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By Francis S. Kendorski

INTRODUCTION Caving offers the lowest cost per ton of any large-scale mining method, but its successful application demands an ore body that conforms to several rigid requirements. The deposit must be of wide areal extent, massive and not spotty in ore values, and insensitive to ore dilution. It must also be a rock mass that breaks up readily. There are only three active caving operations in the US-Climax, Henderson, and San Manuel-but caving methods have recently taken on new importance as deeper lower grade mineral occurrences and ore bodies are found. These deposits are too deep for surface min¬ing methods, and too low grade to support any type of underground mining except a bulk method such as caving. Announced discoveries or indications that may be amenable to caving include: Climax's Mt. Emmons molybdenum discovery in Colorado; Molycorp's Goat Hill molybdenum prospect in New Mexico; the Phelps Dodge molybdenum deposit in Beaver County, UT; Arizona copper occurrences such as Asarco's Sacaton, Hanna's Casa Grande, Noranda's Lakeshore, and Ken¬necott's Safford; Anaconda's suspected deep copper de¬posit in Butte, MT; Anaconda's Carr Fork, UT, deposit; and perhaps others. CAVABILITY'S ROLE IN FEASIBILITY STUDIES Caving is a system of underground mining which removes support from underneath an ore body. As a result, the rock mass fractures, fails, and flows vertically downward by gravity to be collected in previously ex¬cavated funnels. Types of ore that have been mined by caving include molybdenum, copper, iron, nickel, as¬bestos, and diamonds (Julin and Tobie, 1973). It is primarily a large-scale method, with production rates of more than 45 300 t/d (50,000 stpd) having been achieved. However, the initial capital investment before return is very high, often in the hundreds of millions of dollars. The cavability of an ore body or mineral occurrence is a critical item in the feasibility study of a proposed mine, not only from the point of overall minability, but from the point of impact on other costs such as blasting, loading, hauling, crushing, and grade recovered. Aside from the often-asked question of, "Will it or will it not cave?" the real questions are, "Can we afford to make it cave, carry the rock away, and extract the mineral?" The last is not a topic of this chapter, but the first two are. The cavability of an ore deposit or mineral occur¬rence is based on many things, but clearly, if a large enough area is undermined, any rock mass will cave. The result could be a violent collapse as occurred at Urad, CO (Kendrick, 1970), or perhaps the rock mass will cave beyond the ore boundary. Another unfavor¬able result could be ore blocks that are too large for the equipment and orepasses to handle without considerable secondary blasting. Weak rock with numerous fractures may produce a very fine ore when it caves, resulting in dilution and ground control problems. DETERMINING STRUCTURAL DOMAINS It has long been recognized that the geologic nature of an ore body is important to cavability (King, 1946). Such items as weak rock material, intensity of fractur¬ing, and severity of faulting all contribute to the success of a caving operation, and information regarding these is required as a minimum for the cavability determination. In practice, the rock mass-defined as the blocks of intact rock together with the intervening fractures, joints, faults, bedding planes, and other discontinuities-that contains the ore body, as well as the surrounding and overlying rock, must be examined in a systematic and detailed fashion. Surficial geology maps must be pre¬pared, exploration holes drilled, and core logged for en¬gineering information. The fracturing of the rock mass must be studied to ascertain the three-dimensional dis¬tribution of fractures and their characteristics, and faults must be located and described. The strength and other mechanical properties of the rock material, the fracture surfaces, and the fault filling materials must be tested and reported for later use by designers and planners. With this basic information and an understanding of the geologic setting, the rock mass can be divided into one or more structural domains which tend to behave similarly in response to engineering activities (Robertson and Piteau, 1970). One must keep in mind that the determination of the structural domains goes beyond the geologic units present. Several lithologic units may be lumped together, while a single lithologic unit can be divided into multiple domains. Major faults often form their own domain, and the direction of engineering ac¬tivity-for example, cave advance to the north rather than the south-may alter rock mass behavior, resulting in different domains. As an example of the detailed rock fracture map¬ping required for such studies, the structural domain determinations at the Climax mine (Kendorski, 1973) are shown in Fig. 1. The circles are Schmidt equal area projections of the three-dimensional attitudes of frac¬tures (Ramsay, 1967) mapped in detail at various rock exposures. The attitude of fractures is important to the cavability determination since it dictates the directional behavior of the rock mass as it fails, and determines the effectiveness of arching, keying, and rock block inter¬locking. Low-angle fractures must be present to allow movement of the rock in the vertical direction during undermining (Mahtab and Dixon, 1976); if low-angle planes of weakness are absent, the rock mass may arch with a keystone effect, rather than moving vertically downward.

