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By S. H. Ash

THE BARRIER-PILLAR SYSTEM in the Lackawanna Basin consists of 93 barrier pillars between Archbald and Taylor, Pa. These pillars affect 48 mines, have a total length of 87 miles, and confine 21 underground pools, which contain more than 10 billion gallons of water. From an investigation of size, position, and condition of the barrier pillars, it is apparent that those concerned are uncertain, not only as to the method by which the sizes of the barrier pillars were determined but also as to the stability of those that may be expected to act as dams. Where a barrier pillar must act as a dam, its failure may result in loss of life, the mine, or both; it would be far better had it not existed and thereby given a false sense of security.

Jan 1, 1952

Welina mai to the 40th Underwater Mining Institute, UMI 2011 - Marine Minerals: Recent Innovations in Technology. Since the first conference in Milwaukee, Wisconsin in 1970, the UMI Founder Professor Robby Moore always insisted on actively seeking the participation of industry, academia, and government. History has proven the wisdom of this approach, which is probably the key to its survival for so many years. The UMI is very much influenced by the cyclical pressures of the minerals commodity markets. When minerals demand and prices are rising rapidly, industrial participation in the Institute dominates the agenda, and participants share optimistic and aggressive views of the commercial prospects of the day. When metals prices are falling and world economies lethargic, academic experts continue to provide guidance and breakthroughs in the concepts and practices of exploration, technology, and environmental protection. Throughout the ups and downs, government participants provide a stabilizing force with conservative and environmentally sensitive policy statements, patient development efforts with long-term objectives, authoritative resource assessments and, sometimes, much needed regulatory clarity.

Jan 1, 2011

By F. D. Sutterfield

This study was conducted to provide experimental evidence on the effect of modifications of gasoline front-end composition on the photochemical specific reactivities of automotive emissions. Evaporative and evaporative-plus-exhaust emissions from an automobile operated with four fuels of different volatility and varying levels of C.-C5 olefins were irradiated in a 10040 environmental chamber at three sets of initial hydrocarbon-nitrogen oxides concentrations. Reactivity was measured and expressed in terms of rate-of-NO2 formation and dosages of oxidant, peroxyacetyl nitrate, and formaldehyde. The compositional changes that were necessary in reducing fuel volatility were found to have no significant effect on the reactivity of the emissions. However, replacing C4-C5 olefins with saturated components resulted in sharp decreases in all reactivity manifestations observed for the evaporative emission samples. A lesser influence (of C4-C5 olefin replacement) was found with the composite exhaust-plus-evaporative samples; the effect that was observed could be attributed to the evaporative emission portion of the sample. The data therefore suggest that saturation of front-end fuel olefins had no large effect on exhaust emission reactivity.

Jan 1, 1971

This report presents information developed during Bureau of Mines contract H0242016, "Mine Shaft Fire and Smoke Protection Systems" from May, 1974 through June, 1975. Purpose of the metal and nonmetal health and safety project was to evaluate mine shaft fire and smoke hazard problems, and to develop and demonstrate a low-cost, reliable mine shaft fire protection system that would protect against such hazards and would be applicable to a majority of metal and nonmetal mine shafts, including raises and winzes, especially in deep mines. Program effort proceeded through five phases, culminating in the successful in-mine fire demonstration of a prototype system. In addition to this final report, a film is available which depicts components of the system and its successful shaft fire testing at an underground mine.

