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By R. Hart

In this paper, problems that have been experienced with the rockpass system at Kloof Mine No. 3 Shaft are described. Actions that have been taken to overcome the problems are also described. These include the use of slugshots to remove hang-ups, the abandonment and waste filling of passes, and design criteria adopted for an alternative pass system.

Jan 1, 2006

By Chris Bennett, Drupad Desai, Kirit Mevawala

INTRODUCTION The design/build (D/B) philosophy of contract delivery is neither new nor unusual when it comes to at-grade, elevated or high-rise structures. But when it comes to constructing underground facilities, there were no examples to be followed in early 90sin the continental United States or its territories. When DMJM+HARRIS was selected as general architectural and engineering consultant for the Tren Urbano (TU) project in Puerto Rico, one of the requirements of the Federal Transit Administration (FTA) for funding commitment was to use TU as a demonstration project utilizing design/build contract delivery method. Now fifteen years later, New York City Transit (NYCT) has instituted a similar requirement for their first Tunnel Boring Machine (TBM) contract for the Second Avenue Subway. As with most construction mega-projects, lots of things have happened and there were several lessons learned from the TU experience that are now being applied to Second Avenue. Both of these projects require building tunnels and underground transit facilities in heavily traveled corridors of an urban city, in the vicinity of active business and commercial enterprises. To enhance the challenge, there are noise and vibration sensitive and historic urban receptors either over or along both the transit corridors. Column free Tren Urbano station caverns over18 m (60 ft.) wide were built in soft ground conditions within 3.6 m (12 ft.) of the surface under an aging heavy utility corridor, while NYCT tunnels with station structures stretching the limits of rock caverns to 34.8 m (100 ft.), were planned in rocky geology with the presence of shear and fault zones and some mixed face conditions. BACKGROUND During the early period of design/build experimentation, the speed with which the contract procurement packages could be put together enabled the owners to take advantage of the major efforts underway to rebuild the infrastructure that was suffering from post-World War II neglect. Use of design/build for new starts was unheard of and most of the projects were smaller in nature in order to allow the methodology to be tested. Development of functional design packages with the understanding that the D/B

Jan 1, 2005

By Max Roesler

I. INTRODUCTION THE following article concerns the geological occurrence of the iron-ore deposits on the south coast of Cuba. The article is based on a detailed field study, made in the hope that some information would I gained which might be of value in the search for further orebodies, Or in the economic development of the ore already found. LOCATION The iron-ore deposits of the Firmeza district lie near the coast, in the southeastern part of Cuba, in the Province of Oriente. The orebodies of this district form part of a belt of deposits that extends from Sigua, 25 miles east of Santiago, to Sevilla, 5 miles east of Santiago, and lies on the seaward slope of the Sierra Maestra range of mountains.

Jan 10, 1916

By Parviz F. Rad

The Bureau of Mines used a linear cutting apparatus equipped with a 7-inch disk cutter to cut grooves in marble, limestone, granite, and quartzite under a normal force of 7,000 lb. The size distribution of the muck for various grooves was determined through sieve analysis. A statistical search showed that Weibull distribution describes the size distribution better than other available functions. Results indicate that fineness modulus, chip population, and dimension of the largest chip can be used as indicators of cutting efficiency. The results correlate with those obtained from the boring machines and other lab experiments. Application of the principles established through this work to the operation of boring machines is explained

Jan 1, 1974

By Clive Chadbourne

Investigations of world wide coal face strata control practice, the study of theoretical calculations and detailed engineering analysis have been combined to design and select a powered roof support suitable for use in conjunction with the extraction of 4.5-m (14.7- ft) of the 7.5-m (24.6-ft) thick Warwickshire Thick Coal Seam. The interface between geotechnical criteria and engineering design has been closely considered along with the following 3 important factors: Firstly, the need to further improve strata control and operational characteristics whilst producing a wall integrated overall face design. Secondly, to enable the supports to be rapidly transported from face to face in roadways driven at the minimum size for operational requirements. Finally, to provide hydraulic power, automatic control and monitoring systems which will improve operations reduce manpower requirements and improve management information. Clear design requirements were determined in order to allow selection on a commercial basis. A method of tendering is described with the subsequent analysis and selection process. In the event oversupply of coal in the UK resulted in the order not being placed. Brief consideration has been given to supports suitable for reserves to be mined In a few year's time where there is potential for extraction well in excess of 4.5-m (1 4.74.

