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By N. Demirel

Estimating productivity of a walking dragline is of paramount concern to mining engineers and mine planners. Risk based evaluation of the dragline productivity is a valuable tool to estimate the dragline?s long-term performances and availabilities, to develop preventive maintenance plans, and to make future projections about the machine?s performance. This paper aims to provide mining professionals with an overview of risk assessment methodology for productivity of two walking draglines, PAGE 736 and MARION 7820, which have been operating in Tunçbilek open cast coal mine of Turkish Coal Enterprises (TKI) in Turkey. The study encompasses three main stages as: (i) acquiring of monthly maintenance records, operating hours, mechanical and electrical failure hours between 1998 and 2009; (ii) reliability modeling using mean time between failure data; (iii) determining hazard rate and consequences to compute risk associated with dragline productivity. The results showed that that Page 736 (20 yd3) is seemed to be more reliable and less likely to fail when compared with Marion 7820 (40 yd3). The operating hours without failure range from 41 to 51 hours with 50 percent reliability.

Jan 1, 2011

By Barnaby J. Watten, Sibrell. Philip L., Brian J. Vinci, Andrew E. Friedrich

We evaluated a new process for remediation of acid rock drainage (ARD). The process treats ARD with intermittently fluidized beds of granular limestone maintained within a continuous flow reactor pressurized with CO2. Tests were performed over a thirty day period at the Toby Creek mine drainage treatment plant, Elk County, Pennsylvania in cooperation with the Pennsylvania Department of Environmental Protection. Equipment performance was established at operating pressures of 0,34,82, and 117 kPa using an ARD flow of 227 L/min. The ARD had the following characteristics: pH, 3.1; temperature, 10 OC; dissolved oxygen, 6.4 mg/L; acidity, 260 mg/5; total iron, 21 mg/L; aluminum, 22 mg/L; manganese, 7.5 mg/L; and conductivity, 1400 uS/cm. In all cases tested, processed ARD was net alkaline with mean pH and alkalinities of 6.7 and 59 mg/L at a CO2 pressure of 0 kPa, 6.6 and 158 mg/L at 34 kPa, 7.4 and 240 mg/L at 82 kPa, and 7.4 and 290 mg/L at 117 kPa Processed ARD alkalinities were correlated to the settled bed depth (p<0.001) and CO2 pressure (p<0.001). Iron, aluminum, and manganese removal efficiencies of 96%, 99%, and 5%, respectively, were achieved with filtration following treatment. No indications of metal hydroxide precipitation or armoring of the limestone were observed. The surplus alkalinity established at 82 kPa was successful in treating an equivalent of 1136 L/min (fivefold dilution) of the combined three ARD streams entering the Toby Creek Plant. This side-stream capability provides savings in treatment unit scale as well as flexibility in treatment effect. The capability of the system to handle higher influent acidity was tested by elevating the acidity to 5000 mg/L with sulfuric acid. Net alkaline effluent was produced, indicating applicability of the process to highly acidic ARD.

Jan 1, 2000

By Donald A. Dahlstrom, Wai-Ping Kam

The mineral industry and individual processing plants are large consumers of energy. While energy conservation has received some attention in the present Federal Administration National Energy Strategy proposal it is obvious that the mineral industry should also continue to emphasize energy consumption reduction for important economic savings alone. As indicated by other studies, comminution is the largest single consumer of energy in the mineral processing plant (1.3% of total electrical energy consumption in the U.S.A.).1 Fine grinding is the largest portion of this amazing statistic. While substantial energy savings have been demonstrated by new machine developments and improved control methods, undoubtedly there are additional areas in comminution where substantial progress can be made. Some time ago, the U.S. Department of Energy published a report on "Comminution and Energy Consumption" by a committee composed of experts in the field of comminution from industry and academia. They identified the following potential for energy savings by specific areas? Classification device design 9-13% Comminution device design 3-16% Control 9% Grinding additive 3-6% Materials 3% It is apparent that the classification device had the first or second highest savings potential. Obviously, serious research consideration must be given to this technology area. A series of three papers have previously been written on the subject of two stage classification research work for ball mill operation by the authors. Accordingly, a brief review will be made. Previous Research Results on Two Stage Classification The hydrocyclone was selected as the type of classification equipment for this study as it represents by far the majority of the devices used in ball milling. While four different hydrocyclone circuits have been proposed by others,3 only two were considered in this work as illustrated in Figure 1. Flowsheet A is truly counter-current in nature in that the product from the ball milling circuit is taken from the first stage overflow

