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By C. Abbruzzese, L. Piga, P. Fornari, S. Ubaldini, R. Massidda

The effects of certain variables on the extraction of gold by thioureation have been investigated on a quartzose gold-bearing ore using a statistical multifactorial strategy. The factors taken into consideration were milling time (which corresponds to a given grain size), oxidant concentration, thiourea concentration and liquid/solid ratio. The influence of these four variables was ascertained first by a full factorial design at two levels for each variable (16 runs). This permitted the estimation of first-order effects of the factors affecting the process. Then 9 runs were added whose levels were both in the centre of and outside the axes of the previous plan thus originating a central composite design. This permitted estimation both of second-order effects of the factors involved and of parameters of a second-order polynomial model. The results show that extraction of gold depends only on milling time and oxidant concentration, at least in the experimental range considered. The equation fitting experimental data, as calculated by the least squares method, allows a response surface to be drawn. Due to the low gold grade of the ore (6 ppm) statistical analysis could lead to contradictory results, hence strict observance of Gy's rules for sampling and very accurate and precise chemical analyses were required.

Jan 1, 1995

By S. K. Kawatra, S. A. Moffat, K. A. DeLa’O, T. C. Eisele

It was observed that the efficiency of some autogenous grinding circuits was dependent on temperature, with the energy-efficiency of the grinding process decreasing in the winter months, accompanied by an increase in critical-size production. Several possible causes of this phenomenon were suggested, including: • Increased brittleness of the ore during blasting in the pit at low temperatures, leading to increased levels of internal cracking that would lead to rapid breakage to critical size in the mill; •Brittleness changes of the rock in the mill; and • Changes in the durability of the rock caused by either formation of ice on the surface, or freezing of water inside the pores and cracks of the rock. To determine which mechanisms were occurring, drop tests were carried out using frozen and unfrozen rock with varying degrees of porosity, both dry and water-saturated, and which had been blasted for mining in summer and in winter. These tests showed that there was no difference between the summer-blasted ore and the winter-blasted ore, and that durability changes in dry rock over the temperature range from 25ºC to -25ºC were negligible. However, water-saturated rock showed an increased resistance to breakage upon freezing, particularly when the rock was highly porous, or when a layer of ice formed on the surface. Seasonal changes in the durability of rock in grinding are therefore due to formation of ice in and around the rock.

Jan 1, 1995

By Michael T. Ballard

The key to productive computer usage is system software integration with full compatibility among individual components. The majority of software developers in our industry are still in the process of perfecting individual components. As a result, exchange and validation of data between disciplines becomes an arduous process. We at Morrison Knudsen Engineers, Inc. (MKE) have integrated an entire system, allowing exploration, geology, modeling, mine planning, and operation modules to work as a single, complete system with direct exchange and validation of data. The importance of integration to both developers and users of today's mining soft- ware is becoming increasingly apparent as we, an industry, move toward growth and enhancement of the technology of ore reserve acquisition, evaluation, and management. It is also important to understand the present state of integration and where it is leading US. Not long ago, another industry passed through the same stages we are now setting up for the mining industry. The stereo industry began with a few individual components, the record player, tape recorder, and radio. People were able to play records, listen to the radio and record conversations and music only through microphones on their tape recorders. Soon, one enterprising individual discovered he could tape sound directly from the radio or record player by capturing audio output from the speaker wires. Interfaces and patch cords were developed, providing a means to transfer audio information between components with not only little loss of sound quality, but also the elimination of back- ground noise. The industry took another step forward with the introduction of "integrated" stereo, where the components were packaged in one cabinet with shared resources. This reduced overall cost which paved the way for better quality. Today's stereos are now so well integrated that many of the components share data and resources from the same manufacturer, designed to work together for almost perfect data transfer between any of the components. The result is better sound, convenience, and reduced cost. This is the ultimate goal for integration. Any system development passes through these same steps on the road to total interaction. Initially, the components are designed, tested, and marketed individually, often by separate companies. As the users become familiar with the components, the need arises for an automatic interface between the components. This is necessary to cut down on error during data transfer and to eliminate the redundant work required to enter results from one component into the next component in the system. As a result, interfaces must then be developed to aid in this data transfer. After data transfer is accomplished, the next step is resource sharing. Resource sharing is careful design and engineering by either cooperative, individual manufacturers or one firm taking on the task to produce a single package product. Design and resource sharing leads to lower overall cost, while still providing component capability with options to grow as the user grows. The mining software industry has been working to develop some very high quality component software and has indeed accomplished this task in every aspect of the mining industry. However, realizing the importance of integration, some companies with limited individual resources have started working together to interface their individual components. Other firms have undertaken the project of developing complete, integrated systems.

