Search Documents

By E. Cameron

Yeelirrie lies toward the center of Western Australia, 650 km (404 miles) northeast of Perth (Fig. 1). The ore reserves have been estimated as 52.5 kt (57,871 tons) of contained U3O8, at an average grade of 0.15%, of which almost two-thirds average 0.24% U3O8. the ore body is a thin, elliptical, more or less horizontal sheet measuring approximately 9 km (5.6 miles) in length, between 0.5 and 1.5 km (0.3 and 0.9 miles) in width, and up to 7 m (23 ft) in thickness, extending from the surface to a depth of 8 m (26 ft). In spite of its near surface position, there is only one small outcrop of significant mineralization. Carnotite is the only uranium mineral recognized so far, dispersed through a calcrete horizon, and deposited from circulating ground water which was also responsible for the carbonation of the clays completely filling an Early Tertiary drainage system. Calcrete, as seen at Yeelirrie, is quite distinct from the widespread, thin pedogenic horizons, as it often forms bodies many kilometers in length and up to 20 m (65.6 ft) in thickness, elongated parallel to the drainage lines. It is variously referred to as "valley calcrete" or "ground water calcrete" to emphasize the occurrence and mode of origin. The discovery of Yeelirrie in mid-1971 was the successful culmination of a grass-roots exploration program initiated in 1968 as part of Western Mining Cop's program of diversification from its historical position as a major gold producer. The object was simply to find an economic uranium deposit - with no constaints other than those normally taken as applying in the mineral search. There was, therefore, complete freedom in the selection of the exploration model, or models, to be applied and the areas to be considered, though the choice was inevitably influenced by both the nature of world occurrences and the local geology. One of the options avail- able was the sandstone environment. Yeelirrie was the direct result of pursuing this line of investigation through three sequential, but quite distinct, stages: first, a regional study; second, establishing a case for exploring the inland drainage systems of Western Australia; and finally, an evaluation of the calcrete environment. An assessment of the potential for sandstone-type deposits in Australia necessitated going back to first principles, since there were no known precedents in this country for guiding exploration and, as a consequence, the search need not be influenced by established prejudices. Previous uranium exploration during the 1950s had been preoccupied with vein-type deposits, and, although the sandstone environment was undoubtedly being examined in 1968, no discoveries had been announced to that time. When considering the necessary ingredients -a source of leachable uranium, a circulating ground water system, and a suitable reducing environment - it could be argued that considerable areas in the eastern part of the continent were theoretically prospective, but basin depth and the extensive superficial cover of Mesozoic and Cainozoic sediments presented considerable practical difficulties.

Jan 1, 1991

By H. Sevim

In this paper, the research effort in simulating the operation of underground coarse-coal hydrotransport systems (UCCHS) is summarized. The equipment of the system to be simulated is already optimally selected by using an analytical optimization model. The purpose of the simulation model is to test the performance of the system and to obtain the distribution of the operating parameters such as water and power consumption, amount of slurry delivered to the preparation plant, etc. Knowledge of the distribution of these parameters is essential for the efficiency of the design and the operation of the system.

