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Improve the safety of salt mine workers by providing a means for quickly identifying areas within the mine that?s how an increased potential for gas and salt outbursts. Approach Outbursts occur in salt mines when a high-pressure pocket of gas is intercepted during the mining process, resulting in a sudden and sometimes catastrophic expulsion of gas and salt. In one case, the amount of gas released through such an event caused an explosion that resulted in five fatalities. The U.S. Bureau of Mines has designed and developed a gas outburst prediction system that can quickly determine the potential instability of areas within rock salt mines. The determination is based on noise measurements obtained from samples of the salt as they are dissolved in water. This system improves upon technology currently available because it provides information in only a few minutes instead of in several days. In addition, present prediction systems are not only time consuming, but expensive because they require laboratory conditions and highly trained personnel to operate them and determine results.

Jan 1, 1989

By W. J. Kingwell

Where the equipment, technique and materials are available for the construction of large diameter rock socketted piles, this is frequently the most economical and environmentally acceptable method of supporting very large concentrated foundation loads in geoglogically appropriate areas. This paper outlines the current approaches in Australia to design and installation of large diameter rock socketted piles. The equipment and procedures described generally reflect those developed or used by Vibro-Pile (Aust.), a company which, while installing the usual range of driven and bored piles, specializes in the design and construction of large diameter rock socketted piles and possesses special expertise in drilling in high strength rock. A high capacity crane attached drill for large diameter drilling in rock is briefly described. Discussed in detail are the construction techniques employed and structural and geomechanical design methods adopted.

Jan 1, 1989

By A. E. Isaacson

The U.S. Bureau of Mines determined the effect of common sulfide minerals on the corrosion rates of various types of ferrous alloy grinding media. Data obtained from this study will aid in determining the contribution of any electrochemical reactions between sulfide minerals and grinding media to the total grinding media consumption. Common sulfide minerals used in this study were chalcopyrite, galena, and sphalerite. In the presence of oxygen, chalcopyrite was found to increase the corrosion rate, galena was found to decrease the corrosion rate, and the effect of sphalerite was dependent upon the type of grinding media. Possible electrochemical reactions of these minerals in the presence of grinding media are suggested.

Jan 1, 1989

By James R. Craig

The slags generated during gasification of petroleum coke are heterogeneous and con-sist of many different phases. These phases are important because their physical properties affect the operability of gasifiers and because they concentrate many elements that are present in the petroleum coke feed in only minor to trace quantities. An understanding of the chemistry and physical nature of these slag phases is necessary to predict behavior in the gasifier and in considering the ultimate use or disposal of the materials. Slags typically consist of silicate glasses, calcium-silicates, free iron-nickel metallic phases, iron sulfides, and aluminum oxide spinels enriched in iron, chromium, and vanadium. The partitioning of elements among these phases has been analyzed and will be discussed.

Jan 1, 1989

By Jorge Gutierrez C.

CODELCO-CHILE, the world's largest copper producer, began an integrated study of the informatics situation in the corporation at the end of 1980. As a result, a five years strategic Systems Plan was elaborated and approved by top Corporate management. Main points in this plan were: a systems architecture with information integration to the top level management; a higher degree of information technology in the production areas, an optional systems development resources utilization and a high profitability of the plan itself. During the study phase a series of theoretical definitions were fixed and used as a basis for the plan's design. A "common systems" approach was chosen as the development strategy instead of corporate systems or separate divisional efforts. Top management should be highly involved in the revisions of the plan, as well as qualified users should be chosen as project managers. The systems architecture should grant the information integration to the corporate level, in order to support an integrated planning and administration environment for the corporation. A total of 15 projects were defined, involving 570,000 man-hours and shifting the development efforts towards the production and production services areas. The paper presents a critical evaluation of the whole process, showing its good and bad aspects and a positive global balance. It also points some suggestions and hints to any corporation who wishes to get involved in a similar experience.

Jan 1, 1989

By Waghorne E. P

The State Electricity Commission of Victoria is Australia's largest single coal producer. Approximately 19 Mt of coal will be produced in 1989 from the SEC V's newest mine, Loy Yang Open Cut (LYOC), which com- menced overburden stripping operation in October 1982. When the adja- cent Loy Yang Power Station is completed in the late 1990's, LYOC will supply between 35 to 45 Mt/a, depending on power station performance and demand of coal for non-power generation uses. LYOC has been a major challenge for the SECV. It is the biggest single open pit coal mining development undertaken in Australia, with a whole of life capital cost approaching A$1 billion. The mine has supplied a very rapidly growing demand for coal from the expanding power station while developing in breadth, length and depth. Coal demand has consistently been above the figures anticipated during the initial planning because of the substantially improved performance of the 500 MW units of the Loy Yang A Power Station. The superior performance of the LYOC and power station has generated additional electrical energy during the first 5 years of power station operation compared with the initial planning targets- at almost no additional capital cost. This has been a major benefit to the SECV. LYOC will continue to present major challenges for the SECV, particularly in achieving overburden removal and coal reserve targets as development of the open cut continues to full depth over the next 15 years.

