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By J. P. McDonnell, L. A. Beckett, K. Y. Hammy

Dangerously high stress areas can be controlled by proper mine planning and/or destressing. This paper reviews practical methods to detect and destress high-stress zones along coal faces. The US Bureau of Mines investigated stress-related burst problems and destressing efforts at a cooperating mine. Laboratory tests of the drilling yield method for high stress detection were conducted to determine the correlation between the volume of cuttings obtained and the magnitude of the applied stress. A three- dimemiom1 computer modeling program was used to evaluate the effectiveness of stress relief methods.

Jan 1, 1987

By Ben A. Kornhauser

Benin's industrial sector experienced severe economic and financial problems in 1986, including disappointing performances of the Onigbolo cement plant and the Semé Oilfield, plus a shortage of technically trained personnel and experienced management. Oil production remained about 1,000 barrels per day. Import and export trade between Benin and the United States remained minimal. Because much of Benin's outstanding external debt was in U.S. dollars, the stronger dollar greatly increased the debt burden. The 1985 budget of $304 million' was composed of an investment budget of $194 million and a current budget of $110 million. Of the investment budget, 84% was expected to be externally financed. About $45 million was given to three priority projects: the joint Benin-Togo Nangbeto hydroelectric project scheduled for completion in 1986; drilling of new exploratory wells of the Semé petroleum project, and the Dassa-Parakou highway. The budget deficit was projected to exceed $43 million despite a decrease in projected revenue owing to an anticipated decline of 25% in import tax revenue, normally the largest source of Government revenue.

Jan 1, 1987

By Tagawa H

In Japan, geological condition do not only vary in a wide range of strata but are also extremely complex with the existence of faults and aquifers. With respect to rocks, in particular, it is very rare that homogeneous rocks are distributed uniformly. In general, geological conditions are distributed in a wide variety, ranging from earth, sand, soft and medium rocks to hard rocks. Under these geological conditions, when planning of the tunnel construction is to be made out, either blasting method or tunnel boring machines must be selected taking into consideration the geological structures along with the designed tunnel route,' possibility of encountering aquifers, hardness of rocks anticipated and also, the adjacent environ- mental conditions. In the process of select- ing an excavation method,, it is important to make a comparative investigation between the above two methods considering the advantages and disadvantages with regard to the respective operating efficiency, economical efficiency and the conditions and scope of application as well. Furthermore, in addition to these considerations, the recent environmental restriction, which does not allow the blasting in the surroundings of residential areas, must also be taken into account. Because of this, in some cases there is no alternative but to use a static excavation method or a tunneling machine even when these are less efficient than blasting.

Jan 1, 1987

The eastern Asia island-arc systems are regarded as specific marginal structures having the common features of geological development and deep structure. The notions on deep structure of island- arc systems are based on the data of studies of the mantle and low-crustal xenoliths. Analysis of location of deposits and ore occurrences of different ages within island arcs in comparison with, the processes of deep heat and mass transfer allows us to develop a-model of mobilization, migration and accumulation of ore substance in the "crust-mantle" system.

Jan 1, 1987

Studies of the morphology of seamounts within the Hawaiian, Line Islands, Gilbert and Phoenix Seamount groups indicate that the morphology and size distribution of seamounts vary significantly from one seamount group to another. The Line Islands group appears to be the most complicated of all the groups studied thus far. This group is complicated by reactivation of volcanism, which has superimposed volcanics on sedimentary rocks. These seamounts display abundant volcanic features on their summits. Seamounts within the Hawaiian seamount chain display a marked absence of volcanic features due to the . presence of thick carbonate caps. Reef platforms and sealevel benches are very common on these seamounts but are absent from seamounts in most other seamount chains in the central Pacific. Slope angles vary regionally between seamount groups. The minimum slopes are found on Necker Ridge in the central Pacific basin. The maximum slopes are found on ridge-crest seamounts. Roughness increases proportionally with mean slope angle.

