Search Documents

By Edwin A. Zink, Gerald P. Zink, John E. Wolgamott

Recent advances in high-pressure water technology can be effectively employed in underground mining. The new equipment is based on standard industrial water cleaning hardware and is compatible with conventional mining techniques. Three viable applications are addressed: rock drilling, hole notching, and rock bolting. Highlights of test results are presented that were obtained in several underground mines during the last two years of development work.

Jan 1, 1982

Consents Required for Overseas Persons Overseas Investment Regulations 1974 Foreign investment proposals must be reviewed by the Overseas Investment Commission to ensure that these are in accord with national interests. Consent must be obtained from the Commission for: 1. New investment proposals which include: a. An overseas person acquiring 25 per cent or more of any class of share in a company. b. A New Zealand company issuing shares to an overseas person where this will result in that person owning 25 per cent or more of the company. c. An overseas person acquiring business assets for consideration in excess of $100 000. d. An overseas person commencing business in New Zealand. 2. Borrowing in New Zealand: An overseas person must obtain consent to raise funds in excess of $300 000 in New Zealand. 3. Borrowing Overseas: New Zealand incorporated companies must obtain consent to borrow overseas. Current policy is borrowing will be approved where the loan is for a specified fixed term of one year or more.

Jan 1, 1982

The technical parametrization of reserves is a technique which has made an important contribution to the definition and the calculation of optimal mining projects. Its applications to a new open-pit optimization program have already been presented in various papers (François-Bongarçon and Maréchal (1976); François-Bongarçon and Guibal (1981)). The present paper gives a brief description of the general problem of parametrizing reserves before going into the details of the practical algorithms used in two typical cases, i.e. open-pit mining and mining between hanging wall and foot wall.

Jan 1, 1982

By Richard B. Stein

This paper will present an overview of several hydrometallurgical processes which can be used for sea-nodule metal recovery and some simplified economics. Before going any further, here are some of the basic figures from which the economics were developed. The first is to establish a representative composition for a typical nodule feed (Slide 1). This set of chemical analysis figures can be taken as typical for a deep Pacific nodule feed and shows manganese at 30%, copper at 1.1%, cobalt at 0.2%, nickel at 13% and iron at 10% for the metals of economic interest1.

Jan 1, 1982

By V. Svalbonas

In the establishment of a useful failure criteria for complicated, fabricated structures, two basic areas of knowledge must be evaluated: 1. The accuracy of the applied stress analysis must be known in comparison with actual stresses encountered during mill operation. 2. The metallurgical fracture properties of the basic materials must be established with reference to non-destructive examination (NDE) methods to be used during fabrication. Both of the above can only be evaluated by use of full scale tests on the structures, and/or components, of interest. This paper describes such tests and comparisons as applied to several large mill installations. In addition, weldment component fatigue tests arid flawed casting strain gauge tests are also discussed. The combination of such test results allows for the formulation of failure criteria directly applicable to the fabrication and examination procedures followed in grinding mill structure manufacture.

Jan 1, 1982

By Madan M. Singh

Currently longwall coal mining operations require at least 3 entries on both the headgate and tailgate ends because of ventilation and safety requirements. Driving of entries, however, is a slow and costly process. Often it is a bottleneck in longwall development. Single entry gateroads are permitted in Europe and commonly used there. This study entailed ascertaining the feasibility of using a single entry in the United States, without sacrificing safety. This design was conducted for an operating longwall mine in the Black Warrior coalfield in Alabama, An understanding of rock loads and consequent support requirements is prerequisite to the design and successful demonstration of the single entry system. Efforts in this regard were directed at determining center (packwall) support requirements for various single entry widths. Critical to the analysis is knowledge of the nature and extent of side abutment stresses. In collecting geological and geotechnical information relating to the stability of the single entry, Engineers International, Inc. engaged in the following: ? Examination and inspection of the single entry demonstration at the Sunnyside Mine in Utah. Severe ground conditions and unacceptable levels of entry closure were experienced there prior to the tailgate phase. Observations at the mine presented a clear perspective on possible ground control problems for future single entry designs. ? Reconnaissance inspection and classification of roof rock conditions. ? Detailed mapping of roof structure in the areas to be instrumented. ? Installation of convergence stations in the longwall headgate to monitor roof movement during mining. ? Measurement of side abutment stresses in a yield pillar in the area of the convergence measurements. ? Measurements of coal fracture distribution by the detail area method. ? Rock properties determinations of roof, coal, and floor rocks; samples obtained by core drilling. ? Determination of floor bearing capacity by in-situ testing.

