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By Bruce W. Cavender

During the last few years, the minerals industry has been confronted by increasingly stringent environmental regulations that are significantly altering the economics of the industry. Heightened media attention, threats of litigation and decreasing support by the general public have exacerbated the industry's difficulties. Regardless of their merit, environmental issues present a serious threat to the continued viability of mining companies. Firms have reacted to these regulations by escalating their environmental activities to meet the new requirements. They have simultaneously adjusted their corporate schedules to reflect the substantially longer time periods required to obtain construction and operating permits and ensure compliance with legal requirements before mine abandonment. Companies have also been forced to adapt to a considerably greater amount of uncertainty and expense associated with the development of mineral projects. This has resulted in a significant erosion of the profitability of some mining companies. Most of the changes in corporate environmental activities have been reactive. Pending regulations present formidable but uncertain technical requirements for compliance, and future regulatory developments are difficult to predict. This problem is aggravated by depressed market prices for many mineral commodities. Past expansions of environmental standards have led to the closure of mines and processing facilities due to economic hardship, as occurred in the smelting segment of the US copper industry in the 1980s (Cro¬zier, 1992).

Jan 1, 1994

By C. L. Schaidle

Computers and communications technology have revolutionized many industries. In earthmoving, this revolution has just begun. The major changes are still to come but are just around the corner. This article presents a vision of this upcoming revolution in the earthmoving industry. This vision includes basic communication, machine monitoring and diagnostics, job and business management, planning and operations, and machine control. For the industry to realize maximum benefits from the information age, it must have a vision of the future that is shared by technologists, machinery producers and miners. History of the information age During the 1970s, the information age revolutionized retailing, starting with the grocery business. By using bar codes and laser scanners, individual items were connected to the information world of computers and communications. Once this connection was made, the data on what an item was and where and when it moved became valuable information for inventory control and marketing. Not only was the information valuable, it was easy and inexpensive to collect and manipulate. The effort required to provide the consumer with the right product at the right time was reduced. Costs went down and customer satisfaction went up. But there were casualties of this revolution. Many inventory counters lost their jobs. There were also equipment casualties. Cash registers that could not interface with the digital world were discarded long before the end of their useful life.

Jan 1, 1994

By Pierre M. Matheron

TRANSMANCHE-LINK is responsible for designing, developing and implementing the project for a fixed link under the English Channel, comprising two running tunnels of diameter 7.6 metres and a service tunnel of diameter 4.8 metres. The three tunnels will all be 50 km long, with 37 km bored through chalk marl at a depth of 40 metres under the sea bed. The tunnels will be driven from both sides of the channel from intermediate addits above the coastline on either side with a 55 m access shaft at Sangatte in France and two "descenderies" or inclined tunnels addits and a shaft at Shakespeare Cliff on the English side. A total of eleven tunnel boring machines will drive the 150 km of tunnels. The major part of the tunnel linings will be built of precast reinforced concrete segments, and two plants have been specially built to produce the necessary 725,000 segments. Seven million cubic metres will be evacuated on wagons along the tunnels and then lifted by belt conveyor on the English side, and by hydraulic mucking from the bottom on the French side. Preliminary work started early in 1987 with manufacture of the first boring machines, construction of five precasting plants, boring of the Sangatte shaft in preparation of the Shakespeare Cliff entrances. The principal project dates are :

Jan 1, 1987

In conjunction with steady increases in production levels, long-wall operators have applied greater quantities of ventilating air to control respirable dust and methane gas. As a result, air velocities greater than 7.6 m/s (1500 fpm) have been measured on longwall faces. Operators have expressed concern over the potential entrainment of respirable dust at these high-velocities, especially during shield advance as dust falls from the shield canopy directly into theair stream. Laboratory tests to simulate dust liberation by shield movement were conducted at the Pittsburgh Research Laboratory of NIOSH in a wind tunnel designed to study dust entrainment in high-velocity airstreams. Dust was introduced into the tunnel to determine dust concentration as it relates to entrainment, dilution, air velocity, and particle adhesion. Airborne dust samples were obtained by iso-kinetic sampling using BGI cyclones to quantify respirable dust concentration at the various air velocities. Laboratory tests were con-ducted at velocities ranging from 2.0 to 10.1 m/s (400 to 2000 fpm),and significant differences in airborne respirable dust levels were measured. This research is being conducted to provide fundamental information on the entrainment characteristics of respirable dust at high air velocities, which will subsequently lead to solutions for shield dust control. A discussion of the test procedures and results are presented.