Jan 1, 1989

By Jon J. Kellar

The adsorption of oleate at the surface of a fluorite single-crystal internal reflection element has been investigated using Fourier transform infra-red/internal reflection spectroscopy (FTIR/IRS). The application of this innovative experimental technique has added a new dimension to the investigation and understanding of collector adsorption phenomena. It is now possible, for the first time, to measure in-situ and in real time the adsorption density and bonding nature of collector species adsorbed at mineral surfaces. In this regard, oleate adsorption densities were calculated from spectral data, and the equilibrium adsorption isotherms were found to agree quite well with other adsorption isotherms reported in the literature. At low equilibrium oleate concentrations(<10-5 M), monolayer-type cover-age was observed in the chemisorbed region. It was found that in this region the adsorption density increases with an increase in temperature, which sup-ports experimental results from previous ex-situ FTIR studies and thermochemical studies in which it was shown that the chemisorption reaction was endothermic. At higher equilibrium oleate concentrations (>10-5 M), the adsorption density increases dramatically at the point of surface precipitation. The oleate adsorbed in the chemisorbed region has a distinctly different spectrum than the oleate adsorbed in the surface precipitation region of the adsorption isotherm. In the chemisorbed region, the oleate appears to be mono-coordinated at the fluorite surface.

Jan 1, 1989

The dielectric properties of practically all oxide and sulphide ore minerals are such that they heat rapidly when irradiated with microwaves particularly at the standard frequency of 2450 MHz. The presence of carbon or low rank coal mixed with the minerals still further enhances the heating rate. Amongst the patented technologies being investigated are: (i) the direct reduction of oxides with or without carbon included in the pellets or briquettes; (ii) microwave precursor heating of composites ahead of smelt reduction; (iii) microwave smelting of ore or concentrate mixtures with carbon, sometimes assisted with oxygen. Microwaves appear to stimulate endothermic reduction reactions as readily as they do exothermic oxidation reactions. Being a method of achieving "bulk" heating, composites or columns of ore-char blends rapidly heat throughout rather than from the outside inwards as in conventional heating. The microwaves of themselves do not generate any gas - the only gases to be cleaned are the products of reaction in the composites or blends, plus the products of oxygen smelting. In the case of sulphide composites, depending on the quantity and type of low rank coal or char present, sulphur may be eliminated, and collected, in the elemental form. Furthermore, reactions seem to take place at lower temperatures than in conventional smelting but no doubt at the "points" where actual reactions are taking place the atomic or molecular vibrations are such as to satisfy the laws of thermodynamics. Examples are given of the production of unusual products of smelting sulphide concentrates and also the alloys produced from refractory minerals such as chromite and ilmenite. The techniques have been used to produce products with as wide a range of melting points as relatively pure tin and tungsten-molybdenum alloys. Special equipment is being designed and evaluated for these new fields of pyrometallurgy.

Jan 1, 1989

By Robert A. Jankowski, Charles Babbit, Natesa I. Jayaraman

The Bureau of Mines, together with Foster Miller Inc., has developed a compact, high pressure scrubber system for continuous miners. Powered by water energy alone, it can move up to 1.4 m3/s (3,000 cfm) of air and scrub a significant amount of the dust in the air. Full- scale model and underground trials showed excellent performance. Operated at 8.3 x 10[3] kPa (1,200 psi) and 38 L/m (10 gpm), the scrubber has reduced operator and return dust concentrations by more than 50 pct. This paper describes the full-scale model development, system fabrication and underground evaluations of this novel and inexpensive scrubber.

Jan 1, 1989

By N. A. Abdel-Khalek

Laboratory flotation tests were carried out on six Polish samples of different rank. Each coal sample was screened into 7 size fractions. The floatability of size -by- size for various size ranges for different samples was investigated as: well as the original samples. The results showed that in flotation of size -by -size, the intermediate size had the maximum floatability. The range of this intermediate sizes varied with the rank of the coal. Entrainment was shown to be an important mechanism to the recovery of fine particles in flotation of the original samples".