Jan 1, 1987

By Dennis P. Bryan

Natural lightweight aggregate may be defined as inherently low density natural mineral materials. In most all instances they are relatively young volcanic rocks which, because of their geologic environment, are limited to the Western U.S. These Tertiary and Quaternary volcanics are low-density glass and vesicular material including, but not limited to, pumice and volcanic cinder. The distribution is widespread throughout the West with the principal producers being New Mexico, California, Oregon, Idaho and Arizona. The primary user is the construction industry where weight reduction equates to cost savings. Principal products in which natural lightweight aggregate is utilized because of its lower density include lightweight portland cement concrete and lightweight concrete masonry units. In addition, due to location, some natural lightweights compete with normal weight constructions aggregates for uses such as road base and common backfill material.

Jan 1, 1989

By J. M. Dean, R. L. Grayson

Introduction With the continued downward pressure on coal selling prices, mine management must make its operations as efficient as possible. The problem is the same one throughout the mineral industries, streamlining operations to maintain competitive min¬ing costs (Born, 1991). There has been a great deal of research into better using production manpower. But the story is different for operations support personnel. Traditionally, planning man¬power requirements are done annually, with modifications to the operating plan occurring generally quarterly. On the other hand, the demands on manpower are often dynamic, being responsive to changing productivity levels, mine conditions (including water influx, bad roof, poor floor) and unanticipated project requirements (responses to machine breakdowns or a new section setup requirement because of a drop in coal quality in another area). Such changes may impact the manpower structure significantly. At times they may cause serious labor relations problems concurrently. Realignments and the generation of instability in the workforce because of active job switching (bidding) are a result. Most responses by coal operators are reactive rather than proactive, a situation that could be mollified by more accu¬rate and detailed planning of predictable manpower require¬ments. A manpower planning tool is needed that takes into consideration such things as changing productivity levels and conditions as manhour requirements for different work areas are planned, rather than blindly allocated through traditional staffing modes. Mine Management Support System The Mine Management Support System (MMSS) is an integrated decision support system that was developed using Sun Microsystems hardware according to the contract be¬tween the US Bureau of Mines and West Virginia University. The software used in the development of MMSS included X¬ windows (Scheitler and Gettys, 1986) for the user interfaces, LASER (Raman, 1985; Hayhurst, 1990) for the expert sys¬tem and graphics components, and the C language for general programming requirements. Sun DOS was used to allow the use of IBM-compatible applications software on the Sun networks. Sun OS is the operating system. It can be viewed as an enhanced version of UNIX. One of the components of MMSS that was developed to address the many specific objectives outlined in Grayson et al. (1990) is the work scheduling system. MMSS accom¬plishes work scheduling by using a mathematical (goal) programming approach to minimize the amount of switching of workers from their regular jobs to perform other jobs (Grayson and Nutter, 1991). Manpower support program The main objective of MANSUPP is to plan a detailed manpower structure for a mine by incorporating a production schedule, condition-modified work standards and manage¬ment preferences to predict required manhours for various support activities, for example, belt moves. This is accom¬plished by gathering and processing planning information the same way a mine planner would. The program is menu¬driven with the selection of a particular menu item locating the user in the appropriate area within the spreadsheet to review/add information. All of the interactions between productivity, section conditions and management prefer¬ences and their effect on the amount of support work required must be considered. Information regarding the productivity of a particular section, the geometry of the section, work standards for individual activities and section conditions must all be gath¬ered for input into the program. In the initial stages of development, it was decided that the program be developed in an environment that mine planners were familiar with in order to accommodate the use of the program. Lotus 1-2-3 or a compatible (Quattro Pro) met this environmental need. Other reasons included ease of calculation due to built-in functions, powerful command language and macro capabili¬ties. Each of the major components of the program defined are summarized. Production schedule This area allows the user to input a production schedule for the entire mine over 12 periods. Space has been provided for five sections, advance or retreat, and two longwall sections. There are several calculations occurring in this area that do not apply to the determination of manpower, but serve as an aid in production planning. Section description The section description area of the spreadsheet is shown in Table 1. The first three items are calculated in the production schedule area of the worksheet and then transferred to this location. The remaining information is input by the user to be used in later calculations.