Jan 1, 1985

By Adam H. Zimmerman

Introduction Noranda, like similar businesses, is suffering the pain of previously unheard of currency relationships, a cost structure built in better days, and conditions of gross oversupply possible in almost any commodity. Indeed, it does seem like the worst of all possible worlds is out there before us. To understand a Canadian natural resource company, you must know how the country is organized. So far as natural resources are concerned, Canada is not Canada. Canada is 10 provinces and each own the resources situated therein. Thus, the conditions of extraction, exploitation, and operation are all set by the province, while the conditions of trade and currency are set by the Federal government. This means that what may be the rule in Newfoundland may not be the rule in Manitoba or British Columbia. The second thing is that the Canadian currency has been a satellite of the US dollar for a long time. This means that we hold the unenviable and unjustified position of being the country with the second strongest currency in the world. What this has meant to us is what it has meant to an American operator. Since 1980, a pound of copper fetches 214% more for a Chilean than it does for us and a pound of zinc 115% more for a Belgian. From an American point of view, Canada is favored because its dollar is valued at 25% to 30% less than the U.S. However, because of industrial indiscretions in years past, Canada has a locked in labor cost disadvantage that is very hard to cope with. Canada has a unique situation with its labor unions. Many of the unions are, or have been, internationals and therefore gained undue strength in early days. Canada has a third political party of socialist persuasion. It is entirely funded by dues from laor union members. Thus, we have a politicized workforce. And finally, we have a public service that has the right to strike. This had made the public service unions by far the strongest now in Canada. What this means to the mining industry is that there is somebody out there blazing the trail. The unrelenting power of these public service unions probably creates a climate more conducive to excessive wage settlements in industry than would otherwise be the case. Study, Work, and Pray So what do we do when times get tough? In simple terms, we study a lot, we work harder, and we pray a great deal. We study a lot in terms of learning hitherto unknown strengths and weaknesses of our products, processes, and operations. We work hard in the sense that we do everything possible to improve our productivity. And we pray a lot because, so far, anything else we have done has not been enough. Some years ago, Noranda recognized that its principal base and precious metal operations were diminishing. To provide for the future, we should branch out into other resource type operations. These might be countercyclical and also perhaps a little more permanent. For this reason, Noranda entered the potash, aluminum, and forest products businesses. This, of course, was a 'brilliant' strategy that was much applauded in its early days. We built an excellent potash mine, the smallest inte-

Jan 6, 1985

By R. K. Singhal, H. Sahay

Introduction In terms of the world's recoverable coal reserves, Canada ranks 10th, providing 0.6% of the world's total. The US is first with 27.8% and the Soviet Union follows with 24.1%. Figure 1 shows the principal coal mines in Canada. Several provinces contain substantial coal deposits, but the largest deposits are found in the western provinces of Alberta, British Columbia, and Saskatchewan. Conservatively, 90% of the lignitic, 80% of high volatile bituminous, and nearly 100% of subbituminous, and low and medium volatile bituminous coals are located in these three provinces. During the past decade, Canadian coal production of all types increased from 18.8 Mt (2 million st) in 1972, to 25 Mt (28 million st) in 1975, to 61 Mt (66 million st) in 1984. About 38 Mt (43 million st) of this output was classified at thermal and 23 Mt (25 million st) as coking and metallurgical coal (Table 1). The three western provinces currently produce 57 Mt (62 million st) of coal - 95% of Canada's total. The remaining 3.6 Mt (4 million st) (5%) is produced in Nova Scotia and New Brunswick on the east coast. The majority of western coal (98%) is produced by surface mining methods. On the east coast, though, mining is predominantly underground and only 15% is produced on the surface. In 1985, Canada exported close to 28 Mt (30 million st) of metallurgical coal and thermal coal. During the same period, 15 Mt (16 million st) of coal were imported, mostly from western US for use in Ontario and Quebec. Almost 60% of the imported coal was used for thermal applications. The remaining 40% was metallurgical coal for the steel industry. It is generally cheaper to import coal into central and eastern Canada from the eastern US to augment local supplies rather than from western Canada. This is mainly because of high transportation costs. Mining methods The suitability of mining methods in a particular area depends largely on the geological setting. Geology, therefore, simplifies or adds complexities to mining operations, directly affecting the economics. It also influences the flexibility required from the min-

Jan 9, 1986

By B. Law, M. Menabde, B. Baird

Blasor is a new mine planning tool which is being used in the long and medium-term optimization of multi-open-pit operations throughout BHP Billiton’s Base Metals and bulk commodities portfolio. It is not just a scheduler, nor even only a schedule optimizer—although this function lies at the heart of the tool’s functionality—but a pit development plan optimizer, used from ultimate pit design and process plant capacity sizing right through to mining phase design and optimal panel scheduling. The tool uses a mixed-integer-linear-programming optimization engine to determine when material should be excavated and where it should be sent to optimize discounted operating cash flow over the life of operation. The core software design concept of Blasor is to provide a tool which is intuitive and flexible enough so that a competent mine planner can perform a pit development plan optimization without assistance from optimization specialists. To this end, a generalized graphical user interface has been implemented which allows full configuration of the optimization problem, including the definition of all inputs and constraints, specification of the material flow topology, bin and destination class definitions and full specification of the economic model encompassing prices and costs. This paper describes the capability of Blasor and outlines the design concepts underlying its design philosophy.

