of trees. These data have been correlated to determine the relationship between soil compaction and tree survival rate. It is believed that the two soil compaction parameters may ultimately be used to predict tree survival rates on reclaimed surface mined lands.

Jan 1, 2001