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By William C. Geitz

"Lightning has always posed a serious threat to blasting operations, especially wkhin the mining and construction industries and operations involving the manufacture, transport, storage and handling of explosives. In recent years, technological advancements in communications systems and microprocessors have significantiy improved the accuracy and efflliency of lightning detection and warning instrumentation. These advancements have increased the availabilii of highly reliable,accurate and affordable systems for use within the explosives arena."

Jan 1, 1991

By Dale S. Preece

"The computer program DMC (Distinct Motion Code) [Taylor and Preece, 1989a] was developed in 1988 and 1989 to predict the motion of rock following a conventional blast. DMC executes very efficiently on a CRAY type computer due to the high degree of vectorization and also due to the use of spherical elements [TayIor and Preece, 1989b]. Bulking mechanisms developed specifically for use with spherical elements include rotation-induced dilatation and aspect ratio > 1.0 [Preece and Taylor, 19901. Rotation-induced dilatation allows the radius of the sphere to expand as a function ofsphere rotation to simulate the interaction of corners and sides of blocky rocks. An aspect ratio > 1.0 is achieved by kinematically tieing spheres together."

Jan 1, 1991

By S. Srinivasan, R. Coté

"India is undergoing a massive electrification program using local coal to provide fuel for thermal generating plants. The Rajmahal mine in northern Bihar is scheduled to produce coal at the rate of 10 million tonnes per year by the end ofa sixty six month contract with MET-CHEM Canada Inc. for mine development. In order to control maintenance performance and warehouse inventory MET-CHEM is installing some proven computer-controlled programs and will provide extensive training to ensure that the systems are properly used. The programs are Maintenance Planning and Control System (MPCS) and Materials Management System (MMS), both of which were developed and used by Quebec Cartier Mining Company at its iron ore mine in northern Quebec. In addition, a Predictive Maintenance Program (PMP) using vibration analysis will be introduced . This paper discusses the three systems.IntroductionIndia is currently undergoing a massive countrywide industrialization and electrification program. Most of the power will be supplied by coal-fired thermal electric plants.One of the mines being developed as part of the over-all program is the Rajmahal Open Cast Coal project in the Godda District of Bihar, approximately 270 km north , and slightly west of Calcutta.The project is based on an agreement signed in January, 1989 between two government organizations - Canadian Commercial Corporation (Ccq and Coal India Limited (CIL). MET-CHEM Canada Inc. (MET-CHEM), an international consulting engineering organization which has worked in India since 1976, is CCCs Canadian executing agency for the project. METCHEM was the engineer-constructor and mining associate for the development of the 7.5 mtpy Kudremukh Iron Ore Project. This US$430 million project was completed on schedule and under the original budget estimate. The Rajmahal deposit is the responsibility of Eastern Coalfields Limited (ECL), a subsidiary of CIL. The project is to produce coal at the rate of 10.5 million tonnes per year in 1994."

Jan 1, 1991

This paper reviews the various processes successfully in operation to treat refractory gold ores and describes in detail the alkaline pressure oxidation circuit operating at the Barrick Mercur Mine, Utah, U.S.A., on car- bonaceous/sulphide refractory ore and the acidic pressure oxidation circuit operating at the Barrick Goldstrike Mine, near Carlin, Nevada, U.S.A., on sulphide refractory ore. The autoclave process is important to Barrick for the extraction of gold. The Company has operated successfully a 750 ton per day unit at its Mercur property for the past two years and more recently has commissioned a 1500 ton per day unit at Goldstrike. The paper presents data relative to operating costs, materials of construc- tion for autoclaves and peripheral equipment, reagent requirements, and changes required during commissioning for both autoclave systems.

Jan 1, 1991

By O. C. Gaspar

The mineralogical and textural characteristics of the volcanogenic massive sulphide ores from the Aljustrel and Neves-Corvo deposits have been studied by ore microscopy techniques since 1977. Several ore types have been recognized, and the ore paragenesis, ore textures, and behaviours of different ore types during grinding and concentration processes, have been determined. An ore classification was established for use in metallogenetic studies, ore reserve calculations, selectivity during mining, and control of the ore beneficiation processes. In addition, an empirical method was developed for supplying, on time, the qualitative and semi-quantitative information needed for processing the Aljustrel ores and for optimizing the Neves-. Corvo copper and tin concentrators.