Jan 1, 2007

By Steve Kral

It seems that mining has been in the doldrums for awhile. Except for gold, metals prices remain depressed. And economic conditions in the United States and around the globe have put governments in a financial bind. This affects new building and infra-structure repairs, which, in turn, have a major impact the building materials industry. Add to that the severe environmental and regulatory restrictions placed on the mining industry in developing new mines and expanding existing ones. It’s enough to make a mining engineer/geologist/metallurgist go sell real estate. So why do those employed in the mining industry stay in the business and remain optimistic? Many of them will say that they have been through down cycles before and know that an upswing is in the offing. They also know that society will always need the commodities they produce. And they love the challenge. The challenge in mining’s case is producing commodities as cheaply as possible, in an environmentally sound manner and improving the quality of life in the communities where they work.

Jan 1, 2003

By F. Freme

Coal production in the United States increased in2004 by 36 Mt (39.7 million st) to end the year at 1 Gt(1.11 billion st), according to the U.S. Energy Information Administration (EIA). This was a 3.7-percent in-crease from 2003’s 971.6 Mt (1.07 billion st) (Table 1).(All percentage change calculations are done at the short-tons level.) Although U.S. coal consumption rose in 2004, not all coal-consuming sectors had increased consumption for the year. Coal consumption increased in the electric power sectors by 1 percent and declined slightly in the other industrial sector, while coking coal consumption dropped by 2.4 percent. U.S. coal exports rose for the second consecutive year, while coal imports again increased to record levels. Coal stocks declined during the year, as electric generators used their stockpiles to helpmeet increased demands and missed shipments. Coal producers used their stockpiles to supplement their production levels.

Jan 1, 2005

By A. L. Williamson, G. Savci

Hydrologic assessments of existing and proposed waste rock stockpiles (WRS) are typically required for application of operating and closure permits at mine sites. The results of these assessments can be used to determine the applicability of the state groundwater permit program requirements to the operation and closure of these stockpiles. The objective of this hydrologic assessment was to ascertain whether or not the WRS at the Ajo Mine have a reasonable probability of discharging potential pollutants to the underlying aquifer under the operational mine conditions. The hydrologic assessment was performed based on an evaluation of climatic data, prediction of the net infiltration rate through the WRS and prediction of additional hydrologic factors such as the time required to deplete available moisture storage in WRS. The predicted net infiltration rates ranging from 0.13 inches/year (1.1x10-8 cm/s) to 0.24 inches/year (1.9x10-8 cm/s) are below the threshold value of less than 10-7 cm/s recommended by Hutchison and Ellison (1992) as being characteristic of conditions that produce no or negligible quantities of seepage. In addition, the total time required to deplete available moisture storage within the Ajo Mine WRS and for any potential seepage from the WRS to reach the underlying aquifer is estimated to range from 260 years to 1,950 years. Collectively, the climatological and geotechnical investigations and the hydrologic predictions demonstrate that the WRS at the Ajo Mine hydrologically do not have a reasonable probability of discharging pollutants to the underlying aquifer. As a result of this prediction, the stockpile will not be regulated under the state groundwater permit program and operational and reclamation requirements will be limited to managing surface water runoff.

Jan 1, 2002

By Fred Pena

Cyprus Pima Mining Company is located in the Mineral Hill District of southern Arizona, approximately 22 miles south-southeast of Tucson. Cyprus Pima Mining Company is owned 50.01% by Cyprus Mines Corporation, 24.99% by Utah International Incorporated, and 25% by Union Oil Company of California, with Cyprus having the management responsibility. Cyprus Pima's history has been one of continued expansion from an initial plant of 3,000 TPD in 1957; 6,000 TPD in 1963; 18,000 TPD in 1966; 36,000 TPD in 1967; and 53,500 TPD in 1972. The major reason for Expansion IV was that a large volume of low-grade ore had to be moved to get at a higher grade ore in the course of proper pit development. With mining costs already defrayed, this relatively hard, low-grade material became economically profitable for subsequent milling and concentrating treatment. Similar material previously stockpiled was available for ore treatment. In an effort to meet the continuing search for lower unit costs, the largest milling and concentrating equipment had to be examined. The management of Cyprus Pima Mining Company began investigating autogenous, and semi-autogenous milling in 1964 when two carloads of ore selected from the Cyprus Pima pit were sent to the Koppers--Hardinge Operation at York, Pennsylvania for testing. One car contained approximately 40 tons of hard arkosite and the other contained approximately 40 tons of ore classified as soft Hornfels. The purpose of the testing was to determine the amenability of both ore types to autogenous or semi-autogenous grinding.

