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By P. D. Tomlingson

Senior mining mangers that do not get directly involved in the quality of maintenance performance risk the profitability of their operations. Maintenance is not a stand-alone activity. It requires a production strategy that addresses the total life cycle of equipment from procurement to replacement and assures the fully cooperative, mutually supporting interaction of all mine departments. Only senior managers can assure this happens. This paper examines the strategies, policies and actions required to establish and sustain effective maintenance and the profitability that derives from it.

Jan 1, 2004

By C. D. Hebert, T. Gregor, M. Ghazi, G. J. E. Kramer

This paper describes the recent application of gasketed, precast concrete segmental lining design that has improved tunneling productivity and quality. The speci?c segment arrangement includes: six-piece ring with equal 60 degree gasketed segments, juxtaposed key and counter-key segments, trapezoidal and parallelogram shaped segments, inclined and skewed radial joints and plastic circumferential joint connectors. This allows rapid, but accurate ring erection, reducing mine cycle times. The design avoids cruciform joints, minimizes potential gasket damage and eliminates the need for separate left and right ring molds. The implementation on the Los Angeles ECIS and NEIS sewer projects is described.

Jan 1, 2003

By J. P. Savely

This paper describes the development of a trim blast design to improve the stability of a final pit wall. Description is given of the effects of rock characteristics, rock type, and pit plans on the blast design. Currently, six benches have been mined with trim blasting. A more stable final wall has resulted and the successful program has reduced mining costs over an extended time period. Low-cost blast monitoring and field observation were used to determine peak particle velocity and blast damage. Using criteria developed from this relationship, trim blasts were designed and evaluated.

Jan 1, 1987

By N. M. Grant, W. G. Prast

Jamaica has extensive deposits of marble, gypsum, and limestone, offering prospects for commercial sales to nearby US markets, notably the Gulf Coast and Southeast. Stare-owned and private Jamaican industrial minerals producers have made limited sales to date but expect to increase exports during the balance of the 1980s. Restraints include Jamaican government controls on access to essential foreign exchange for new capital investments and distribution of profits. Jamaican efforts to identify market opportunities in the US are reviewed, and the outlook for further exports of carbonates is discussed.

Jan 1, 1987

By T. L. Myron

In recent years increasing attention has been given to improving both the chemical and physical properties of sinter. The first step toward this goal was the production of a self-fluxing-sinter. More recently, blast-furnace operators have found that significant improvements in blast-furnace performance can be achieved by improving and controlling the physical size of the sinter. The results of full-scale blast-furnace tests have shown that blast-furnace production can be improved by using a closely sized agglomerate. The improvements obtained by the use of pellets, a closely sized agglomerate, are well known. In contrast, blast furnaces charged with sinter having a wide size spectrum have generally not yielded results as satisfactory as those from furnaces 1) * charged with pellets. Beginning in 1958, Appleby-Frodingham charged plus 3/8-inch sinter to their blast furnaces. Further tests by other companies in Canada, 2) the United States, 3) and Australia showed that blast-furnace production could be improved by about one percent when the plus 3/8-inch material in the burden was increased by one percent. Because of the promising results obtained with screened sinter, an extensive test program was initiated to determine an effective means of producing sized sinter in U. S. Steel's sinter plants. This paper describes the work done by the Applied Research Laboratory in this program.