Jan 1, 1982

By Thomas Henderson

Strategically, intermaterials competition is important to companies involved in raw materials extraction, smelting, refining or other processing, semi-finished and finished goods fabrication, and end-use consumers. In other words, just about every company involved in manufacturing. The array of materials covered by other papers in this session is testimony to the subject's breadth. In trying to provide an over- view of such a broad topic, the purpose has been to relate some of the common characteristics of the markets, economics and technology of raw materials, and to describe some of the ways in which Intermaterials competition impacts the markets, economics and technology of raw materials.

Jan 1, 1982

By Anshumali Gangwar

This paper outlines the chance constrained binary integer program developed by the author in his doctoral dissertation at Columbia University, New York, 1973. The optimum planning of a mining program involves the determination of a production schedule which maximizes the net present value of the mining property. The actual mining process has an inherent stochastic and discrete nature. In particular, the demand for the mined product and the grade of the mineralized material in the ore are the two most important stochastic mining variables. The decision to mine or not to mine any block of a mining property is a binary integer variable. This paper outlines the formulation of pit production scheduling problem as a chance constrained binary integer program. The deterministic equivalents of these chance constraints are nonlinear in binary variables which have subsequently been linearized. The planned objective is to meet with a stipulated high degree of reliability, all the random demands as they materialize with a random supply of the commodity being marketed as determined by the eventuating random grade values of the exposed ore blocks and the mining system's production constraints such that the discounted total production costs over the entire planning horizon are minimized or the profits maximized. The emerging surface of the mine in each scheduling period is determined by the values taken by the binary decision variable associated with each block of material in each scheduling period.

Jan 1, 1982

By Donald O. Capstick

The local geology, the lack of recorded mining activity, and our field investigation and associated sampling indicate a low potential for mineral resources. Claim records and the literature review failed to show any lode or heavy mineral placer mining claim locations that are definitely in the area or anomalous mineral concentrations in the study area. Field investigations revealed no claims, prospects, or mineralized areas.

Jan 1, 1982

By Carl P. Venzke

Mining lignite in the Gulf Coast often requires some interaction with shallow ground water system. Suggestions for determining ground water data and analysis requirements for regulatory compliance are given. Simple methods for estimating mine inflow seepage, ground water level declines, and changes in ground water chemistry, which may result from mining, are discussed. The mining of lignite often results in interaction with shallow ground water systems. An evaluation of the interaction is required as input to mine permitting and engineering. Your evaluation will proceed more smoothly and produce more meaningful results with some planning prior to performing your evaluation. The following are tips to consider in planning and carrying out a successful study.

Jan 1, 1982

By J. A. Kosek

Work has been carried out under Bureau of Mines Contract HO 395132 to develop improved sensor cells for use in direct-reading detectors and diffusion exposure meters. A pumped CO sensor cell was developed which has a shorter response time, improved temperature cycle characteristics, and improved linearity and stability at high CO concentrations. Diffusion CO sensor cells have shown good response level stability and linearity up to 1000 ppm. In addition, a new sensor cell catalyst has been developed for NO2 sensor cells which has a much shorter response time and improved response stability characteristics.