Jan 1, 1996

By Ahmed I. A. Salama

This paper describes the development of computer density control for heavy media cyclone circuit at the Coal Research Laboratories of CANMET. The control objective is to reach and maintain the medium density set point in minimum time. A description of the mechanical components and instrumentation are presented. The control strategy and computer software are discussed. Testing and evaluation of the installed system are presented.

Jan 1, 1989

By Betty L. Gibbs, Jean A. Arcamone

Introduction Microcomputers are becoming more convenient to use at all levels in the business world, including the mining industry. The state of the mining industry requires that we become more productive and innovative in our analysis of deposits and operations. With the help of computers, examination of options to increase productivity can be performed quickly and inexpensively. Effective computer use to design underground workings combines the calculating power and speed of a computer with the technical expertise and judgment of an engineer. Computer programs can perform in minutes calculations that might take several months for an engineer. But the engineer must be on guard when using computers for calculations. It is easy to assume the results produced by a computer program are always correct. However, the computer is only a sophisticated calculator. It cannot recognize logical errors or transposition of numbers. Also, some intuitive or obvious decisions made by an engineer are difficult or impossible to program effectively. In this article, selected commercial programs are discussed. These programs can provide engineers with tools to evaluate engineering designs for underground mines. The programs perform much of the tedious calculation. The engineer, though, must still make decisions and conceptualize designs. The software mentioned in this article runs on microcomputers and minicomputers. The mention of particular software, however, does not imply endorsement. Mining projects After a decision has been made to proceed with an underground mining project, more detailed evaluation of the mining method and extraction sequence begins. If a mine is already in operation, schedules and plans are needed to more clearly define future production. Existing operations can benefit from identification of bottlenecks in material movement and produce extraction options to make the mine more efficient. Detailed studies for a new mine are based on the technical engineering design. These studies provide specific details to determine equipment requirements. Detailed studies done during a project are similar to short-term planning and control carried out daily by the mining engineers. The engineering design phase includes: • Study of the infrastructures - entries, shaft, access from surface to underground; • Definition of the mine layout, hydrogeology, geotechnical considerations, transport, and ventilation; • Choice of machines and equipment; • Mine scheduling, including waste extraction and production sequencing; and • Economics, including labor and supplies. Further detailed studies include: • Blasting patterns; • Detailed geotechnical calculations; • Secondary ventilation; and • Production cycles along with coordination of the workings. Objectives The primary objective of underground mine planning is moving material out of the mine at the least cost. Development of the production schedule considers location and volume of ore units, transport distance, equipment and manpower interactions, and grade or quality of material. Two methods can be used to determine the scheduled material removal: optimization or trial and error. The microcomputer programs discussed here do not cover optimization for underground mine planning. For several reasons, optimization is often a "black box" approach. Although optimization is possible with linear programming techniques, few mining operations can be described effectively with linear equations. An interactive trial-and-error approach is desirable because engineering judgment can be inserted as a plan develops. Because of the large number of factors in an underground operation, an optimization technique seldom covers all possibilities. Few of the programs available consider all of the possible parameters. The programs use an interactive sequencing or a simulation approach and are either event-oriented or deposit-oriented. The most desirable programs offer an integrated approach. They consider a broad range of operating conditions including equipment, labor, costs, material movement, timing, and mine layout, among other factors. The two types of models generally used in designing underground workings include: • The interactive model, which requires direct, incremental input from the user. Outlines of the section to be mined may show on the screen. The engineer causes the model to develop piece-by-piece. The program may offer feedback on parameters such as tons and grade, or other values, as the section is "mined." • The simulation model, which is usually an automatic technique. Parameters related to the process are entered. The program then calculates the mining sequence over a designated time period or until the economic material is exhausted. A simulation model imitates step-by-step performance of equipment or other processes.