Jan 1, 1994

By Ch. Schroeder, F. Collin, R. Charlier, Y. J. Cui

The paper proposes two numerical models ot the mechanical behaviour of chalk. First, an elasto-plastic constitutive law reproduces the different plastic mechanisms of the chalk and the influence of pore fluids by introducing the concept of suction. Secondly, a model able to reproduce time dependence behaviour. Eventually, the paper gives a simulation of an academic reservoir during depletion and waterflooding phase. Der Artikel stellt zwei numerische Modelle des mechanischen Verhaltens der Kreide vor. Das erste ist ein elasto-plastisches Modell, das verschiedene plastische Mechanismen der Kreide und den Einfluss von Porenflüssigkeit, unter dem Begriff der Suktion, reproduziert. Das zweite Modell berücksichtigt darüberhinaus das zeitabhängige Verhalten. Schliesslich zeigt die Veröffentlichung eine Simulation einer theoretischen Lagerstätte während der Entleerung und der Wasserinjektion. L'article propose deux modèles numériques du comportement mécanique de la craie. Le premier est une loi élasto-plastique qui reproduit les différents mécanismes plastiques de la craie et l'influence du fluide interstitiel par l'introduction de la notion de succion. Le second est un modèle prenant en compte les effets différés. Enfin, l'article présente une simulation d'un réservoir académique durant les phases de déplétion et d'injection d'eau.

Jan 1, 2003

By G. C. Lammers

The object of this study was to determine the economic feasibility of hydraulically transporting Sandow (Tex.) lignite 100 miles and dewatering and thermally drying the transported lignite to a surface-dry condition. The most important factors involved in the feasibility of hydraulic transport, are the degradation incurred during transit, the length of the line, and the cost of alternative methods of shipment. In pipeline tests in which roughly 75 miles of hydraulic transport was simulated the percentage of minus-325-mesh solids increased from about 1 to 41 percent for both lignite and bituminous coal; in the micron sizes the coal fared considerably better than the lignite. Such degradation, even though it enhances flow through the pipe-line, severely aggravates the dewatering problem on lignite. Cost studies indicated that continuous vacuum filters offer the most economical means of dewatering minus-1/8-inch material. Surface moisture, if high, must be removed by relatively expensive thermal drying.

Jan 1, 1958

By E. Morrice

As part of its efforts to maximize process efficiency and decrease energy requirements in mineral processes, the Federal Bureau of Mines has investigated methods for beneficiating bastnäsite ores from Mountain Pass, Calif. The results of a bench-scale study on the flotation of bastnäsite ore are presented. Flotation at a pulp temperature of 40° to 45°C yielded a cleaner concentrate containing 58.7 pct RE203 at a rare-earth recovery of 67 pct. These results are comparable to those reported for the commercial beneficiation method in which the pulp is heated to boiling before flotation. An attempt was also made to recover a barite flotation concentrate from the bastnäsite rougher tailing. Concentrates containing only 70 pct barite were obtained.

Jan 1, 1982

Development of a Froth Dropback Measurement Device

Sep 13, 2010

By D. W. Olson

Garnet has been used as a gemstone for centuries. However, garnet’s angular fractures, relatively high hardness and specific gravity, being chemically inert and non-toxic and free of crystalline silica, and its ability to be recycled make garnet ideal for many industrial applications. Garnet is the general name given to a group of

Jan 1, 2005

By Davy A. T, Hansen J. O

The causes of ferrosilicon loss from Dense Media Separation (DMS) plants, and the related properties of ferrosilicon, are identified. Two characteristics, corrosion resistance and saturation magnetisation, are examined in detail. The chemistry of the corrosion mechanism is described and its relationship to plant parameters discussed. Methods of reducing corrosion losses are proposed. Lack of particle homogeneity, and its influence on corrosion and abrasion is noted. The relationship between low magnetic susceptibility-and increased magnetic separator losses is demonstrated experimentally.