Jan 1, 1982

By Ray L. Tobie, Douglas E. Julin

GENERAL DESCRIPTION Block caving is a distinct caving method applied mostly to large, massive, ore bodies because of its in¬herent low cost and high production capabilities. Areas of sufficient size are removed by undercutting so that the mass above will cave naturally. Drawing of the caved ore at the bottom of the ore column causes the caving action to continue upward until all of the ore above the undercut level is broken into sizes suitable for handling. When properly applied, block caving results in a lower mining cost per ton than any other under¬ground method. There are three distinct forms: (1) dividing the horizontal area into rectangular or preferably square or nearly square blocks, drawing evenly over the entire area to maintain an approximately horizontal plane of con¬tact between broken ore and caved capping; (2) divid¬ing the horizontal area into panels across the ore body, retreating by undercutting manageable areas from one end of the panel to the other and maintaining an in¬clined plane of contact between the broken ore and caved capping (thus the name panel caving); and (3) no division of horizontal area of the ore body into defi¬nite blocks or panels (this is termed mass caving). Undercutting may be from wall to wall, retreating from one end of the ore body to the other, maintaining an inclined plane of contact between the broken ore and caved capping. The total active caved area is deter¬mined by the size of block that will not produce undue stress on workings below the undercutting level and by total production requirements. This type of operation is also referred to as panel caving at some properties. SUITABLE ORE BODIES Block caving in its various forms is applicable to deposits of various shapes and ores of various strengths. Its success is governed by rigid requirements and limi¬tations. In unsuitable deposits or where improperly em¬ployed, the loss of ore may exceed that of any other mining method. Good planning, systematic work pro¬cedures, careful supervision, and good judgment con¬tribute to its success. Ore Characteristics Included as a necessary characteristic in an ore body suited to a successful block-caving operation is a proper fracture pattern. Ore hardness should be another gov¬erning factor, and the toughness or softness of the ore should be considered. There must be sufficient horizon¬tal area available for expansion of the undercut, if neces¬sary, to start the caving process. Large, massive, ore bodies usually meet these conditions. Veinlike deposits must be wide and dip rather steeply to conform to the block-caving limitations. The capping must be of such a nature as to cave when the underlying ore is being removed since the weight of the overburden aids in crushing the ore. The most favorable capping character¬istic is that it breaks into coarse pieces and resists attrition as the block is drawn. Soft capping, by breaking into fine pieces and sifting into the ore or channeling through the ore to the drawpoints, can seriously dilute the ore and hinder the extraction of clean ore from the blocks. Types of Ore In block caving, a fairly uniform distribution of val¬ues in the ore is necessary. Grade values may range from low grade to high grade, but most often the sys¬tem is applied to low-grade ores. Wide veins, thick beds, or massive deposits of homogeneous ore overlain by ground which will cave constitute suitable ore bodies. The ore must be such that it can be supported while blocks are being developed and undercut but breaks up readily when caved. Some applications include porphyry copper, disseminated molybdenite, hematite in the Lake Superior iron district, limonite deposits in northern Spain, the diamond mines of South Africa, asbestos and nickel in Canada, and massive magnetite in Pennsylvania. Size and Shape Outline of the ore body should be fairly regular, and the sides of the ore body should dip steeply. It may not be economical to mine small portions of ore extending into the walls of the deposit, and low-grade inclusions in the ore cannot be left unmined. Some dilution of the ore, as mining progresses, by low-grade or barren cap¬ping is inevitable and, unavoidably, some clean ore is left between drawpoints. Determining Cavability The use of rock mechanics is sometimes advantageous in helping to determine the cavability of an ore deposit. The US Bureau of Mines has information and testing ability which can assist in determining the cavability of ore types. Several competent consulting orga¬nizations knowledgeable in rock mechanics can also as¬sist in evaluating the cavability of an ore body. Some recent work has been done to better define the cavability index of various ore bodies; an example of how this was determined is discussed by McMahon and Kendrick (1969). The intensity of the fracture pattern is a critical parameter to be analyzed. The question to be answered is, "How intense must the fracture pattern be?" Table 1 is a tabulation of the size of rock fragments that appear at the drawpoint of various block-cave mines around the world. These are indicative of the fracture-pattern spac¬ing and, as can be seen, they vary substantially from the almost sandy material at the Mather mine to fairly sizable blocks at the Grace mine. Several sets of fractures are essential to promote good caving. Ideally, two vertical sets at nearly right angles to each other and a third set nearly horizontal are required to insure a good caving ore body. Since initial caving of an ore mass is almost always by the action of gravity acting on these planes of weakness, it is doubtful