Jan 1, 1987

By Ronald S. Tanaka

In the planning stages for a dozen years, the 9.11 mile long Mount Macdonald Tunnel is the focal point of the $600 million dollar Rogers Pass Project. The paper will discuss the construction of the tunnel that is being carried out from both ends. The eastern portion contractor has used a tunnel boring machine to excavate the upper part of the tunnel and at the west end contractor selected the conventional drill and blast method. A ventilation shaft located near the mid point is the main part of a ventilation system unique in the Western Hemisphere.

Jan 1, 1987

By Andrzej M. Wala

The determination of the air quality needs to dilute diesel exhaust gases to a safe level must be individually evaluated for particular cases. One such case is when diesel-powered vehicles are working in long dead- end headings with forcing auxiliary ventilation. The vehicles perform specific operations in a cyclic order required by the technical process. The dynamics of this process in certain conditions has a vital influence on environmental conditions in the working area and in the rest of the heading. Recent studies on diesel gas behavior in long headings have shown a zone of increased concentration of pollutants (accumulation) between the face and the mouth of the heading. To be able to control these accumulations of pollutants, use of the concept of planned air discharge by using the Coanda-type ducts is proposed. The main objective of this paper is to demonstrate an application of computer simulation of that process. It is shown that, by planning the additional air discharge, the concentration of diesel gases can meet required limits along the heading.

Jan 1, 1987

By D. M. Kjos

Large-diameter autogenous and semiautogenous grinding mills represent the primary thrust of the expanding grinding technology. In spite of initial difficulties, large autogenous and semiautogenous mills have reached an acceptable level of technology that provides the mineral engineer with a reliable, low cost means of ore comminution. A successful milling installation begins during the design stage of the grinding mill and the plant in which it is to be installed. This is particularly true in autogenous and semiautogenous mills. Critical mill and plant design factors should be considered while the mill and installation are still only "paper." Various current liner designs will be discussed ranging from lifter bar/plate to integral types. Modes of operation such as "high-low" will be considered. Liner maintenance procedures ranging from laydown area in plant design, proper mill shutdown methods, to installation and bolt tightening complete the equation to yield optimum performance possible for any particular grinding application. The objective of this paper is to discuss trends in wear materials, designs, and operating practices, and to provide some guidelines for good practice as we move through the 1980s. We will put together concepts that relate to the designs, materials, and applications so that higher performance can be obtained by the operator for his specific application. The concepts are shown as being in series became they are dependent on each other to achieve the desired performance: designs times materials times application results in higher performance (Arnson, Parks, and Kjos, 1983).

Jan 1, 1987

By Houghton BF

Ruapehu is an extremely active andesitic composite volcano, built in at least four cone- building episodes over the last 250 ka. The volcano was constructed by a variety of extrusive and subplinian, strombolian, phreatomagmatic and dome-related explosive eruptions from summit, flank, and satellite vents. The volcano may be subdivided into the cone itself, of volume 110 km3, and a surround- ing epiclastic ring plain of similar size. Four facies associations can be recognised at Ruapehu,-two each on the cone and on the ring plain. Neither cone nor ring plain provides a complete record of the history of the volcano. The cone is dominated by the products of extrusive eruption, as primary pyroclastic deposits are seldom preserved, being rapidly removed by erosion from the steep water- saturated and/or snow-covered flanks of the cone. The ring plain consists of the products of mostly explosive activity forming an alter- nation of primary pyroclastic fall deposits and material transported from the cone by lahars, floods and debris avalanches and then rapidly reworked in sediment-choked hyperconcentrated Streams.

Jan 1, 1987

By L. Wade

The advent of relatively cheap computing power has precipitated a rapid growth of computer usage in the mining industry. In order to obtain most benefit from this development a need is recognised for the future mining graduate to be trained in computer literacy. This paper outlines the type of training required and describes progress to date with such a programme at the University of the Witwatersrand. Certain challenges concerning the teaching effort are discussed.