Jan 1, 1974

By J. J. Gusek

There are hundreds of passive treatment systems accepting mining influenced water (MIW) throughout the world. Some systems do not perform to design expectations while others, including volunteer systems, have successfully operated relatively unattended for decades. The primary reasons for this situation include the common misconceptions that (1) a “cookbook” approach to design is valid for a wide array of MIW chemistries and site conditions, and (2) low maintenance means “no maintenance.” Passive treatment systems for MIW are typically manmade ecosystems that are designed to handle a specific range of metal loading conditions and MIW geochemistry. Thus, when design conditions are exceeded, the suite of microbial to macroscopic ecosystems may be slow to recover or mature. This should be no surprise to designers. But when a particular system fails, it may be inappropriately attributed to the technology, not the design. This paper presents a standard “phased” design protocol that appears to work and provides examples of sub-par performance of selected passive treatment systems.

Jan 1, 2002

By Samer Sadek, Brian Hagan

We are thrilled to welcome you to the 2025 Rapid Excavation and Tunneling Conference (RETC), which will be held in Dallas, TX. This year’s conference will showcase the continued trend of strong industry interest, as there will be a record setting 115 papers being presented over the course of three days. The set of papers compiled in this book captures the latest and greatest information on a broad array of topics within our fascinating tunneling industry. We hope that the compilation of selected papers in this book will provide a comprehensive recap of the conference while also providing a source of future reference for contractors, engineers, and anyone in general who is a student of our beloved and unique industry. Since its inception in 1972, RETC has been the preeminent tunneling forum to promote ideas, tell stories, share lessons learned, and promote new technologies. RETC prides itself on its focus towards highlighting real-world experiences and practical ideas, with the intent to help the entire industry learn from one another and grow. The need for us all to stay sharp and remain on the cutting edge of technology has never been stronger – the technology and ideas that have been applied in aerospace are now attempting to mix with tunneling, and the advancement of AI continues to permeate all industries. However, no amount of technology or AI can fully replace the human element, and in our tunneling industry, the human element is key and is what sets us apart. In tunneling, every project is different, because the ground is always different. We can only take what the ground will give us, and we must rely on our past experiences to get through present day challenges. Most importantly, we must rely on each other. This is the heart of what RETC is all about. For those of you attending this conference, we encourage you to attend as many sessions as possible and engage with your colleagues to discuss during the breaks in between sessions. This sharing of ideas is what keeps us connected and helps to expand our industry. Please also try to engage with the scholarship students and the newcomers who will be in attendance, as it is the new ideas and fresh energy from the next generation that will continue to make our industry thrive into the future. The program chairs thank and greatly appreciate the efforts made by our session chairs, co-chairs, authors, the members of the RETC Executive Committee, and most importantly the SME staff towards making this RETC possible.