Jan 1, 1975

By T Baumgartl, D R. Mulligan, D Doley, A Schneider

In arid and semi-arid areas evapotranspiration (ET) cover systems are often used to mitigate contaminated seepage from hazardous mine waste into the adjacent environment. The theory of ET covers is based on the water balance equation with the aim of minimising seepage. While cover systems are commonly trialled, the influences of variability in climate and cover structure on water balance equation parameters are seldom investigated.Water balance equation parameters and their variability were analysed for two ET cover trials constructed from benign waste rock in semi-arid Australia. Seasonal and inter-annual variations in rainfall critically influence cover performance. For successful cover system operation, the average return periods for higher than average rainfall should be taken into account. In addition, failure of ET covers has a higher probability in areas with marked rainfall seasonality. Water holding capacity and plant available water content are low in covers constructed from waste rock. Changes in water holding capacity due to variation in particle size distribution are likely and critically influence cover performance. The application of topsoil can be beneficial for water ingress control through run-off, but a balance has to be struck between run-off, erosion and plant available water. Changes in vegetation composition only influence evapotranspiration water losses at plant coverage exceeding 50 per cent, which is unrealistic in semi-arid areas. This study showed that the capacity of ET cover systems to hold and dispose of received rainfall is often lower than assumed by industry practitioners. Furthermore, in order to improve reliability of long term cover performance, the variability of rainfall and water holding capacity of the cover has to be included in water balance models.CITATION:Schneider, A, Baumgartl, T, Doley, D and Mulligan, D R, 2012. Variability in parameters of the water balance equation and their influence on evapotranspiration cover performance, in Proceedings Life-of-Mine 2012 , pp 293-300 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 10, 2012

By Hamid Maleki

A comprehensive study consisting of stress determinations, core logging, laboratory testing, and numerical analyses was conducted to investigate the cause and potential alternatives to the coal bump conditions that developed in the Second North Panel of the Little Dove mine near Buntington, Utah. Roof rock characteristics were such that a cave did not develop above this 420 ft wide panel. After 700 ft of pillar retreat, severe coal bump conditions developed during pillar mining. The coal bump conditions resulted from excessive pillar stress which was caused by load transfer from the extracted, noncaving, portion of the panel. Site specific data and numerical modeling techniques were used to back-analyze the bump prone condition. This back- analysis lead to the identification of critical stress, closure, and energy release levels. These critical levels were then used to evaluate alternative pillar mining sequences in the hope that the potential for coal bumps could be reduced. It was found that while alternative sequences offered some potential improvement over the pillar mining sequence used in the mine, alternative pillar mining sequences would not significantly reduce the potential for bumps. For the roof characteristics at this mine, coal bumps are best avoided by developing narrow panels or significantly wider panels, which incorporate properly sized barrier pillars. Narrow panels, on the order of 300 ft, would not cave, but panel pillar stresses and the potential for umps would be moderated by the reduced r' panel width. Wider panels, of approximately 650 ft, would allow a cave to develop, also reducing panel pillar stresses and coal bump potential.

Jan 1, 1987

By Edgar S. Rush

This study was conducted to make a limited evaluation of experimental and standard tractor dozer blades. A field test program was conducted in the southeastern part of Kansas on strip-mined areas where the spoil banks are parallel with rest-to-crest distances between 90 and 120 ft and maximum dozing distances usually less than 50 ft. This evaluation was a part of an overall joint Pittsburg and Midway Mining Company--U. S. Bureau of Mines (USBM) Specialized Reclamation Field Test Program primarily centered on the field t sting of experimental high-volume lateral relocation blades. The three blades evaluated were the 60-ft-wide angle (A) blade mounted on two 41B tractors. a 48-ft-wide A blade mounted on two D9H tractors, and a 13-ft-wide reclamation universal (Rec U) blade mounted on a D9H tractor. In addition to the experimental blades, three commercially available blades were tested: A 20-ft universal (U) blade mounted on two side-by-side (SxS) D9H tractors; a 20-ft U blade mounted on a 418 tractor; and a l2-ft straight (S) blade mounted on a D8H tractor. The dozer blade evaluations compared measured blade performance with soil and other site characteristics and with estimated earth-moving performance rates based on earthmoving methodology that accounts for the traction and speed of the tractor. The earthmoving methodology was also validated with data collected during this program.

