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By Gary S. Brierley, Tracy J. Lyman

INTRODUCTION Geotechnical engineers play a major role in tunnel design primarily because tunnels are constructed entirely within the ground. In general, this role can be divided into two major tasks: subsurface investigations and project design. Under subsurface investigations, it is necessary for the geotechnical engineer to accurately describe the ground in which the project will be built. Under project design, it is necessary for the geotechnical engineer to work together with other members of the design team to make certain that the tunnel fulfills its intended purpose at least cost. Given in the paper are the authors' opinions about what constitutes an adequate scope of services for these two tasks on a tunneling project. SUBSURFACE INVESTIGATIONS o Background Study All subsurface exploration programs for tunnels begin with a thorough investigation of background information about the proposed site. Such background information includes geologic, reports topographic maps, aerial photography, and case history reports of other nearby tunnels. Once completed, it is necessary to study the background information so that the proper scope and magnitude of subsurface exploration work is performed in a manner that provides maximum input to a knowledge of those intact and rock mass properties that are important for an understanding of the entire ground mass. The blind application of field and laboratory techniques, no matter how sophisticated, is wasteful and potentially

Jan 1, 1989

Because of the different types of reagents used for the flotation of sulfide and nonsulfide minerals, it is convenient to consider these two groups of ores separately. The metal sulfides and native metals are substantially all floatable with xanthate and similar collectors.

Jan 4, 1982

By Theodore Budd, Joseph A. Sopko

Ground freezing was selected to provide excavation support and ground water control for the construction of a 457 cm diameter tunnel between two underground structures for a major sewer project in Milwaukee, Wisconsin. Initial plans called for installing horizontal refrigeration pipes around the perimeter of the tunnel. Due to the possibility of difficult conditions associated with horizontal drilling, the contractor elected to drill inclined pipes from the surface. The surface location, however, crossed a city thoroughfare with an extensive system of buried utilities. This paper discusses drilling techniques and utility protection, as well as tunneling methods and production.

Jan 1, 1991

By D. Spitty

Mining companies often have many disparate systems and repositories of data in their organization for planning and scheduling outbound mining supply chains. To optimize ore quality, throughput, transport logistics scheduling and delivery to contract, planning teams need to model and manage the value chain accurately and achieve a consolidated, enterprise view of operational performance. Planning teams coordinate a complex series of activities to ensure production forecast accuracy. They also negotiate and execute complex contracts often with disconnected and limited visibility of production forecasts, quality, and variability with little ability to accurately market potential product specifications over longer time horizons. This market is becoming increasingly dynamic, with increasing variability and the time for planning teams to react is decreasing. This is driving the need towards using science to generate the necessary scenarios required to support the decisions made by planners on a frequent basis. Resource-to-Market is a highly flexible, user-configurable supply chain management system for the mining and metal processing industries. This provides an integrated view of the supply chain that supports the dynamic nature of planning in a mining company, embraces variability of elements across the supply chain with the ability to optimize across all the functional areas of the operation to enable optimal decision making for often competing objectives such as throughput, quality, cost, revenue and profit.

Feb 23, 2014

By Jorgen Elbrond, Xiaoli Tang

In this paper we apply continuous-time option pricing theory (Dixit 8 Pindyck 1994) to show how to obtain an optimal investment rule for a mining project which requires sequential in- vestments. The application per se is to some extent very simple. The main purpose of the paper, however, is to draw the attention of mining people to how the option pricing theory may be used to capital investment decisions. This topic in economics is quite new but is attracting a lot of attention.

Jan 1, 1996

By L. Rainey, W. E. Wallace, B. L. Razzaboni, P. Bolsaitis, V. Vallyathan

The hemolytic activity of milligram-sized mineral dust samples from coal mines collected in personal dust samplers were measured by a modified Harington assay method which increases the sensitivity of the technique. Measurements were conducted on a large number of samples from different mines characterized for gravimetric quartz content and the relative bulk concentration of common contaminants (Al,Ca,Fe). The results of these measurements were compared to the hemolytic activity of pure quartz and of mineral samples obtained from roof-bolter dust boxes of two coal mines. No correlation could be established between hemolytic activity and the compositional variables tested. The results suggest that the distribution of minerals among individual particles and the surface characteristics of particles, rather than the bulk concentration, determine the hemolytic activity of respirable mine dusts.