Oct 1, 2025

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

8.1 INTRODUCTION Under room and pillar mining if the extraction ratio is low, (i.e., < 50%) a pillar can support the overburden without collapse and there will be no surface subsidence whatsoever. In other words, if the pillar sizes are properly determined to support the overburden weight, the roof strata cannot cave and there will be no surface subsidence, provided the entry width is small and properly reinforced so that a continuous roof fall leading to piping or the total collapse of the roof does not occur. Under the prevailing mining conditions in the US if only development mining is em¬ployed in room and pillar mining (i.e., no pillar extraction), the extraction ratio is usually less than 50% and generally no surface subsidence will occur. If pillar mining is employed, surface subsidence may occur, depending on the extraction ratio and the size of the remnant pillars (or stumps) left in the gob. The higher the extraction ratio, the smaller the stump pillars left behind in the gob. As the size of the stump pillars becomes smaller, the possibility of their support¬ing the roof without collapse is smaller. If all stumps are crushed completely, the roof will collapse and surface subsidence will occur. Again, whether surface subsidence occurs, it depends on whether the remaining stumps can support the overburden or not. Therefore, since the weight of the overburden which the stump pillars have to support is proportional to the mining depth, a fixed¬size stump pillar can support the overburden at a shallow depth, but will collapse under greater depths. In this context extraction ratio is not the only parameter for determining whether surface subsidence will occur. Furthermore, during pillar mining a pillar can be cut away in many ways to finally reach the same extraction ratio. Therefore, the safest way to determine whether or not sur¬face subsidence will occur in room and pillar mining is to compare the strength of all stump pillars in the panel of interest with the weight of the overburden that the pillars have to support. If they are too small to support the overburden, surface subsidence will occur. Under normal mining practices the characteristics of surface subsidence profiles vary with methods of mining. In the US there are two types of coal mining methods, i.e., longwall and room and pillar mining. Longwall mining is indisputably a total extraction method, but different percentages of coal recovery are achieved in room and pillar mining. Recovery is much higher for sections with pillar extraction than those without pillar extraction. For those without pillar extraction, coal recovery increases with increasing entry width or decreasing pillar size. For those with pillar extrac¬tion, the total coal recovery depends on the amount of coal ex¬tracted from each pillar which is in turn dependent on the roof conditions and methods of pillar extraction. Bauer and Hunt (1981) analyzed the characteristics of the subsidence profiles due to the three types of mining methods in Illinois. Fig. 8.1 shows the range of locations associated with the following profile features: profile edge, maximum tensile curvature, maximum slope, maxi¬mum compressive curvature, and maximum subsidence. The scat¬ter of the data increases with decreasing percentages of extraction. The profile is much sharper for longwall mining and becomes milder as percentage of extraction decreases; for longwall mining the profile edge is always beyond the opening, while in room and pillar mining it may fall within. The location of maximum tensile strain moves outward, while that of the maximum compressive strain moves inward as the percentage of extraction decreases and the maximum subsidence decreases with decreasing extraction ra¬tio. The general concepts discussed in this chapter may not apply to the entry development sections between two longwall panels where roof caving in both panels are very severe and overlap each other. Consequently, it must be treated differently. 8.2 CASE STUDIES Kohli et al. (1982) described several case studies on surface subsidence due to room and pillar mining with pillar extraction. In one case, the seam was 6 ft thick and ranged from 650 to 800 ft deep. The panel was 720 ft wide (Fig. 8.2) and was developed with seven entries. Each entry was 18 ft wide and the pillars were driven at 88 ft center-to-center between entries and crosscuts. Dur¬ing retreating, two additional pillars (pillars J and K) were devel¬oped, two blocks ahead of the pillar line, to take the barrier pillar, 160 ft wide, between panel No. I and No. 2. Pillar extraction began by taking a central slice across the whole panel, beginning from pillar 0 through J. After that, each pillar was sliced by 6 wing-slices, 3 on each side, leaving 4 stumps, 2 on each side. One of each pair was triangular shaped approximately 6 ft wide by 26 ft long. The other was trapezoidal, 26 ft long by 16 ft and 10 ft wide at the upper and lower bases, respectively. This resulted in a total extraction ratio of 85% within the panel. Obviously the stump pillars were not large enough to support the overburden and col¬lapsed completely. The final subsidence profiles were rather smooth, just like those under total extraction (Fig. 8.3). The max¬imum subsidence on Lines A and B was about 3 ft for an average mining height of 6 ft, but the locations of the maximum subsidence were skewed toward panel No. 1. Along Line D, the central por¬tion was flat-bottomed, but the maximum subsidence was only 2 ft, mainly because Line D was only two blocks from the right-side edge. Notice in every profile there was heaving of as much as 0.3 ft, beyond the edges above the solid coal. In another case (Fig. 8.4), the seam was 6 ft thick under 650 to 850 ft cover. Three panels, 710, 400, and 350 ft wide, respec¬tively, were extracted side by side. The entries were 18 ft wide and the pillars at 88 ft center-to-center between entries and crosscuts. Pillar extraction was practiced the same way as described previ¬ously. According to the mine maps, there was no barrier pillar left between the adjacent panels. Thus after extraction the three panels formed a common gob of more than 1460 ft wide. This was re¬flected in the development of the subsidence profile along the county road. After Panel No. I was mined, the maximum subsi¬dence of 1.2 ft occurred at Monument No. 1. This was increased to 1.6 ft after the extraction of Panel No. 2 and went to a further 1.8 ft after the extraction of Panel No. 3. The final maximum subsidence of 4.3 ft occurred at Monuments No. 6 through No. 8, while the remaining portion of the county road showed rebound. However it must be noted that the subsidence profiles were rather bumpy and fluctuated, perhaps an indication of the irregular stump pillars that were left and crushed at various time after mining. Moebs (1982) surveyed the subsidence profiles of four room

