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Improve the safety of mine workers by developing a means of forecasting impending roof falls in underground mines. Approach The Bureau of Mines, through in-house and contract research, has developed the Roof Fall Warning Device. This battery-operated, portable electronic system forecasts roof falls by detecting and interpreting high-frequency rock noise, The technology has shown potential for detecting stress-related failures in a variety of underground environments. How It Works All geologic materials produce high-frequency acoustic emissions when they encounter an increase in stress. These ultrasonic frequency range events ( >20kHz) are well above the audible range of human hearing, very small in amplitude and duration, and can only be detected with sophisticated electronic equipment.

Jan 1, 1990

By D. E. M. Plaumann, B. S. Fee, R. D. Hansen, R. R. Klimpel

"The steps from experimental curiosity through to commercial product can be slow and tortuous in spite of the quality of the technological advances offered by the new development. Data generation and interpretation need to be done in lab tests as well as full-scale evaluations and, in each, the advantages of the new reagent must be clearly identifiable and measurable.The Dow Chemical Company has patented a novel new collector for the flotation of zinc. Fl (2-hexylthioethylamine hydrochloride) has several unique structural features that suggest atypical mechanisms for zinc collection. Laboratory data have demonstrated significant flexibility with respect to grade and recovery balance at dosages lower than those typically used for xanthates.In mill trials, the same phenomanon is evident - the choice between high grade and high recovery allows one to select the desired quality of zinc concentrate. One trial in particular was run over a three month timeframe and Fl gave improvements in recovery of 2.5% and a reduction in lead levels with less than 0.5% loss in grade. The dosages of other reagents in the flotation circuit were also reduced.Data demonstrating improved recovery and grade in lab trials will be discussed. Extensive data from the mill trial will illustrate how Fl works in both rougher and cleaner circuits."

Jan 1, 1990

By J. D. Cole

In order to reduce the number of longwall face moves and to increase the rate of gateroad construction, super longwall panels, 1000 feet wide and 12000 to 14000 feet long, are planned for Wolf Creek Collieries No. 4 mine. The development of the longwall panels at the mine has evolved from 5-entry, to 4-entry, to 3-entry systems. A three-entry system including pillar size and entry supporting method for the super longwall panels was designed for long-term stability. The design procedures included field observation and studies, laboratory properties tests, in-situ stress measurement, and computer analysis. Three pillar design methods consisting of PILLAR, ALPS, and the Wilson Method, and one entry supporting method, ROOFBOLT, were adopted in this study. The procedures, methods, and results are discussed in detail.

Jan 1, 1990

By David H. Tang

Massive pillar failures were observed at two underground coal mines. The results of stability analysis using traditional pillar design formulae did not agree with the underground observations. Finite element models were used to analyze the causes and mechanisms of the pillar failures. The results were confirmed by the underground observations. Finally, the improved mine plan for each case was derived to ensure the stability of the underground structure.

Jan 1, 1990

By John Brulia, Grant ODell

The AIRDEK blasting method has recently been introduced as an overbreak control blasting technique. This paper discusses the use of a modified AIRDEK blasting method for use in open-face blasting to make cap stone riprap (6-20 ton size) at the Clinton Point quarry of New York Trap Rock Corporation, Lone Star Industries.

