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By J. R. Riding

In situ solution mining of uranium has environ- mental advantages over conventional mining. The leaching of uranium, however, alters the groundwater quality in the aquifer where the mining occurs. Currently, regulations require that the groundwater be restored to approximately its original condition. This paper, a summary of a study funded by the Bureau of Mines, reviews the state of the art in restoring groundwater quality after in situ uranium leaching. Current restoration practices discussed include disposal of liquid wastes in deep disposal wells and evaporation ponds, producing from all wells during restoration, and recirculating water purified in surface plants. Methods for predicting the effectiveness and cost of current techniques are presented. Possible alternative techniques are also described. Two restoration operations are discussed.

Jan 1, 1979

By S. L. Bessinger

Introduction Extensive testing in the past ten years has shown that where a uniform natural gamma background is present in the strata bordering a seam, the thickness of the boundary coal left in place after mining can be determined by measuring the attenuation of that radiation (Nelson and Bessinger, 1989). Measurements made by the authors in underground mines in Pennsylvania, West Virginia, Ohio, Illinois and Kentucky and by others in Wyoming and New Mexico have shown the presence of such a gamma background (Nelson. 1989). Natural gamma coal-thickness sensors of several configurations have been tested in mines owned and operated by the Consolidation Coal Company (Consol) in Pennsylvania and West Virginia (Nelson and Bessinger, 1988). This paper describes the installation of a natural gamma coal-thickness sensor on an operating continuous miner. Previous tests had shown that the NGB-1000 coal-thickness sensor manufactured by American Mining Electronics, Inc., of Huntsville. AL, is an accurate, mine-worthy instrument. This large gamma detector consists of a sensing head and a control panel. The sensing head contains thallium-doped, sodium iodide scintillating crystal, which is coupled to a photomultiplier tube. The control panel contains the electronic components required for calibration, count conversion and display to the operator. Methods Conditions at a Consol mine in northern West Virginia require that 10 to 15 cm (4 to 6 in.) of coal be left at the roof boundary of continuous miner development sections. This roof coal is required because the shale of the immediate roof is friable and unstable. In the past, operators have used a dirt band that is usually visible near the top of the seam as a guide in maintaining the proper cutting horizon. However, this is not always reliable. Earlier observation showed that the actual thickness of the coal left on the roof varied widely; further, it was noted that occasional, accidental excursions into the immediate roof required supplementary roof control measures, such as installation of planks or center bolts. Thus, it was concluded that operators needed a better source of guidance for control of the cutting horizon, and a roof-coal thickness sensor was scheduled for installation. The NGB-1000 sensor was installed on a Joy 12CM10 continuous miner in June 1988. The sensing head was mounted on the cutter boom of the miner, and the control panel was mounted in the operator's cab. Power for the sensor was initially derived from an intrinsically safe battery power supply. Initial measurements with the sensor showed that the calibration was the same as that used in earlier tests at two other mines, indicating the uniformity of the natural gamma background above the Pittsburgh seam. Operating personnel were initially skeptical of the instrument's accuracy, and were hesitant to use its readings as a guide in maintaining a proper cutting horizon. Because gamma attenuation, the instrument's operating principle, is somewhat abstract, attempts to demonstrate the instrument's accuracy by explaining that principle were generally ineffective. It was found, however, that an operator could usually be convinced of the usefulness of the instrument by placing a large piece of coal of fairly uniform thickness over the instrument's sensing head and allowing the operator to see that the instrument reading increased by an amount very near his estimate of the thickness of the piece. The mine was provided with seven battery power supplies and a charging station. The charging station was kept in the lampman's office, and the mechanic on each shift was instructed that he was responsible for two battery power supplies each day: a freshly charged one to be taken in at the beginning of his shift and a depleted one to be brought out at the end. This system worked well for a few weeks, but eventually some battery power supplies were left in use so long that their batteries were discharged too deeply to allow recharging. In addition, transport and recharging of the batteries represented an additional task for the mechanics, who were already very busy. Consequently, a request was filed with MSHA to allow the sensor to be powered through intrinsic safety barriers by an electronic power supply connected to machine power. The permit was granted, and the sensor was connected to machine power. After the sensor was connected to machine power, the only operating problem experienced was occasional failure of cables. A supply of the required cables was made and delivered to the mine so damaged cables could be quickly replaced. Much of the cable damage could be eliminated by slight modifications to the miner during a rebuild, so that cables could be installed in more protected locations. After the sensor had been in operation for about two months, a survey was made to determine its effect on continuous miner operations. In previous research, coal thickness measurements made in 88 locations by the natural gamma method were compared to measurements made in the same locations by observing drill cuttings and by inspections of drill holes with a borescope. That research showed that the gamma method is at least as accurate as the other two methods (Nelson and Bessinger, 1989) and is also much easier to use. The object of the survey described here was not to assess the accuracy of the natural gamma measurements. but rather to determine the effectiveness of the sensor output as a guide for the operator in maintaining control of the cutting horizon. Thus a smaller, hand-held gamma detector