Jan 1, 1987

Results of direct shear tests on rock discontinuities and triaxial compression tests on intact rocks are presented and - discussed. The main parameters considered area stress functions, angle of internal friction and cohesion variations. Primary objective of this work is to determine relationships that adequately describe the rock behaviour for design of mining excavations, while still maintaining a certain degree of simplicity.

Jan 1, 1987

By Juniper LA

ERM Consultants Pty Ltd was established in 1980 for the purpose of introducing a disciplined coal technology and power station planning service, to support Australia's efforts in establishing a major export steaming coal industry. At that time, major coal exploration programs were mounted on more than 50 potential export coal deposits with proven open-cut reserves to export 200 Mt/a of coal. The fact that Australia achieved an export trade of only 30 Mt/a, equivalent to the energy requirements for a population of around 5 million people, illustrates the very small achievement to date. The main reasons for this small export steaming coal growth have been: 1. Failure to convince potential overseas coal buyers of the benefits of coal-fired power generation, and the ability of proper power station design to overcome environmental problems, and achieve reliable operation and long life when burning Australian coals. 2. Failure to promote Australian power engineers to advise on the use of Australian coals, resulting in Northern Hemisphere power station experience dominating in market countries. 3. Failure of governments to draw on privately practising Australian power engineers and coal technologists in technical workshops, presentations and assistance to overseas countries, to ensure that personnel whose business it was to serve the follow-on needs of countries were readily available. The result of these failures has been that: 1. Only a fraction of prospective overseas coal-fired power projects have proceeded. 2. Australia has had no influence in the design of overseas power stations to ensure that potential customers would be confident that Australian coals could be reliably burnt in their boilers.

Jan 1, 1987

By B. Pesic, J. E. Wey

Introduction One important class of manganiferrous ores is manganiferrous-silver ores. They occur in the oxidized portions of the silver deposits of the western United States. Silver is often associated with manganese oxides, which in some ore deposits are dispersed through calcite, causing the black color of the host rock, known as black calcite. Black calcites can occur in carbonate rocks (0.3 to 50 kg Ag/t) and in volcanic rocks (less than 30 g Ag/t). Silver mineralization associated with manganese oxides and black calcites can occur in veins (Hewett, 1968) or as disseminations (Graybeal, 1981). In the US, silver-bearing manganese veins are located in a broad arc that extends from southern Colorado to southwest New Mexico, southern Arizona, and southeast Califor¬nia (Hewett, 1964). Areas of disseminated silver-manganese mineralization include the Creede and Silver Cliff districts of Colorado and the Tombstone and Hardshell districts of Arizona (Graybeal, 1981). These deposits are also characterized by significant amounts of silver halides - cerargyrite (AgCl), bromargyrite (AgBr), and iodargyrite (AgI). Black calcites are also common in these deposits. Oxidized silver ores containing the higher oxides of manganese are generally refractory to hydrometallurgical methods of treatment. In the past when these ores could not be smelted, they were treated generally by cyanidation at very low efficiency. The US Bureau of Mines (USBM) studied the problem of treating silver-manganese ores in the early 1920s (Clevenger and Caron, 1925). It was found that the refractory silver in the original ore was insoluble in all the common solvents for metallic silver and its salts. The conclusion was that to obtain the highest recovery of silver, all the manganese had to be dissolved or the higher oxides of manganese reduced to manganous oxide. More recent results from treating refractory silver¬manganese ores were given by USBM (Scheiner et al., 1973). The silver ores from Candeleria District, NV, and Round Mountain District, CO, were investigated. Electrooxidation experiments recovered only 34% silver with minor amounts of manganese dissolved. Sulfurous acid pretreatment followed by cyanidation revealed that silver extracted was proportional to the amount of SO2 used. A similar approach, using sulfurous acid pretreatment followed by cyanidation, was also proposed by Rhoades et al. (1984). Hazen Research Inc. performed extensive testing on silver and manganese dissolutions from Ag-Mn ores obtained from the Candeleria and Round Mountain ore deposits. The methods examined were direct cyanidation, pretreatment with sulfurous acid followed by cyanidation, malonitrile leach, and leaching with ammonium hydroxide-sodium thiosulfate under slight oxygen pressure. The results were not satisfactory. The importance of the vast reserves of Ag-Mn ores and the lack of an efficient method to recover these metals warranted a search for new technologies. One novel method for extraction of these metals is treatment of Ag-Mn ores with acidified thiourea solutions. Preliminary results of the leaching of silver and manganese from Ag-Mn ores were very encouraging (Pesic, 1984a) ; thus, it was decided to examine the new lixiviant in more detail. Experimental Ore from the Round Mountain District was studied. It was crushed, ground, and dry sieved into monosized fractions in the range of 16 to +400 mesh. The ore composition was about 90 g Ag/t and 3% Mn, depending slightly on size. The leaching experiments were performed in apparatus described elsewhere (Pesic, 1982 and 1984b). All experiments were performed at constant temperature conditions. The leaching residues were analyzed for silver and manganese. Atomic adsorption was used to analyze the solution samples and fire assaying to analyze the leaching residues (for silver). The standard experimental conditions are given in