Jan 1, 1992

By Jr. Raleigh

Three run-of-mine bituminous coals, which ranged in rank from low volatile to high volatile A, were floated at nominal -28 mesh (590 µ m), -100 mesh (150 µ m), and -400 mesh (37 µ m) feed particle sizes with selected pyrite depressants and a dispersant. For the coals tested, pyrite and ash-forming minerals were usually rejected best at a -100 mesh feed particle size. Depressant additions tended to improve flotation selectivity between pyrite and coal. When joint dispersant-depressant systems were used at -100 mesh (150 µ m) feed particle sizes, the total sulfur content of the clean coal decreased further. For a comparable coal yield, less fuel oil collector was required for the flotation of -100 mesh coal than was required for the flotation of either -28 or -400 mesh feed.

Jan 1, 1990

By D. H. White

The term "block caving" as used in this text includes panel caving and mass caving as described by Julin and Tobie (1973). This method reportedly was conceived in 1895 when a block of ore ranging up to 200 ft (61 m) in width was undercut at the Pewabic Mine on the Menominee Range in Michigan (Bucky, 1956). Over the years this method has evolved largely as a consequence of trial and error in which operators became acutely aware of what nature would allow and what it would not. Today block caving remains somewhat of an art rather than a science where experience often dictates what needs to be done. With the plunging prices of base and specialty metals in the early 1980s caving mines sought to reduce operating and development costs in order to return to profitability. For some this became an impossible task given the design, grade and operating costs of the day and closure became the only alternative. One lesson learned from the experiences of the 80s is that survivability depends on cost competitiveness and this implies the efficient use of resources and technology. To this end applied rock mechanics serves as a useful tool. The purpose of this paper is to show how Geomechanics can be used? in block caving to facilitate sound decision making and how this equates to dollars saved. Features of mining method selection, design and operation are discussed as related to this theme.

Jan 1, 1990

By BHAMIDIPATI S. SASTRY, KATTAMURI PAVAN KUMAR, ADITYA PANDEY

Several laboratory methods are available to determine the thermal conductivity of rocks, but most of them are complex and cumbersome. The present study explains the working principle of Lee’s apparatus, which is relatively simple, easy to fabricate and use, and provides consistent results. In the present study, thermal conductivities of sandstone cores obtained from an Indian coal mine are determined using Lee’s apparatus. An approach is discussed to determine the temperature gradient of sandstone specimens while cooling and is used to calculate thermal conductivity. The thermal conductivities of different sandstone specimens have values between 2.37 and 2.59 Wm−1°C−1. For different sandstone cores obtained from the field, properties including specific gravity, specific heat capacity, thermal diffusivity and porosity, along with thermal conductivity, were determined and highlighted in this study.

The Earth?s population is approaching 6.6 billion people. More than half live in urban areas. And, as those figures continue to grow, the need to make wise use of the world?s natural resources as well as its living space will also grow. Thus, the concept of sustainable development ? meeting the needs of the current generation while preserving resources for future generations. The use of underground space is only one part of the sustainable development concept. But it is an important one. Tunnels and underground space are environmentally friendly and contribute significantly to sustainable development. But it takes years to plan and build tunnels and other underground infrastructure. And the demand for infrastructure in the world?s mega cities has grown significantly. In December, about 100 people representing several developed and developing nations spent a day at the United Nations (UN) in New York City discussing the future of underground space development throughout the world. The meeting was put on by the UN?s Department of Economic and Social Affairs and the International Tunnelling and Underground Space Association (ITA). The conference was titled ?The Use of Underground Space as an Unexpected Solution for Promoting Sustainable Development.? Its aim was to promote practical solutions to the use of underground space and tunnels as feasible alternatives to promote sustainable development throughout the world. A panel of speakers from government, academia, the UN and the ITA stressed that development is not sustainable without infrastructure. And, as the world?s population grows, there is now an urgent requirement to efficiently plan for the use of underground space to preserve it for the future benefit of mankind. The benefits of the use of underground space are many, they said. Among them: ? Tunnels channel clean water in and waste water out. This promotes health and sustainability worldwide, particularly in developing countries. ? The use of tunnels and underground space helps conserve energy and increases its efficient use ? the use of tunnels cuts commuting time and so saves energy. ? Tunnels, microtunnels and other underground structures promote the more efficient use of space in large cities ? the bulk storage of water, fuel and other goods. ? Underground structures are subject to less stress than surface structures, making them safe havens for natural and man-made hazards, including earthquakes. And, because underground structures are more durable, lifecycle costs are less than surface structures. ? Underground structures promote the multiple use of available land. Land owner-ship at several layers increases land use and provides more usable space. Han Admiraal is director of the Center for Underground Construction in the Netherlands. He said that urban planners need a new vision concerning the use of underground space. Going underground protects historical and archaeological surface facilities, he said. Underground space use can also protect populations located in adverse climates. And sensitive environmental areas on the surface can also be protected from development. In addition to the transportation of people, freight and water, underground development can also store water, as well as provide storage for waste, hazardous materials, carbon dioxide and geothermal energy. The upshot of this new awareness and vision for under-ground space is that its use should be considered before surface development, Admiraal said. And planners and developers are placing more emphasis on underground space development as part of their overall development plans for urban areas. That was not always the case, he said. In the past, underground space was not considered until after the surface space had run out, he said.