Jan 1, 1992

By D. Brady

When deciding to deploy rescue teams underground the decision makers need to be able to determine that there won?t be an explosion whilst the rescue teams are underground. Previously general body concentrations in areas likely to be travelled were compared to explosive limits on a one off basis with no formal process looking at trends or other areas. A new approach is being adopted that takes into account the rate of change of gas concentrations with triggers set to enable a withdrawal of personnel prior to a possible explosion and influences such a barometric pressure changes. This paper explains the rationale behind the changes made and the advantages and implications of adopting such an approach.

Jan 1, 2012

By V. Izaxon

Current practice in mining frozen, underground placers is to support the mine openings by leaving remnant pillars, which are kept frozen to maintain their stability. These pillars may be partially extracted depending on mining conditions, but this practice may be risky, and roof falls are common. Instead of allowing the mined-out areas to cave, the extracted entries could be filled with waste material, which would then be frozen, using cold ventilation air. A finite difference model for analyzing the effects of various parameters on the freezing of backfill in underground mines in the Arctic has been developed and tested. The model also accounts for properties unique to a frozen rock mass, including those that change with temperature. Examination of the characteristics of ice-cemented mining waste materials as backfill indicates that with proper engineering control, a backfill system can be designed for use in production mines. The system will allow increased extraction ratio while maintaining the stability of underground openings with minimum heat impact on the surroundings. These simulated results establish the relationships among the strength, the temperature, and the freezing characteristics of a given material. When coupled with site observations these relationships will facilitate the optimal design of ore pillar recovery methods.

Jan 1, 2004

By Steve Kral

For an industry that provides more than half of the nation’s energy needs, the U.S. coal industry still attracts negative publicity. However, the nation’s energy appetite continues to increase. And political leaders and the public are beginning to understand that alternative fuels will not be enough to keep up with that appetite. Does that mean the nation will now embrace the coal industry? No, according to speakers at the Rocky Mountain Coal Mining Institute (RMCMI) meeting. The industry still needs to sell the public on coal’s advantages over other fuels. And the industry must continue to develop technology that will allow coal to meet and exceed strict clean air and clean water regulations.

Jan 1, 2002

By Phillip E. Butler

Since early 1973, the Pennsylvania Department of Transportation (PennDOT) has been actively engaged in the utilization of coal mine refuse in the design and construction of highway embankments. The Soils and Geological Engineering Division of the Bureau of Materials, Testing and Research has the task of managing the program which includes field investigations, laboratory testing, engineering evaluation, planning, coordination, implementation, construction control, and review of construction performance. The objectives of the utilization program, in removing colliery refuse banks and utilizing the material in construction, are the environmental and aesthetic rehabilitation of those areas in the Anthracite and Bituminous coal fields which have been plagued for such a long time by air and water pollution, and unsightly landscapes; and the economic rehabilitation of those areas occupied by refuse banks by providing usable land which can now be developed as residential, business, or industrial sites.

