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By David M. MacGillivray

1. INTRODUCTION The economic importance of bringing a new mine to production in the shortest possible time, is well known. In recent years the rate of escalation of mining costs has accelerated more rapidly than at any time in the past. This fact has enhanced the need to reduce time schedules and made it an overriding and predominant objective when planning new shafts. The squeezed profit margins and widely fluctuating metal prices have also increased the emphasis being placed on this aspect. Moreover the increase in the present value of future profits due to the reduction in the time element, can be so substantial that expenditure on equipment and additional labour can be justified conditional on sufficient gain in shaft sinking speed being achieved. The emphasis on time saving becomes more abundantly clear when considering the very large increase in the capital required to bring a modern underground mine to production. As an example, the initial capital expenditure requirements for a large new gold mine in the Western Transvaal, which has commenced production recently, is estimated at R200M, and a major extension to another deep level mine in the same area is estimated at R300M. With the uncertainty of future metal prices and the recent trends in increasing inflation, it is becoming more difficult than ever to estimate the profitability of proposed mining projects and any cost saving due to more rapid sinking of shafts can only assist in this respect. Since the shaft systems are frequently the most expensive set of underground excavations and no other underground work can commence until they are completed, the speed of shaft sinking is subject to closer scrutiny than in the past. In the following sections of this paper the factors contributing to the high average advance rates achieved by South African shaft sinkers are discussed. It is difficult, if not impossible, to estimate the effect of any single factor, in isolation, on the overall sinking achievements. However, the cumulative effect of improvements made in the inter-related activities is, probably, the most important contributor. Although there has not been any single major technical change or innovation to shaft sinking practices in the last decade, the average sinking speeds have increased, due to improved application and technical improvements in established procedures. 2. GENERAL When discussing South African shaft sinking techniques and average sinking rates compared to those achieved in other parts of the world, it should be remembered that the size and depth of South African shafts are often considerably greater than in most other countries. Typical examples of shafts either in the course of sinking or recently completed are -

Jan 1, 1979

By M. Saidman, R. Pizzuti, R. Hirschfeld, A. J. Desai, J. Rand

Two bedrock tunnels, 170 to 250 feet deep and with a length of about 17,000 feet each, will be used to convey cooling water from the Atlantic Ocean to the Seabrook, N.H., Nuclear Power Plant. Seismic reflection and refraction surveys were used to obtain preliminary information about overburden and bedrock conditions. A major boring program, including core orientation and water-pressure testing, was undertaken to provide detailed geologic data. The results of the geotechnical investigation were summarized in terms of rock type, frequency and character of joints, degree of weathering, modified core recovery (RQD), pressure-test results and strength and hardness. These parameters were used as a basis for evaluating the feasibility of using a tunnel-boring machine, for designing and estimating the initial support systems, and for evaluating the grouting and tunnel lining requirements.

Jan 1, 1976

By Julius Rubinstein, Victor Badenicov

The development of column flotation is the most significant achievement in the area of mineral processing in the last few decades. The high efficiency of column flotation allows a reduction in process time, a decrease in the number of cleaner stages and in the volume of the circulating load in the flotation circuit, and, as a result of this, an increase in consistency and reliability of operations. Unique multisectional column flotation apparatuses were developed. Such designs have a number of essential advantages as compared to monocells. A change from monocells to multisectional column allows to provide favourable conditions for separation of particles of various floatability. To attain that aim particular hydrodynamics and aeration regime is established in each section of the column, operational variables being adjusted according to the floatability of the material. Therefore in multisectional column machines the material-apparatus feedback can be established, process variables optimized depending on the characteristics of the floated materials. This concept forms the basis of column designs we have developed. For the first time column cell with alternating slurry Rows (combination of co- and counter-current flows) were developed and commercialized . Successful operation was reported of the new generation of columns with cell volumes of 10 to 80 m3 and the height of 4-6 m in copper, molybdenum, antimony, tungsten and nickel ores and coal slurry processing at different plants. Operation experience of these cells showed their considerable design and operational advantages and verified the proposed options and relationships. The new apparatus is provided with a pneumohydraulic aerator allowing to control bubble size distribution, the service life of the aerator is not less than two years. A multilevel flotation model was developed and used to work out a technique of column design and process parameters calculation. A method of the apparatus design parameters calculation based on laboratory test results (scaling up) was worked out. The method is based on flotation macro and micro-hydrodynamics simulation.