Jan 1, 1989

By J. A. Pagliero, R. T. Quiroz, S. H. Castro

Selected voltammograms in tetraborate buffer solutions in the presence of ethyl xanthate or isopropyl xanthate at pH 9.3, for chalcocite, covellite, chalcopyrite, and enargite mineral electrodes, are presented. The concept of critical Eh of dixanthogen condensation (Ehc) is introduced, and the line of Ehc is thermodynamically defined in plots of log [X i] vs Eh, for methyl, ethyl, propyl, and butyl xanthates. A reaction scheme of xanthate oxidation in four steps, involving the dixanthogen condensation step, is proposed. A first attempt to interpret mineral flotation from a more general point of view is made. The electrochemical mechanism of dixanthogen formation and condensation is considered as a particular case of a more general and relevant phenomenon, which is the decomposition of the collector giving hydrophobic colloidal forms, whose associative behavior in bulk solution and at the mineral/solution interface is governed by colloid chemistry.

Jan 1, 1989

By Bret Boster

Facilities at Amax Gold&apos;s Sleeper Mine process some 330 kt of high grade ore and 4100 kt of low grade ore annually to produce 6.8 t of gold and 7.8 t of silver. High grade ore is processed in a conventional milling facility employing gravity concentration, CIC and CIP unit operations for gold and silver recovery. Low grade ore is processed using heap leaching and carbon adsorption methods.. Presented are the evolution and descriptions of the Sleeper processing facilities and discussions of selected&apos; operating results.

Jan 1, 1989

By Sidney L. Hansen

This report was written because of concerns of the possible error involved when stopping leakage is incorrectly assumed to be turbulent. It is common practice to use turbulent flow to characterize each airway branch for computer models of mine ventilation circuits. This report addresses computer methods to accurately model air-leakage paths. A graphical method is described for deriving the equations of leakage through stoppings. The significance of modeling leakage according to the proper flow regime (turbulent or laminar) is demonstrated by the following method. A hypothetical mine was developed to represent present-day conditions. The stoppings of the mine were chosen to leak according to laminar flow properties. The mine was represented by constructing two base models. One base model used turbulent leakage equations for each stopping, while allowing the corresponding resistances to vary. The other base model used the correct laminar leakage equations and held corresponding resistances constant. The mine circuit was then expanded to demonstrate future development. The expanded portion was designed with stoppings that were identical to those in the base mine. The mine in the future state was represented by two projection models. Each projection model was an extended version of its associated base model; one used turbulent leakage equations and one used laminar leakage equations for stoppings. The laminar projection was theoretically correct and is used as a basis for comparison of differences in airflow quantities. Rather than modeling every leakage path for stoppings, a more practical approach is also discussed. A good level of accuracy is maintained by combining leakage paths if the proper flow equations are used. This method was used on the hypothetical mine projection and the flows were very similar to the theoretical values.

Jan 1, 1989

By M. J. Meulendyke

Within the mineral processing Industry. a range of grinding conditions exists which include semi-autogenous grinding (SAG), rod milling. and conventional ball milling. Each of these mill environments presents a unique environment for grinding media, requiring the application of specific physical and chemical properties for optimum grinding media performance. The environments are characterized by varying degrees and combinations of abrasive, corrosive, and impact wear. An extensive test program has been conducted to determine the extent wear rates vary between these different applications. Test results are related to production results, ball size, and mill operating conditions.

Jan 1, 1989

A simple and cost effective technique to increase fragmentation and burden velocities without making major modification to the overall blast design is with ALTERNATE VELOCITY LOADING OR BOOSTERING OF ANFO. The technique requires the placement of a cartridge or slug of explosive, having higher density and detonation velocity than ANFO, every few feet in an ANFO column. The greater the difference in density and detonation velocity of the Alternate Velocity Load to ANFO, the more pronounced are the results. Emulsions were selected as the Alternate Velocity test explosives because they detonate closer to ideal conditions than most other commercial explosives.

Jan 1, 1989

By G. Tamaro

The World Financial Center is situated on a 60,000 square meter site at Battery Park City at the southern tip of Manhattan Island. The foundations for the buildings and the related infrastructure posed difficult design and construction problems since the site was filled land in the Hudson (North) River. Foundation construction was made difficult by both the geology and the existence of two railroad tunnels which passed under the site. The soils at the site were unsuitable to support construction of heavy structures, and as a result, all of the foundations had to be carried down to bedrock, or the glacial till over rock. Two buildings were supported on piling and special battered caissons which provided lateral support against wind loading. The other two buildings were supported directly on rock, requiring excavation to depths of 19 meters (63 feet) below grade.