Jan 1, 1991

By J. W. Oberholzer, C. F. Meyer

The increased use of continuous miners to extract thicker coal seams has necessitated the use of enhanced ventilation systems in the headings. Due to the increased face size, more ventilation is required to effectively dilute the liberated methane down to acceptable levels. If more air is directed to the face an increase in the entrainment of dust creates an increased potential for workers to be exposed to dust. To enable the ventilation systems to reduce the methane levels and the levels of the airborne dust the ventilation systems in the heading have to be carefully designed. The matter is made more complicated through the use of other ventilation methods like jet fans, air-moving sprayfans on the continuous miners and high capacity scrubbers on the continuous miners. To enable the design of a balanced ventilation system in seam heights of over five metres requires methods that consider the system in a three- dimensional manner rather than in a two-dimensional fashion. Through the use of computational fluid dynamics (CFD) coupled with appropriate methods of taking underground face ventilation readings these problems can be solved in a cost effective way. Using computer modelling, ventilation methods can be designed and assessed instead of using costly underground trials to test the alternatives. Use of this system has led to a higher level of ventilation design as well as a more effective method to combat the health and safety hazards in coal mine headings.

Jan 1, 1995

By V. Y. Kirillin, V. A. Rumjantsev, S. A. Tchesnokov, Yu A. Veksler, V. F. Kalmykov, A. N. Telgarin, A. T. Shakirov

Mining in outburst hazard seams may be safe and effective if some preventive measures, such as lowering gas and rock pressure as well as speed regulating of a continuous miner in cutting the seam would be practised. The driving speed should be optimal as the low speed lowers labour productivity but the high speed may cause gaso-dynamic phenomena. At this mine the driving speed is regulated by seismo-acoustic control of the seam condition.

Jan 1, 1985

By Richard Newcomb

Since the report of the 1972 Rapid Excavation Conference in the city of Chicago, speculation has continued concerning the estimates of tunneling demand. Little has been published that would persuade me to modify substantially the rather tentative estimates that originated with the National Academy of Sciences-National Academy of Engineering (NAS-NAE) study of 1968 which were recomputed by the United States in the survey of the Organization for Economic Cooperation and Development (OECD) in 1970. The OECD estimates, of course, hedged the really difficult question of forecasting civil construction tunneling demands. In the United States contribution, this was done by predicting both an upper and lower bound for important categories of demand. A discounting procedure was then applied to each of the major sectors of expenditures, permitting a forecast that reflected the current subjective assessment of how extensively and how likely cities were to adopt plans that required tunneling. This was done for water, utilities, transportation and other novel underground facilities. The purpose of this paper is a modest one. In it I wish to describe the efforts made since 1972 to generate more thoughtful and more robust estimates of urban sector demands, and to apply what has been learned to the most difficult category of predictions: those for urban mass transit systems. The estimates of the Underground Construction Research Council funded by the National Science Foundation have been described at an earlier panel of this Conference. The principal effort I am familiar with is that of