Jan 1, 1995

By Jerry W. Danni, John E. Hardaway

Corporations today must comply with an ever growing number of complex and increasingly stringent environmental laws and regulations. An environmental audit program is an effective means in which to uniformly and systematically assess compliance, and to assure management that environmental liabilities are being minimized. This paper describes the design and implementation of Homestake Mining Company's environmental audit program, which has as its primary focus the objective verification of compliance with external requirements and internal good management practices. Major elements of the audit program discussed in the paper include: pre-audit preparation; on-site audit activities; and the post-audit report.

Jan 1, 1992

By K. P. Madhusudhanan, R. K. Bhatia, K. S. Narasimhan, R. N. Singh

A typical case study of a coal washery of capacity 500 t/h raw coal input has been presented and discussed with particular reference to the techno-economics for flotation column vis-a-vis the conventional flotation cells, keeping parameters like input capacity and product ash same. The results presented indicate that substitution of flotation cells by columns in a coal washery results in advantages of increased fine coal recovery, better quality of concentrates, lower capital and production costs etc.,. The effect of increasing the specific capacity of the column by design modifications on the cost benefit is also analysed.

Jan 1, 1988

By D. III Earley, R. L. Blake

The Bureau of Mines is investigating the potential for in situ mining (ISM) of gold and silver mineralization. This preliminary study examined samples from several types of deposits. It used light optical microscopy and the electron microprobe to characterize the ore and gangue minerals and textural features of these samples. This included the spacial relations between the target minerals and likely natural fluid channel ways. Low-grade disseminated deposit types from the western US were found to contain fracture- hosted or matrix-hosted gold and silver minerals, some of which are encapsulated by quartz or pyrite. Successful ISM application to gold and silver deposits needs this data in order to understand potential problems of the lixiviant reaching the ore minerals.

Jan 1, 1991

By A. J. Hudson, M. R. Yenchek

Faulty insulators on mine trolley/track haulageways may allow leakage of currents into the mine roof, which may ultimately result in the combustion of the roof material. The National Institute for Occupa¬tional Safety and Health (NIOSH), Pittsburgh Research Laboratory (PRL), devised a passive means to detect overheating insulators on di¬rect current systems. The detector consists of a spring- loaded car¬tridge that ejects a reflective streamer of white Teflon tape when subjected to elevated temperatures. The cartridge assembly can easily be installed over the outer metallic shell of an existing trolley line insu¬lator. If an insulator overheats due to ground leakage currents, the vis¬ible streamer alerts mine personnel traveling on the haulageway.

Jan 1, 2000

By Victor F. Hollister

This section describes two exploration models currently used in the search for porphyry exploration deposits: the hood and the vertical cylinder. Each has alternate names within industry and in the literature. The hood is also known as the Climax or Henderson and the vertical cylinder has also been called the Mt. Pleasant model. The paper by Hollister (1978, abstract herewith) refers to the vertical cylinder as the zoned model in reference to the horizontal sulfide and silicate zonation evident in and peripheral to the vertical cylinder of molybdenite mineralization. The distinct ore body geometry in each model type necessitates differing drilling and exploration strategies. Drilling for a hood shape is clearly different from drilling for a vertical cylinder type target. The paper by Wallace et al. (1968, abstract herewith) on multiple intrusion and mineralization at Climax, CO, well describes the hood model. That description is supplemented by the paper by Wallace et al. (1978, abstract with Chap. 37) on the geology of the Urad and Henderson deposits. The paper by Hollister (1978, abstract herewith) describes the vertical cylinder model.