Jan 1, 1990

By T. C. Rao, N. Suresh, M. Vanangamudi

Experiments have been conducted on a 76¬mm water-only cyclone treating cowl below 2 mm size having different proportion of -0.075 mm fines. The effect of cone angle of the cyclone (compound cone) has been analyzed on water split, separation of -0.075 mm fines, separation of coarse solids, and on separation behavior of individual size ructions of the feed. It has been noted from the results that there exists a linear relationship between the flow rate of water in the feed and flow rate of water reporting to overflow stream. This relationship is independent of the cone angle and, with changes in the fines content in the feed, only the intercept of the straight varies, keeping the slope constant. Further, it has also been found that the percentage of fines below 0.075 mm reporting to the overflow is directly proportional to the percentage of feed wafer reporting to the overflow. This relationship is found to be independent of the cone angle and the fines in the feed. The performance of the water-only cyclone has been analyzed by plotting partition curves for different experimental conditions. In addition to this, the Rosin-Rammler equation has been fitted to the partition curves of the hulk feed and individual size-fractions. Tile analysis of the results has revealed that the specific gravity of separation increases with increase in the cone angle of the cyclone while it decreases with increase in percent fines present in the feed. Mathematical relationships have been developed to relate the variation in SG50 with cone angle and percent fines in the feed.

Jan 1, 1990

By T. J. Lien

AMAX Coal Company's Belle Ayr coal dryer is the first industry attempt to commercialize sub-bituminous coal drying which has been the subject of laboratory and pilot plant tests for almost two decades. This paper presents the historical background, construction, start-up and operation of this adaption of fluidized bed coal drying technology to Powder River Basin coal. The flowsheet and operational problems encountered during plant start-up are discussed together with general material balance and product quality.

Jan 1, 1990

By Gary Repetto

Hiring trends in the construction materials industry have remained steady through the years, with some seasonal and geographical variances. However, after several years of a depressed market, the base metals industry has begun to actively hire only over the past two years, due to the continued strength in the prices of copper, lead, zinc, molybenum, etc. The expanding precious metals industry, which for the most part escaped the depressed markets of the mid-1980s, actually preceded the base metal companies in hiring of engineers and operations personnel. The coal industry has not seemed to rebound much from the cutbacks of the early 1980s. And the uranium industry, which began its decline a year or two earlier than the other mineral industries, has remained nearly nonexistent in the United States. In nearly all of the mineral industries, new hires have been mostly in the engineering and operations areas, not exploration.

Jan 1, 1990

The Kanowna Belle deposit was discovered in 1990 following encouraging assays from soil sampling and RAB drilling. At the end of September 1993, diamond drilling had been completed to a vertical depth of 1,000 metres and a resource of 22 million tonnes grading 5.73 grams of gold per tonne containing a million ounces of gold had been defined. The deposit remains open at depth. Pre-production mining for the open pit began in November 1992, construction of the oxide treatment plant began in January 1993 and the first gold was poured in September 1993. Sulphide ore roasting commenced in December 1994 and the underground mine development commenced in July 1995. The Kanowna Belle project is owned by the Golden Valley Joint Venture (GVJV), an unincorporated joint venture with equal shareholdings between North Gold (W.A.) Ltd and Delta Gold N.L. North Gold are the managers of the development and operations and Delta Gold are the managers of exploration throughout the GVJV tenements.

Jan 1, 1990

In the last few years a number of mineral laboratories were established in Indonesia coinciding with the increase in gold exploration in the region. Prior to this, much of the analytical work was sent outside the country,however this is no longer neccessary.

Jan 1, 1990

A novel fracture-plane control blasting technique with particular application in wall-control blasts in mines employing medium to large diameter boreholes is described. It consists of a string of nested holes, each nest consisting of a large diameter charge-hole flanked on either side by a small diameter satellite hole. Each nest is shown to be an analog of a pressurized hole with diametral notches along its length. This 'equivalent-notched' hole concept for generating controlled fractures along preferred directions has been successfully investigated in the laboratory and in the field. The technique has been used to generate controlled fractures on a quarry bench in highly jointed limestone. The resulting blasts with a 250 mm diameter central charge-hole and 50-75 mm satellite holes show that two nests of such holes almost 5 m apart could be joined by a single co-linear fracture. The design range of diameter ratio between charge-hole and satellite hole is 3 to 6 and spacing is 3 to 5 charge-hole radii. With careful matching of explosives and decoupling, and combination of diameter ratio and spacing, it would be possible to connect two nests of such holes more than 20 charge diameters apart by a single controlled fracture plane. The relative merits of the technique against existing wall-control blasts are discussed, and guidelines for practical fracture-plane control blast designs are discussed.