Jan 1, 1982

By James H. Boettcher

INTRODUCTION A complex interaction of worldwide economic and political forces is increasingly requiring 3 primary participants for the successful development of large natural resource projects in developing countries. They are the host government of the developing country (the "host government"), one or a consortium of international natural resource companies, (the "Resource Company") and one, or more likely, a syndicate of international lenders. The host government typically controls the rights to its country's natural resources and establishes the economic ground rules for their development. However, because of worldwide inflation and the depletion of easily accessible, high-grade resources, the nominal and real capital development and operating costs of projects have been spiraling. Moreover, the depletion of high-grade and mineralogically uncomplicated resources also raises the technical and operating risks associated with resource recovery. Thus, despite increasing political self-consciousness and economic nationalism in developing countries, international resource companies are still often necessary project sponsors since they can provide, among other things, the required technical and management expertise and equity capital. The presence of these factors, and often the addition of worldwide market access in a project, is often critical in determining whether or not the project will be considered creditworthy by international commercial lenders. The international commercial lender is often the critical third party in project development, due in a large part to the ever escalating-costs of project developments relative to the financial resources of many companies and even a growing number of countries. In addition, lenders have other reasons for taking more than a passive interest in all aspects of a project's development. These reasons include the following: 1. Projects are often financially structured such that the primary security for a loan, once completion and performance standards are met, is the cashflow of the project rather than recourse to its sponsors. 2. Lenders, in addition to the "project risk" just described, are frequently asked to assume various elements of "political" risk which nay put them in a sensitive economic position between the host government and international resource firms (This is discussed later). 3. International banks today have large loan portfolios of developing country debt with final maturities ranging from one to fifteen years. The various current projects undertaken are the building blocks of most developing country economies that will hopefully contribute to the long run economic development of a country as well as generate the foreign exchange necessary to repay foreign loans in the future. In this regard it is useful for lenders to realize whether a given project "makes sense" in terms of a country's natural resource endowments and competitive advantages over other countries. The type of framework discussed in this article would help lenders to better make such assessments. In order to facilitate the continued international flow of capital and technology to developing countries and of readily available supplies of raw materials from them, it is important for each of these three parties to increase its awareness of the goals and objectives of the other parties as well as the bargaining process that results in the legal, financial, credit and fiscal structures by which a joint venture project ultimately proceeds. Each of the parties faces increasingly complicated accept/reject decisions when they are faced with difficult choices among. a wide range of alternative structural combinations each of which has different implications for risk and reward to them. Therefore, by increasing the mutual, 3-way awareness of the decision processes of the other parties, it should be possible to: • provide better information and results in the formation of more rational expectations by all parties going into negotiations, • facilitate the project formulation process by allowing parties to focus more clearly on the areas of common interest and conflict, • result more frequently in final structures and agreements that better reflect the economic and political realities associated with a project and thus • result in more creative, innovative agreements that should reduce the need for changes to them and thus promote the kind of long run political stability conducive to attracting capital and further investment.

Jan 1, 1982

By Takahide Wakamatsu

In Japan all the complex sulfide ore deposits of base metals have been developed as underground mining. The underground mining cost is extremely high as compared with open pit mining case. Therefore, in milling section of base metal mines, technical advance for maximum recoveries of valuable constitutents in ore has been required all the time to utilize as much ore mined as possible. At present, in mill plants treating "Kuroko", complex sulfide ore, concentrates of copper, lead, zinc, pyrite and barite are produced, with gold and silver contents in the copper, lead, and zinc concentrates being estimated as extra profit. As in the case of Kuroko milling plants, gold and silver contents in the lead and zinc concentrates of lead-zinc ore milling plants are also varuable from an economical viewpoint. Silver content is very high in Kuroko crude ore as well as lead-zinc ore.

Jan 1, 1982

By A. E. Michon

I am Alfred E. Michon, Vice President- International for Burlington Northern Inc. I work for BN's holding company and my responsibilities include co-ordinating the activities of our eight subsidiary companies as they relate to international commerce--an increasingly important aspect of the overall business of our company. Until last April, I was President of the Fort Worth and Denver and Colorado and Southern railroads, subsidiaries of BN. Prior to that, I headed the marketing and pricing area of BN's coal transportation business. Based on my experience in the energy industry, both domestic and international, I would like to discuss the world-wide trend towards the reliance on low-sulfur coal in lieu of natural gas and oil for the generation of electricity. Since pontification on the energy scene world- wide is best left to consultants with scenario-spitting computers, let me in- stead emphasize this trend through two examples. First I will describe the regulatory and economic factors which have encouraged the replacement of natural gas by low sulfur coal as a boiler fuel in the US. BN's investments in track and equipment were instrumental in this conversion. Secondly, I will show how this same combination of factors has created a large demand for steam coal in the Far East. Again, our company's strategy is to facilitate conversion to coal overseas through timely and sufficient investments.