Jan 1, 1982

By Steven W. Hunt, Phillip U. Santacroce, Roger C. Ilsley

Consolidation grouting from the surface prior to mining a shaft is commonly performed to reduce groundwater inflows to a manageable rate. This paper describes the inflow reductions obtained within dolomite and limestone formations at several shafts and chambers due to grouting programs for the Milwaukee Water Pollution Abatement Program. The resulting inflow reduction factors are compared to results reported in the literature for other projects. Post-grouting pump tests are also evaluated as an aid in grouting assessment. Important considerations for estimating shaft inflows from pump test results are discussed. These considerations include loss of grouted mass during mining and influence of blasting and rock features on grouting effectiveness. This information should be helpful to design engineers and contractors who need to estimate inflows after pre-excavation consolidation grouting has been performed.

Jan 1, 1993

By William Bogan, Mark Vaivoda, Richard Daniele

Many factors must be considered when performing engineering and construction work for a major minerals project. Dravo's Afton copper smelter in British Columbia illustrates some of the E&C factors considered when setting up this new operation. In March 1978, Afton Mines Ltd., a Tech Corp. subsidiary, began blister copper production at the world's first integrated copper ore mining, milling, and smelting operation to use Top Blow Rotary Converter (TBRC) process smelting technology. This key TBRC smelting element is licensed by INCO Ltd. to Dravo Corp. The TBRC process uses a single vessel of modular design. It rotates for mixing and provides complete processing capability, from concentrate through blister copper. The Afton facility is about 16 km west of Kamloops, a town in south-central British Columbia. To make its operation as economic as possible, Afton officials considered several options for the copper smelter, the first in modern times in the province. Inability to extract precious metals-primarily gold-from the concentrates ruled out hydro-metallurgical processes. The final choice was between a conventional electric furnace/ Peirce-Smith converter combination and the TBRC process. The TBRC process was chosen for its versatility in processing the various Afton concentrates and grades and its 40% lower capital cost compared to the electric furnace converter system. The TBRC smelter -including concentrate slurry receiving, drying, storage, smelting, off-gas cleaning, and copper casting-had an installed cost of about $25 million. In December 1974, a pilot program was conducted by Teck, Dravo, and INCO at INCO's Port Colborne, Ontario, research facility. The pilot program demonstrated the TBRC's ability to smelt, convert, and clean copper slags. After the successful pilot effort, Dravo performed additional research to find an effective fixation system for high grade, intermittent SO2 gases. Once the go-ahead was given, design and procurement for the Afton copper smelter was provided by the Denver Division, Dravo Engineers and Constructors. Commonwealth Construction, Vancouver, constructed all Afton facilities. Afton's single furnace smelter is designed to produce 25-kt/a blister copper in 363-408 kg cake form. The product is sold to England for electrolytic refining. The TBRC process is only one of several innovations proposed by Dravo and chosen by Afton to insure the most modern smelter in North America and meet all British Columbia's environmental restrictions. Conventional smelting methods use a separate furnace for each process step. The TBRC process employs but one furnace. The Afton TBRC vessel measures 6.4 m in length and 4.3 m in diameter. The furnace is supported on a set of motor-driven rollers. These permit the vessel to rotate at variable speeds to 40 rpm. Rotation provides good mixing, high reaction rates, and effective heat transfer from the refractory sides to the molten bath resulting in a low thermal gradient. The furnace can tilt through a full 360° for charging, firing, and pouring. Smelting at Afton is accomplished in sequential fashion. Flotation concentrate and limestone flux are initially charged to the hot, empty vessel. Using the water-cooled, oxy-fuel lance, the initial charge is smelted. Once sufficient molten bath is obtained and slagging completed, the metallic concentrate is charged. Materials are charged through the water-cooled, variable position additive chute mounted on the TBRC