Jan 1, 1990

By L. Woollacott, R. P. King

This paper presents data collected from full-scale plants in order to verify the predictions of a new simulator of CIP or CL operations. Good agreement was found between the experimental data and the simulator predictions. The simulator is able to predict the effects of many of the complex operating phenomena in GIP and CL plants that previous simulation techniques could not describe. This is illustrated by predictions of how factors, such as the manner of carbon transfer, concurrent leaching, and gold loading on eluted carbon, can affect the performance of an adsorption plant.

Jan 1, 1990

By Kevork Chouzadjian, Gary Davis, Nicholas Katsikaros, Bruce Kelley, Mellie Mavatoi

A process has been developed to recover gold and copper from two waste materials at the Bougainville Copper Limited mine in Papua New Guinea. It involves the bioleaching, in reactors, of a pyrite concentrate to liberate refractory gold and generate sulphuric acid, ferric sulphate and biomass for bacterial leaching of a chalcopyritic waste rock dump. Gold is to be recovered by cyanide leaching and copper by solvent extraction/electrowinning. The reactor bioleaching was developed in continuously operated reactors of 1 m3 capacity by CRA Advanced Technical Development at Cockle Creek, while the dump leaching was developed in 750 kg columns on site at Bougainville Copper Limited. The process was to be piloted on site.

Jan 1, 1990

By Kennedy JT

This is a question that will be asked many times and by many individuals during the various evaluation stages of any new project. However, the question itself will often have different connotations to the different groups invariably involved in such an exercise. As examples, consider just three of the several different groups involved in the development of a new mining project - Financiers, Consulting Engineers and the Sponsors of the project (potential borrowers). To the Financiers, a 'bankable project' will be one against which they will be prepared to lend funds (but not necessarily all of the funds requested by the Sponsors). This usually means that in the first instance the technical information presented to the bank has satisfactorily covered all of the requisite areas to the levels of accuracy required. More importantly, the financial evaluation of the projected economic performance of the mine, as a whole, is considered sound and a set of arrangements under which the bank is prepared to advance loan funds have been structured which fully satisfy the bank's credit criteria. To Consulting Engineers preparing a feasibility study (or a part thereof), on behalf of the project Sponsors, the term 'bankable' invariably only refers to the technical completeness and the level of detail contained in the report which they are preparing. Their scope of work will not necessarily have been broad enough to fully satisfy a bank's requirements. It is unusual to see any specific references to overall project viability or profitability in Consulting Engineers' feasibility reports, other than those which are automatically associated with the use of the term 'ore'.

Jan 1, 1990

By James M. Prudden, E. P. Jucevic

The Divide mining district occupies the center of a Tertiary caldera hosting the famous Divide silver lode and the crosscutting Gold Mountain mines. The northwest-southeast trending silver lode hosted ore with typically a 100:1 silver:gold ratio, high molybdenum content and argillic alteration dated at 16.5 m.y. within the Fraction Tuff. The east-west trending Oddie Rhyolite flow dome at Gold Mountain experienced possibly several periods of resurgence with repetitive silicification, brecciation and attendant precious metal deposition forming stockwork type mineralization. Silver-gold ratios average 10:1 for the mineralization phase of this 16.4 m.y. intrusive event. Similar chalcedonic mineralization registering a 3:1 silver:gold ratio cements conformable breccias within the Oddie Rhyolite basal flows unconformably overlying the Siebert Tuff on the northern flanks of Gold Mountain. Gray and red chalcedonic breccia matrix in the King Tonopah member of the Fraction Tuff contains a 50:1 silver :gold ratio.