Jan 1, 1978

By Greaves M. C, Amos M. D

A study was made of the instrumentation and technique of atomic absorption spectroscopy developed by Walsh of the Commonwealth Scientific and Industrial Research Organisation (C.S.I.R.O.), Australia.The method was evaluated for the determination of silver in lead sulphide concentrate. The precision of the procedure developed is equal to that of the uncorrected fire assay method and the accuracy is greater.Brief mention is made of the use of this technique for the determination of silver and other elements in ores and concentrator products.INTRODUCTIONThe fire assay method, although accepted on a world-wide basis as the umpire method for the determination of silver in ores and concentrates, is freely recognized as yielding results which are lower than actual due to unavoidable losses.King (1934) investigated the influence of the cupelshape, size and material on silver losses during cupellation. Using 100 mg silver prills he recorded silver losses ranging between l. and 10 per cent under extreme conditions and averaging approximately 2 percent under conditions which might be considered normal. Guerin (1957) made a detailed study, under carefully controlled conditions in a furnace similar to that described by Esdaile (1952), of the effect of temperature on silver losses during cupellation. He concluded that if cupellation were carried out at 840°C., then the amount of lead retained by the silver prill was insignificant and that the silver losses were governed by the equation: Y = 0·055 XO.74where X = the final weight of the silver priIl (mg)and Y = the silver lost (mg)

Jan 1, 1961

This Bureau of Mines report and its companion report (Information Circular 9142) have been prepared to assist in the preparation of prefeasibility type estimates for capital and operating costs of beneficiation of various types of mineral occurrences using current technology. The handbook provides a convenient costing procedure based on the summation of the costs for the unit processes required in any particular mining or mineral processing operation. The costing handbook consists of a series of costing sections, each corresponding to a specific mineral processing unit process. Contained within each section is the methodology to estimate either the capital or operating cost for that unit process. The unit process sections may be used to generate, in January 1984 dollars, costs through the use of either costing curves or formulae representing the prevailing technology. The mineral processing handbook includes individual cost estimation sections for unit operations associated with comminution, beneficiation, solid-liquid separation, hydrometallurgy, and special applications as well as infrastructure and plant general and administrative costs. When using this system for estimating cost data for a mineral processing facility or for checking or verifying processing costs from an existing facility, a minimum amount of background information is necessary.

Jan 1, 1987

Tailings embankments can develop a high phreatic surface if the original design for the embankment does not include drainage facilities or if existing drainage facilities become ineffective. Subsequent raises can develop a seepage surface due to a high phreatic surface that can lead to stability problems. The U. S. Bureau of Mines amended contract J0100013 to initiate this study of horizontal drains in tailings embankments. This study developed a technique for determining the length of and spacing between parallel drains through the use of the finite element model UNSAT2. The analysis is based on the combined output of a vertical planar mesh and a horizontal planar mesh. The slot opening in the drain pipe and the length of the perforated section are determined from an analogy to water well design. The pipe diameter and gradient can be determined from Manning's equation. To the authors' knowledge, this is the first attempt at horizontal drain design using a finite element model. Additional research is recommended in this area.

Jan 1, 1982

By J. N. Van der Merwe

"A major shortcoming of the statistical back-analysis of coal pillar strength is that it relies on the asmined pillar dimensions, not taking into account time-related pillar scaling with subsequent reduction in pillar width. The paper describes an investigation where the rate of pillar scaling was applied to the pillars in the databases of failed and unfailed pillars. The reduced pillar sizes were then used in the same method of statistical back-analysis that had been used in the past.This resulted in an equation for pillar strength which predicts significantly greater pillar strength than the previous statistical analyses, which is similar to the strength which had been found earlier by direct testing of large specimens underground. It is concluded that the lower strengths found by previous statistical analyses are due to the incorrect pillar width being used and that by adjusting the pillar sizes to compensate for scaling, more credible results that correspond to direct testing are obtained.As the newly derived strength equation is time-dependent, it follows that the safety factors and probabilities of failure are likewise time-dependant. An equation to determine the probability of failure is also developed. This results in the safety factor being close to unity at a probability of failure of 50%, which is aligned to statistical expectation. IntroductionSince the Coalbrook mine disaster, caused by massive pillar collapse, there have been several attempts at analysing and defining the strength of coal pillars. It was realized in the very beginning that performing classical strength tests on coal specimens in a laboratory and then transferring those results to real coal pillars could not be successful. The scatter of results is one problem and, more seriously, there is a size effect (at least for small specimens) that made the transformation of strength results to much larger coal pillars underground all but impossible.Two main schools of thought then emerged. Some researchers preferred to perform direct strength tests on large specimens underground, while others relied on statistical back-analysis of failed and unfailed pillar cases, attempting to determine the differences in size and shape that would allow a satisfactory prediction of failure. The latter school of thought resulted in the method that was widely accepted by the South African coal mining industry, described in the landmark publication by Salamon and Munro (1967)."