Jan 1, 1991

By Pierre M. Gy

The final purpose of exploration is to esti- mate the grade and tonnage of the various qualities of ore contained in a given mineral deposit. This estimation cannot be directly carried out on the whole of the ore body. It usually requires four steps: Core Drilling Campaign The ore body is represented by a series of cores further divided into core sections of equal or unequal length. Core Splitting The core sections are longitudinally split into two halves: the first half is kept for various examinations and physical measurements, and stored for further reference; the second half (core sample) is used for determination of the chemical analysis. Core Sample Reduction The chemical analysis cannot be directly per- formed on the core samples. It requires the constitution of assay portions usually weighing from a few decigrams to one gram (more in precious metals assaying) and passing through a 100 or 150 mesh screen.

Jan 1, 1979

By Steven W. Hunt, Phillip U. Santacroce, Roger C. Ilsley

Consolidation grouting from the surface prior to mining a shaft is commonly performed to reduce groundwater inflows to a manageable rate. This paper describes the inflow reductions obtained within dolomite and limestone formations at several shafts and chambers due to grouting programs for the Milwaukee Water Pollution Abatement Program. The resulting inflow reduction factors are compared to results reported in the literature for other projects. Post-grouting pump tests are also evaluated as an aid in grouting assessment. Important considerations for estimating shaft inflows from pump test results are discussed. These considerations include loss of grouted mass during mining and influence of blasting and rock features on grouting effectiveness. This information should be helpful to design engineers and contractors who need to estimate inflows after pre-excavation consolidation grouting has been performed.

Jan 1, 1993

By K. G. Sutterer, R. J. Sweigard, U. Graham, T. C. Hopkins

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, 1998

By W. de Moura, R. Fueyo, M. M. Botz, J. C. Scola

The Cerro Vanguardia mine is an AngloGold Limited operation in southern Argentina that includes multiple open pits and a hybrid Merrill-Crowe and CIL circuit to recover gold and silver from oxide ore. Operations were commissioned at the site in 1998, which included a plant in the metallurgical circuit to recover cyanide from mill tailings. The cyanide recovery plant was initially configured to process tailings slurry and achieved greater than 90% cyanide recovery from tailings containing about 600 to 800 mg/L WAD cyanide (as CN). The cyanide recovery circuit was operated in this manner for approximately eight months, during which time the consumption of sulphuric acid and sodium hydroxide was relatively high, leading to high rates of scale formation in the acidification tank and stripping towers. In July 1999, several piping changes were made in the cyanide recovery system to permit its operation with clear solution, which reduced the sulphuric acid consumption and eliminated scale formation in process equipment. The cyanide recovery system currently operates with a two-stage counter-current decantation (CCD) circuit which provides clear solution for processing in the cyanide recovery plant. The cyanide recovery efficiency now averages about 90% to 92% from solution containing about 350 mg/L WAD cyanide (as CN). Recovered sodium cyanide now accounts for about two-thirds of the total cyanide added to the leaching circuit. This paper presents a description of the cyanide recovery plant and details regarding its current operating efficiency.

Jan 1, 2004

By S. Barkhoudarian, R. R. Gupta, R. F. Steinberg

A study of the feasibility of using acoustic signals to detect discontinuities ahead of excavation has shown that reflecting interfaces in a homogeneous rock can be easily identified. Moreover, discontinuity interfaces in a very complex field site (where the rock face was weathered, was full of jointed rocks, and had a destressed zone running along the mine walls) could be identified with a reasonable level of confidence, using a cross-correlation technique for signal processing. The results of this study go a long way toward proving the feasibility of the technique. However, further development work is needed to optimize an operating system in a hard rock environment where boring machines are used for excavation.

Jan 1, 1997

By Jerome C. Neyer

Within most of Canada and the northern third of the United States, the soils overlying bedrock are of glacial origin. Tunnelling in glacial soils presents numerous challenges to the contractor, including abrupt changes in soil type, boulders and glacial erratics, water bearing fine sands and silts, toxic or explosive gases, and glacial till. This paper examines the available techniques for geotechnical exploration in glacial soils; the relationship between subsurface conditions predicted by various techniques and conditions actually encountered during tunnel construction; and potential improvements in the planning and implementation of geotechnical explorations. Case histories of geotechnical exploration and tunnel construction in glacial soils are also reviewed.