Jan 1, 1965

By William A. Rhoades

INTRODUCTION Ever since miners were faced with the task of moving ore, some form of scraper has been in use. At first, men and beasts of burden supplied the power to move the scraper, and later, machines were developed for this purpose. In the early 1900s, a few mining properties used small pneumatic single-drum winches to pull loaded scrapers to a raise or ore pocket, and the empty scraper then was dragged back to the muck pile by a miner, as shown in Fig. 1. Just prior to 1920, an improvement was introduced, using two single-drum hoists. As illustrated by Fig. 2, the second hoist was used to return the empty scraper to the muck pile. However, this arrangement still re¬quired two men, one operating each hoist. The next developmental step was to eliminate the second man by locating the hoists side-by-side and using one man to control both hoists. As illustrated by Fig. 3, this involved the use of a tail rope over a sheave to pull the scraper back. The greatest progress in development and the great¬est increase in the use of slusher haulers occurred between 1920 and 1930. In 1921, the Sullivan Machinery Co. designed and built the first two-drum scraper oper¬ating on the principle illustrated by Fig. 4. It was powered by a 4.5-kW (6-hp) Turbinair(r) motor and would pull a 450-kg (1000-1b) load at 0.61 m/s (120 fpm). In 1922, this unit was shipped to the Verona Mining Co. of Caspian, MI, and it experienced immediate success in the Lake Superior iron ore district. Since the two-drum slusher was much less expensive and more efficient than hand mucking, the Lake Superior mines were saved from financial disaster when iron-ore prices fell 25% between 1923 and 1925. Immediately there¬after, a demand developed for slushers that would oper¬ate with electric power, which was considerably cheaper than compressed-air power. In 1923, the Sullivan Machinery Co. responded with the first electric-powered double-drum hoist. During subsequent years, design improvements in¬cluded separate tail-drum gearing to increase the tail¬drum speed, as welt as a number of safety features such as rope guides. One result of these improvements and their utilization by the Michigan iron mines was an in¬crease of 100% in the tons of ore per miner per day in those mines between 1924 and 1929. Since the two-drum slusher was capable only of straight-line mucking, it was not a practical machine for use in open stopes. In 1929, the Sullivan Machinery Co. introduced the first three-drum slusher. As illustrated by Fig. 5, two tail drums and one hauling drum were provided. A tail sheave could be placed at each side of the stope, and the ore then could be loaded and hauled to a central point from the entire width of the stope. During the 1930s, progressively larger slushers were demanded. By 1940, two- and three-drum units were available with motor power as high as 45 kW (60 hp), and slusher power continued to increase after 1940. Be¬tween 1951 and 1952, Joy Manufacturing Co. designed a 112-kW (150-hp) two-drum Blusher for the Climax Molydenum Co. Although there has been no demand for a slusher more powerful than this, 150- to 225-kW (200- to 300-hp) slushers are quite feasible at the pres¬ent time. During the last 30 years, many slusher improvements have been made to the operating life, operational safety, and ease of operation and maintenance. Increased tail-drum speeds have decreased overall scraping times. Rope guards, totally enclosed drums, and operator shields have reduced the hazards of injury due to wire¬rope breakage. Improvements in lubrication have made the slushers relatively maintenance-free, with long operating lives. The introduction of spring-actuated drag brakes prevented uncontrolled unreeling of dis¬engaged drums, allowing the development of practical remote-control slusher operation. Remote control now is available in a choice of all-air, all-electric, or air¬electric slushers. APPLICATIONS Quite simply, slushers are used to load and transport material (ore), generally over a short distance of from

Jan 1, 1982

By W. M. Hart, Q. H. Shen, J. S. Chen, S. S. Peng

The automatic data-acquisition systems that are now available can continuously monitor and record changes in leg pressure and changes in advancing ram stroke in every shield. These systems can record shearer position at any moment during a mining operation. The data obtained can be used to improve production and maintenance management and can be used to provide better roof control at the longwall face. Research now being conducted jointly by West Virginia University and Cyprus Amax Coal Co. is aimed at developing a longwall-management system (LMS) for mine operators. The LMS software package, which works in the Microsoft Windows NT environment, performs data interpretation and analysis, production management, maintenance management and ground-control management for longwall mining.

Jan 1, 1997

By Anthony D. Songer, James E. Diekmann, Jarrett E. Carlson

Computer Aided Design (CAD) systems are currently recognized as a necessary tool for the management of projects. Currently, CAD is used for TBM and conveyor setups, concrete lift design and overall constructability reviews. Typically, such CAD models exist only in 2 dimensions. The advent of more powerful computers, enhanced CAD programs and after market animation packages provides tremendous potential to the Tunneling industry. In particular, effective application of these technologies enhances cost, time and quality in field operations.