Jan 10, 1980

By J. E. Feddock

To succeed in today's competitive coal market, coal companies must continuously improve production and lower cost. However, the coal industry's historical management practices must change to remain viable? The practices of the current day efficient coal mine manager are reviewed and examined using W. Edwards Deming's definition of management. The statistical tools, including Pareto Charts, Control Charts and Scatter Diagrams, which identify the problems management must approach differently to increase productivity at a coal mine, are discussed.

Jan 1, 1993

By David J. Starbuck

For small precious metals mining to show a comeback a different perspective must be taken than that of larger mining companies. This perspective must be much the same as that of past successful smaller mining enterprises such as when the US had a need for Uranium. Abandoned mines and environmental concerns in older mining districts have discouraged many from entering with the attitudes of why try there if so many unsuccessful mines exist. A small mining venture can be successful there but must have a "think smart'' attitude. There must be a thorough understanding of deposits, utilization of advanced technology and a properly managed mining operation. "THINK SMART" MINING The small mine operator is usually looking for small high grade deposits, consequently, long term success depends on a series of small successful mining operations. The small miner must succeed right-off or credibility and future project funding will suffer. No veteran of even a few years in the mining industry needs to be told that a dollar spent on production today fails to yield as much as it once did. More efficient equipment and techniques have helped soften the problem, but there is little likelihood that a mining company can do much to control inflation, wages, regulations, or grade. That leaves the small miner to "think smart" as one area where operating dollars can still be stretched to produce more than they presently do (Gardner. 1981). In the planning stage of a mining venture, when most options are still open, the main controllable elements are market timing, deposit selection, cutoff grade, mining method, mine design, mining sequence, rate of production build up, process design, project financing structure, project management, and project ownership structure. During planning, optimum criteria can be established for each of these. Once a mine is in production, these options are foreclosed or at least severely constrained. The more thought given to a mining program using all information available the less the risk of encountering disabling surprises. Thus the intent of this paper is to suggest the "think smart" attitude most small mine operations use for long term success. If one looks at a number of successful mining ventures, whether large or small, there is a general logic most have followed to be successful. They have used proven exploration, mining and processing techniques along with economic evaluation and experienced personnel to improve their odds. LOGIC IN DEVELOPING A FEASIBLE VENTURE Most successful small mine ventures achieve positive cash flow as quickly as possible by seeking out those deposits which require the least time and expense on activities leading up to production. To do this they look for deposits that are the most accessible, easily investigated, mined and processed with the cheapest fundamental methods. The general sequence of events starting with district selection are deposit selection, preliminary feasibility, exploration, detailed economic feasibility, mine planning, development and production. Each successive step becomes more costly requiring intermediate decisions along the way. District Selection Small operations should look for known deposits which favor the occurrence of the type deposit sought rather than efforts in unproductive areas. Known deposits in developed areas have some advantages over remote areas: 1. More alternative methods of transportation are available. 2. A larger stable work force is available. 3. The area is usually more pro-mining. 4. Power, water, housing, technical services, skilled services, schools, recreation and shopping are available.