Jan 1, 1990

By Morland R, Peck R

The Joint Committee of The Australasian Institute of Mining and Metallurgy (AusIMM) and the Australian Mining Industry Council (AMIC) have published a Code for the Reporting of Identified Mineral Resources and Ore Reserves. The Code is the result of an initiative begun in 1971 to achieve industry self regulation of Resources and Ore Reserves reporting which resulted first in guidelines for reporting standards but which have now been incorporated in ASX Listing Rules as a Code with significant sanctions ensuring compliance. This paper describes the background to the Code, its key provisions, and comments on practical aspects of working with the Code and compliance issues.

Jan 1, 1990

By R. Balia

The upper part of the "Contatto Ovest" orebody, at the San Giovanni Pb-Zn sulphur mine (Sardinia, Italy), is mined by a sublevel caving method. With increasing mining depth, a progressive caving of the hanging wall and discontinuous subsidence occurs. The orebody, which is located very close to the contact between the Cambrian limestones and the Silurian shales, strikes NE-SW for more than 100 m and dips 75-80' NW. The limestone footwall is massive and strong while the hanging-wall consists of very weak shales. The mine considered is located near a town so that the observed subsidence effects must be taken into account for both stability of the nearby railway and houses and morphological and environmental impact. A limiting equilibrium analysis to predict the progress of hanging wall failure with increasing mining depth was used. A suitable computer program was developed for solving the model by a iterative procedure. The progressive hanging wall caving and its consequent superficial effects were predicted perfectly by means of the computer program used and later confirmed by a geophysical test (seismic tomography). Our study ends with a further analysis, carried out using the same procedure, which allows to have a different geometrical situation with the presence of a pillar to protect the mill area.

Jan 1, 1990

In southeastern China, offshore Tertiarybasins are buried underneath the broad continental shelf areas from Taiwan to Hainan Island. These basins bear relatively similar characteristics of structure, stratigraphy and tectonics. Based on age and tectonic framework, these Tertiary basins are divided into two groups of Paleogene basin and Neogene basin (Fig.1 and 2). However, observations of extensional structures indicate that the Paleogene basins are rift basins; and the predominant structural features are NE-SW trending half grabens and fault blocks. In a regional scale, these half grabens and adjacent uplifts represent a horst-and-graben structural style. Neogene basins are downwarp basins lying on the tilting continental shelf. Late Tertiary sequences are relatively undeformed but locally with minor folding and thrusting during the Pliocene-Pleistocene.Seismic stratigraphy and well data indicate that the Early Tertiary strata are commonly tilted and disturbed as nonmarine to marginal marine facies deposited in the wedge-shaped half grabens; the Late Tertiary strata are generally parallel undisturbed marine facies accumulated in the enlarged downwarp basins overlying the infilled half grabens. In general, three major regional unconformities formed during the Late Cretaceous, the Late Eocene and the Middle Miocene. Widespread extrusive basaltic flows are commonly associated with these unconformities.

Jan 1, 1990

Although small scale mining is regarded by many as of historical value only, this kind of mining activity is still much more widespread than is usually assumed. It has been estimated that it produces as much as ten per cent of the global mineral output. More significantly this figure is often much higher for many of the developing countries of Africa, Asia and South America, signifying the relatively greater contribution of small scale mining to the economies of those countries. It is also noted that small scale mining has always been a feature of mineral production in New Zealand and Australia. An attempt is made to define small scale mining, and the factors determining the suitability of small scale mining operations are discussed. The state of the art in small scale mining is reviewed and the author endeavours to rationalise the important parameters which contribute to successful small scale mining operations and discusses how these parameters may be optimised. The benefits of small scale mining to the mining industry as a whole and to the community at large are outlined. The paper concludes by emphasising the necessity to maintain small scale mining and 'explores' its future 'prospects'.

Jan 1, 1990

By Lynn B. Hales, Randy Ynchausti

Expert systems are now being used effectively to streamline and improve the performance of supervisory computer control strategies. Their advantages have led to use in both batch and continuous applications. Expert systems in the context of real-time process control, will be defined and examples of their successful implementation in autogenous, semi-autogenous and ball mill grinding circuits will be discussed.

Jan 1, 1990