Jan 1, 1992

By Ronald L. Wiegel

In the 2000 page Handbook of Mineral Dressing by A. F. Taggart, the subject of material or metallurgical balances is covered in only six pages of eve-straining type. Although Taggart's work was compiled before 1945, and there has been significant progress since then in most areas of mineral processing, the practicing metallurgist's approach to metallurgical balances remains exactly the same as described in those six pages. There are several portions of Taggart's text appropriate to introduce the subject of this paper which I would like to quote: "Milling Calculations. Computations of per¬formance in milling are complicated by the fact that it is a continuous rather than a batch operation, that the quantities of solid materials handled are large and usually mixed with water, hence difficult or impos¬sible to weigh. Fortunately it is possible to determine many facts concerning perfor¬mance without knowing weights, if the value of various constituents is known in some common unit, e.g., the content of some par¬ticular metal or mineral, or of water, or some ingredient soluble therein, or of par¬ticles of a particular size or falling within some particular size range, or the like."

Jan 1, 1979

By Paul L. Bearden

The accumulation, handling, and utilization of sludges formed from wet process phosphoric acid is one of the major problems in the industry. The purpose of this paper is to explain some of the considerations and techniques that can be employed to provide some measure of control over the problem. An acid made from a Central Florida phosphate rock is used to illustrate the effects of one process design approach used to provide one type of control. Other approaches or techniques are discussed on a general basis. In every case, the discussion is purposely limited to conventional dihydrate processing in which phosphoric acid is produced from the filter at a strength of approximately 30% P205 and is subsequently concentrated to higher strengths such as 44 and 54% P205.

Jan 1, 1966

By K. S. Narasimhan, T. C. Rao, R. Bhima Rao

Investigations have been carried out to evolve a grinding aid useful in grinding a 40% iron-bearing magnetite containing quartz as the major gangue, based on studies conducted with pure magnetite, pure quartz and its synthetic mixture. These investigations established that an addition of 200 g of CaO per metric ton of ore was the most effective in grinding quartz preferentially over magnetite at 75% solids concentration by weight. The limited rheological studies conducted suggest that the effect could either be due to dispersion or the structural modification of quartz. More importantly, a new concept, that of Critical Solids Concentration, where two different minerals behave like one with respect to response to communication in a tumbling mill, has been introduced for the, first time. Above this concentration, one of the minerals is ground at a faster rate than the other, whereas the reverse is the case below this concentration.

Jan 1, 1992

By James E. Breland

Society's growing concern over the number of deaths and serious injuries occurring in coal mines, coupled with a growing sentiment to develop and promulgate improved mandatory health or safety standards, was no doubt the basis for passage by Congress of the Federal Coal Mine Health and Safety Act of 1969, being Public Law 91-173 approved December 30, 1969. Even prior to passage of the Act, strong reaction was quick to arise concerning the effect of such legislation upon the coal mining industry. Initial response varied from mild forms of criticism to' the expressed fear of complete suspension of operations and mine closings. Primarily responsible for these early forms of skepticism were speculative or fanciful cost estimates which led operators to contemplate a less than prosperous existence. However, in spite of this unfavorable outlook, the majority of the operators have faced up to the situation and have been striving to comply with the Act and the regulations issued thereunder. While encouraging strides have been made toward implementation of the Act, it must be recognized that noticeable results have been attained only through many months of determined effort and, as anticipated, at quite heavy expense to the operator.

Jan 1, 1973

By R. E. Johnson, L. V. Araújo, B. R. Palmer, L. M. Abrantes, G. W. Warren

The behaviour of chalcopyrite - mineral specimens and a Portuguese concentrate - in 2M chloride solutions prepared from hydrochloric acid and sodium chloride, has been characterized by cyclic voltammetry. The study has shown the influence of the potential and of the presence of impurities in the reaction schemes and their relative extent. The dissolution of chalcopyrite concentrate under potentiostatic control has been investigated and found to confirm the effect of the selected potential on the surface modification/rate of dissolution. An attempt has been made to correlate the information obtained with the response of the concentrate electrode to constant current treatments.