Jan 1, 2004

By Osvaldo Bascur, Laurent Garrigues, Nouna Kettaneh, Svante Wold

The chemical, oil, semiconductor, mining, and paper and pulp industries, as well as most other modern industries, are rapidly expanding the range of measurements used to characterize raw materials, process steps, intermediates, and final products. In addition, process variables such as temperature, pressure, and flow become more and more numerous, providing extra information on the state of the process. However, no matter how many sensors are added, the underlying sources of variations that drive the process behavior remain constant. On the other hand, the measuring frequency of these data has increased from once a day or once an hour to once, ten, or even hundred times a minute. This gives masses of data that are swelling in both directions (more variables and more observations). These data need to be properly stored, managed, and analyzed to provide diagnostics about the state of the process as well as an understanding of the relationships between different parts of the process and the product properties. Projection methods such as PCA (principal components analysis) and PLS (projection to latent structures) compress process data to informative summaries of the original variables. These can be shown on line, providing an efficient, graphically oriented suite of diagnostics regarding the "health" and performance of the process. The power of these methods is illustrated by two examples of industrial data in the mining industry.

Jan 1, 2000

By W. A. Heitbrink, M. Schmitz, J. A. Organiscak, A. B. Cecala, E. Ahrenholtz

Mobile excavation equipment operators at surface mines generally have the highest exposure to airborne respirable silica dust. Operator cabs on newer equipment are usually enclosed and equipped with heating and air conditioning systems. Many newer cabs are also equipped with air filtration systems. However, some newer cabs and many older cabs have either inefficient or no air filtration systems. The U. S. surface mining industry is still populated with older equipment and many of these have cabs that provide little or no respirable silica dust protection. Collaborative field studies were conducted as part of a partnership involving NIOSH, Clean Air Filter®, Red Dot, MSHA, and several mine operators to demonstrate that effective dust protection can be provided by these cabs at a nominal cost to mine operators. This effort encompassed adding an external make-up air fan and filter system to a retrofitted roof-mounted heating and air conditioning system in three older equipment cabs, and attempting to seal the cab enclosures to achieve interior cab pressurization. Abetter than 90 percent dust reduction was measured inside two of the three enclosed equipment cabs. It was possible to achieve positive cab pressurization inside these two cabs. A less significant dust reduction was measured inside the third cab, where positive pressurization was not achieved. These field studies demonstrate the key elements needed to improve enclosed cab dust protection in a cost-effective manner.

Jan 1, 2003

By Isabel F. Barton, Eytan Bos Orent, Mark D. Barton

A new examination of tabular uranium (U)-vanadium (V) deposits within the La Sal district places mineralization in the context of the complex fluid flow history that has occurred in the Paradox Basin and Colorado Plateau. As the only currently producing district of this deposit type in the region, the La Sal district provides excellent opportunities to study deposit- and district-scale features that can serve as exploration guides where exposure is limited. The absence of major structures along a narrow and elongate mineral trend that runs E-W across the southern part of the Utah-Colorado border indicates a regional lithologic control. The trend was likely influenced by Jurassic drainage patterns, as indicated by paleocurrent directions shown in Fig. 1. Fluvial sandstone host rocks in the Jurassic Morrison Formation contain significant evidence of multiple superimposed fluid systems that have progressively changed local mineralogy. Apart from the presence of ore minerals, remnants of fluid systems are preserved as cements including quartz overgrowths, compositionally distinct carbonates, and sheet silicates. New geochronology methods provide constraints on the timing of initial mineralization and later remobilization. U-Pb ages of calcite associated with ore minerals provide evidence for Early Cretaceous mineralization, whereas textures and K-Ar ages show that early-formed V-minerals were replaced at the expense of V-bearing micas and clays during the Eocene. The paragenesis of minerals in U(-V) deposits of the La Sal district reflects the complexity of a sedimentary