Jan 1, 1986

By H. L. Burmeister

This is one of a series of publications by the Bureau of Mines dealing with mining methods and costs at representative operations in the United States. The report describes all phases of the mining methods for the open-pit operation and milling practices employed at the Vermont Asbestos Mines in Lamoille and Orleans counties, Vermont. A brief history of discovery and development of these asbestos deposits is given, and the ore deposits are described. Methods employed in exploration, sampling, and estimation of tonnage and grade are outlined. A breakdown of available cost figures is summarized in the last section. All asbestos ore produced in this area has been won by the use of surface-mining methods. Two quarries, the Lowell and the "C" Area, are in operation. The quarries combined are producing and the mill is processing approximately 3,500 tons of ore per 3-shift day The average 40,000 tons of crysotile asbestos fiber produced at this plant annually accounted for 96 to 98 percent of the total fiber produced in the United States in 1958. The mine is located (fig. 1) approximately 4 miles north of Eden Mills village on the southeastern flank of Belvidere Mountain (fig. 2).

Jan 1, 1962

By H. Walqui, G. Rajala, G. Suardini

The Empire mine began operations on 1963. Low grade Magnetite ore is processed to produce iron pellets for blast furnace feed. Three expansions were added to the original plant and several equipment upgrades have been completed to improve the plant performance as the ore characteristics have been changing through the life of the mine. Size reduction is carried out by two grinding stages, the first one using autogenous grinding and the second one using pebble mills. Pebble crushing is also used to break the critical size fraction and increases primary grinding capacity. This paper describes changes in the configuration of the grinding circuits that have helped increase plant throughput and reduce power consumption by more efficiently utilizing assets available. Understanding the different components of the size reduction circuits and plant sections has allowed shifting part of the load from one section of the plant to another without affecting plant throughput.

Jan 1, 2007

By R. V. Ramani, J. M. Mutmansky, P. C. Luna, V. A. Marple, Honglin He, B. A. Olson

The development of a sampling instrument for the assessment of an underground coal miner’s exposure to airborne respirable coal mine dust on a continuous and real-time basis has been long identified as essential for timely initiation of control actions. A respirable dust dosimeter (RDD) which operates on the principle of increasing pressure across a filter media with increasing dust mass on the filter has been developed by the National Institute for Occupational Safety and Health. Comparisons of the performance of the RDD with an U.S. approved gravimetric respirable dust sampler (GRD) have shown that the RDD may meet the requirements for measuring miners’ exposures on a cumulative, near real-time basis such as mid-shift and end of shift exposures. Recently, the performances of the RDD and GRD were compared by conducting side-by-side area sampling experiments in a controlled experimental environment in the laboratory and in underground coal mines under normal operating conditions. In this paper, the results from the in-mine study are presented and discussed. The experimental design for the in-mine study included two mines in different coal seams in different geographic coal regions. To ensure a wide range of concentrations, the experiments were conducted in a continuous miner section in Mine 1, and a longwall face in Mine 2. Airborne dust sampling was conducted for four different shifts at each mine. In each shift, two samples of different exposure durations were collected from two different locations. Each sample consisted of the readings of three dosimeters and the exposed filters from the three paired GRD samplers. As a result, a total of 96 comparative samples were obtained, 48 for each mine. The data were analyzed for the precision of the RDD and GRD measurements and for the relationships between the differential pressure of the RDD and the mass of dust on the paired GRD filter. The analyses indicate that, on the average, the RDD and the GRD track the airborne respirable dust concentrations well, exhibiting both a high correlation between the two measurements and a reliable predictive relationship of one from the other. Details of the experimental design, data analyses procedures, results, conclusions and recommendations of the underground experiments are presented in this paper.