Jan 1, 1993

By R. Codell, D. L. Hughson

The authors benchmarked the integrated finite-volume code MULTIFLO against the analytical solution of Philip et al. (1989) for cylindrical underground openings. They found that the numerical simulation of dripping threshold flux was consistently higher than the analytical solution for rectangular and unstructured grids. The magnitude of this error was proportional to the alpha parameter characterizing capillarity. This error may bias estimates of seepage into drifts for repository performance towards nonconservatism.

Jan 1, 2002

By W. S. Weldon

The use of spiral separators for the beneficiation of fine coal typically in the size range -2+0.1mm is now well established process technology. Developments during the mid 1980's resulted in the production of cost effective, efficient large diameter coal spiral separators. Recent developments and research have been geared to optimize metallurgical performance, materials handling and equipment geometry of large diameter coal spiral separators.

Jan 1, 1997

By Mike L. Aziz, Keith D. Ferguson, Glenda Ferris

The Equity Silver mine has been a severe producer of Acid Rock Drainage (ARD) since 1982. The mine was closed in 1994 and a compacted clay cover installed, but ARD continues to be produced. Three permanent employees manage the collection and treatment system at the site. The site still poses a significant environmental risk to the environment and downstream users and requires a high level of diligence. Various stakeholders' perspectives of the risk posed by Equity, and what constitutes acceptable risk, will be examined in this paper from a company operation staff, corporate environmental manager and downstream environmentalist perspective.

Jan 1, 2000

By J. B. Gwiazda

Maintenance of a constant load setting throughout longwall support units and selection of the proper initial bearing capacity depending on the type of roof strata are the basic factors that ensure good performance of roof support in a longwall. These requirements can only be met by hydraulic support. The greatest advantage of hydraulic support is achieved when uniform pressure is imposed on the roof throughout the length of the longwall. Such support, however, is provided only if each of the support units acts with the same force against the roof, i.e., has the same setting load. In such cases, the roof behaves like a uniform plate without bending and shearing stresses, thereby ensuring an undisturbed structure. Without a positive set value system, achieving an equal setting load for all units of the longwall support is impossible. Due to alterations of the feed line pressure of support units as well as some reasons related to man's psychology, operators extend the height at different setting loads. This produces nonuniform roof stress, and disturbs the structure. Consequently, the roof usually cracks. The author has developed a positive set value system, which is described in this Technical Note. Selection of the setting load Two pressure values in the feed lines are usually applied in longwall hydraulic systems. Lightweight support is fed by 25 MPa (250 bar) liquid, while heavy duty units receive a nominal pressure of 31.5 MPa (315 bar). Such pressure is required not only for the props but also to power the adjust¬ment jacks and the advancing ram. If the feed pressure is too low, there will be difficulty in shifting the unit despite the inversion system of the advancing rams. On the other hand, for many roof types, the feed pressure often appears to be too high when applied as the setting load pressure. An excessive setting load acts too strongly against the roof, crushing weak strata close to the roof. The author has recognized a case where an excessive setting load destroyed not only the nearby roof strata but also the strata above a 2-m (6.6-ft) sandstone layer. In addition, an excessive setting load relieves the side¬walls, increasing the resistance when using cutting machines. As a result, the yield of coarse coal is diminished, and increased fines dominate in the final product, lowering its economic value. As indicated, selection of the proper setting load, depend¬ing on the mining and geological conditions of the extracted seam, is extremely important. In some mines, measures applied to prevent disturbances include reduction of the feed line pressure by adjusting the feed pump valve. The disadvantage accompanying reduced feed line pressure is more difficult operation in advancing the ram. Due to the reduced feed line pressure, the force of the advancing ram is much lower than the designed value. Other designs suggest using a third feed line. However, installation of supplementary valves on the support units is required, a time-consuming and expensive procedure. The disadvantages of the powered supports are eliminated by a system designed by the author. So far, such a method of setting load control has not been used in any type of support. Setting load control unit The designed positive valve set for prop loading and the setting load control correspond to existing control systems for hydraulic powered support. The layout of the unit connected to the hydraulic prop control is presented in Fig. 1. The unit is marked LIDS. It incorporates three valves that may operate separately or connected. Valve A automatically opens and closes with liquid flow in the prop feed circuit. The valve is opened when the canopy touches the roof and closed when the support unit is withdrawn. Valve B serves as the setting load control. Valve C automatically opens and closes the flow in the line connecting the under-piston space of E to the prop F with the separator G. The valve block of each support prop is marked BZ. The UDS unit is connected by the hydraulic lines to the F prop control circuit. A valve is connected by H to pressure line J and by K to the G separator. In the UDS-3 version, line L is connected to M, linking the over-piston space of F prop with the G separator. Valve B is linked with valve A by a connector; it is also connected to the under-piston space E of prop F by line P. Valve C is fixed between lines K and P, connecting space E of prop F with the separator G. When setting the support, the liquid flows from line J through separator G, the BZ valve, and valve C to the space E of prop F. When reaching the roof with the canopy, valve A is opened and C closes. In this way it is impossible for the operator to cause the liquid pressure in space E of prop F to reach the level of line J. The prop pressure is set by valve B of the UDS unit. When withdrawing the support, valve C is automatically opened and A closed. Three UDS units have been fabricated and are designated