Jan 1, 1987

Progress on this project will be verbally reported and a description given of the main features. A detailed feasibility study was completed in December 1986, and the Joint Venture has issued an Environmental Impact Statement. This was open for public comment until 16 February. Issues presently being considered include economic justification traffic, air quality, noise, marine fauna and flora, visual impact, heritage and construction impact. Detail design and construction is likely to commence in mid 1987, following determination of the above matters.

Jan 1, 1987

By J. F. T. Agapito, C. E. Brechtel, M. E. Adam

Full-scale stopping and simulated over- cast structures were constructed in large opening (30 ft high by 55 ft wide) room and pillar excavations in an oil shale mine. The program was undertaken to develop construction techniques and to generate data on structure costs and leakage rates. Leakage rates were measured using both sulfur hexafluoride tracer gas and "brattice window" methods at varying differential pressures. The measurements were conducted before and after a full-scale face blast to characterize the effects of blasting on leakage, and blast air pressures were measured across the stoppings. The operating performance of different combinations of permanent and temporary stoppings was evaluated by developing an operating model for a two-panel oil shale mine. The operating performance for the different stopping combinations was then compared to the system cost to evaluate the overall performance.

Jan 1, 1987

By W. B. Evans, D. P. Taylor

"ANFO has two major disadvantages as an explosive low density and no water resistance. ANFO can be blended with more dense, water-resistant explosives to form ""Heavy ANFO"". The use of emulsion or slurry explosives as a matrix is an attempt to correct deficiencies on the basic ANFO while maintaining cost effectiveness.This paper will deal with four main topics.1. Product description, general properties, strengths and weaknesses.2. Technology of ""Heavy ANFO"" , the emulsion matrix concept and the range of products.3. Relative performance and economics in various rock types.4: Current status in Canada and worldwide, and the expectations for future use.IntroductionANFO has been in use for roughly three decades and remains the explosive of choice where conditions are suitable. ANFO has not become the universal explosive - despite its undoubted superiority in cost effectiveness - because it has serious flaws as an explosive. The most serious of these flaws are the low density and absence of water resistance in ANFO. Low density implies a low concentration of explosive energy in a borehole. The amount of energy available can be increased by. adding an energetic material, generally aluminum, or by drilling more holes. Both solutions add considerably to the over-all costs. The absence of water resistance in ANFO is inherent and can only be overcome by changing the fundamental nature of the product. The history of research in the explosives industry since the advent of ANFO is mainly the story of the various attempts to overcome one or both of ANFO's shortcomings.Many technologies and products have been developed to compete against ANFO, among them slurries, emulsion s and the so-called Dense ANFOs (ANFO with an extra nitroalkane liquid sensitizer). None of them was cost-competitive with ANFO so their market penetration has been limited to wet holes or specialized applications. The exception to this result is Heavy ANFO. The aim here was to have the best of both worlds, the high density and water resistance of emulsions or slurries plus the low cost of ANFO. The concept is very simple. ANFO is about 50 % air, roughly 30% in the prills and 700,10 between the prills . The air in the prills provides the necessary sensitivity but the air between them is waste volume. If one fills this volume with a high density, waterproof product, the resultant mix will be denser and more water resistant than ANFO and with very little added cost. This basic concept was invented by B. Clay in the 1970s and is covered by Canadian Patent No. 1 115 959. The water resistance and/or density of the mix can be tailored by changing the emulsion level. Because Heavy ANFO is relatively inexpensive while providing good in-hole densities and water resistance, it can compete successfully against all other bulk products. It competes against ANFO and Al / ANFO by allowing pattern expansion and reducing over-all costs while it competes against emulsions and slurries on price."