Jan 1, 2008

By Steven W. Hunt

"A paper called “Global Experience with Soft Ground and Weak Rock Tunneling under Very High Groundwater Heads” was presented at the North American Tunneling 2006 conference (Holzhäuser et.al 2006). It summarized global experience with earth pressure balance (EPB) and slurry shield tunneling on nine projects that encountered groundwater heads ranging from 6 to 11 bar. Since then, additional projects have been completed with groundwater heads ranging from 7 to 15 bar. Of these, the high pressure tunneling experience on the Lake Mead Intake No. 3 project in Nevada and on the Eurasia Tunnel (Istanbul Strait Crossing) had the greatest lengths of tunneling at face pressure over 7 bar. Experience with sustained pressurized face tunneling at groundwater heads over 7 bar and risk management observations are the focus of this paper. INTRODUCTION High groundwater head, particularly at 7 bar or more, is a major challenge when tunnelling in high permeability ground and on drives long enough to require cutter changes. It has a strong impact on design and operation of Tunnel Boring Machines (TBMs) in order to protect the main bearing from contamination, prevent excessive groundwater inflow, ensure face stability and enable access to the cutterhead and excavation chamber for maintenance. During the past 20 years, TBM manufacturers and suppliers have made tremendous improvements that allow tunneling at groundwater pressures to 17 bar or more. The most significant risk with high pressure tunneling is generally that of excavation chamber access and potentially the cutterhead for cutter changes, cutterhead repairs and TBM maintenance. Hyperbaric interventions are possible and safety variances have been approved for saturation dive interventions at pressures as high as 17 bar (Lake Mead Intake No. 3). While high pressure hyperbaric intervention equipment is available and safety approvals can be obtained at many locations, few contractors consider the cost and risk of hyperbaric interventions over 7 bar to be acceptable as the primary means of excavation chamber access. Experience with high pressure tunneling prior to 2006 was summarized in a paper entitled “Global Experience with Soft Ground and Weak Rock Tunneling under Very High Groundwater Heads” (Holzhäuser et.al 2006). That paper provided information on 9 projects: South Bay Ocean Outfall, San Diego; Channel Tunnel (French Side), France; Storebaelt Tunnel, Denmark; 4th Elbe Tunnel, Germany; Wesertunnel, Germany; Westerschelde Tunnel, Netherlands; St. Petersburg Red Line, Russia; Nara Prefecture Water Conveyance Tunnel, Japan; and Tokyo Wan Aqua Line Tunnel, Japan – see Table 1."

Jan 1, 2016

By George A. Savanick

Borehole (slurry) mining, in which a tool incorporating a water-jet cutter and a downhole slurry pump mines phosphate through a borehole, was field tested in northeastern Florida as part of a Bureau of Mines program to increase the domestic availability of critical minerals. Approximately 1700 tons (1.54x106 kg) of phosphate ore were mined at 40 tph (10.1 kg/s) from a depth of 250 ft (76 m). The borehole was filled with water during mining for roof support and to assist slurry pumping. Underwater cutting was enhanced with an air-shrouded water jet. Mined cavities were backfilled to prevent subsidence after abandonment. Roof subsidence during mining was avoided only when the cavity was filled with water. Environmental monitoring before, during, and after mining included hydrological studies and measurements of water quality. Significant water quality changes occurred only in the zone being mined and were confined to the immediate area of the borehole.