Jan 1, 1975

By G. Biles, K. Loughran, R. Anand

The Eskay Creek Mine, a high-grade gold and silver underground mine in northwestern British Columbia started operations in late 1994. For the first three years of operation, ore was crushed to minus 2 inch; blended to satisfy smelter terms and direct shipped to smelters in Japan and Canada. Before commencing the above operations, preliminary evaluations had indicated that an extremely complex metallurgical facility, requiring a large capital investment, would be required to recover the precious and other economic metals. Subsequently markets for raw ore were identified and underground mining and ore transportation operations, at a nominal production rate of 300 tonnes per day, were commenced. Exploration diamond drilling in 1995 and 1996 discovered additional lower grade mineralised zones, which are less economic or uneconomic as direct shipping ore. Test work demonstrated that these lower grade zones could be upgraded to marketable concentrates in a simple flotation mill. The mill was built in 1997 and has been in operation since late 1997. The mining rate now has increased to 400 tonnes per day including 250 tonnes per day of the direct shipping ore and 150tonnes per day of the mill ore. Prime Resources Group Inc. wholly owns the Eskay Creek Mine. Homestake Canada Inc. owns 50.6% of Prime’s shares and manages and operates the mine on Prime’s behalf. This paper discusses the mining and milling operations as well as ore shipment and smelter contracts&apos; administration.

Jan 1, 1999

By Donald W. Gentry

This section deals with one of the most fascinating aspects of mining the evaluation of mine investment opportunities. Be-fore proceeding further, it is important to clarify the meaning of some fundamental terms used frequently in the text. 6.0.1.1 Mine Valuation vs. Evaluation The words "valuation" and "evaluation" in a mining context are often used interchangeably. However, for the purposes of this section, a distinction is made between the two terms in accordance with commonly accepted practice. The word valuation in a mining project context has the rather narrow meaning of placing a dollar or other currency value on the worth of the project as a whole. In other words, the value of a mining project refers to a measure of the desirability of ownership of that property. As such, the major item of interest is, "what is the mine worth?," or `what is the value of the mine?" The value of a mining project may actually be determined in the marketplace at any specific point in time, or it may be estimated by one of several methods. The topic of mine valuation is discussed in more detail in Chapter 6.1. The word evaluation in a mining project context connotes the broader meaning of determining the numerical values of all

Jan 1, 2008

By Paul Richardson

This paper will review several projects completed during the period from 1976 through 1984 which have been carried out utilizing big hole drilling concepts. The projects discussed will be from various industries to demonstrate the extent that big hole drilling methods are being used along with the current state of development. There will be a discussion of projects planned for the future where big hole drilling methods are the only technology being considered. Also included in the discussions will be an overview of the most recently completed heavy oil recovery project. During the next decade, big hole drilling methods will be used more and more in all industries where underground access is required. The safety, speed and economics associated with shaft sinking using drilling methods are becoming more and more recognized and the technology is rapidly becoming an accepted shaft sinking method.

Jan 1, 1985

By R. W. Fedors, S. T. Green, G. R. Adams, C. Manepally, L. B. Browning

This paper provides estimates of large-scale temperature gradients that can be used to support modeling of natural convection and cold-trap processes in thermally perturbed drifts. Temperature influences estimates of the quantity and chemistry of water contacting engineered components (e.g., drip shields and waste packages) in a potential high-level waste repository at Yucca Mountain, Nevada. Temperature gradients drive natural convection and cold-trap processes, which could affect the distribution, quantity, and chemistry of liquid-phase water contacting drip shields (waste packages).The confluence of high temperatures, liquid-phase water, and high chloride may lead to corrosion of drip shields and waste packages. An overview of the evolution of environmental conditions in thermally perturbed drifts is presented to provide a context for the estimates of temperature gradients. A mountain-scale conduction-only model is used to estimate temperature gradients and temperature differences for a drift located at the center of a potential repository. Thermohydrologic models and heat transfer algorithms are used to evaluate the reasonableness of the conduction-only results. Estimates of temperature using an in-drift heat transfer algorithm account for the possibility of drift degradation and formation of a rubble pile on the drip shield. Temperature differences between the center and ends of the drift are estimated to rapidly increase to 80 °C soon after repository closure. That temperature difference decreases over time to 15 °C after 10,000 years. Local temperature gradients are generally estimated to be less than 0.2°C/m, though the gradients can be much larger near changes in lithology and near the end of the drift. The estimates of temperature gradients do not account for intermediate- and small-scale variations, such as those influenced by differences in heat loads between waste packages, intra-layer variations in thermal properties of the surrounding fractured rock, or localized drift degradation.

Jan 1, 2004