Jan 3, 1988

By H. Knorre, A. Griffiths, J. Loroesch

Introduction Hydrogen peroxide is known to the mining industry as a powerful oxidant. able to attack and to destroy cyanide, the most important leaching reagent (Knorre and Griffiths, 1984; Griffiths, 1988; Griffiths, 1988). [ ] The most recent development, however, is the use of H2O2 as an oxidant in the cyanidation of precious metals. This application may appear to be a contradiction to the above mentioned detoxification process. This can, indeed, be the case if certain conditions are not considered carefully. Degussa has developed a new process to enable the application of H2O, in this field without having any detrimental effect on the cyanide. The incentive to seek an oxygen supplier like H2O2 instead of air was the fact that one of the most important conditions for the fast dissolution of gold is the presence of physically dissolved oxygen in the pulp (Kydryk and Kellog, 1954; Warstell, 1987). [ ] Complete gold recovery within a reasonable leaching time may only be achieved if the pulp is saturated with dissolved oxygen. Gold losses in leach operations mainly occur due to the following reasons: In some cases, the saturation of oxygen in the pulp cannot be achieved by aeration due to the difficulty to transfer oxygen from the gaseous into the liquid phase. This happens, for example, in pulps with a high viscosity. In such cases, even violent aeration only results in a low concentration of dissolved oxygen in the pulp. In any case, the starting phase of leaching requires the highest amount of oxygen. Therefore, it is especially important to raise the dissolved oxygen level to saturation in the starting phase. Peroxide assisted leach process (PAL) The intention of the process is to introduce oxygen in a liquid form. As a result of intensive research work, it could be shown that hydrogen peroxide can be used as a source of oxygen in the leaching of gold ores. To avoid side reactions, the following conditions must be applied: Hydrogen peroxide must be diluted before it is added to the pulp. The dosage of H2O, must be properly regulated based on the oxygen level of the pulp. An important part of the continuous O, control is a special oxygen electrode, which resists the extremely abrasive action of the pulp.