Jan 1, 1982

By John E. Miller

Unit Rig & Equipment Co., manufacturer of Lectra Haul trucks, is continually studying methods of reducing the operating costs of large haulage trucks. Reduction of haulage system operating costs is an important goal that equipment operators and equipment manufacturers constantly try to improve on. One of the most variable and important factors affecting operating costs is actual truck operating practices. An examination was centered on methods to optimize truck utilization. It was found that a very effective method of accomplishing this goal would be an automatic truck control (ATC) system to automatically control a fleet of haulage trucks in a predetermined pattern. Economic studies were conducted which showed a very favorable reduction in mine operating costs by use of an ATC system. In 1970, Unit Rig & Equipment Co., in conjunction with SAAB-SCANIA began preliminary development of adapting, for truck use, a proven automated control system, previously used for train systems, small trucks, and military target vehicles. In 1974, the first prototype system was installed on a Lectra Haul M-100 and tested extensively at Unit Rig's test track in Tulsa, OK. This truck and system were then displayed publicly at the 1974 convention in Las Vegas. In 1976, the system was redesigned for production to maximize reliability, ease maintenance, and to accommodate future control and-status reporting developments proposed for haulage trucks. The new design equipment was manufactured, and a full system test will be conducted in an actual open-pit mine for an extended period to evaluate reliability, compile economic data, and obtain application information to evaluate complete mine haulage system conversions to ATC. System Description The ATC system is designed to provide automatic control of all the vehicle functions normally accomplished by the vehicle operator. The basic system consists of the on-board control equipment and the wayside control equipment. The on-board equipment receives commands from the wayside equipment and controls all the truck functions. In addition, on-board sensors monitor all critical truck functions and provide instructions to the truck and system to assure safe operation. The wayside equipment consists of a buried guidewire, block control units and a central controller which provides predetermined signals to the on-board equipment for speed control, steering, and for auxiliary functions (dumping, horn, etc.) through the guidewire located in the truck's path. The wayside equipment also controls vehicle separation, system status, and provides truck location to a central display panel. The central control panel can vary the speed level signals over any segment and can also command an emergency stop to halt all the units. [Fig. 1] illustrates a typical ATC installation. If ATC is used in operations which require flexibility and mobility at the end of the ATC guidance network, the trucks can then be operated by either radio remote control or manually to complete their assigned functions.