Jan 1, 1987

By W. L. Oliveira, J. R. Sobrinho, V. M. Hamza, S. M. Eston

The Ipueira III chrome mine is located in the northeastern part of the state of Bahia, Brazil. Extraction is actually at depths less than 300 m, but below level 200 serious environmental problems have been encountered with respect to control of air quality, toxic gas, dust and thermal comfort. At the request of the mining company the University of São Paulo started a research program to investigate the origin and occurrence of the critical problems and to propose solutions. A ventilation survey was carried out first which revealed the existence of several air leakages and short circuits that contributed to substantial reductions in the air supply to some of the main producing levels. Computer simulation of the ventilation network showed that extending the intake air shaft to deeper levels was the most convenient and economic solution to improve the air quality. The ventilation survey was followed by a mapping of the toxic gas emissions and thermal comfort levels in several parts of the mine. The air quality conditions were evaluated as a function of gas emission and heat generation associated with production and development activities. The results show that environmental conditions are already critical in most of the working levels and neither an increase in production nor deepening of the mine can be taken up without substantial changes in the ventilation system. INTRODUCTION Environmental concern is growing in Brazil and several underground mines are starting environmental engineering programs. The LACASEMIN - Laboratory of Environmental Control and Mine Safety of the Mining Engineering Department of the University of São Paulo - was contacted by Mineração Vale do Jacurici to start a research program for investigating the origin and occurrence of environmental problems that existed in the Ipueira III chrome mine. This research program involved field measurements of air quantities with gas levels monitoring, evaluation of heat stress parameters, determination of adequate flow patterns through computer simulations and training of mine technical staff. This paper presents the results of the first 4 months of this research program. The Ipueira III mine is located in the northeastern part of the state of Bahia, near the city of Senhor do Bonfim at about 400 km inland from the state capital city of Salvador. Chromite mineralization is quite widespread in this area and often associated with mafic and ultramafic rocks which cut across regional gneisses and migmatites. ROM production in 1992 varied between 25,000 to 40,000 tons per month, 25% being of lump type (38% of Cr2O3) and 75% being of fines. Lump is manually separated and fines are concentrated in a nearby plant. All the production goes directly to the group processing steel plants near Salvador. The Ipueira III mine is currently under some adverse economic situation because of imports from South Africa and Russia, which have better grades and sometimes a lower content of phosphorous. Consequently there has been little progress in the development of new mines and even in those currently under operation the extraction is becoming more difficult due to the lack of investment in improving mining methods and ventilation systems. In spite of such difficulties the company has backed up studies for initiating an environmental engineering investigation of the Ipueira III mine. MINING METHODS AND VENTILATION SCHEMES The mining methods adopted have changed as a function of extraction depth, rock mass strength and ore body geometry. Initially the orebody was found to be fairly continuous and dipping at about 55 degrees from surface

Jan 1, 1993

By U. Paschedag

Today's modern longwalls have to produce high outputs with maximum availability and running time with the additional requirement of ever increasing panel width and length high-performance face conveyors require intelligent solutions for the integration of drive systems and chain tensioning devices into the overall longwall automation. The fully automated chain tensioning system allows the operation of an AFC with optimum chain tension at all times regardless of actual load on the conveyor. For the heavy-load start-up, the accurate load-sharing and an efficient overload protection of modern AFC's WESTFALIA and Dodge jointly developed the integrated WB/CST drive system.

Jan 1, 1995

By F. E. Kottlowski

Widespread high-calcium limestones in New Mexico region are low -in magnesium, but some units include shale interbeds deleterious for sulfur removal usage. Thick limestones in Mississippian Escabrosa, Lake Valley, and Leadville, Pennsylvanian Madera and Hermosa, Pennsylvanian-Permian Horquilla, Permian Hueco and Capitan, Cretaceous U-Bar, and some Cenozoic travertines are high-calcium units. Significant outcrops are in mountains of southwestern, south-central, central, southeastern and north-central New Mexico, southeastern Arizona, southwestern Colorado, and northwestern Chihuahua. Coal-fired powerplants are mainly in northwestern New Mexico and eastern Arizona, thus transport is mainly by railroad.