The works recorded in this Test Report have been performed by Rade Roncar - Electrotechnical Institute of Zagreb, SFR Yugoslavia in collaboration with Bureau of Mines. The main objective of these investigations was to investigate the possibility of fabrication of thin-walled square enclosures of satisfactory safety factor in accordance with requirements of effective technical regulations. The results and the investigations can be divided in three main fields: - investigations of thin-walled enclosures with the view of determination of pressures causing technological deformations before performing tests in accordance with effective applicable regulations, - finding the safety factor by means of tests of metal-foam pressure vents, - comparison of enclosures with and without pretreatment by technological deformation.

Jan 1, 1987

By J. K. Richmond

This is a progress report summarizing more than 5 years of a long-range Bureau of Mines research program. The purpose of this program has been to investigate the fire and explosion properties of Green River oil shale in the Bureau's Experimental Mine, in laboratories, and in the field. The lean limits of explosibility of oil shale dust, by small-and large-scale tests, are reported as a function of grade, ignition source, and particle size. A limited number of laboratory tests on the autoignition of oil shale dust layers and the spontaneous combustion tendencies of oil shale are described. Moderate-scale rubble fire tests were conducted to determine flame spread rates as a function of ventilation flow. With the aid of a system to continuously monitor methane emissions in a deep oil shale mine, the characteristics of the methane flow are reported as a function of ventilation and blasting procedures, and are compared with gas yields from core samples. Tentative predictions as to the emission of the methane to be expected in deep oil shale mines, far from the outcrop, are offered. Brief reference is made to a parallel investigation into the fire and explosion hazards of oil shale mining and processing by a Bureau contractor; detailed results of the latter investigation are to be found in the contractor's reports.

Jan 1, 1982

By M. Radwan, S. Shimada, S. Z. El-Tawil, K. A. El-Barawy, Y. Miyamoto

This study presents the results of synthesizing monolithic siliconoxynitride, Si2N2O, ceramic from a mixture composed of reclaimed silicon and natural desert sand by using the nitriding combustion synthesis method. Single-phase Si2N2O powder was prepared by the combustion of a mixture composed of silicon and pulverized sand in 3 MPa nitrogen gas. The combustion reaction completed in 2 min and the combustion temperature reached 1577°C.The as-synthesized Si2N2O powder is agglomerate of fine particles with sizes < 5 µm and has various morphologies; rod-like and irregular crystals, irregular kinking, hollow crystals and grown pseudo-hexagonal prismatic crystals. Porous Si2N2O compacts (24.5–47.1% porosities) were fabricated from the synthesized Si2N2O powder at different calcia-alumina additives (5–20 wt%) by normal sintering at 1500°C for 1 hr in N2atmosphere.They showed superior oxidation-resistance at high temperatures up to 1500°C in an oxidizing atmosphere of Ar/O2/H2O(70/20/10 kPa).Near-full dense Si2N2O compacts were also successfully fabricated from the synthesized Si2N2O powder with 5 wt% oxide additives by using the spark plasma sintering at 1600°C.DenseSi2N2O had good mechanical properties (18.7 GPa Vickers hardness, 3.3 MPa.m1/2fracture toughness and 363 MPa strength) and excellent chemical and oxidation resistance.

Jan 1, 2004

Electrostatically charged water droplets efficiently suppress breathable dust produced during open air rock crushing operations, according to recently completed independent tests conducted for the Environmental Protection Agency. Since a primary rock crusher produces very heavy clouds of dust, this application was selected as an appropriate test site to measure the efficiencies of new "charged fogging" equipment in mining and mineral processing operations. EPA&apos;s Industrial Environmental Research Laboratory, Research Triangle Park, NC, contracted TRC-Environmental Consultants Inc. of Wethersfield, CT, to conduct a full-scale demonstration of a recently developed electrostatic fogger, designed to project a charged fog spray at distances up to 15.2 m. Test results indicated overall fogger efficiencies of approximately 70%. The Fogger IV* employed in these tests is reportedly the largest charged logger ever made, with an extremely long operating range. The original fogger was designed for indoor dust control; this fourth generation version is designed for fugitive dusts, indoor and outdoor, and has an operating range up to 15.2 in.