Jan 1, 1991

The Martha Hill project operates with a nett surplus of water, due to the catchment of rainwater on the tailings dam and the requirement to de-water the open pit mine. It is necessary to discharge this surplus, treated as required, to the Ohinemuri River which flows past the process plant.   The treatment plant, adjacent to the process plant, handles all effluent from the Martha Hill operation including water pumped from the mine, excess water from the tailings decant, and seepage from the tailings dam underdrains. To-date the plant has treated and discharged over 800 000 tonnes of water.

Jan 1, 1991

By A. Vien

MOCCA is a Multivariable Optimal Constrained Control Algorithm developed specifically for non-square industrial control applications with practical difficulties such as interactions, time delays, constraints, modelling development, etc. MOCCA consists of an off-line simulation/translation module, for tuning the control parameters, and an on-line module that implements the designed control law. This paper describes an evaluation of MOCCA on the Hemlo grinding circuit which comprises one open circuit ball mill and two closed circuit ball mills in series. In this case a 4x4 unconstrained control problem was considered. The manipulated variables included the fresh ore feed rate and three pump box water additions. The controlled variables were the grinding circuit product particle size and three pump box levels. In this application soft constraints were implemented through control action and control error weighting. The feedforward capability of MOCCA was used to compensate for a measured water flow disturbance to one of the pump boxes. MOCCA performed very well during plant evaluations when compared to the original classical multi-loop control strategy and proved to be quite robust. Perhaps most importantly, the process engineers and plant operators have a high level of comfort both in understanding MOCCA's general operating principles, and with its demonstrated performance.

Jan 1, 1991

By J. P. Hedlund

Molycorp's gravity type panel-caving operation employs a system of short raises to transfer ore from the Grizzly Level to the Haulage Level. The raises have normally been developed using a conventional drill-and-blast method or a combination conventional/raiseboring method. A new method was needed that would be less labor intensive, provide a safer work environment for personnel, provide a stable raise that could be self-supporting and a method that would be cost competitive with the conventional system.

Jan 1, 1991

By S. D. Van Nort

Editor’s note: This is the first of two MINING ENGINEERING articles about the Grasberg deposit. The second, focusing on open pit mine development, will appear in the April issue of the magazine. The Grasberg porphyry copper-gold deposit of Freeport Indonesia Inc. lies within the Ertsberg Mineral District in central Irian Jaya, Indonesia. The Grasberg deposit was discovered during a drilling campaign initiated in the mid-1980s. Production at the open pit de- posit commenced in December 1989. The Grasberg copper-gold ore body is contained within a young igneous complex of dioritic composition that intrudes limestones of the Tertiary New Guinea Group. Alteration is typical of porphyry copper deposits worldwide except that higher grade primary chalcopyrite with significant gold values is associated with a centrally located zone of strong quartz stockwork. Irian Jaya comprises the western half of the island of New Guinea. The Ertsberg District lies 70 km (43 miles) inland from the Arafura Sea at an altitudeof3500 to45OOm (11,480to 14,764 ft). It straddles the Papuan fold belt. This belt forms the east-west trending chain of mountains that extend the entire length of New Guinea and is the site of numerous mineral districts.

Jan 1, 1991

This paper will present a series of examples drawn for a number of Australian and international mining companies showing their recent attempts at optimisation of capital. The results will be compared, contrasted and discussed in the light of six factors that are considered crucial to any analysis of this subject. The factors are: ò the market availability of capital ò the corporate strategy and performance ò the capital structure appropriate to the corporate positioning within the industry ò the parties to the optimisation equation ò the measurement of success of optimisation The factors above are not mutually exclusive and are generally interdependent so their order above is of little consequence. Other papers presented at this conference will dwell in more depth on all these factors, therefore this paper shall focus only on the key elements of each factor. By way of summary this paper will also address the issue of the longevity of optimisation - is it temporary or long term.