Jan 1, 1990

By Deepak Malhotra, Linda Battich

INTRODUCTION Mineral processing plants generally operate efficiently within the technical, economic and management constraints applied to them. They have no choice, because the dynamic and competitive nature of the mineral business dictates that survival and/or prosperity of the company depends on being a low cost producer. Progressive mineral companies realize that market downturns will occur, and they must continuously strive for lower unit production costs rather than be satisfied with the status quo. Mineral companies generally tend to reduce costs during market downturns. This short-term solution is achieved by high grading of ores, and cut-backs In waste stripping, exploration, and capital expenditures.(1) However, to remain a low-cost producer in the long term, companies must enhance revenue and reduce cost simultaneously. This Involves continuous evaluation of technologies and reagents, periodic audits to locate revenue losses; and gathering and analyzing statistical plant data to clearly understand the Impact of process variables on efficiency. Mineral companies are caught in a Catch-22. They need resources to accomplish the objectives outlined above. Most mill stuffs have been cut to the minimum level necessary to maintain production. Resources such as time, manpower and money are scarce, and mill metallurglsts struggle to use these resources productively. Is your flotation plant optimized? History Indicates that successful operations constantly tune the flotation circuits to Improve metallurgy or reduce cost. This Is the essence of evolutionary change In mineral processing operations. A plant auditing approach can play a key role in assisting the process engineers to achieve the overall objective of enhancing metallurgy and reducing cost with limited resources through evolutionary improvements. FLOTATION SYSTEM The flotation process is the most widely wed concentration process In the world today. The number of variables that can affect the flotation results Is very large, maybe over 100. These variables can be divided Into three main groups: (2) (1) ore and mineral properties; (2) reagent treatment; and (3) flotation machine characteristics. Some of these variables can be controlled while others have to be accepted. Recently, Investigators (3,4) have attempted to describe the flotation process as an engineering system which includes chemistry, equipment and operating variables. Though some of the variables are Independent, most are co-dependent. thus making it difficult to develop simple cause and effect relationships. For example, it is easy to understand the effect of reagent change on recovery and grade In the rougher circuit, but very difficult to quantify Its impact on filtration downstream. Plant audits on a periodic basis are necessary to develop an understanding of the Interactive nature of the system. Auditing provides comparisons of plant operating performance before and after variable changes. OVERVIEW OF PLANT AUDITING An audit Is a formal, thorough and periodic examination of a system. There are various types of audits (i.e., geological, environmental, metallurgical. economic, etc.), and each serves a different purpose. (5) The discussion here is related to plant and/or metallurgical audits. Neale and Flintoff note that two key factors governing changes In an operation are: (1) the opportunity must be recognized; and (2) the justification for change must exist. (6) Both factors emphasize the critical role of successful plant auditing. Without plant audits. many opportunities for improvement must go unrecognized. On the other hand, when a situation ripe for improvement Is recognized. the hard data from a plant audit can reveal the expected impact of an operating change.

Jan 1, 1993

By Friedrich Steinhäusler

RADON SOURCES AND CONTROL MEASURES IN THE MINING ENVIRONMENT Most of the contamination of the mine atmosphere by radon 222 is due to radon emanating from solid or fractured ore surfaces of walls, roof and floor. Also radon gas emanates from broken ore either from storage in backfilled mined-out areas as applied in e.g. shrinkage stopping methods or from ore spillage along intake airways mainly due to the use of trackless haulage. To a lesser extent water itself can represent an additional source of radon, which emanates into air from open drainage ditches or seepages along intake airways. The contribution from water can be controlled effectively by isolating the water from the primary intake air system, e.g. by diverting the water through pipes and/or sealing of seepages by grouting. However, control of radon emanating from rock surfaces creates a major technical problem with significant impact on the economic aspects of mining operations, if adequate radiological conditions must be maintained. Basically this can be achieved by suppressing the emanation process itself, confining already emanated radon or by removal of radon from the mine atmosphere. Extensive research has been carried out on the rate of radon emanation as a function of barometric pressure changes (Pohl-Rüling and Pohl, 1969). It could be shown that the radon supply consists of a permanent and variable component. The former results from the surface of the rock and depends mainly on the emanating fraction of its radium 226 content; the latter originates from within the rocks and is a function of the suction effect of decreasing barometric pressure, rock porosity and fissures. The practical application of this barometric pump effect for depressing the rate of radon emanation, e.g. by pressurizing the mine atmosphere, is limited due to high costs for providing a sink for absorption of radon and air as well as lack of permeability in most uranium ore bodies (Schroeder et al., 1966). Mine air cleaning by removal of radon can be achieved with the use of cryogenic methods, chemical removal, adsorption into charcoal beds, use of a gas centrifuge or general ventilation techniques. Technical problems have so far prevented the application of any of these methods other than ventilation. It is common practice to use the age-of-air concept, i.e. fresh air is delivered to the worker as directly as possible and removed quickly afterwards thereby maintaining the air "young". Engineering principles for quantity distribution of air through underground working areas are straightforward for general mining situations where radon constitutes an environmental contamination problem. However, in cases of high uranium ore content this concept may result in high costs with regard to installation and energy requirements for effecting both frequent air changes as well as sufficient heating of the air in cold seasons. Taking into account that the investment in ventilation systems is a major cofactor for the overall ore production costs this can be a limiting and decisive component in the assessment of the economic feasibility of specific mining operations and mineral reserves in general. Effective control of the radon flux from the rock surface prevents the initial contamination of the mine air with radon directly at the source. A radon diffusion barrier for practical application in mining requirements should fulfill the following requirements: - reduction of radon emanation rate by at least an order of magnitude - high mechanical strength - ease of sealant application onto surface to be coated - water resistant - low fire hazard - resistant to temperature changes encountered in mines - high cost efficiency in relation to exposure reduction achieved (direct and indirect costs) - low degree of maintenance. In the past several materials have been tested as sealants for controlling the emanation of radon from surfaces of rock and building materials. Epoxy paints reduce radon emanation rate only by a factor of 2 to 6 (Auxier et al., 1974; Eichholz et al., 1980; Keith Consulting Engineers, 1980). Although it is possible to prevent the escape of more than 99 % of the radon to the environment with gel seals over 80 mm thick (Bedrosian et al., 1974), practical applicability is very limited. Multilayer coatings of epoxy resins with various additives require meticulous preparation and flawless application of seamless four-layer coatings in four days to impede radon diffusion (Culot et al., 1976), otherwise results from this method have not been totally satisfactory (Leung, 1978). Aluminium foil laminated with polyethylene and paper on each side is under test as radon barrier but results are not available yet (Ericson, 1980). However, this method has the inherent disadvantage that possible malfunctioning electrical installations can cause fire or electrical shock through the sealant. Polyurethane foam coatings have been used on stoppings as very effective sealants. It does, however, represent a potential danger of spontaneous ignition and it is expensive (Rock, 1975). Thus, there is still need for a material which has similar properties as outlined above. In the following results are reported from investigations on the suitability of various materials as radon diffusion barriers.