Jan 1, 1990

By D. Koch

Bentonites and bentonite containing sealing materials are used since many years for sealing purposes in foundation, dike construction, hydraulic engineering and landfill construction, especially for encapsulation of old waste deposits In the near future compacted bentonites will be important components of multi-barrier systems for dry charge of old mines, for underground disposal of hazardous or radioactive wastes. Because of their exceptional physical, structural and chemical properties, bentonites are offering manifold possibilities to protect the environment against the negative effects of dumping grounds. Often the compliance with legal regulations for waste dumping or the isolation of contaminated areas is possible only by using bentonite containing sealing systems. The essential properties of bentonite, bentonite containing building materials and the different techniques of making horizontal technical base liners and vertical cut-off walls are explained. For horizontal technical base liners the adsorption ability, the ion exchange capacity and the swelling behavior of bentonites are important. For cut-off walls bentonite controls the rheological behavior of the slurry and is responsible for the low permeability of the hardened bentonite-cement-wall. In the multi-barrier systems of repositories for chemical or radioactive wastes compacted bentonites are considered to be favourable sealing and backfilling materials because of their high swelling capacity, their adsorption and ion-exchange ability and their plasticity in water saturated state.

Jan 1, 2005

By H. M. Giegerich

About Cominco Only the original Broken Hill zinc deposit in Australia is larger than Cominco's Red Dog deposit. Indeed, the third largest zinc deposit in the world is Cominco's own Sullivan mine in British Columbia. The production plan at Red Dog is based on mining 1.9 Mt/a (2.1 million stpy) or ore, to produce 635 kt (700,000 st) of zinc and lead concentrates. At full production, Red Dog will be the largest zinc mine in the Western world. It will also be one of the lowest cost producers in the Western world. And Red Dog will be one of the first major hardrock mines to operate in Alaska in modern times. The Red Dog project will be the third and largest of Cominco's Arctic mining developments in the past 13 years. The company's Black Angel mine in Greenland started up in 1973. And the Polaris mine, high in the Canadian Arctic, began production in 1982. Red Dog is one of the world's great mineral deposits. It is a unique combination of large size, high grade, and a waste-to-ore ratio less than 1:1. The present mineral reserve (Table 1) is estimated to be 77 Mt (85 million st), at a grade of 17.1% zinc, 5% lead, and 82 g/t (2.4 oz per st) of silver. Mine life is estimated at nearly 50 years. Cominco is the largest producer of lead and zinc in the Western world. Cominco's smelter in southern British Columbia is the largest lead and zinc plant in the west. Cominco also produces copper, steel, tin, gold and silver, along with potash, ammonia, urea, and phosphate fertilizers. But Cominco's major products are lead and zinc. At present, Cominco produces more than 10% of the Western world's needs for these metals. Background-Red Dog The Red Dog mineral deposit is located in northwestern Alaska, about 960 km (600 miles) by air from Anchorage, Alaska's largest city. The Red Dog region is home to more than 5000 people living in 11 villages. The largest village is Kotzebue, with a population of about 2500. The village is located about 144 km (90 miles) southwest of the mine. The country around Red Dog features rolling hills, leading into mountains to the north and east. The deposit, at an elevation of 305 m (1000 ft), is in permafrost. But the area is not nearly as cold as that encountered in the Canadian Arctic, or on Alaska's North Slope. At Red Dog, the permafrost is relatively fragile. It can be thawed fairly easily, a factor in engineering designs. Red Dog Creek flows through the mineral deposit. One of the natural phenomena at Red Dog is the presence of significant heavy metal contamination in the creek. This has eliminated all fish in the vicinity of the deposit. The contamination, and resulting mineral stain, led to the discovery of Red Dog. The staining is caused by rain and snowmelt. This leaches the heavy metals from the mineral zone, which comes right to the surface in many places. As mining progresses, this surface mantle will be removed. This will