Feb 1, 2025

By Donald C. Moore

Introduction Asamera Minerals (US) Inc. and its joint venture partner, Breakwater Resources Ltd., discovered ore grade gold mineralization on their 20 km2 (5000 acre) Wenatchee, WA land position in February 1983. Due to the high grade nature of the discovery ore and the known reserves of ore in the "B Reef' and "B West" zones previously outlined by other companies, a decision was made to construct a mine/mill operation near the known ore occurrences. Further drilling in the discovery area quickly expanded known gold occurrences to more than 3.6 Mt (4 million st) with tentative in-place ore grade of 7 g/t (0.25 oz per st) and minor silver values. Based on existing knowledge of the ore body and the rapidly increasing ore reserve, a decision to build a 1.8-kt/d (2000-stpd) mine and mill complex was made in the second quarter of 1983. A schedule was devised to begin immediate mine development, shaft sinking, environmental and land use permitting, and mill and tailings dam construction (Fig. 1). Meeting the scheduled startup date, April 1, 1985, required a fast track schedule in all areas. To this end, Asamera purchased the Oracle Ridge Partners concentrator. This was an assemblage of new equipment designed for use as a copper concentrator in southern Arizona. The purchase contained all of the major mineral dressing equipment - crushers, screens, rod and ball mills, etc. and an engineering package. It did not include most of the other required items, such as buildings, conveyors, pipelines, tanks, and pumps. At the same time, core samples were sent to two independent process development laboratories for initial flowsheet development. Due to the refractory nature of the carbonaceous ore, cyanide leaching was not feasible. Flotation was selected as the concentration process. Further testing showed that autoclaving of the flotation concentrate followed by cyanidation would result in overall recovery of about 85% gold. A mine manager was hired to begin assembling an operations staff, hire an environmental consulting firm, and begin mine development. Environmental and land use concerns were major obstacles due to the mine's close proximity to a city of 20,000 people. These concerns had to be rapidly defined so as to mitigate any adverse impacts from and mining processing operations. Baseline data dealing with weather, air and water quality, and sound were measured before start of mine construction. Concentrator and flowsheet development remained static until October 1983 while definition drilling and mine development proceeded. In late October, a process engineer was hired to coordinate development of a process flowsheet, purchase the remainder of the concentrator equipment, prepare a concentrator construction contract, finalize concentrator detail engineering, and combine environmental and process requirements with a tailings dam design. Process development There were only 17 months remaining to mill start up from the hiring date of the process engineer. Therefore, the process flowsheet had to be finalized rapidly. To accomplish this, samples of drill core from the highest grade (and therefore potentially the most commercial) ore zones were sent to an outside metallurgical laboratory to confirm beneficiation tests on the flotation process. Test results again showed that flotation would provide about an 86% gold recovery. Therefore, all further testing was concentrated on flotation and autoclave/cyanidation of flotation concentrates. Focusing on a well known process such as flotation was important in accomplishing the rapid design and construction of the concentrator. If, during these next phases, we were continually changing design concepts, layout, and process flow, the mill startup would have been delayed many months. Once a process flowsheet is selected the process engineer must obtain the process criteria needed to design the beneficiation system. For example, it was known in early December that the Oracle Ridge rod and ball mills were too small to grind 1.8 kt/d (2000 stpd) of Wenatchee ore. A decision had to be made to purchase a large, used ball mill and convert the Oracle Ridge ball mill to a rod mill. The process engineer must be cognizant of the process criteria needed to size and select equipment. If not, the process engineer must use the professional services of the equipment manufacturing companies to review the requirements that the equipment is asked to perform. For the Wenatchee system, this resulted in the adaptation of a ball mill to a rod mill with a weight limit of grinding rods to protect the mill bearings and drive trains. When a decision is required, the process engineer has to present the facts and options in a manner that allows a rapid decision. This information must include costs, equipment availability, and effect on the construction schedule. At the Cannon mine, there were process development details that resulted in decisions similar to the ball mill purchase. These included an increased flotation residence time from eight to 25 minutes, an increased thickener area requirement, a high pressure tailings pumping system, and area constraints in plant layout. All of these decisions had to be timely and required assistance from manufacturers' service engineers, and knowledge of the alternate costs and effects on construction completion. Equipment procurement It was decided in early 1983 to build the ore milling facility with Oracle Ridge equipment, augmenting it with used equipment