Jan 1, 1974

Hoses provide a variety of critical functions in nearly every mining operation. Care must be taken when selecting, installing, and maintaining hoses to insure maximum hose life. This article provides some tips on selecting, installing, and maintaining hoses, and gives some background on hose construction and safety. In the mining industry, hoses are used for everything from hydraulic systems that power drills and hammers, to suction systems that carry away dust and debris. Hoses are used on such a large scale that a detailed discussion of specific applications would require many volumes. Dayco Corp. has, however, provided these basic and brief guidelines on how to select and maintain hoses for mining applications. Hose Construction Industrial hoses are classified as much by construction as they are by application. So, it is a good idea to start any discussion of hoses with a description of their basic construction. There are four basic components to hoses: the tube, reinforcement, cover, and couplings. The tube is the inner core or lining, and is usually made of smooth rubber or plastic. Rubber or plastic composition is scientifically determined to be compatible with the materials passing through it, such as fluids, chemicals, gases, or substances. Other considerations in compounding rubber or plastic for the tube are temperature ranges and stresses. In practice, the required compound can be precisely chosen from various charts listing them according to application. There are, however, applications where the compounding of tube rubber or plastic must be customized. The reinforcement hose layer immediately surrounds the tube. As its name implies, this layer gives the hose strength and provides protection for the tube component. Reinforcement must be able to contain the inner forces-pressure and shock-transmitted through the tube, and such external forces as twisting, bending, and crushing. So it is usually made of high tensile strength cord, fabric, or wire that is wrapped, wound, or braided around the tube. The cover is the outermost layer, so it may encounter oils, acids, water, dust, abrasion, and other potentially damaging influences depending, of course, on the application. An appropriate cover material must be selected, usually a rubber compound. Couplings, even though they are a hose attachment, are as vital as any other component and should be considered part of the hose. Couplings are usually made of carbon steel or malleable iron; however, bronze or stainless steel might be used if corrosive chemicals are involved and brass or aluminum might be used for flammable fluids. A coupling is usually in two parts: an insert that fits into the hose bore and contains the threaded male, female, or other type of connection, and the ferrule or collar that fits over the hose and secures the coupling in place. There are, however, some one-part couplings that fit securely into the hose without a ferrule. These are usually limited to low pressure applications and are secured to the hose by clamps or metal bands. Some fittings can also be permanently "built-in" as the hose is made. Couplings can be classified as reusable or permanent. The reusables can be removed when the old hose expires and used again on a new hose. The permanent types are crimped or swaged on at the factory or in the field (using special equipment) and must be discarded with the hose. Although couplings are most commonly thought of as having threaded fittings, there is another type called "quick connect." These either have a crow-foot or jaw-type design that permits a fast, "snap" connection. This can

Jan 6, 1982

By R. E. Brewer

Pilot scale flotation tests were conducted with a 1-ft-diam column at the Barrick Resources (USA) Mercur mine, Tooele County, UT, to scavenge unleached (0.01 to 0.018 oz/st) gold values from the tailings of a carbon-in-leach (CIL) circuit. The optimal recovery was 35 pct of the unamenable-to-leaching gold, at a grade of 0.353 ounces of gold per short ton, using a mixture of dithiophosphate, xanthate, and diesel fuel as a collector. This was achieved by floating approximately 1.6 wt pct of the CIL tailings. The gold values are believed to be contained in arsenic-bearing minerals, attrited carbon, and carbonaceous material in the ore. Redox potentials were measured with a gold electrode during the conditioning stage prior to flotation. The correlation between flotation recovery and redox potential values could be used to control reagent additions. Treatment of a previously leached and weathered tailings material, averaging about 0.055 ounces of gold per short ton, was also investigated using the column. The tailings were first water leached at approximately 600 C, and the water-leached tailings, which contained approximately 0.03 ounces of gold per short ton, were then fed to the column flotation unit. The effects of pH and sodium sulfide addition on gold flotation recovery and redox potentials were examined. maximum gold recovery, 36 pct, was achieved at pH 8.5 with a sodium sulfide addition of 0.18 lb/st.

Jan 1, 1989

By J. L. Weaver

The spiraling rate in phosphate rock demand during the period 1957 to 1967 led producers to expect a continuation of a high growth rate. Consequently they expanded production capacity to meet the expected demand. Both the domestic and the world demand has shown little growth over the past three years. Florida producers operating at less than 75% of installed mining capacity, produce all that their markets will absorb. We expect that the nest few years will bring only a slight improvement in this condition. An increased demand in the domestic agricultural market will be partially offset by a continuing erosion in the export market.