Jan 1, 1982

By Bryan J. Travis, Thomas L. Cook

INTRODUCTION Our growing concern for adequate and secure sources of energy and minerals has stimulated vigorous exploration for new sources, research toward a better understanding of geological processes, and development of new extraction technologies. The need for control, or at least prediction, of subsurface fluid flow is important for many of these technologies for example: primary, secondary and tertiary recovery of oil; ground water and waste management; in-situ fossil energy extraction (oil shale, coal, tar sands); and solution mining of uranium, copper and other minerals. These technologies, especially the last two, are characterized by highly complex systems. A partial list of the physical processes occurring would include flow in porous/fractured media, multi-phase and multi-component flow with heat transport, chemically active fluids and soils, tracers, diffusion and dispersion, fracturing and dissolution. A great deal of understanding of how these processes behave and interact can be obtained from models. MODELS Theoretical models are valuable because they: 1) provide a frame of reference for interpreting results of laboratory and field experiments; 2) once validated by experiments, allow a variety of geometries, injection/production strategies, etc., to be examined (at relatively low cost) for efficiency and stability; 3) can provide guidance to the design of experiments and field operations. Most models are based on the fundamental principles of mass, momentum and energy balance. But from this starting point, many paths can be taken. For example, there is the theory of Payatakes (1973) which concentrates on the microscale dynamics. In this approach, the rock or soil matrix is represented by a complex of characteristic channels (such as periodically constricted smooth tubes). Detail of flow within the characteristic channel is calculated very accurately. A difficulty with this model is that description of a representative channel can require several parameters which may not be easily measured. Also, it is not clear how the channels can be combined practically to model a large scale flow. Another type of model is the "global" one described by Bear (1972). Here, the continuum equations for conservation of mass, momentum and energy are averaged over a distribution of pore channels, resulting in a set of conservation equations in which the small scale structure of the medium is replaced by quantities such as porosity, permeability, dispersion coefficients and tortuosity. This approach allows computation of large scale flows. However, additional constitutive equations are needed which relate averaged quantities such as permeability to observables such as local saturation, particle size distributions, and others. An important difference between models is the way they handle the momentum equation. Payatakes' model solves the full equation. In others, it is replaced by a simpler relation such as Darcy's law (valid for slow flow rates) or by Forchheimer's equation which extends Darcy's law to higher flow rates. These simple relations can nevertheless match a great deal of experimental data (Dullien 1975). The permeability term which appears in Darcy's law and in Forchheimer's expression has been related to other quantities such as porosity and particle surface area. The Kozeny-Carmen equation is a well-known example, valid for some ranges of porosity and particle sizes and for some materials. Several other semi-theoretical, semi-empirical formulations have been devised, none of which are entirely satisfactory. One goal of researchers has been the ability to predict permeability of a porous material from basic measurable quantities such as grain size distributions without recourse to adjustable parameters. This effort has proceeded from consideration of distributions of idealized, non-intersecting channels, to intersecting channels, to consideration of both distributed pore radii and pore neck radii. This last approach has been used successfully to predict permeabilities (ranging over several orders of magnitude) in sandstones (Dullien 1975). Additionally, studies on explicit networks of channels (e.g., Fatt 1956) and percolation theory (e.g., Larson et. al. 1981) have been used to examine interconnectivity effects in porous media with the hope of eventually being able to predict permeability accurately. To be of more than theoretical interest, a model must be compared s controlled laboratory conditions where boundary and initial conditions and relevant material properties can be accurately determined. Also, extraneous forces can be eliminated so that the interactions between processes of interest can be clearly seen and flow models can be vigorously tested. In contrast to the well-defined environment and

Jan 1, 1982

By J. W. Smith