Jan 2, 1989

By Mark Godfrey, Wickus Slabbert, Debra Miller, Dave Dew

Sao Bento Mlnerai;;ao Mine (SBM), located 100 kms northwest of Belo Horlzante, Brazil, was commissioned In 1987t1l to produce 185 kg per month of gold from 240 tpd of refractory sulphide flotation concentrate. The concentrate Is processed by a Sherrill Gordon design pressure oxidation circuit followed by conventional CIL gold recovery process (Flgur .. J). The original plant design foresaw expansion to 480 tpd, and In this regard the acidic effluent neutralisation, CIL and carbon circuits were designed for future expansion to treat the higher tonnage. The pressure oxidation section was sized for 240 tpd with the Intention to double the Installed plant equipment to provide 480 tpd capacity when required. This decision was based In part on the novelty of pressure oxidation to treat refractory sulphide concentrates in 1984 when the process design was finalised. General Mining, Metals & Minerals (Pty) Ltd (GENMIN), has been actively Involved for the past 30 years in the development of bacterial process for the oxidation of refractory gold concentrates; the results of this development program have provided the registered process BIOx®. The successful Implementation of BIOx® technology for treatment of refractory gold concentrates at GENMIN's Fairview Mine In October 1986t2l, as well as the substantial experience accumulated in laboratory and pilot testing of some 40 other sulphide concentrates, Justified reconsideration of the oxidation process best suited to provide the Incremental sulphide oxidation capacity planned for SBM.

Jan 1, 1992

By Abbas Zaidi, Betty L. W. Ou

Wastewaters generated during the extraction of gold from the ore can contain a variety of contaminants such as cyanide, heavy metals and arsenic. Proper management of these wastewaters is therefore necessary to minimize the negative impact of gold mining and milling operations on the environment. The Wastewater Technology Centre (WTC),located in Burlington, Ontario, Canada, has been involved in several studies related to the evaluation of various effluent treatment technologies which are relevant to the treatment and proper management of gold mill effluents. These studies have included bench and pilot scale tests, and the evaluation offull-scale systems. Furthermore, the WTC staff developed protocols for cyanide analysis in gold mill effluents, and a mathematical model for predicting the degradation of cyanide in tailings ponds. The information generated by the WTC staff has been referenced in several reports and papers published over the last ten years (Schmidt et.al. 1982, Simovic & Snodgrass 1989, Whittle et.al. 1989, Zaidi et.al. 1989, Zaidi et.al. 1991). Recently, the WTC has started to develop a micro­computer based expert system for use by decision makers in the gold mining industry and relevant government agencies who are involved in process design, process evaluation, costing, evaluation of the best practicable technology, approval of suggested effluent management systems, and so on. This paper presents some relevant background information and a discussion of the latest version of the expert system being developed by the WTC.

Jan 1, 1992

By Bruno Sceresini

Prospectors and small scale mmmg companies have long expressed the wish for a highly mobile mineral processing plant. This is especially so in the case of gold mining as relatively small deposits can be highly profitable due to the relative ease of producing a marketable product when compared with the refming and marketing costs incurred with base metals. This paper will concentrate on gold ore treatment in fitting with the theme of the 1996 Randol Gold Forum but the principles may also be applied to base metal ores. The development and application of the Atomaer Filblast Gas Shear Reactor as a cyanidation tool has removed the con­straints of plant size in pulp cyanidation applications. KC Dodd and Associates, Consulting Engineers and Australian Mining Advisers, Pty Ltd, have designed a 1,000,000 and a 250,000 tpa fully modularised ore treatment plant. Various module configu­rations can be arranged to treat a wide variety of ores ranging from simple gold ores to gold-copper and base metal ores. This paper will limit the discussion to comparing the capital and operating costs of a conventional and a modularised 1 million tpa gold treatment employing a number ofnovel concepts which complement the compact, high capacity Filblast Cyanidation Process and the AARL pump Cell Adsorbers. The design described in the paper not only reduces equip­ment sizes and allows for rapid deployment of a sizeable capac­ity plant but also offers significant capital and operating cost benefits.