Jan 1, 1981

By N. M. Grant, W. G. Prast

Jamaica has extensive deposits of marble, gypsum, and limestone, offering prospects for commercial sales to nearby US markets, notably the Gulf Coast and Southeast. Stare-owned and private Jamaican industrial minerals producers have made limited sales to date but expect to increase exports during the balance of the 1980s. Restraints include Jamaican government controls on access to essential foreign exchange for new capital investments and distribution of profits. Jamaican efforts to identify market opportunities in the US are reviewed, and the outlook for further exports of carbonates is discussed.

Jan 1, 1987

By D. R. McGregor, B. V. Clingan

A practical application of recent design concepts makes it possible to design a column cell to fit a specific set of conditions. The design and operating parameters of a column cell installation that replaced a conventional two-stage copper flotation cleaning circuit at Magma Copper Co., San Manuel, AZ, using these design concepts is described. A survey of other mineral processors using column cell technology was conducted. The results of this survey are also discussed.

Jan 1, 1988

By Edwin G. Johnsen

Underground mining is relatively safe today, but no technique or equipment is completely fool proof and 100% reliable. The only sure way to prevent accidental death or injury to underground workers is to remove them completely from the hazardous environment. This alternate approach to underground work is now feasible. Tunnelling and mining systems can be built that could be remotely controlled by men operating consoles in a surface control room. This concept, called a teleminer, would use recently developed remote control technology to remove man from underground work but still give him the capability to remotely operate mining and excavating equipment as if he were actually in the working area. It is appropriate to present this concept in the session "Environmental Controls" because the rationale for environmental control in underground areas can be significantly modified if man is excluded from the underground operation. The development of teleminers cannot only reduce or eliminate most of the requirements for conventional environmental control, but it can also create new and powerful techniques for rapid tunnelling and excavation. TELEMINER CONCEPT The concept of remotely controlled mining machines is neither new nor untried.(1)(2) Conventional remotely controlled mining equipment employs the standard techniques of extending the controls of the equipment to a remote console. For example, the rotary cutters on a remotely controlled tunnelling machine are started or stopped by a human operator turning a switch on the remote control console.