Our continuous search for underground productivity improvements has been brought about by the diminishing ore grades in existing underground mines. The need for more efficient mining methods is a result of the economic problems facing our industry today, and this has caused us to evaluate underground haulage methods which have traditionally been the "bottleneck" in the flow of material from the ore in the natural state to the surface processing facility of any underground mining operation. Small improvements in the face haulage systems have yielded much greater benefits as they relate to overall mine productivity so it's only natural that we are all concerned with the best method of moving ore from the face to the main line haulage. In a recent paper titled "Underground Haulage Trucks - Gaining Momentum Worldwide", Richard A. Thomas concludes that the use of trucks to haul ores in underground mines is on the increase spurred by the convergence of a number of technology advances and economic realities. Perhaps the most important stimulus for the growth of trackless haulage is the high degree of haulage flexibility in underground operations. On the economic side, the demand for higher productivity from underground mines has resulted in larger physical dimensions of haulage roads, that is, higher backs and wider drifts to provide more room for high capacity haulage units. In the process of determining the most effective type of equipment for haulage, the power source must be a major consideration. For the purpose of this paper, we will limit the comparison to rubber-tired trackless haulage vehicles and not try to make a comparison between rubber-tired haulage, continuous haulage systems and rail-mounted haulage. Cost is perhaps the only really measurable factor when making a comparison between electric and diesel haulage. You will find that some costs will be very well defined in absolute terms. In other areas of comparison, cost can be fairly well estimated, and yet in still others, the costs are totally arbitrary. Let's take a look at some of the cost considerations. (Figure 1) first of all, is the initial cost of the equipment. This capital cost quite often is a determining factor in the type of haulage vehicle to be selected, yet this initial cost is perhaps the most insignificant of all costs when evaluating an operation over the long term. Of much greater concern, is the cost of maintenance. This cost will often run three times the original capital investment during the life of a single piece of haulage equipment. This factor can include rebuild to extend the life of the original capital investment, but certainly includes the labor and materials necessary, plus the inventory to keep the equipment in good repair. Perhaps one cost which is now playing an even greater role in the rubber-tired haulage operation, is the cost of fuel. Conoco has recently come up with some rough estimates which indicate that diesel fuel will cost an average of three times the equivalent kilowatt output in direct electric power. Diesel fuel is almost twice the cost of stored electric power. (This of course relates to the efficiencies of charging and recovery of power from lead acid storage cells.) These particular figures of course will vary from one area to another but I think that there is enough significance here to certainly warrant the further study of fuel costs for each particular area or mine. Another cost is breakdown expense. This must be treated differently from maintenance costs because a potentially larger expense is involved, more than just parts and labor. Now we have to deal with the cost of lost production time, which can have a much greater overall effect. Mine plan economics are another cost consideration where we can't make a comparison without looking at specifics. Here you must look at the movement of power centers vs. the flexibility and freedom of movement of vehicles. The determination must be made as to what types of equipment will fit into any predetermined mine plan and if a change in the planned roadway dimensions for the mine plan itself would be more economical so that more efficient type of equipment could be utilized. Finally, two of the most important aspects to be considered with potential ramifications far beyond what we have mentioned previously, is the cost of health and safety, which is really the cost of meeting current and future government regulations, reasonable or otherwise. And of course, when making any consideration here it is impossible to come up with anything more than an educated guess on the cost of meeting the new regulations. Now let's take a look at some of the advantages of diesel vehicles as well as advantages offered by electric vehicles, both battery and cable powered versions (Figure 2). Much of the data used in this comparison is based on experience with three vehicles manufactured by Jeffrey Mining Machinery Division, Dresser Industries. Jeffrey manufactures all three types, each with approximately a 15-ton capacity, even though few of these Jeffrey vehicles are used in uranium mining operations. Much of our experience comes from the 4114 diesel powered RAMCAR which is a 4-wheel drive, articulated steering,vehicle powered by a Caterpillar 3306NA engine and using a powershift transmission. This will be compared with the performance of the Jeffrey 404H battery powered RAMCAR with articulated steering which utilizes a separate 35 HP DC drive motor on each of two wheels with solid-state speed controls, and the final comparison will be made on the Jeffrey 4015 cable-reel shuttle car which is powered by two 60 HP constant