Jan 1, 1996

By G. Deschenes, P. J. H. Prud'homme

A laboratory study was carried out to evaluate the effect of oxygen and lead nitrate on the recovery of gold by cyanidation of a free milling gold ore, which contains 0.4 % copper as chalcopyrite. Efficient gold extraction is achieved only under specific conditions. The recovery of gold was increased from less than 90% to up to 98% by addition of lead nitrate. In the pre-leaching, the kinetics of oxidation of soluble sulphides are not an accurate indication for the length of the treatment. Even though the consumption of cyanide was reduced due to the inhibition of the dissolution of chalcopyrite by increasing additions of lead nitrate, cyanide consumption had to the held above 1.85 kg/t to maintain good recovery of gold. The continued addition of lead nitrate above 300 git had no impact on the recovery of gold. It was also found that the addition of lead nitrate at the start of cyanidation gave the same performance as when added during pre-leaching. The addition of oxygen increased the recovery of gold by 1.5%. The concentration ofNaCN had to be maintained in the range of700 mg/L because of the high concentration of copper in solution. The recovery of gold dropped significantly when the average NaCN concentration fell below 640 mg/L. Application of the findings of the laboratory study at the industrial scale led to improved plant performance.

Jan 1, 1997

By I. S. Parrish

Reserve audits have increased in recent years as more companies, especially juniors, enter the ranks of producers. Corporate and individual investors are seeking corroboration of stated reserves. The reserve audit satisfies this need. An audit assures investors that the reserves, as presented, are a reasonable and accurate approximation of the quantity and grade of the economically viable material present. The reserve audit verifies that there are no fundamental errors in logic, style or the data base, and that the reserves, as given, may be used for mine planning or economic forecasting. Reserves that pass an audit may be used with confidence in preparing cash flow projections and in deriving net present value or internal rate of return on any given project. This article describes what a consultant does while performing the reserve audit. In performing an audit there are four general areas of concern that must be checked: definitions, parameters, data and procedures. In each of these, the auditor must convince himself that the reserve study has complied with governmental regulations and guidelines, professional standards and industrial practices. Any deviation from these norms must be identified and its effect upon the appropriateness of the reserves evaluated. By concluding that a reserve study passes his audit, the reviewer is stating that there are no fundamental errors in logic or style and that spot checks have revealed no substantive errors in procedure or mechanics. The responsibility for the reserves remains with the entity that compiled the original study.

Jan 1, 1990

By Rolf Lange

Introduction The Harzwasserwerke, a public body of the Federal State of Lower Saxony, supplies drinking water to an area bordered by Braunschweig, Bremen, the Northern and the Western edges of the Harz-Mountains. From the very beginning in 1928, the Harzwasserwerke have been systematically constructing reservoirs in the western Harz which have the function of collecting and storing the frequently occuring flood waters as well as providing drinking water. The Grane-Reservoir with a capacity of 45 Million cu.m., the last of the big reservoirs, was built in 1968-1970. A system of connecting tunnels effectively enlarges the natural catchment area of this reservoir and the surplus waters of the Oker and Radau valleys - where floods occur particularly during the spring - are being conducted to the reservoir. By building the 4.800 m long "Radau-Tunnel", the waters of the Radau valley will now also be used more efficiently and its surplus waters will pass to the Grane Reservoir via this new tunnel and the Oker-Grane-Tunnel which was finished in 1970. The Project The Radaustollen has been planned and put out to tender by the Harzwasserwerke as a conventional "Freispiegelstollen". The horseshoe profile has a cross-section of 8 m2. Lining was required only in disturbed rock areas; lining of the whole tunnel was not necessary. The gradient of the tunnel is 4 % 0 rising = 25 m over the total length of 4.800 m.