Jan 1, 1994

By Kenneth A. Rogers, Richard F. Hill

Introduction A number of processes for deriving more convenient liquid and gaseous fuels from coal are commercially available or in final stages of development. Generally, synfuels from coal processes have efficiencies ranging from 50 to 70%. Considerable engineering design and development work are necessary to bring forth commercial plants using the various technologies-but technological breakthroughs are not expected or needed. Gasification While a variety of solids handling, gas contacting, and gas quality upgrading techniques may be employed in the various gasification processes, the primary goal is the same-to convert a sulfur-containing solid to an essentially sulfur-free gaseous product. The gaseous product may be a mixture of hydrogen and carbon monoxide with nitrogen. Definitions are not rigorous, but high-Btu gas is generally over 900 Btu/scf(33 534 kJ/m3) and low-Btu gas is generally below 350 Btu/scf(13 041 kJ/m3). Medium or intermediate gas falls between these values. High-Btu production is more difficult, as it requires additional upgrading of a low- or intermediate-Btu gas stream to produce a commercially acceptable product. The carbon/ hydrogen ratio is adjusted either by rejecting a portion of the carbon, increasing the hydrogen, or a combination of both. The chemical processing steps include production processing gas containing carbon oxides and hydrogen by the reaction of carbon and steam (gasification); reaction of hydrogen and coal to form methane (a hydrogasification process); reaction of hydrogen and carbon monoxide to produce methane (methanation); and the removal of impurities. The gasification processes share a number of common techniques. The coal received at the plant site must be further cleaned and crushed or ground before it can enter the gasifier. Conventional cleaning methods are used to remove extraneous materials such as metal, rocks, etc. For some processes the coal must be finely ground so it may be fluidized or entrained in a flowing gas stream. For other processes crushing and sizing only are required. Agglomerating coals may be pretreated by heating, mild oxidation with air, or other procedures to assure smooth gasifier operation and to avoid reactor plugging. Nonagglomerating coals Such as lignite and subbituminous coal normally do not require pretreatment. Feeding a solid material such as coal to a higher pressure reactor is a difficult task. Dry feeders using a series of pressurized lock hoppers, or wet systems in which a slurry is pumped into the reactor, are used. The gasification step is the heart of the process. Here, the solid feed material is contacted with synthesis gas (carbon monoxide and hydrogen). The coal is devolatilized and a portion of the fixed carbon converted to methane. The gas-solids contacting methods used include fixed beds, fluidized beds, moving beds, entrained beds, and free-fall systems. The gasification process, overall, is endothermic and the heat required to maintain reaction rates is usually supplied by burning a portion of the coal feed. External heat sources such as electric resistance heating, molten salt or solid heat carriers, and the introduction of a hot hydrogen stream also have been tested. Following the gasification step the particulate materials and heavy hydrocarbons contained in the reactor effluent are removed by a water quench and solids separation system. If low-Btu gas or synthesis gas is the desired product, the raw gas is scrubbed to remove carbon dioxide and sulfur compounds and then is used directly. However, if high-Btu gas is desired, methanation is necessary. In most gasification processes, the hydrogen content of the gasifier

Jan 2, 1980

By Hans Skretting, Abraham A. Dor

This paper briefly reviews the historical development of the Rotary Kiln-Electric Furnace Process, which was first applied commercially to the treatment of qarnieritic ores in New Caledonia in the mid-fifties. It describes various technological improvements introduced, since, in industrial plants or developed in pilot facilities where a wide variety of nickel oxide ores has been treated success- fully over the years. Major categories of ores are characterized. The effect of their physical and chemical properties on their performance in the electric furnace is discussed. The relationships between ore composition, ferronickel grade and slag composition are analyzed and their effect on slag and metal tapping temperatures, nickel recovery, and electrode voltage are discussed.

Jan 1, 1979

By Matias Pentinnen, Wayne Dickinson

Electrowinning is a key process for copper production contributing roughly twenty percent globally and thirty to forty percent of production in the Americas1. Copper grade is assessed largely on deposit smoothness and on level of impurities in the metal. Smoothing aids are essential to create dense, low porosity deposits and guar has long been the material of choice for this purpose. Guar is, however, poorly stable under the strongly acidic electrowinning conditions, underlying ongoing research to identify an effective, acid-tolerant replacement. Current efficiency is also a critical factor in controlling copper production costs and chemical additives should ideally improve current efficiency as well as improving deposit smoothness.

Feb 1, 2025

In spite of the tremendous amount of research conducted in the last few decades. no single blasting theory has been developed and accepted that adequately explains the mechanisms of rock breakage in all blasting conditions and material types. Given specific test environments, conditions and assumptions, individual researchers have contributed valuable information and insight as inputs into blasting theories, although a simple "plug-in" type formula for predicting optimum fragmentation, muck pile geometry and casting distance, is still largely unresolved. There is as yet, no consistent and widely applicable theory of blasting, but only a number of limited and disconnected theories; many of which are empirical in nature and based on ideal blasting conditions. Blasting theories have been formulated and based on pure speculation, years of blasting experience on a trial-and-error approach, laboratory testing, field investigation, and mathematical and physical models adapted from other disciplines of science.