Jan 1, 1987

This paper summarizes seven years of Italian ex­perience with the use of large calibration chambers for the calibration, under closely controlled stress and strain conditions, of some in situ testing devices which are used in sand deposits. At the present time two calibration chambers are operating in Italy, one at E.N.E.L.-C.R.I.S. (Milan) (*) and the other at I.S.M.E.S. (Berga­mo) (**). Both chambers can accomodate cylindrical samples 1.2 m in diameter and 1.5 m in height. A detailed description of these chambers can be found in Bellotti, et. al (1982).

Jan 1, 1987

By L. Adler

A systematic, balanced and inclusive formulation of the vast input data for mine design is presented. Since the quality of this statement severely influences subsquent design it is extremely important to senior mining engineers and the profession-at-large. If unfocussed, chaos can result along with serious ommisions. The basic categories, each a traditional one are: 1) Natural Conditions (geology and geography), 2) Company Capabilities (monetary and managerial), 3) Public Domain (regulations, contracts, good will, etc.) and 4) State of Art (mining engineering professionalism). To further reduce the data additional organizing principles were used: the distinctions of mining (vs. civil) engineering, proceeding from the general to particular, the basic engineering dimensions, and separating dependent from independent variables. The results are a unique and unified corpus, which anticipates the mine design procedure.

Jan 1, 1987

By M. Leroux, S. R. Rao, J. A. Finch

"Poor Pb/Zn selectivity during Pb flotation in laboratory tests on a Mississippi Valley-type Pb/Zn ore was traced to a pH effect. In the pH range 9.5-11 sphalerite floated readily without copper activation. Compared to sphalerite flotation with copper activation this procedure gave equivalent selectivity but reduced flotation rate.Possible mechanisms of this sphalerite flotation without copper activation are discussed. Activation by Fe(OH) 2 is suggested, the Fe++ions being derived from superficial oxidation of pyrite in the ore.INTRODUCTIONGalena and sphalerite commonly occur together. The usual practice is to float galena first followed by the flotation of sphalerite after activation with copper (II) sulphate. If ores contain pyrite it is depressed by maintaining an alkaline pH (9- 10) and using NaCN as depressant.In flotation tests with a Pb/Zn ore from Polaris selective flotation of galena could not be achieved consistently as a considerable amount of sphalerite, even though unactivated, floated. A systematic study was carried out to determine the cause of this problem. This led to the unexpected finding that sphalerite floated in the alkaline pH range 9.5-11.0 without preactivation with Cuso 4 . This paper describes the results of this study and discusses a possible mechanism of the flotation of sphalerite."

Jan 1, 1987

By Robert Martinez

A proven high grade reserve of gold mineralization located in Mexico is evaluated to determine which gold recovery process is best suited for this deposit. The processes evaluated are; Heap leaching, Vat leaching and a CIP circuit. All qualify as viable options, however each one presents a different economic picture which is impacted substantially by the financial constraints of the project. Taking this into consideration the most economic process was selected.

Jan 1, 1987