Jan 1, 1983

By Mark Leggett, Kevin Roberts

The need to modernise and increase the safety provision of older road tunnels raises challenges in maintaining the operation of the tunnel during such improvement works. The Mersey Kingsway twin road tunnels located in Liverpool UK, constructed in the late 1960s, have had three new cross passages constructed to allow emergency evacuation from one tunnel to the other tunnel and provide safer access for emergency services. The 3200m long road tunnels are lined with an unusual reinforced concrete steel-faced segmental lining with a paint finish. Construction of the cross passages occurred during night possessions with the tunnels returned to normal operation during the daytime. Constructed through water bearing sandstone and lined with precast concrete segments, the passages required advance ground treatment and support works. This paper presents the historical background to the Mersey Tunnels and describes the procurement strategy, design and construction approach adopted for these important safety improvements.

Jan 1, 2003

By P. H. Qi

Activated carbon loaded with gold from different halide solutions has been characterized by thermal analysis techniques. The mechanism of gold uptake by carbon varies from predominately adsorption for gold iodide to predominately reduction for gold chloride. TGA and DT A measurements confirm the existence of adsorbed gold-halide species within the micropore structure of carbon. These results suggest that the ration of reduced; adsorbed gold increases for gold halides in the order Au-I > Au-Br > Au-Cl. In the case of Au-I, TA results for the loaded carbon were compared with pure compounds of 12, AuI and AuI3.

Jan 1, 1996

By C. Sun

With complex component, higher salt content, low biodegradability, DSD acid oxidation wastewater could not be efficiently dealt with traditional methods. It is pointed that the coal water slurry could be made with DSD acid oxidation wastewater of different concentration and the density of coal water slurry could be up to 70%, while its viscosity is only 850~930 mPa?s. The coal water slurry could be perfectly jetted and burnt under different conditions. The higher density the DSD acid oxidation wastewater has, the better properties the coal water slurry have. The pollution components and characteristic group of DSD acid oxidation wastewater are similar to the additives of coal water slurry, so it could be used as a kind of usable additive of water coal slurry. It is so reasonable and feasible to make coal water slurry with DSD acid oxidation wastewater that the pollution of DSD acid oxidation wastewater can be solved completely.

Feb 23, 2014

Passive seismic monitoring is a useful tool for measuring wave propagation in rock mass in deep underground mining. About 20000 mining ? induced seismic events of a hard rock mine, are identified and investigated. The travel times of source-receiver pairs allow us to demonstrate temporal change in velocity. It was found that the average P wave velocity is about 6000 m/s in the mining regions. Velocity investigations on the data during about three months around the main shocks show a significant decrease of the average seismic wave velocity after the main shocks. The sudden drop of average velocity change after the main shocks implies the creation of new fractures in the rock mass due to the main shocks. Afterward, the average velocity increased to a normal level after a time duration of several days. A reasonable explanation for the post seismic velocity increase is that opened cracks begin to close due to crack healing.