Jan 6, 1981

Seam correlation in the central Rapahoe Sector (Greymouth Coalfield) can be enhanced by detailed lithostratigraphy and chronostratigraphy. Rewanui Coal Measures are overlain comformably by lacustrine, deltaic and fluvial strata, and this upper contact can be located using lithological and geophysical log character. The Cretaceous-Tertiary Boundary (KTB) occurs near the top of Rewanui Coal Measures and has been identified palynologically in 16 drillholes. The Rapahoe Sector can be subdivided into two palynostratigraphic domains which adjoin along a basement normal fault which was downthrown to the north during coal measure deposition. The KTB provides an isochronous surface which is independent of the lithostratigraphic datum. Using the KTB as a datum, the æUpperÆ, æMainÆ and æSubmainÆ seams can be reliably correlated throughout the southern and central Rapahoe Sector. Similarly, the æSubmainÆ seam can be correlated with æcÆ seam of the Strongman Mine area, though other Strongman seams are absent from the central and southern Rapahoe Sector.

Jan 1, 1996

By T. C. M. Pillay, John Chipman

The Si-0 equilibrium in liquid iron was investigated in some detail by Gokcen and Chipman1 who reported equilibrium constants of the following reactions: In each case the thermodynamic equilibrium constant K was obtained by extrapolating K&apos; to infinite dilution. Their results on reaction [I] were consistent with those of earlier observers, and there seems to be little doubt as to the approximate validity of the equilibrium product determined. On the other hand, the results on reactions [2] and [3] indicated unusual curvilinear relationships between the activity coefficients of silicon and of oxygen and the silicon concentration. Since a linear relation is observed in all other similar instances, it was concluded that some source of error had affected the gas-metal equilibrium relationships. Recently the authors undertook a restudy of these equilibria with the view especially to establishing the equilibrium constant of reaction [2]. Their experiments, however, were discontinued before a tbroughly satisfactory answer had been obtained and consequently have remained unpublished until the present time. Quite recently Matoba, Gunji, and Kuwana2 published the results of a very thorough study of these equilibria. It is the purpose of the present note to Compare these three sets of experimental data, a comparison which leads to Confirmation of the results of Matoba and coworkers. The experimental arrangements described by Dutilloy and Chipman were employed. A controlled mixture of Hz, H,0, and argon was led into the induction furnace over the surface of the Fe-Si melt contained in a silica crucible. On account of the slow approach to equilibrium, runs were continued for at least 8 hr and, in some cases, as much as 12 hr. Samples were taken by means of silica tubes at the start and during the final 4-hr period of each run. Out of twelve runs only seven appeared to have approached equilibrium with sufficient certainty to be reported here. The results of these experiments, all at 1600°c, are shown by the triangles in Fig. 1. Equilibrium was approached from both oxidizing and reducing conditions and the direction of approach is indicated by the shape of the triangle. Attempts to extend the study to higher silicon concentrations were unsuccessful on account of the transfer of silica from the metal bath to the upper portions of the crucible by means of a silicon-monoxide mechanism. Matoba, Gunji, and Kuwana used similar methods and approached equilibrium from both sides. Their results at three temperatures are shown by the solid lines of Fig. 1. A line corresponding to 1600 deg is interpolated from their equations and is shown by the dotted line. The results of Gokcen and Chipman at 1600 deg in the range 0.02 to 2.0 pct Si are also shown. At concentrations up to about 0.6 pct Si, these investigators approached equilibrium from both directions, and their results in this range appear to be trustworthy. Above 1 pct Si, however, all of their experiments involved oxidation only, as shown by a decrease in the silicon content of the bath. It now seems certain that they failed to reach equilibrium at these higher silicon concentrations and that the curvilinear relation shown by their results is incorrect. It is evident that their results in the lower silicon range are in good agreement with those of Matoba and coworkers. In fact, a straight line drawn through their results would parallel the dotted line and would differ from it by only 0.05 in log K. The new data also lie close to that line. It may thus be concluded that the three sets of data are in good agreement and that the equations proposed by Matoba and coworkers for reaction [2] are satisfactory . They take the limiting value of log K&apos;, at 0 pct Si as log K ,. The slope of each line gives the value

Jan 1, 1962