Jan 1, 1988

By A. D. Davis

The disposal of spent ore from cyanide heap-leach processing facilities is of concern to the mining industry, regulatory agencies, and the public. Disposal of several hundred million tons of additional spent ore is planned in the western United States during the next decade, with increased amounts likely if gold prices rise. In the past decade, more than fifteen million tons of spent ore have been disposed of in the Black Hills. South Dakota's off-loading criterion for cyanide has been set by the state's Department of Environment and Natural Resources at 0.5 parts per million (ppm) as weak acid dissociable (WAD) cyanide. Nitrate off-loading limits vary for each mine in the state, depending on ore type and other factors. Nitrate concentrations in leachate from spent ore depositories could be caused by conversion from other nitrogen-containing species. One likely source of nitrate is residual explosives from blasting of ore. Previous work on the combustion products of nitrogen explosives has shown incomplete 3xidation (Johansson and Persson, 1970). Another likely nitrate source is degradation of cyanide to ammonia, followed by oxidation to nitrite and nitrate.

Jan 1, 1994

By J. Lorengo, C. H. Bucknam

"Standardization of the Inductively Coupled Plasma Mass Spectrometry (ICPMS) method for gold in cyanide solutions was undertaken to provide a more sensitive method to quantify the gold content than the atomic absorption method standardized in 1994 (E1600). The gold concentration range covered is from 0.001 mg/L Au - 0.3 mg/L Au (0.00005 toz/t Au – 0.009 toz/t Au). Interlaboratory testing was carried out with the assistance of the American Society of Testing and Materials (ASTM) International on two committees to determine the within laboratory and between laboratory reproducibility. Three barren solutions from metallurgical operations were measured in triplicate to satisfy statistical requirements for Committee E1 on Analytical Chemistry of Metals, Ores and Related Materials. A synthetically prepared matrix representing the metallurgical processing solutions was used to prepare Youden pairs to satisfy the requirements of Committee D19 on Water. Results of the standardization program are presented. INTRODUCTION Analysis of process solutions for gold concentration requires accurate and sensitive analytical methods in order to manage process control and metallurgical accounting. Flame atomic absorption spectrophotometry (FAAS) has been the work horse of the assay lab for this duty for decades. In 1994 the FAAS standard method was approved by the American Society for Testing and Materials (ASTM) (1). Six process solutions were collected and preserved by measuring the pH and adjusting to greater than pH 10, if necessary. Duplicate solutions were provided to eight laboratories in random order for analysis by FAAS covering the gold concentration range of 0.19 µg/mL (0.006 toz/t.) to 10.7 µg/mL (0.312 toz/t). A high precision method was used, which involved bracketing the sample with the higher and lower standards nearest to its concentration repeating readings three times and averaging the results. The optimum precision for the FAAS gold method was found to be at the 1.00 µg/mL (0.029 toz/t) and lower scope limit 0.3 µg/mL (0.009 toz/t) gold concentration. Since tailings solutions typically have concentrations below the lower scope limit, use of ICPMS was developed at Newmont USA Limited (Newmont) to assay the lower range solutions."

Jan 1, 2016

By Pradip

It is possible to beneficiate low-grade phosphate ore slimes containing predominantly siliceous gangue by a combined selective flocculation-flotation scheme using commercially available reagents. The presence of clays, in particular, montmorillonite and attapulgite, has a disastrous effect on the efficiency of separation. Suitable remedies to overcome this problem are not yet available. Intensive R&D efforts are required in the areas of the design and synthesis of specific reagents, the effect of particle size, and the design of appropriate process equipment to carry out flocculation and flotation of slimes.