Jan 1, 1991

By L. A. Taylor

The production of oxygen on the Moon utilizing indigenous materials is paramount to a successful lunar colonization. And several processes have been put forth to accomplish this. The LLOX generation schemes which have received the most study to date are those involving?: 1) the reduction of ilmenite (FeTi03) by H2, C, CO, CH4, CO-CI2, & Cl2 plasma, 2) magma electrolysis, both unadulterated and fluoride-fluxed, and 3) several others, including carbo-chlorination, HF acid leaching, fluorine extraction, magma oxidation, and vapor pyrolysis. The H2 reductions of ilmenite and magma electrolysis processes have received the most study to date. They are both feasible schemes with various pros and cons, including their feedstock requirements. However, all processes should be addressed at least at the onset of our considerations. There is an obvious need for considerably more experimentation and study. Some of these requisite studies are in progress, and this paper reviews several of the most studied and feasible processes for winning oxygen from lunar materials.

Jan 1, 1991

By Gao Dazhao

This paper presents some research results of pile foundation performance. Measurements on the bearing behaviour and driving effects of piles have been carried out during pile testing and pile driving. It has been found that the ratio of end resistance to the ultimate load depends on the pile length, and the ratio in general is less than 40% for single piles. However for pile group, the end resistance seems to be greater than skin friction. The characteristic curves of skin friction and end re­sistance appear as interaction between soils and pile. The contribution of skin friction to the pile bearing capacity not only depends on soil properties but also on the relative position of the soil layer. The pore pressure and the lateral pressure in ground have been observed during the stage of driving piles. Based on the available data, the radius of plastic region and the coefficient of pore pressure A can be found analytically. The pore pressure time process curves which may be used for practice have been predicted by means of numerical method.

Jan 1, 1991

INTRODUCTION The SAIMM publishes technical information on various aspects of the minerals industry through several different media. (a) Monograph Series Books in the Monograph Series are high quality, detailed discussions on specialized topics. (b) Symposium Series This series consists of the proceedings of international conferences which are held in South Africa. (c) Special Publications Series This series covers titles which do not form part of the Monograph and Symposium Series. (d) The SAIMM Journal Papers published in the Journal cover al relevant areas of technical interest by striving for a balanced content and maintaining a consistently high technical standard. (e) School and Colloquia Notes The papers from al local schools and colloquia are published and handed out at registration. Should authors wish to have their papers considered for publication in the Journal, they should adhere to the guidelines outlined below.

Jan 1, 1991

By Raja V. Ramani, Sachin Shankar

Re-entrainment refers to dislodgement of particles deposited by both atmospheric and nonatmospheric processes and their subsequent insertion into a flowing field. Formation of sand dunes, snow drifts, soil erosion and fugitive dust emissions are a few examples of the natural occurrence of re-entrainment. Re-entrainment studies have been done for the estimation of potential hazards from nuclear fallouts. The phenomenon of re-entrainment has been utilized for the cleaning of wafers and filters. Re-entrainment is associated with both surface and underground mining activities. However, studies on dust re-entrainment in mine atmospheres are limited. Understanding the re-entrainment phenomenon is important because dust particles lying seemingly harmless on the ground and adhering to numerous surfaces can get re-entrained and become a health and safety hazard. There are significant differences in the kind of re-entrainment encountered in underground mines and those in other fields of interest. These major differences are air velocity, direction of air flow, particle size, amount of particles, and time of exposure. While numerous studies have been done in other fields to identify the role of interacting variables and their contribution to the mechanisms of re-entrainment, no similar reported work is available for dust in mine atmospheres. In this paper, recent research efforts on re-entrainment are reviewed. The most suitable form of representing re-entrainment in underground coal mine atmosphere is presented. Various approaches to studying re-entrainment phenomenon in mines are also outlined.