Jan 1, 1989

By T. F. Dumm, L. G. Austin

"INTRODUCTIONGomez and Austin (1,2) have recently described calibration procedures for quantitative chemical analysis of particles by energy dispersive spectroscopy using particles mounted and polished in a resin matrix and scanned by an SEM under computer control. Their software is specifically designed for the analysis of Si, Al, Ca, Na, K, Fe and S in coal particles, and in this case the resin is loaded with iodine (3) to enable the exposed cross-section of an embedded coal particle to be differentiated from the matrix. However, the basic ideas of their procedures could be extended to any system of particles where it is desired to measure inorganic species in particles containing light elements such 0, C, H and N which are not directly detected. In these circumstances it is necessary to perform a quantitative determination of the measured components, so that the equivalent volume of light elements in the excited sample volume can be estimated by difference using ZAF and other corrections applied to the raw count intensities.Part of their procedure involves a new technique (2) for estimating background spectrum intensities; the intensity for a particular energy window is then subtracted from the total measured intensity for that window to enable the concentration of the corresponding element to be calculated. In addition, corrections for overlap of peak spectrums are applied. For example, Figure 1 shows some typical spectrums for known materials for the system they used, demonstrating a wide Gaussian spread about the theoretical peak energy. Since background spectrum and peak overlap corrections require a knowledge of the composition of the material, as does the application of the ZAF corrections, it is necessary to have an iterative solution of the equation sets, starting with estimates of the composition based on initial count rate corrected solely for dead time and detector efficiency."

Jan 1, 1989

The area around Big Bell was actively explored and sporadically mined for gold from 1904 onwards. The lease was named Big Bell in 1913. The property became established as a major mining centre with the development of the Big Bell underground mine in 1936. Mining operations commenced in late 1937 and ceased in January 1955, after milling 5.56 million tonnes of ore and producing nearly 21 tonnes of gold. In 1969 Australian Consolidated Minerals Ltd (A.C.M.) acquired the deposit then explored it alone and in joint venture until the current joint venture agreement with a subsidiary of Placer Pacific Limited (PPL) was negotiated in 1984. Following exploration and evaluation of near surface mineralisation, and a reassessment of the remnant pillars underground, the concept of a large open pit in conjunction with an underground mine evolved. The feasibility study was completed in October 1987, and the decision to go ahead was formally announced on 2nd December 1987. Placer Dome Technical Services Ltd were contracted to be the Project Managers, commencing construction on site early in January 1988 and handing the plant over to the operators 13 months later. The capital cost of the project at handover was estimated to be $133 million. The operating team commenced pre-production stripping of the open pit on 1st May 1988. By 31st January 1989 almost 16.0 million tonnes had been stripped and 350,000 tonnes of ore stockpiled.

Jan 1, 1989

By Fred H. Seymour

In spite of the progress made by geostatistical theory over the years, evaluation of low grade open pit gold deposits continues to be challenging. Many Carlin type deposits are modelled from exploration drilling spaced on 10C foot centers. From these drill holes, 50 by 50 by 20 foot blocks containing about 4000 tons of material are estimated. The block size is a compromise between being large enough for a good geostatistical estimation and being small enough for practical pit limit analysis and mine planning. Most of these gold deposits are highly variable and include ore and waste zones that are too small to be properly defined from exploration drilling information. Because of this, selective mining is controlled by sampling closely spaced blast holes where the density can be as high as 50 blast holes per exploration drill hole intercept. Figure 1 illustrates an example of the ore/waste contact definition before and after blast hole sampling. With exploration information only, a tentative ore/waste contact can be drawn between the exploration blocks.

Jan 1, 1989

By Werner A. Ruemmele, Steven R. Wardwell

INTRODUCTION The first phase of the Los Angeles Metro Rail Project consists of 7.1 km (4.4 miles) of subway and stations running through downtown Los Angeles from Union Station to MacArthur Park. Shank-Ohbayashi has two of the tunnelling contracts on this initial phase: A-171 and A-146. Contract A-171, the Wilshire/Alvarado Line, involves tunnel construction beneath 7th Street from the 7th/Flower Station to the Wilshire/Alvarado Station. The project consists of the excavation and lining of 3000 m (9900 ft) of twin-bore, 6.7 m (22 ft) excavated diameter, 5.5 m (18 ft) finished diameter subway tunnels. Contract A-146, the 5th/Hill to 7th/Flower Tunnels, comprises 1220 m (4000 L.F.) of twin-bore tunnel identical in cross section to the tunnels in Contract A-171. The majority of the excavation on Contract A-171 is beneath city streets in a weak siltstone/claystone bedrock with cover varying between 10 m and 25 m (32 ft and 82 ft) to the street surface. Approaching the 7th/Flower Station some fine-grained alluvium is encountered. The tunnels on both contracts are excavated with an open face digger equipped shield. On Contract A-146 the tunnel alignment is a 305 m radius curve of approximately 550 m (1800 L.F.) length underneath several multi-storied buildings of various construction. Excavation is still ongoing on Contract A-146. The contractor&apos;s choice for initial tunnel support on both contracts is a system of precast concrete segments similar to what the contractor had used on 7 miles of tunnel in Phoenix, Arizona, for the Arizona Department of Highways.

Jan 1, 1989