Feb 23, 2014

By W. Zhang

"The adsorption of collector on chalcocite has been studied in situ in aqueous solutions by applying an atomic force microscopy (AFM). The AFM images show that xanthate, such as potassium ethyl xanthate (KEX) and potassium amyl xanthate (PAX), adsorbs strongly on chalcocite mainly in the form of insoluble metal xanthate, which binds strongly with the mineral surface without being removed by flushing with ethanol alcohol. The result clearly shows that the adsorption of xanthate on chalcocite is totally different from its adsorption on chalcopyrite, during which oily dixanthogen is the main adsorption product on chalcopyrite surface. AFM images also showed that increasing solution pH to 10 doesn’t prevent the adsorption of xanthate on chalcocite much and the result confirms with the fact that chalcocite floats well in a wide pH range up to 12 with xanthate being used as a collector. INTRODUCTION In flotation, the adsorption of collector on mineral surface is vital for a successful flotation process to achieve a satisfying metal recovery. Historically, many works have been carried out to clarify the adsorption mechanism of collectors on sulfides. (Gaudin and Schuhmann, 1936, Poling and Leja, 1963; Allison et al., 1972, Fuerstenau, 1982; Leja, 1982; Woods, 1984) The adsorption of xanthate on chalcocite surface in aqueous solution also attracted the interest of many researches. Gaudin and his colleagues (Gaudin et al., 1934; Gaudin and Schuhmann, 1936) studied the solubility of potassium ethyl xanthate and its reaction products in organic solvents and firstly proposed there was initially chemisorbed xanthate (X-) on chalcocite surface followed by insoluble cuprous xanthate (CuX). Allison et al. (1972) studied the reaction products of various sulfide minerals with xanthate solutions and reported that the measured rest potential of chalcocite in 6.25×10-4 M KEX solution at pH 7 was +60 mV and the reaction product of PAX on chalcocite was cuprous xanthate. Mielczarski and Suoninen (1984a, 1984b) applied the XPS and studied the adsorption of potassium ethyl xanthate on cuprous sulfide. It was reported that there was a relatively rapid formation of a well-oriented monolayer of xanthate ions followed by a slow growth of disordered cuprous xanthate molecules on top of this layer. Richardson et al. (1984) carried out an electrochemical study of chalcocite flotation with the addition of ethyl xanthate. It was proposed that cuprous xanthate and possibly cupric xanthate were adsorbed hydrophobic species on chalcocite surface due to the exchange and charge transfer oxidation reactions. Leppinen et al. (1989) applied an in-situ FTIR study of ethyl xanthate adsorption on sulfide minerals under conditions of controlled potential and they concluded that, for chalcocite, there were three different potential regions of xanthate adsorption, including chemisorption, copper ethyl xanthate formation on the surface and multilayer formation."

Jan 1, 2015

By John S. Egbert

Many of you are familiar with the Washington Metro Project. However, inasmuch as some may not be, and others may want to refresh their memories regarding certain facets of the project, I will cite a few summary details about the rail transit system we are constructing. That summary will also give each of us a common point for departure as I develop the principal thoughts that I want to leave with you. The Washington Metropolitan Area Transit Authority (WMATA) is an interstate agency established by Compact between the District of Columbia, Maryland and Virginia and approved by the United States Congress. Currently, the Authority has approval to build and operate a 101-mile (162.5 km) regional rapid rail transit system as shown on Appendix A. Of that total, 38 miles (61.2 km) will be in D. C., 32 miles (51.5 km) in Maryland and 30 miles (48.3 km) in Virginia. (Mileage figures, because of rounding error, do not add to 101 miles.) Referring again to the 101-mile total, 48 miles (77.2 km) will be underground, 42 miles (67.6 km) on the surface and 10 miles (16.1 km) on aerial structures. Of the 48 miles (77.2 km) that are underground, 15 miles (24.1 km) are rock tunnel, 14 miles (22.5 km) are earth tunnel, 0.5 miles (0.8 km) 9.s sunken tube and 19 miles (30.6 inn) are cut-and-cover construction. The system will include 86 stations, with 51 of them underground. Referring again to the full 86 stations, 43 will be in D. C., 23 in Maryland and 20 in Virginia. We currently have 37 miles (59.5 km) of line and 41 stations in operations as shown on Appendix B. Also shown on Appendix B is another 16 mile (25.7 km) increment and 13 stations which have been substantially completed, but are not yet in service. Additionally,

Jan 1, 1981

By J. E. Carr

A bewildering number of continuous thickeners and clarifiers are used in mineral industries and other heavy industries. General types are: 1. Conventional Thickeners (Fig. 1). 2. Thickeners with Flocculating Feedwells (Fig. 2). 3. Solids Contactors (Fig. 2). 4. Tray Thickeners (Fig. 3). 5. Lamellas (Fig. 4). 6. Conventional Thickeners with Lamellas 7. High Flow, Fluid Bed Thickeners (Fig. 5). These units must be adapted to varied applications. They must provide operating flexibility to meet process needs. Such factors multiply the decisions which must be made prior to the selection of a thickener. The seven types of thickeners listed above, with their variations, share design concepts which limit their application and which can be used to evaluate their performance. Some of these are listed: 1. Feed velocities must be limited and/or controlled. 2. Natural or reagent flocculation is necessary. 3. Horizontal settling area is the basis for capacity. 4. Overflow velocities must be limited and/or controlled. 5. A controlled underflow is necessary. Applying these needs to the basic process concepts is thickener selection. The basic function of a thickener in the minerals industry is the separation of a thickened sludge containing fine solids from water. To this primary separation function are frequently added others to give a list as follows:

Jan 1, 1977

By T. Umadevi, A. Pratap Singh, R. Sah, K. Abhishek

"It was possible to beneficiate a low-grade iron ore fines sample from Bellary-Hospet, Karnataka, India assaying 56% Fe, 9.1% SiO2 and 5.2% Al2O3 and produce two concentrates, namely, a sinter-grade fines concentrate (43.7% by weight), assaying 63.6% Fe, 2.6% SiO2 and 1.7% Al2O3, and a pellet-grade concentrate (30.7% by weight) assaying 64.7% Fe, 2.9% SiO2 and 1.7%Al2O3. Rejects (25.6% by weight) assayed 32.5% Fe, 27.9% SiO2 and 15.4% Al2O3. The mineralogical characterization indicated that the sample consisted of 69.5% ironbearing minerals (56% hematite, 7.5% martite and 6% goethite-limonite), 12.5% quartz and 15.2% clay, and the rest were minor minerals. Liberation size was found to be in the size range of 25 to 100 µm. The process flow sheet consists of jigs, spirals, grinding and low- and high-intensity magnetic separation of the deslimed feed. IntroductionJSW Steel Ltd is a 10-Mt/a integrated steel plant. To produce 10 Mt/a hot metal requires nearly 16 to 20 Mt/a iron ore fines. The fast depletion of highgrade iron ore fines, increased industrial demand and an increase in iron ore prices have necessitated the exploitation and use of low-grade iron ore fines in the steel-making process after beneficiation. Thus, the beneficiation of low-grade iron ores by removing the associated gangue minerals and enhancing their grade is essential. The use of these iron ore fines in sinter and pellet making has prompted the undertaking of systematic studies on low-grade iron ores.Finely disseminated low-grade iron ores with siliceous impurities have been upgraded by gravity, magnetic and flotation-based processes (Burt, 1994; Svoboda, 1987; Houot, 1983). The processing of low-grade Indian hematite ore containing high levels of alumina-bearing minerals as impurities present separation challenges and pose special problems in martite and magnetite, in association with quartz and clay as the gangue-forming minerals. Alumina is mainly contributed by clay (kaolinite, montmorillonite, illite, alunite), lateritic material and gibbsite; some alumina occurs as solids in iron oxide minerals, namely, goethite and limonite. Silica is mainly contributed by quartz and the associated clay. achieving a high-grade concentrate (Pradip, 1994; Singh and Mehrotra, 2007). Hematite ore basically consists of varying amounts of hematite, goethite,"

Jan 1, 2015

By H. R. Manouchehri

The responses of calcite, feldspar, and quartz minerals In a laboratory free fall electrostatic separator, before and after tribocharging with stainless steel, PVC, and copper plates, have been investigated. The effect of H3BO3 and BaCl2 chemicals pre-treatment on the electrical properties of the minerals is examined. The changes in the electrical properties are discussed with the determined charge, dielectric constant, and electrical conductivity of the mineral samples. Electrical properties of the minerals and their responses to the electrical field during separation, after tribocharging and chemical pre-treatment, are explored for the need to characterize the electrical behaviour of the minerals.