Jul 1, 2019

By Antonio Marinucci, Robin Mao

The new Hangzhou West Railway Station, which is currently in the early stages of construction, will be located in the city of Hangzhou, China. To accomplish the ambitious goals of the project, the construction work and station building was divided into three project areas. The original design utilizes 1,580 drilled shafts with diameters of either 800 mm or 1000 mm (32 or 40 inch) to support the new Station and its various ancillary structures. The drilled shafts will be tipped into the moderately weathered argillaceous siltstone a distance between 5 and 15 m (16.5 and 49 ft), resulting in an effective pile length ranging from 35 to 43 m (115 to 141 ft), respectively. For the first phase, approximately 550 production drilled shafts will be installed. Eight (8) sacrificial drilled shafts each with a diameter of 1000 mm (40 inch) were installed to a depth ranging from 50 to 57 m (164 to 187 ft), and were tested to confirm the design parameters used for the first phase, to evaluate the contractor’s installation means-and-methods, and to provide guidance whether redesign is warranted for the subsequent two phases. Bi-directional static load testing was performed using a donut-shaped Super Cell to apply unidirectional axial loads up to 13,200 kN (2,970 kip). This paper will describe the bi-directional testing and select results obtained therefrom. The axial compressive and uplift resistances determined from the testing verified that the available axial resistance of a single drilled shaft exceeded the minimum design requirements.

By Walter E. Vanderpool

Three drilled foundations for an elevated water-tank were instrumented, tested and monitored during construction and the first two years in service. One shaft was load tested by the Osterberg method. A void was detected in one shaft by cross-hole sonic logging, pulse-echo logging and concrete coring. The void was instrumented, hydrostatically tested and pressure grouted. The shaft was ?abandoned? and replaced by two smaller shafts with a straddle beam cap. One of the replacement shafts and the cap were instrumented. The strain that appeared in the abandoned shaft, the replacement shaft and the cap were monitored during the remainder of the construction, through the commissioning test and the first two years of service. The results demonstrate the precision and sensitivity of the vibrating wire strain gage.

Jan 1, 2004

By Lever R. R

The paper discusses assay methods generally used when prospecting for gold, and also the applicability of various chemical methods, it describes a new paper chromatographic technique.for making fairly rapid semi-quantitative assays for very fine gold. Testing of the method in field work shows that this simple method could have applications in geologic work, in prospecting and in certain routine mine sampling work. It is not yet a method that can be used to detect anomalies in traces of gold dispersed around an orebody, as is general practice in geochemical prospecting.INTRODUCTIONAccording to the English economist Harrod (1958), "the acute shortage of gold in the world-because currency value has not been adjusted in line with the fall in the goods value of the various currencies-has been a familiar fact for some time now". Harrod calculates that a rise in the price of gold to double its present value is necessary to rectify this condition, and that, if this rise were to take place, increase in production and reduction in private hoarding might well bring annual accretion to world stocks from the presentaverage of about $464 million to a figure close to the $2,000 million that would probably eiiminate these shortages.Any increase in the price of gold is bound to lead to a great increase in prospecting at working mines, in abandoned areas and possibly in untouched country. Prospecting, techniques for base metal orebodies have improved greatly in the last thirty years; but methods available to detect gold occurring without accessory metals have not received the same attention. With this in mind a paper chromatographic method of assaying for gold has been developed by Lever (1958). In the field this semi-quantitative method has proved...

Jan 1, 1959

Discussion of the paper of R. J. COLONY, presented at the New York Meeting, February, 1921, and issued With MINING AND METALLURGY No. 169, January, 1921. R. J. COLONY (author's reply to discussion).-The work of Sosman and Merwin on the system lime-ferric oxide, mentioned by Mr. Rankin, was not overlooked. When studying portland cements and portland-cement clinkers petrographically, however, the lime-iron compound was difficult to correlate with the very definite dicalcium ferrite described by those investigators, which possesses such well-defined optical properties. In portland cements, the calcium ferrite (or ferrate?) is an indefinite, fuzzy, and generally amorphous, or apparently amorphous substance that is distributed interstitially with respect to the other grains, from which it was very difficult to derive any satisfactory results. For this reason, the writer, tentatively, chose to regard it as related to the aluminate, and assigned to it the composition 3CaO.Fe203, which may be incorrect, however, as Mr. Rankin suggests.