Jan 1, 1997

By A. I. A. Salama

A computationally efficient technique for generating a balanced set of density or size separation data is developed. The technique proposed utilized minimization of a modified form of error squares to generate the optimum estimates of outputs mass yields (splits) and balanced direct mass distributions of feed and outputs. The estimated separation data set satisfies mass balance conditions of the streams mass distributions around the separator. The technique proposed avoids the generation of small negative values for the estimated feed and outputs direct mass distributions. Actual data are used to demonstrate the technique proposed.

Jan 1, 1996

By N. Edmonson

Frasch sulfur production/pricing decisions are based on market demand, less nondiscretionary sulfur supply. Price covers the cost of Frasch production and byproduct sellers accept the Frasch price structure. Large stocks have led Canadian byproduct producers to price aggressively at times, but their near-term drawdown suggests more passive price policies in the 1990s. Expanding continental nondiscretionary supply is combining with sizable Frasch supply increments to weaken prices. Simulations using a market model embodying these structural characteristics indicate that expanding demand may not result in substantial recovery from 1992 price lows before 1996.

Jan 1, 1995

By Robert C. Peddicord

Application of Quality Management philosophies and techniques commonly referred to as Managing for Continuous Improvement, Team Management , or Managing for Consistency is required in today's mining, manufacturing, and service industries in order to meet quality demands, beat competition, lower costs, optimize operations, effectively use personnel, improve morale, and enhance profitability. Most of these phiosophies and techniques are known to today's managers but either have fallen into disuse or were never allowed to surface in the corporate environment of the organization. Managers should review and adopt the philosophies and techniques of Quality Management and use them to revitalize their organizations and bring about a "paradigm" shift in the way we manage, thereby achieving the goals listed above.

Jan 1, 1991

By Giuseppe Bonifazi

This study examines the problems involved with the control of characteristics of the products resulting from comminution operations. A methodology of investigation based on texture analysis procedures by image processing techniques of the comminution product is proposed. Some examples of applications are considered with particular reference to comminution products of different textural, structural and mechanical characteristics. The advantages and the limites of this method of approach are, indicated, both as regards performance of the investigations and subsequent processing of results.

Jan 1, 1989

By Michael E. Allen

The building of sanitary and storm drainage sewers in urban or environmentally sensitive areas often requires the use of tunnel construction procedures. While hydraulic considerations may require only small diameters, traditional tunneling techniques make small sizes the least economical. Current state-of-the-art techniques using highly mechanized systems of pipe jacking can provide cost effective solutions to the problems of construction of small size tunnels. The characteristics of mechanized pipe jacking allow rapid advances under difficult ground conditions. The basic pipe jacking cycle is used with a variety of excavation systems to permit the contractor to satisfy engineering as well as economic parameters. These characteristics and several of the systems available are outlined.

Jan 1, 1981

By K. G. Sutterer

The prevalent use of coal combustion byproducts in engineering applications has been with Class C and Class F fly ash as admixtures in structural concrete. But, the use of fly ash and bottom ash byproducts from modern desulfurization processes is receiving increased attention. The University of Kentucky has been conducting research into civil- and mining-engineering applications of these products. The studies have included extensive investigation of the geomechanical behavior of the materials and the effect of mineralogy on this behavior. These studies indicate important mineralogical considerations in the selection of materials for a specific application and highlight the importance of quality control before and during usage on specific projects.

Jan 1, 1997

By Regina N. Tempel, Mae S. Gustin, Mark A. Engle

This study characterizes the hydrogeochemistry of groundwaters near opalite-hosted epithermal hot-spring type mercury deposits in the Ivanhoe mining district, Elko County, Nevada. Local groundwaters generally range from Ca-HCO3 to Ca-Mg-Na-SO4 type waters with background mercury concentrations ranging from 0.014 to 0.32 ug/l. Leaching experiments conducted on mineralized rocks, using typical water chemistries to represent local groundwaters, yield total mercury concentrations ranging from 6.3 ug/l to 27.4 ug/l after one year of reaction. Geochemical modeling indicates dissolved mercury is dominated by HgO(,) and that precipitation of quicksilver controls mercury concentrations to an upper limit of 63 ug/l.

Jan 1, 2000