Jan 12, 1986

By Reul A. Dejú

The mineral olivine has been the subject of continued research by various authors. Paik (1967) conducted infrared and flotation studies of the adsorption of sodium alkyl benzene sulfonates on olivine. These studies are of interest from two points of view. First, in the metallurgical field it is of interest to understand the mechanism of silicate flotation using sulfonate collectors and second to a hydrologist studying the pollution of surface or subsurface waters it is of interest to study the reactions taking place when water plus sulfonates encounter a porous (silicate) medium. On the basis of Paik's study he was able to postulate a possible mechanism for the attachment of RSO3 (sulfonate radical) to the olivine surface. Parks (1969) has been studying the important influence of the structure of a silicate such as olivine on its dissolution mechanism and its related surface charge. Also Luce, a student of Parks (1964, 1965) has been studying the kinetics of dissolution of olivine using the techniques of direct solution analysis and infrared analysis. Certainly a classic in the study of silicate dissolution is the work of Murata (1940) on the reaction of orthosilicates (olivine in particular) with strong acid solutions. Many authors (Dejú and Bhappu, 1966. 1967. 1968, Dejú, 1969; Rhoades and Krueger. 1968, and Faust and blunter, 1967) have reported studies of the behavior of silicates immersed in water (especially orthosilicates) and have found that there is an exchange of cations from the silicate surface for H+ from the water. Studies by Dejú and Bhappu have also included the system olivine-water-amine.

Jan 1, 1971

By Leons Kovisars

Two-thirds of the world copper produced in 1979 incurred cash costs between $0.35 and $0.89 per lb, averaging $0.62 per lb. North American costs are higher at $0.48, $0.88, and $0.68 per lb, respectively. Variable cash costs are $0.20, $0.58, and $0.39 per lb for the world; $0.29, $0.63, and $0.46 per lb for North America. Cash costs are relevant for comparing existing operations and evaluating market pricing during periods of excess supply. Analysis of full costs of production (cash costs plus income taxes, profit, and non-cash items) becomes relevant in evaluating the incentive price required to develop new production plants. In mid-1979 this cost (incentive price) was about $1.10 per lb; it is expected to approach $2.00 per lb by 1985.

Jan 1, 1979

By Guy G. Jr. Granger

INTRODUCTION Due to the current depressed state of the mining industry, many mining companies have been forced to operate at less than maximum capacity. This paper will describe how the AMAX Henderson Molybdenum Mine and Mill near Empire and Parshall, Colorado respectively have utilized operations scheduling and budgeting to achieve production targets at minimum operating costs The AMAX Henderson Molybdenum Mine and Mill have been operating most recently at approximately sixty percent of maximum capacity. OPERATIONS SCHEDULING Production Targets. The production targets are tons, operating days, tons per opera- ting day, head grade, recovery, and pounds of molybdenum. One specific objective of operations scheduling is to meet the production target for pounds of molybdenum. Present market conditions dictate that production be adjusted to match sales of molybdenum. Over-production and creation of molybdenum inventories is unacceptable. In summary, the product ion target for pounds of molybdenum must be met, but not exceeded. Capacity. The AMAX Henderson Mill single stage open crushing circuit capacity is 48,000 dry short tons per day. The AMAX Henderson Mill single stage semi-autogenous primary grinding mill circuit capacity is 38,000 dry short tons per day. All other AMAX Henderson Mi 11 circuits such as rougher flotation, regrind, cleaner flotation, lead leach, filtering, drying and concentrate handling are sized to accommodate the 38,000 dry short tons per day and pro- ducts from same. The tailing delivery system is designed to accommodate tailing from a 38,000 dry short tons per day operation. Constraints. One mill production scheduling constraint is that the mill operating schedule must be the same as mine production, ore haulage and crushing. There is a total crushed ore stockpi1e storage capacity of 240,000 dry short tons. This breaks down to 60,000 dry short tons of crushed ore over the three reclaim pan feeders for each of the four primary grinding mill circuits. However, there is only approximately 10,000 dry short tons of live crushed ore available over the three reclaim pan feeders for each of the four primary grinding mill circuits. Dozers must be utilized to re- claim and push the other crushed ore. Primary grinding mill throughput is