Jan 1, 1997

By John C. LaScola, Gerald L. Finfinger, Michael A. Trevits

Methane gas is an ever-present problem facing the underground coal mining industry. Mine operators are mandated by law to maintain safe concentrations of methane gas within the mine environment. Ventilation is the method of choice used by all mine operators to reduce gas concentrations. When gas emissions are such that ventilation alone cannot control the gas, methane drainage methods must be applied. In the 1970’s, there was a concern that unprecedented gas emissions would be experienced as mine operators began new developments in the deep and gassy Blue Creek and Pocahontas No. 3 Coalbeds. Such concern was well founded as significant gas volumes are being emitted as these mining operations mature. In 1971, the U.S. Bureau of Mines began to tabulate and track the change in mine emissions. These data were extracted from the underground coal mine quarterly air quality-quantity inspections performed by the Mine Safety and Health Administration. At that time, approximately 6560 Mm3/d (231.7 MMcfd) of gas were emitted from 430 underground coal mines. It was determined however, that the mines emitting less than 2832 m3/d (100 Mcfd) contributed only 2.1 percent of the total daily gas flow. In 1988, underground coal mines emitted 8350 Mm3/d (294.9 MMcfd) from 487 mines. This report evaluates the changing nature of U.S. mine gas emissions over the last 18 years.

Jan 1, 1991

By J. D. Miller, C. L. Lin

As the techniques and resolution for three-dimensional spatial analysis have advanced in the last decade, it is now possible to map in detail the microstructure of multiphase materials in three-dimensional digital space. In this regard, three-dimensional X-ray microtomography offers a unique imaging capability. Spatial resolution on the order of 10 µm can be achieved with the use of microfocus X-ray generators. Recently, a state-of-the-art cone beam X-ray microtomography system was installed at the University of Utah for the quantitative analysis of multiphase materials in three dimensions. This facility was designed to obtain 2,048 by 2,048-pixel reconstruction over a 10-mm diameter, while also allowing for the imaging of somewhat larger (40-mm) objects. The system is capable of handling high-density materials, even materials having a density as high as 8.0 g/cm3. This unique, one-of-a-kind instrument can be used to obtain three-dimensional spatial reconstruction for many applications, such as three-dimensional liberation analysis, pore structure analysis of particle beds during filtration and the air-void system of concrete structures. The utilization of X-ray microtomography not only allows for the quantitative analysis of multiphase systems but also allows, for the textural characterization and determination of phase continuity. This paper presents information regarding the current use of this new facility and a review of potential applications for the advanced analytical system. Key words: Cone beam X-ray microtomography, Three-dimensional analysis, Material characterization

Jan 1, 2003

By D. E. Ranta, G. H. Giroux, A. W. Randall, D. A. Barr

Zinc-lead ores of the Pine Point District, Northwest Territories, Canada, are hosted in paleokarst cavities within a Middle Devonian carbonate barrier complex. Of the nearly 100 deposits found, most are irregularly distributed along two main regional stratigraphically controlled trends. The ores, which occur predominantly as open space filling, form deposits most of which average one million tonnes in size with an average grade of 10% combined zinc plus lead. Geological features related to karsting control not only distribution of deposits but also their shape, size and grade. The higher grade ore in these deposits generally occurs in a relatively small core area. Consequently, accuracy of reserve estimation is dependent on drill-hole density and understanding of karst geometry. Several case examples will be reviewed to demonstrate the relationship between shape, size and grade of deposit, geological reserves and drill-hole density, along with a discussion of geological ore reserve estimation methods.