Jan 1, 1979

By M. K. Gangal, E. D. Dainty

The CANMET diesel-related work, carried out in cooperation with the Canadian mining industry, resulted in the identification of several useful R/D studies. One such study was the development of a dash-mounted alarm signal system to indicate overexposure of production LHD diesel vehicle operators to toxic contaminants in a mine environment. The resulting instrument has been called the [CO2 Exposure Meter]. This meter is particularly applicable to LHD machines because previous investigations have indicated that operators of LHDs and some haulage truck drivers are exposed to up to 200% of the contaminant concentrations measured in the general mine return air. This paper describes the development of the system which continuously monitors and displays the operator's exposure to diesel pollutants, and indicates an overexposure by an alarm light. The overexposure limits are preset by mine personnel based on carbon dioxide (CO2) measurements, which in turn are related to simultaneous spot respirable combustible dust (RCD) measurements (or to Air Quality Indices - AQI, if available). The CO2 settings are, in general, related to the engine/exhaust treatment selections, vehicle duty cycle and local ventilation rates and efficiency. The system continuously displays one of three lights: green for underexposure, yellow for caution, and red for overexposure. Overexposure can occur for several reasons, such as: reduced ventilation, malfunction of the diesel vehicle, and excessive airborne contaminants. The paper confirms satisfactory operation of the system in a laboratory-simulated mine environment, as well as in field trials.

Jan 1, 1993

By D. J. McCracken

The lithium review did not arrive in time for publication in the June issue The estimated consumption of lithium minerals as raw materials to the glass, ceramic and metallurgical industries in 1992 was 85.5 kt (94,200 st). That equates to about 12 kt (13,200 st) of lithium carbonate equivalent (LCE). An additional 150 kt to 200 kt (165,000 to 220,000 st), or 7.5 kt to 10 kt (8200 to 1100 st LCE), were used in the production of lithium chemicals. The 1992 consumption represents an overall decrease of 3.5 kt (3800 st), or 500 t (550 st) LCE, from 1991. This was a direct result of a worldwide reduction in glass demand due to the economic recession. There are three major producers of lithium minerals. Gwalia Consolidated Ltd. (formerly Lithium Australia Ltd.) in Western Australia and Tantalum Mining Corp. (Tanco) in Manitoba, Canada, both produce spodumene ore. Bikita Minerals, in Zimbabwe, is the largest producer of petalite. Bikita also has the capacity to produce small volumes of spodumene concentrate. The Cyprus Foote spodumene operation at Kings Mountain, NC, ceased production in 1992. It once produced about 2 kt/a (2200 stpy) of "high iron spodumene" for uses other than in the manufacture of lithium chemicals. The lithium products of the major producers are shown in Table 1. The current resources of 13 Mt (14.3 million st) of LCE in the western world will supply demand for more than 50 years.

Jan 1, 1993

By F. Lincoln & B. Rodier, G. Poniatowski, N. Kawashima, T. J. White, J. H. Kyle, G. F. Eaton

The history of Australia is a narrative of the discovery and development of its mineral wealth. The gold strike at Ballarat, Victoria, in 1851 transformed the colony by triggering the first great influx of migrants to Australia, and the development of subsequent mineral discoveries lead to a vast resource industry. However, beneficiation of base and precious metal ores carried with it an environmental penalty, not addressed until the last quarter of this century. In particular, the extensive deposits of gold, silver, lead, copper and zinc reside in sulphurous ores which often contain arsenic, antimony and mercury as significant contaminants that are released as unwanted by-products during smelting and refining. Until recently, these toxic concentrates were discharged to the atmosphere or receiving waters, collected in tailings ponds close to the smelters, or dumped at sea. Although such procedures . were acceptable in the past, more stringent environmental controls have required a re-examination of these practices and encouraged intensive efforts to develop enduring solutions to the disposal of these wastes. From this research has emerged a promising new generic technology called Xtaltite (pronounced crystal-tight). In this approach, geochemical principles are employed, first, to reduce the toxicity of heavy metals to low levels, and second, to identify and engineer suitable repositories for the permanent disposal of the consolidated waste form. In this paper, we emphasise the application of Xtaltite to the disposal of arsenious smelter fumes derived from gold winning. The principles ofXtaltite will be described and its technical and economic performance compared with conventional technolo­gies.