Jan 1, 1998

By Manfred G. Raschke

INTRODUCTION In the past decade, the international coal trade has been undergoing a period of gradual change. This change will continue through the remainder of this century until by the year 2000 the international coal industry will look very different from the industry which existed in the early 1970&apos;s. The industry which will emerge from the thirty year period of change (1970-2000) will be different in many ways. -The volumes of coal transported will be much larger. - The primary type of coal traded will be steam coal rather than metallurgical coal. - A much broader group of countries will be participating in the trade both as suppliers and as consumers. - The trade will be dominated by a relatively small number of large producing and trading companies. - The coal mined for international shipment will be primarily surface- mined. – The United States will play a decreasingly important role in international coal trade. In the course of this paper I propose to address three questions which are crucial to the formulation of an understanding of the changes outlined above : (1) Which supplier nations will be most successful in the international metallurgical and steam coal trade in the next decade and a half? (2) What emerging trends will shape the international coal trade in the 1980&apos;s and 19901s? (3) Where are U.S. producers likely to fit in this scheme of things? As a background to my remarks, I should note that what follows is based on five years of work in a consulting capacity on coal supply and demand issues worldwide. Although in the course of this work I have had occasion to develop mining and transportation cost figures for all of the countries discussed below--both my own and those obtained from coal producers--it is apparent that success in the marketplace can be determined in some instances by considerations other than costs. Nevertheless, my comments today about international competitiveness will be dominated by cost considerations; there are, after all, not many markets that reward the high-cost producer with success. Let us begin by establishing some criteria for success in the international coal market and then compare some of the producer nations to some of these criteria. The criteria are: - Low delivered cost, - Good quality coal, - The producer&apos;s partnership in a joint mining venture with an importer or a consumer of coal, - The producer&apos;s international business orientation and commitment to penetrating the market, - The producer&apos;s reliability as a supplier, and - Political pressure exerted by the producing country on consumers.

Jan 1, 1986

By B. P. Boisen

INTRODUCTION Application Measurement of rock deformation is essential to stability and behavioral monitoring of underground openings. The difficulties of obtaining adequate sample distribution, density, and orientation can frequently be overcome by the use of single and multiple position borehole extensometers. In its simplest form, a borehole extensometer consists of an instrument head, usually anchored in the collar of a borehole, and a number of in-hole anchors, each of which is fixed in place at a known distance from the collar. As rock adjacent to the borehole deforms, the component parallel to the borehole direction causes a distance change between adjacent in-hole anchors, as well as a distance change between individual anchors and the instrument head. These changes are measured by means of a mechanical link (usually wire or rod) extending to the instrument head from each anchor. The resulting data can be used to compute the distribution, magnitude, rate, and acceleration of deformation in the material intersected by the extensometer&apos;s borehole. Wire Vs. Rod Extensometers Since the early 1960s myriad varieties of borehole extensometers have become available through the combination of various special features of two basic instruments, the wire and rod versions of borehole extensometers. Recent publications have recommended shallow depth limitations for wire extensometers, and favor rod extensometers for a broad range of borehole inclinations and depths. There are three main reasons for using a deep wire system: its cost effectiveness; the fact that tremendous depth means tremendous rod weight which will cause the rod to buckle or rub against the borehole or casing wall; and users&apos; attitude and proper understanding of how to install and apply a wire-type extensometer. Here experience plays a big role. Over the years, many have learned the hard way that untensioned rod extensometers are simple and inherently inexpensive, but limited to vertical up holes where sensitivity is not influenced by friction between the rod elements and the borehole wall or protective conduit, the inertia of the rod elements, or the direction of the movement to be measured. In deep, horizontal, or inclined holes, and in instances where compressive as well as tensile strains or displacements are anticipated, tensioned rod or wire systems are preferred. System Components Borehole extensometers are made up of at least the following five principal components: the instrument head; the collar anchor assembly; the downhole system of anchors and rods or wires; the signal cable if the head is equipped for electronic readout; and the readout apparatus, whether mechanical or electronic. These components are shown in Fig. 1. Borehole Requirements Most extensometers are designed for installation in nominal 75 to 57-mm (3.0 to 2.25-in.) diam drill holes. Either a diamond drill or a percussion drill hole is satisfactory, provided the variation in drill-hole diameter is within the tolerance of the standard anchor design. The basic system may be modified for other hole diameters by changing the dimensions of the collar anchor and downhole anchor assemblies. Some instrument heads and collar anchor assemblies require enlarged borehole collars, though usually not over 150 mm (6 in.) for a depth of 1 m (3 ft). It is desirable, although not essential, that holes be free-draining. Holes must be clean and free of debris before installation. Depth/Orientation of Extensometer Boreholes Extensometers are designed to measure axial strain components in the instrumented drill hole. As the drill hole is axially deformed, the distances between individual downhole anchors and the instrument head change, as do the distances between adjacent anchors. The distance changes measured by a multiple position borehole extensometer, for example, are reduced to functions of time, hole depth, anchor position, or other parameters of significance in terms of the structure under investigation.

Jan 1, 1982