Jan 1, 1972

Magnetic separators are commonly used as an effective and low-cost method to concentrate paramagnetic or ferromagnetic minerals. These versatile separators are often used in multistage circuit configurations to further improve concentrate recovery and/or grade. Although these circuits are generally very efficient, field studies suggest that the layout of multistage circuits can be less than ideal for many industrial operations. To illustrate this shortcoming, a theoretical analysis has been conducted to compare different circuit configurations for magnetic separators. The resulting knowledge base has been used to establish generic engineering guidelines for the layout of multistage circuits. The potential improvements in separation efficiency that may be realized through the application of these guidelines have been demonstrated using a simple case study.

Jan 1, 2004

By Ed Van Eeckhout

The rockburst monitoring system at the Sunshine Mine has recently been improved to increase the certainty of burst locations and to output location results in a manner amenable to easy interpretation. Three methods of location calculation were used: a computer code provided with the hardware in-place (the MP-2501, a code based on the least-squares method (Blake et a1, 19741, and a nonlinear iterative code written by the principal author. The more accurate locations are given by the latter two codes, but still are only correct to within about 100 ft. This error is due to uncertainties introduced by the geologic and mining variations versus the assumptions made in the location codes. Software was then written to make two-dimensional plots of burst location by level, so management could monitor problems easily.

Jan 1, 1986

By Z. Eisenstein, H. K. Heinz, F. M. Kuwajima

Due to its complex rheological behaviour, shotcrete induces a ground-structure interaction that differs significantly from other types of tunnel linings. For the same reason, the instrumentation of shotcrete linings presents special problems, particularly when it comes to estimating the stresses transferred to the lining during construction. The shotcrete characteristics which affect the stress distribution are initially discussed. Measurements obtained in a recent soft ground tunnel are also presented. The conclusions are aimed at introducing practical recommendations for the design of tunnels where shotcrete is used as initial and/or final support.

Jan 1, 1991

By Mark Springett

Microcomputers have rapidly evolved to the level at which they can perform almost all of the computational tasks required for exploration, evaluation and exploitation of mineral deposits. The present capabilities of microcomputers are reviewed by examining their use on typical projects from the initial capture of exploration data to the subsequent technical and financial evaluation by microcomputer. Emphasis is placed on the need for compatible software and on the importance of a consistent hardware acquisition policy.

Jan 1, 1987

By William Wraith

The availability of computer resources and data management technology, together with the prudent use of scientific management concepts, has made it possible to achieve important improvements in the control of maintenance and materials activities in the mining and minerals processing organization. The introduction of minicomputers and. the greatly improved efficiency of computer systems in general have put the use of computer technology within the reach of even the smaller mining companies which probably could not have afforded them just five to ten years ago. A number of progressive companies have implemented computer-based maintenance, purchasing, and supply inventory control systems. Using modern safety stock, demand forecasting, parts reliability analysis, and other control concepts, these new systems have helped minimize production losses by reducing the frequency and severity of supply shortages and unplanned repairs. At the same time, these systems are helping to conserve scarce capital resources by better utilization of supply inventory investments, reduced expenditures for maintenance, less frequent equipment replacements due to improved maintenance reliability, and greater capacity utilization of existing facilities.

Jan 1, 1979

By Lynton Gormely

Oxygen transfer in a stirred tank bioreactor has been modelled mathematically to determine the trends in transfer efficiency (kg transferred per kWh) with transfer rate, tank depth, superficial velocity, and mixer power.

Jan 1, 1990

By M. Misra, I. Anazia

The effects of the enzyme, peroxidase, on the sedimentation and consolidation characteristics of Florida phosphate slimes were investigated. Results indicate that pretreatment with the enzyme was beneficial for slime dewatering and consolidation. Biological activity, resulting from slime pretreatment with the enzyme, induced higher mechanical binding between slime particles.

Jan 1, 1990

By Tracy Braun, Dan Lampshire

Over the past decade, heap leaching at Cortez has evolved from a rather small operation producing around 30,000 ounces per year of gold to an operation scheduled to produce over 400,000 ounces in 2004. Evolution and expansions in the heap leach operations are discussed including plant design criteria and some of the design features in the various facilities. Operating parameters and production forecasting are also discussed.

Jan 1, 2005