Jan 1, 1992

By Richard L. Bullock

Drilling of small diameter blast holes in the conventional tunnel driving system or mining operation still consumes a significant part of the time and money required to extend an opening in rock. The use of pneumatic drills for most small hole applications has been the dominant tool used by miners and tunnel men alike throughout the world. But now, a, trend has been started that is showing major inroads into the traditional areas of pneumatics drilling for all types of rocks. Operators dealing in very soft materials, such as coal, salt or potash, traditionally had the option to use hydraulic power for their drilling tools. Twelve to fifteen years ago, drillers in medium hard, but nonabrasive rock extended their drill machine option by helping to develop a drill that still used air to power the hammers, but relied on hydraulic power for the rotational torque and feed thrust. (1) This was a significant step forward, particularly for those who drilled in rocks that were compatible to rotary-percussion bits. However, this application was in fact somewhat limited to the limestone and dolomite formation of mid-United States and the softer sediments in Europe. Now high performance rock drills have been developed, using all-hydraulics for both the hammer and rotation, that have many advantages over the conventional pneumatic systems. In two previous papers on this subject, (2)(3) this author reviewed in detail: 1) the characteristics of each of the manufacturer's products that were on the market; 2) The specific advantages of the all-hydraulic drilling systems; 3) Data from the applications of these drilling systems that was in use; 4) What was needed to further develop this drilling system and utilize its potential in the mining or tunnelling cycle. This paper will attempt to update previous papers, without reiterating many details of drill descriptions or

Jan 1, 1976

By Boleslav Taraba, Antonín Taufer

Thermovision monitoring of surface temperature has been examined for the purpose of detection of spontaneous combustion of early stage. Measurements were carried out in bituminous and subbituminous coal mines. It was found that surface temperature heterogenities can be considered as common phenomenon in mine openings. However, the most of the observed temperature heterogenities were not connected with coal spontaneous combustion of early stage. These, so called [non-spontaneous combustion] temperature heterogenities in surface of mine openings were found to be caused by: l. Different conditions of heat transfer between opening surface and air stream; 2. Low temperature (natural) oxidation of coal; 3. Dissipated heat loses of working machine. Sites of early stage spontaneous combustion of coal were characterized by: 1. More significant, local rise in surface temperature comparing with low temperature coal oxidation; 2. Evolution of carbon monoxide with local concentration near the surface of such site more than about 15 ppm (bituminous coals) or 30 ppm (subbituminous coals). INTRODUCTION Mine fires are a serious hazard to life and result in a considerable loss of coal reserves. Thus, great attention is paid to investigation of new methods enabling already early detection of self-heating of coal. The earlier a fire is observed, the easier would it be to deal with. Detection methods used in coal mines are mainly based on: 1. [Mine air analysis]. Changes in composition of mine air are examined. Products of spontaneous heating of coal, not being present in mine air under normal conditions, are considered as indicators of anomalous behaviour of coal (carbon monoxide, unsaturated hydrocarbons) (Mackenzie-Wood and Strang, 1990). 2. [Temperature measurements]. Sites of higher temperature level comparing surroundings are looking for underground using various direct or indirect methods of temperature measurements. This paper summarizes experience from thermovision monitoring, as one of the latest indirect temperature measurement technique, used for the purpose of early detection of self-heating of coal in mine openings. INFRARED THERMOVISION Infrared thermovision device of AGEMA Infrared systems AB (Sweden) was used for the in situ measurements. The constant value of emissivity factor, 0.95, was pre-set as the most probable level of emissivities of coal and rocks in mine conditions.

Jan 1, 1993

By Robert A. Haney

During the last ten years, longwall mining systems have undergone many changes. Panel widths and lengths have increased. Longwall faces have become more automated. Average production from individual longwall panels has increased from 1,000 to 3,600 tons per shift. To control the dust generation resulting from the higher production, longwall dust control systems have integrated various dust control techniques. Systems designed to control dust generated at the crusher/stageloader, shearer, and supports are common to most longwall faces. A survey was made of the dust controls that are currently in place on all the longwalls in the U.S. This survey addressed the types of controls used to reduce dust generated at the crusher/stageloader, shearer and roof support movement. Additionally, information on face ventilation rates, cutting cycle and level of automation was obtained. The purpose of this paper is to review the dust control practices that have been implemented throughout the United States and to identify those controls that are being used on high production longwall faces. Additionally, a model is used to demonstrate how ventilation and automation affect occupational exposure. Automation of roof support movement can offer some of the greatest reductions in occupational dust exposures. While technically feasible, its full benefit has not been fully realized by the industry. Until technology to fully automate longwall mining systems becomes more reliable, future dust control systems must rely on increased ventilation, application of headgate dust collectors, improved shearer dust controls and improved shield dust suppression systems.