Jan 1, 1986

By Marvin Barnes

The Sacaton mine is a relatively new open¬pit copper mine owned by Asarco, Inc., which has been in production only a few years. The mineral deposits consist of two ore zones; a western, near-surface zone minable by open-pit methods, and a deeper eastern zone which will have to be mined underground, probably by block caving. The copper deposits are related to small quartz monzonite intrusives implaced into Precambrian granites. Both rock types act as hosts for the copper mineralization, which has been secondarily enriched sufficiently to constitute ore. In the western zone the enriched supergene chalcocite has been subjected to postenrichment oxidation processes with partial destruction of the chalcocite blanket. The deeper eastern chalcocite zone has not been as severely affected by later supergene processes. Several mineralogical populations are represented in the total copper deposit. Leached capping overlies the chalcocite enriched zone, and in the western ore body there is a very irregular interface between the leached and enriched zone, which is complicated by oxide copper minerals irregularly distributed. Primary lower-grade chalcopyrite mineralization occurs below the enriched zone. When mining commenced near the top of the enriched zone, considerable difficulty was encountered in correlating the actual grade of ore in place with the estimated grade of the mining blocks. The mineralogical complexity and fairly wide spacing of diamond drilling made reliable grade estimation of individual ore blocks a difficult procedure.

Jan 1, 1979

By S. K. Bhatt

This paper reviews major developments in continuous haulage technology for underground coal mines. Haulage systems in use and development are investigated through a comprehensive literature search and visits to mines and manufacturers. The systems include flexible conveyor train, mobile conveyor, multiple- unit continuous haulage, extensible and belt turning systems. Strengths and weaknesses of the systems are assessed in light of their operating under remote control and their application to the computer-assisted continuous mining machine being developed by the US Bureau of Mines. Through mining scenarios, candidate haulage systems are conceptualized to be consistent with the capabilities of the mining machine.

Jan 1, 1991

By Chee Theng

"In 2013, Coeur Mining had more than $55 million in general and administrative (G&A) costs and less than $100 million in cash flow. This year, its G&A costs stand at $30 million, down by more than 40 percent, its all-in sustaining costs have shrunk by more than 30 percent, and its cash flow is above $200 million. To realize this, the company aggressively reduced both its corporate overhead cost and operating cost and repaid more than $300 million in debt.The more robust balance sheet meant the precious-metals producer was well positioned to reap the rewards of an upsurge in commodity prices in the early part of 2016. Its stock price soared from $1.75 in January to $15.98 in August. Although the stock price has since dropped to around $9 due to a stronger dollar and a more hawkish Federal Reserve that recently raised U.S. interest rates, shifting the opportunity-cost argument away from buying gold and silver, Coeur remains attractive to analysts in light of its prudent spending and improved fundamentals.Focus on balanced portfolioCoeur is the largest primary silver producer and one of the largest gold-producing companies in the United States and one of the largest silver companies in the world. Incorporated in 1928, the U.S.-listed company has a total of five operations: three in the United States, one in Mexico and one in Bolivia. About two-thirds of its revenue comes from the United States.The company is conscientious about having a balanced portfolio, so no single mine accounts for more than about 30 percent of its business. Being in three different jurisdictions provides further diversification, and its revenue split of about 60 percent from gold and 40 percent from silver gives it some metals mix. This year, it expects to produce about 466 t (15 million oz) of silver and 10.3 t (330,000 oz) of gold."

Feb 1, 2017

By Shahzad Moosa, John M. Pitt

Statistical variability in rock strength can be evaluated by rapid, inexpensive ultrasonic pulse velocity measurements, an important consideration since rational probabilistic design in rock is often hampered by the cost of obtaining sufficient strength data. Experimental ultrasonic pulse velocity measurements on a set of 96 limestone specimens showed two distinct statistical populations. Both populations followed Weibull distributions, with flexural strength distributions paralleling pulse velocity distributions. Thus, experimental results suggest that strength variability may be predicted from a few rationally selected strength measurements and several ultrasonic tests. The correspondence between strength and velocity may then be used to develop an experimental transformation function, allowing the development of a statistical distribution function for strength based on the known statistics of velocity. Comparison of experimental groups with full sets of corresponding strength1 velocity data showed the technique offers a fairly accurate description of the statistics of strength.

Jan 1, 1986