Jan 1, 1989

By Zhen-lu Zhao

The manipulators possibly used in underground mining must deal with unpredictable obstacle while keeping certain positions and orientations of end effector, and in some cases, are required to possess redundant joints in order to be more flexible. This kind of manipulators might be fitted with jumbo drill or platform as auxiliary to potentially deal with some utility works in versatile way, such as installing rock bolts, guniting, blasting, charging, surveys and measuring work, etc.. This paper describes numerical procedures of performing inverse kinematic problems for redundant manipulators .The procedures, based on the generalized pseudoinverse of Jacobian matrix, are developed to lead to kinematic solution at both singularity and ill conditioning, and to guarantee continuous sequence of positions of the end effect or. Furthermore, the solution to optimization and obstacle avoidance is investigated. A numerical example is shown to illustrate the approach.

Jan 1, 1989

By Richard V. Good, John B. Harvey, Lloyd S. Jones

INTRODUCTION The term "Rapid Underground Excavation" is generally associated with high speed tunnel advance with large volumes of excavation, and indeed this is the type of work for which most of the recent innovations in methods and new machinery have been developed. However, the term applies as well to any underground excavation process that results in an earlier project completion than would be expected with conventional methods, and hopefully with a decrease in total unit excavation cost. Often significant progress has been made during the primary stages of an underground construction project and then an inordinate amount of time and effort has been expended on small units of "miscellaneous" excavation which has delayed the overall project completion and escallated overall unit costs. Construction at the Nevada Test Site of the Atomic Energy Commission for underground testing frequently requires significant amounts of so called "miscellaneous mining" such as short access drifts, cross cuts, alcoves, niches and concrete keyways. Many of the keyways must be excavated without disturbing the rock beyond the excavation lines and construction scheduling often dictates that much of the work must be accomplished without disturbing sensitive electronic equipment already installed. In order to cut down on lengthy and costly delays required for the tedious manual excavation of much of this miscellaneous mining, a market search was made for suitable mechanical excavation equip-

Jan 1, 1997

By Thomas E. Krakowski

INTRODUCTION This paper presents a method of calculation of internal moments and thrusts in tunnel liners of any material. The method is intended for hand calculation, but as it is numerical in nature it can be programmed for use in computers. The information required for design or analysis is presumed active internal and external pressures, the effective moment of inertia and cross-sectional area of the tunnel liner, the liner's modulus of elasticity, and the coefficient of subgrade reaction of the material surrounding the tunnel. Starting with active external and internal pressures and following the procedure described herein using the structural properties of the liner and surrounding medium, external passive reactions and internal moments and thrusts are calculated. The method is intended for use by design engineers. GENERAL Experience has shown that flexible tunnel liners have less internal bending stresses than those calculated using classical structural theory applied to free-standing arches. In fact, liners which are very flexible in relation to the surrounding soil or rock have virtually no bending moments when compared to free-standing arches supporting equal active loads. In order for this phenomenon to occur, the original active pressure diagram must be "modified" by additional external reactions (passive pressures) from the surrounding material, so that the thrust line within the lining follows the centroid of the tunnel arch more closely than that of a similar free-standing arch. These passive pressures are reactions developed through outward deflection of the tunnel liner. Thus, the outward moving portions of a

Jan 1, 1979

By Peter Keppler, Stephen D. Bundy

"Due diligence" is a review or audit of a facility or business to assess and quantify risks and operating status before an acquisition. Due diligence findings can be used to negotiate the price, general terms, and indemnification provisions in the purchase and sales agreement. In addition to assessing out- standing liabilities, necessary capital improvements, and the adequacy of operating budgets, due diligence should include "nontechnical" considerations, such as local community acceptance and relations, and the effect on the company's public image and operations. This paper will discuss how these considerations can be addressed in the due diligence process and factored into the transaction. Also, innovative means for risk reduction and risk transfer, during and after the transaction, will be discussed.

Jan 1, 2001

By R. L. Grayson, Y. J. Wang

An application of material requirements planning (MRP) to coal mine inventory control is presented. MRP is an efficient material control system that integrates the production planning and inventory management functions. Net material requirements are determined from the production forecast utilizing bill of material files, the inventory status file, and the purchase order status file. Net requirements are computed for each period in a specified planning horizon, and purchase orders, offset by lead time, are initiated routinely to ensure timely receipt of materials. The MRP system is especially useful in production-inventory systems in which con¬sumption of materials is directly production dependent.

Jan 1, 1987