Jan 1, 1985

By Allan E. Hall, Kuda R. Mutama

Jet fan (ductless fan) ventilation in underground mines and tunnels is a subject requiring further attention. At present there are no accepted procedures or guidelines for this type of ventilation. The main reason has been the absence of sufficient general data, which has hampered the development of rules. There is great potential for using jet fans in terms of both effectiveness and economics because they eliminate the need for ventilation tubing. In the present studies a procedure is described and results are presented from a jet fan modeled in a square section wind tunnel. The major purpose of the studies was to provide fundamental data on jet fan performance after it was realized that previous work had been limited and too site specific. The jet fan position in relation to the tunnel walls was varied in order to study the influence of confining walls on entrainment rates and the resulting aerodynamics. A clearer understanding of the fundamental principles of jet fan applications was obtained.

Jan 1, 1995

By Norm Steenson

Rapid excavation includes rapid support and is the central theme of this paper. Over the last few years, enormous strides forward have been made in the excavation and material handling aspects of underground excavation. However, the technology necessary to support these rapidly created openings has lagged behind the other aspects. This paper would attempt to bring you up-to-date on the progress made in bringing ground support using shotcrete into the same productivity rates as the other cyclic operations. Shotcrete has become an acceptable material for temporary and permanent support for undergound openings. However, coarse aggregate shotcrete has been an expensive construction material. It has been confined in the main to difficult ground conditions where conventional methods of support have proved to be even slower and more expensive than shotcrete. There are two main factors influencing the productivity of shotcrete equipment. (1) Structural shotcrete as opposed to gunite requires 40% to 45% rock minus 3/4" in the mix design. The equipment to handle such aggregate content has been difficult to develop on a volume basis owing to the attritional nature of the material which causes intense wear problems on

Jan 1, 1974

By Mark P. Schmidt, Douglas D. Schlepp

Water Only cyclones were introduced into commercial operation for cleaning of metallurgical and steam coal around 1950. Since its original introduction as a primary cleaning device, the employment of Water Only cyclones as recleaning and scalping devices has also grown in popularity. Examined are examples and uses of the water only cyclone as primary, re- cleaning, and scalping devices for fine coal cleaning. Also evaluated are conditions that should exist to ensure favorable cleaning in Water Only cyclones.

Jan 1, 1988

By K. H. McDaniel

Eight mine weather stations (MWSs) installed at the Waste Isolation Pilot Plant (WIPP) to monitor the underground ventilation system are helping to simulate real time ventilation scenarios. Seasonal weather extremes can result in variations in the natural ventilation pressure (NVP), which can significantly affect the ventilation system. The eight MWSs, which previously collected and stored temperature, barometric pressure and relative humidity data for subsequent NVP calculations, were upgraded to provide continuous real time data to the site-wide central monitoring system. These data can now be utilized by the ventilation engineer to create real time ventilation simulations and can indicate trends that assist in the prediction and mitigation of NVP and psychrometric related events.

Jan 1, 1999

By H. Bogart

The Golden Sunlight Underground Mine located near Whitehall, Montana was portalled from the bottom of the existing Golden Sunlight Pit in July 2002. Gold was mined by sublevel stoping in the larger ore zones and longhole back stoping in the narrower ore zones. The stopes varied from 30 feet to 100 feet in width, extended up to 200 feet in height, and were completely unsupported. Underground production averaged 1,500 tons per day with a staff of35 people. The mine operated with a break-even cut-off grade of0.080 ounces per ton.

Jan 1, 2004

By Priscilla P. Nelson, Steven D. Glaser, Thomas D. Rourke, O&apos

Construction records from six projects which employed full-face TBMs to drive 18 km of tunnel in sedimentary rock have been analyzed. More than twenty individual causes of delay could be identified. Delay causes are characterized on the basis of frequency and duration of incidents. Average utilization and downtime distributions are presented for each project, and frequency distributions of downtime per shift are discussed.

Jan 1, 1985