Jan 1, 1995

By G. E. McCormack

The Development of Water Gel Explosives Water gels are the most recent development in the evolution of commercial explosives. They are replacing dynamite, having proven themselves to be excellent alternatives to this standard explosive. Water gels have steadily displaced dynamite over the past two decades. In 1959, they accounted for only 1 percent of the market they share with dynamite. By 1965, the share taken by water gels had grown to 21 percent. In 1970, it was more than 40 percent, and today it is nearly 70 percent. Black powder, the first widely used explosive, revolutionized mining and quarrying in its day. However, when nitroglycerin dynamite became available about a century ago, it rapidly displaced black powder because it provided greater energy for a given weight, much higher velocity for better rock shattering performance, and water resistance for easy use in wet conditions. During the past 50 years, ammonium nitrate has played a dramatically increasing role in explosives. First, it was used as an ingredient in dynamite, and then as the main component in nitrocarbonitrate blasting agents. About a quarter of a century ago, it began to find use in a simple and inexpensive mixture with fuel oil that has revolutionized the explosives industry and today fills about 80 percent of the requirements for explosives in the U.S., and certainly the bulk of blasting requirements worldwide. Water gels and dynamites share the remaining 20 percent. Water gel explosives based on ammonium nitrate have also been developed during the past quarter century. These explosives contain

Jan 1, 1979

By James W. Martin, Robert R. Faddick

INTRODUCTION Virtually every sector of society in our country feels the impact of tunnels, either through the transportation of water, commodities, or people. The economic implications are staggering. The Committee on Rapid Excavation (1) reported that during the near future, 1968-1975, underground excavation activity will comprise 946 miles of tunnels (subways: 85 miles; underground urban highways: 123 miles; intercity highway tunnels: 210 miles; water supply tunnels: 528 miles) and 5,119 million tons of crude ore; metals: 874 million tons; nonmetals: 899 million tons; and coal: 3,346 million tons. It is estimated that the cumulative demand for underground excavation in the decade 1970-1979 will be 13 billion dollars for construction-oriented demand and 16 billion dollars for mining-oriented demand. The respective figures for the decade 1980-1989 are estimated at 22 billion dollars and 18 billion dollars. Of the many advantages claimed for tunnels (2, 3, 4, 5) the environmental considerations are becoming increasingly important. Transportation tunnels particularly for rapid transit systems, offer reductions in noise pollution and air pollution while improving aesthetics and optimizing land use (fewer problems of right-of-way and disruption of utilities). Considerable interest has been shown recently in sub-surface construction and mining (6, 7, 8). Recognizing the future demands for tunnels has led to considerable study of methods to improve rates of tunnel advance per day, safety, and the overall economics. The search for higher rates of advance has Led away from what has heap termed conventional methods (drilling

Jan 1, 1974

By R. H. Grau

This Bureau of Mines report describes methane liberation trends from all U.S. coal mines liberating over 100 Mcfd (100,000 cfd) (2.8 Mm3/d). Detailed are results from the latest Bureau survey performed in 1985 and shown are mine and company name, location, coalbed and methane liberation quantity. The report shows that in 1985, there were 180 mines producing more than 100 Mcfd (2.8 Mm3/d) and the total quantity of methane liberated by these mines was 303,900 Mcfd (8,605 Mm3/d). This data is compared with previous studies performed in 1971 , 1973, 1975, and 1980. From 1971 to 1985, there was a 10% decrease in the number of mines liberating at least 100 Mcfd (2.8 Mm3/d) but there was a dramatic 34% increase of liberations from these mines. The increase seems to be caused by new mines being developed in deeper, gassier coalbeds, particularly in Alabama. Likewise, in comparing the ten highest liberating mines in 1975, 1980, and 1985, an increase in methane liberations each year was experienced. The report classifies mines by three levels of liberations: greater than 100 Mcfd but less than 500 Mcfd (2.8 to 14 Mm3/d); 500 Mcfd to 1 ,000 Mcfd (1 4 to 28 Mm3/d); and greater than 1,000 Mcfd (>28 Mm3/d). It was found that 87% of liberations were from mines producing over 1,000 Mcfd but these accounted for only 38% of all the mines in the study.

Jan 1, 1987