Jan 1, 1995

By H. J. Chen, Y. Luo, S. S. Peng

Surface subsidence resulting from underground coal mining can cause problems for buried pipelines. In this paper, a technique for assessing the level of stress on a subsidence-affected pipeline is introduced. The main contributors to the stress are identified, and mitigation techniques for reducing the stress are proposed. The proposed mitigation techniques were then successfully tested.

Jan 1, 1998

By Debbie Nakamura, Daniel Tempelis, John E. Shamma

The Metropolitan Water District of Southern California established a Board of Consultants to assist them in administering the design and construction of the Inland Feeder Program tunnels. The Board acts as an expert review body for the owner, looking at key issues that can potentially impact the success of the program. The use of the Board evolved over the life of the project, and its composition was modified to better address the needs of the owner, and the Program requirements. The experience, function, and value of such a board is analyzed and discussed in this paper.

Jan 1, 2003

By P. Tsang, S. S. Peng

The stability of longwall chain pillars depends not only on the mechanical properties of the coal and surrounding rocks but also on geological and mining conditions. To evaluate the effects of each variable, orthogonal experimental design was employed in a significance analysis. The study concluded that the stability of longwall chain pillars is mainly controlled by the ratio of pillar stress to pillar strength, the ratio of the Young's moduli of roof to coal and floor to coal, entry width, pillar width and the internal friction angle of coal. Additionally, horizontal stress, panel width and mining height also play a significant role.

Jan 1, 1996

By Lee W. Abramson, Mee Shing Owyang

The Lake Merced Transport tunnel is 18 feet in diameter and 1.6 miles long constructed within dune sands, beach sands, and the Colma Sand Formation. It runs beneath highway right-of-way from an existing pump station near the shore of Lake Merced to a point near the Pacific Ocean, where it will connect with the existing transport/storage tunnel. The final tunnel lining was originally designed as a cast-in-place concrete lining to be constructed within steel ribs and wooden lagging initial support. The contractor opted to use a precast concrete segmental initial lining thus requiring a redesign of the final lining. The redesigned lining incorporates composite action from the initial lining thereby eliminating the need for outer steel reinforcement. A computer model was used for analyses which included operating conditions, ground and construction loads, and possible effects of liquefaction and earthquakes.

Jan 1, 1993

By C. Stephan, E. Weiss, J. Trackemas, M. Sapko

The National Institute for Occupational Safety and Health (NIOSH), Pittsburgh Research Laboratory (PRL), in collaboration with the Mine Safety and Health Administration (MSHA), the mining industry, and seal manufacturers recently conducted a series of full-scale experiments within the underground experimental mine at PRL’s Lake Lynn Laboratory. The purpose of the experiments was to evaluate the explosion-resistant characteristics of several new seal designs for rapid deployment during mine emergencies. These seals can be deployed in 6 to 10 hr and are capable of withstanding explosion overpressures in excess of 140 kPa (20 psi). These novel seal designs use available mine materials, do not require conventional rib hitching, and, most importantly, can substantially reduce exposure time for coal miners during sealing and mine recovery operations.

Jan 1, 2003

By Yehia El-Ibiary, M. P. Evans

One way of increasing conveyor systems productivity is by monitoring the key parameters in the systems. In this paper, a new line of smart bearings will be presented and discussed. The new bearings are capable of monitoring temperature, vibrations, and belt speed for early detection of potentially serious problems. The new smart bearings have built in sensors that are carefully integrated and protected for long life service. These bearings are going to be the key to increasing the up time of belt conveyors in the future.

Jan 1, 1996