Jan 8, 1921

By W. G. Willson, Y. L. Li, P. D. Rao, D. E. Walsh

The combination of high moisture and low heating value has restricted most low-rank coal (LRC) usage worldwide to mine-mouth power generation. The objective of this study was to subject two Alaska low-rank coals to hydrothermal drying to enhance their marketability in the Pacific Rim markets and to evaluate the chemical and physical properties of the dried products as a function of process conditions. Coals from Usibelli Coal Mine and the Beluga coalfield have a heating value of approximately 18.5 MJ/kg and contain about 28% moisture. Hydrothermal treatment (at 275° to 325° C) of lump coal, from the Usibelli Coal Mine and the Beluga coalfield, enhanced the heating value of the material, on an equilibrium moisture basis, from 18.5 MJ/kg to nearly 27.8 MJ/kg. The product coal, with a high heating value and only 0.2% S, is an environmentally-acceptable premium fuel; additionally, with the Hardgrove grindability index of the coal greatly improved, its value is even further enhanced. An increase in hydrothermal drying temperature promotes vesiculation of resinite. Also, ulminite reflectance increased to 0.92%, and ulminite was subjected to widespread vesiculation; this resulted in a coke-like structure indicative that the material went through the fluid stage.

Jan 1, 1993

[AARONSON, E.: Discussion on Recent Developments in Fractionation as Applied to Tube Still Distillation, G26, 418 Abbe. See Microscope. Abbe apertometer, 95, 16 ABBOTT, W. L.: A.S.M.E. president, M26,113 biography, M26,113 ABORN, R. H.: Discussions: on Effects of Columbium in Chromium-nickel Steels 113, 159 on Pure Iron and Allotropic Transformations 84, 342 on Prevention of Intergranular Corrosion, 100,329 ABORN, R. H. AND BAIN, E. C.: Discussion on Widmanstätten Structure in Ironcarbon Alloys 105, 252]

Jan 1, 1936

The scope of this paper is to introduce a mathematical model based on matrix algebra in order to determine similitude quantities, which can be arranged in specific formats to simulate the field conditions and associated behaviour. The formulation of a typical mathematical model applicable to Geomechanics is demonstrated here. The examples provided are intended to facilitate comprehension and application of the proposed model in practice.

Jan 1, 1989

The optimum cut-off grade policy maximizes the net present value (NPV) of an open pit mining operation subject to the mining, processing, and refining capacity constraints. The traditional approaches to cut-off grade determination ignore the escalation of the economic parameters such as metal price and operating costs during life of an operation, and consequently lead to unrealistically higher values of the objective function. Further, the NPV of a mining operation declines due to the depletion of the available reserves, causing a decline in the optimum cut-off grade, i.e. higher cut-off grades in the early years of an operation and lower cut-off grades during the later years. Hence, low grade material mined in the earlier years may be stockpiled for processing during later years to offset the effect of escalating economic parameters on NPV. This paper demonstrates the combined impact of introducing economic parameters, escalation and stockpiling options into the cut-off grade optimization model. The model promises an enhancement in NPV as illustrated in a case study incorporating practical aspects of an open pit mining operation.

Jan 1, 2011

By F. Stober, D. Wanblad, J. Ndlovu, L. R. Nelson, L. P. S. de Villiers

The single six-in-line furnace of the Polokwane Smelter is the largest installed high-intensity furnace for platinum group metals (PGM) base metals sulphide smelting in the world. The furnace employs state-of-the art technology to deliver a planned throughput of 650 000 t/a dry concentrate at a design 68 MW power input. This furnace, at double the capacity of previously existing PGM furnaces, offers low unit operating and capital cost through the resulting economies of scale. Key features of the design include:

Jan 1, 2005