Jan 1, 1982

By A. S. Winters

INTRODUCTION Homestake Mining Co. owns and operates the Bull¬dog Mountain mine near Creede, CO. Lead-silver con¬centrates are produced from ores extracted from narrow veins which dip from 1.04 to 1.39 rad (60 to 80°). An¬nual mill throughput is approximately 90 700 t (100,000 st). Ore shoots average 2 m (7 ft) in width and the ore is often weak, muddy, and poorly consolidated. Walls can be either strong or highly fractured along the strike of the veins. Cut-and-fill methods were initially selected to mine the deposit and considerable overhand mining occurred during the initial stages of the mine. Because of un¬stable ground conditions, mine management recognized that other methods would have to be employed. Undercut-and-fill mining was adapted to extract the loose ore from narrow veins and is presently the primary method used. Approximately 80% of the annual pro¬duction is extracted by this system. Loading ramps are positioned along the strike of the vein on 90-m (300-ft) intervals to allow for 45-m (150-ft) long cuts in each direction from the extraction raise. This interval was selected for efficient slusher operation and stope cycling. Loading ramps rather than chutes were selected for ore movement into 4.5-t (5-st) Granby-type cars because of extremely sticky ore conditions. Mined-out areas are filled with deslimed mill sands. Sand is pumped from the mill into two mine storage dams where the water is decanted. Each dam has a 544-t (600-st) capacity. Sand is pumped into the mine at a 30 to 40% slurry through 2195 m (7200 ft) of 51-mm (2-in.) thick wall pipe. When called for, sand is reslurried within the dams to a density of 55 to 65% and pumped to the particular mine opening requiring fill. Dry cement is added to the slurry prior to pumping. The capacity of the mine fill system is 20 t/h (22 stph). DEVELOPMENT Vertical development below the main adit level oc¬curs on 61-m (200-ft) intervals from an internal winze. Main haulage drifts or laterals are 2.7 x 2.7 m (9 x 9 ft) in section and driven parallel to the vein structures. Ground conditions generally dictate that better progress can be realized in the footwall than in the hanging wall. A distance of approximately 21 m (70 ft) is maintained between vein and drift openings to accommodate a smooth 18-m (60-ft) radius curve for crosscuts which are driven on 91-m (300-ft) intervals. Approximately 18 m (60 ft) of tail room is driven past the vein inter¬section to accommodate train loading. Ore and waste are hauled using diesel or electric driven locomotives operating over 18-kg (40-Ib) rail [762-mm (30-in.) gage]. Loading ramps are established above each crosscut¬ vein intersection. Scram drifts are then driven in the vein to determine the width and grade of the ore. If a prior decision to mine the block had been reached, then the scram is driven only far enough [about 12 m (40 ft)] to establish a drawpoint and scraper tail room. In most cases, the drawpoint is a 2.1 x 2.1-m (7 x 7-ft) cutout driven about 2.4 m (8 ft) into the footwall. On the level above, a raise bore station is established in the footwall to one side of the crosscut-vein inter¬section. The station is of sufficient size to accommo¬date a Robbins 41R raise boring machine. Support for the station is accomplished with 1.2 and 1.8-m (4 and 6-ft) roof bolts and wire screening. Once completed, a 152-mm (6-in.) concrete slab is poured and the raise drill set in position to center the 1.5-m (5-ft) diam hole approximately 1.8 m (6 ft) from the vein footwall. A 229-mm (9-in.) pilot hole is then drilled to the scram cutout below and reamed back to full diameter (see Fig. 1). STOPING Initial mining in a typical undercut-and-fill stope be¬gins from the top of the borehole. The initial cut can be either immediately beneath the track level or the old scram drift depending upon the particular situation. Cuts vary but are generally 2.4 to 3 m (8 to 10 ft) high. Support is accomplished by square-set timber, overhead caps, or roof bolts and screening depending upon ground conditions. Once the initial cut is removed, underhand timber and screen is installed and cemented sand fill placed. The stope is then ready for undercut mining. Prepara¬tion work begins with sinking 4.5 to 6 m (15 to 20 ft) on the borehole plus cutting a slot to the vein. As sinking progresses, hanging sets are installed to provide man¬way and service facilities. Hanging sets 1.7 m (5 ft 8 in.) long and 1.6 x 2.2 m (5 ft 4 in. x 7 ft 4 in.) in section are installed with steel hangers similar to shaft sets. Framed 203 x 203-mm (8 x 8-in.) timbers are made up in advance and shipped to the stope during sinking operations. When manway and service facilities are completed to the floor of cut to be mined, generally 3.65 to 4.3 m (12 to 14 ft) below the previous sand fill, the ore is removed to the hanging wall plus a round each way along the vein. Levelers or long stringers are then installed over the raise opening to support the work deck, slusher, and grizzly opening. All waste and ore from the sinking process is fed by gravity to the raise (see Fig. 2). Once the stope is equipped, mining pro¬gresses outward in each direction from the grizzly open¬ing. Stope equipment consists of 907 kg (2000 lb) pull air tuggers, timber skips, 11-kW (15-hp) ventilation fans, 15 to 22-kW (20 to 30-hp) electric slushers, 762 to 1270-mm (30 to 50-in.) scrapers, 67-mm (25/a-in. ) jackleg drills, as well as other drilling and blasting supplies. In narrow stopes [generally less than 2 m (7 ft) wide], no support is required for the underhand caps of the previous fill. Where wide sections in the vein occur, segment braces are installed beneath the caps to insure that the sand support cannot slip away from the hanging wall. Sections as great as 6 m (20 ft) wide and 4.5 m

Jan 1, 1982

Although the diesel engine is normally considered a tried and proven power source, many new and exciting diesel design concepts are being evaluated in engine development laboratories around the world. Three such programs currently underway at Cummins Engine Company are discussed. The turbocompound engine converts into power exhaust heat energy which is normally wasted. It does this by incorporating after the turbocharger a low pressure gas turbine which is gear driven to the crankshaft. The adiabatic engine has no conventional cooling system. It converts into useful power most of the heat energy normally rejected to the coolant. The series boost turbocharged engine uses seperate low and high pressure turbochargers to increase engine output and improve transient performance. These design concepts make possible increases in diesel engine thermal efficiency from the current 33 to 38 per cent range to the 50 percent range.

Jan 1, 1982