Jan 1, 1991

By Randy J. Mikula

Cleaning of low-rank coals can have several meanings, depending upon the definitions of the terms "low rank" and "cleaning." In general, low-rank coals would be lignite or subbituminous according to the ASTM classification. For the purposes of this summary, cleaning is defined to be any process which materially reduces the proportion of inert material in the coal. For low-rank coals, this often means a reduction in moisture content since moisture is the major inert component in these coals. A brief discussion of conventional cleaning processes is included, as is an extensive reference list.

Jan 1, 1991

By R. W. Smith

The flotation response and electrokinetic behavior of Chlorella vulgaris and Chlamydomonas sp . when using dodecylamine hydrochloride as collector were studied in the absence and presence of Pb(I1). Also, an electron microscopy study was made of the algae after Pb accumulation. The flotation behavior of the organisms after Pb accumulation appears at least partially related to the location of the abstracted Pb onto or into the organisms.

Jan 1, 1991

By Edward F. Divers, J. Drew Potts

Powered dust-filtering helmets (dust helmets) have become increasingly prevalent in the underground mine environment in recent years. Many longwall operations use dust helmets to reduce the respirable dust exposures of miners required to work downwind of crusher, roof support and shearer operations. While continuous mining sections are usually less dusty, use of diesel equipment represents a new potential health problem. The U.S. Bureau of Mines recently conducted a study to determine the efficiency of a dust helmet on diesel-size particulate. Two underground evaluations were conducted on continuous mining sections that were using diesel haulage vehicles. Model No. AH21 Racal airstream helmets equipped with AS22-3 prefilters, AS23-3 main filters and AS60476 tyvek full-face seals were tested. Helmets were placed on mannequin heads and mounted in the ram car cabs. Andersen Model 298 (eight-stage) personal cascade impactors were used to sample air inside and outside of the helmet. Impactor stages 8 and the final filters were analyzed to determine submicrometer (0 - 0.93 µm) particle concentrations. Results from this study showed that the dust helmet was 94% (± 3% at 95% confidence level) efficient on submicrometer particles. Typically, very little coal dust is observed in the submicrometer size range, therefore, these particles were assumed to be from diesel exhaust. Results from this study indicate that proper use of the dust helmet on continuous mining sections that are using diesel haulage vehicles may be beneficial to the health of miners.

Jan 1, 1991

By David Siu

Many problems were encountered with the mechanical wedge-type splices used for the 15-inch square precast prestressed concrete piles installed at an industrial plant site. Many of the wedges were breaking during installation of the splices and after pile driving resumed following splicing. Dynamic monitoring of the piles and uplift loading tests confirmed that the problems were associated with cracked or damaged wedges. More ductile, annealed wedges were subsequently used, and, while not completely satisfactory, they were found to perform better than the original more brittle wedges. Introduction Long precast prestressed concrete piles were installed to support heavy, settlement-sensitive structures at an industrial plant in Port Alberni, British Columbia, Canada. The piles were driven through soft compressible silts and clays to toe bearing in a dense sand and gravel deposit or on bedrock. Each pile consisted of two or three segments joined with mechanical wedge-type splices trademarked DYN-A-SPLICE. Shortly after construction began, problems arose during pile installation, and these problems were, later, identified to be related to the wedges, or clamps, used to connect the splice plates.

Jan 1, 1991

By Morrison R

Optimisation has two distinct applications in the concentrator ò the first is in the area of the flowsheet and the operating parameters of the various unit operations ò the second is associated with the higher levels of process control. The Plant Metallurgist is faced with a library of complex theories relating to optimisation. The practical reality of optimisation lies in a combination of steady state simulation to ensure that the process route will permit maximum productivity and an appropriate process control system which will permit achievement of the production and quality objectives.

Jan 1, 1991

By David E. Siskind

In the early 1980's, the Bureau of Mines published four reports of structural response and damage from surface mine blasting, vibration monitoring, and analysis methods. These findings replaced simpler and less restrictive Bureau criteria dating back to 1962 for ground vibration and 1943 for airblast.

Jan 1, 1991