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By Malcolm J. McPherson, Daniel J. Brunner

This paper describes an experiment conducted to investigate the law of airflow on a mechanized longwall coal face. Background to the Square Law relating frictional pressure drop and airflow is presented and deviations from this Law are discussed. The procedures used to investigate the Law of Airflow for the longwall are described and the results are presented. The results verify the Square Law relationship for airflow along a mechanized longwall face.

Jan 1, 1987

The height of permanent slopes at the Panguna mine of Bougainville Copper Limited will vary from 350 to 950 metres. A few degrees difference in slope angle has a large effect on the ore/waste stripping ratio. Optimum slopes can be achieved if longer batter slopes (exceeding 45m height) are excavated using bulldozers to trim parallel to controlling fracture surfaces. Unnecessary slope flattening by incorporating benches can cost millions of dollars in lost ore. Faults and other major weaknesses, which can result in wedge failure or erodible zones have been treated successfully with shotcrete, rockbolts and cable dowels. To minimize support effort and interference with mine production, early identification and treatment of unstable areas is important.

Jan 1, 1987

By Priscilla P. Nelson

Many concepts concerning equipment selection, performance prediction, and evaluation of support requirements for tunnel construction in soil or hard rock tunnels cannot be extrapolated directly for application in soft rock (compressive strength between 1.0 and 35.0 MPa). Case histories for small diameter (less than 3.5 m) tunnels in Austin, Texas, are analyzed to gain insight into particular problems encountered during tunnel excavation in weak sedimentary rock, and the performance of different excavation systems are compared.

Jan 1, 1987

By Mark E. White, John H. McCowan, Michael C. Costello

Minproc Engineers has carried out the design construction and commissioning of thirty two process plants in the period 1978-87. Twenty eight are gold silver recovery plants, and of these twenty two were gold alone and six were gold and silver. In most plants carbon was used for gold adsorption. Desorption has been carried out using the USBM Homestake method, the Anglo American Research Laboratories method, and the Micron Methanol method. Electrowinning has utilised steel wool, stainless steel wool, and aluminium cathodes. Electrorefining using polished stainless steel cathodes is practised. This paper summarises the experience gained in these operations

Jan 1, 1987

By C. Babbitt, J. O’Green, N. I. Jayaraman

In many mines, dust-laden air from an entry being driven by a continuous miner will contaminate the intake air to the roof bolter operator and other downwind personnel. Through a US Bureau of Mines (USBM) contract, Foster-Miller Inc. has evaluated several control techniques to reduce the respirable dust exposures of downwind personnel. One fan and tubing technique consisted of bypassing the miner-generated dust directly to the section return. The results of the evaluation of this technique revealed that reductions in dust concentrations of 90% or more can be achieved at downwind roof bolter locations. A second method was to clean the dusty air from the upwind continuous miner by using a dust collector. The cleaned air was then supplied to the bolter through collapsible tubing. An underground evaluation showed reductions of 82% to 96% when the dust collector was operating. A third method was to reduce the quantity of dust contributed by the miner to the return airstream. A water-powered scrubber was installed over the throat area of the continuous miner. More than 1.18 m3/s (2500 cfm) of dusty air moved through five tubes with dust collection efficiency exceeding 75%. Underground evaluation results showed that return dust concentrations were reduced by about 60%. This paper discusses the ventilation and dust control techniques used for personnel downwind of the continuous miner.

Jan 1, 1987

By D. B. Stephens

Assessing the occurrence of natural ground-water recharge at mine and mill waste disposal sites may be crucial to addressing regulatory agency concerns regarding the potential impact of waste seepage on ground-water resources. Recharge has been shown to occur even in semi-arid areas where annual lake evaporation exceeds precipitation. Permanent storage of waste seepage in the unsaturated zone is not to be expected if recharge occurs under natural conditions. Establishing the direction and rate of fluid movement in the vadose zone by field measurements is an important element that should be included in the site selection process.

Jan 1, 1987

By Jacques Mongrain, Serge Barbeau, Gary Brierley

The Communaute Urbaine de Montreal is currently involved in construction of the South Interceptor which consists of 53 kilometers (33 miles) of 1,800 mm (6.0 ft) to 5,400 mm (18.0 ft) diameter tunnels for the purpose of collecting, storing, and delivering sanitary and combined sewage to the treatment plant. Work is divided into ten separate contracts; nine of which have already been bid. The purpose of this paper is to describe construction activities that have been performed through the end of 1986 with emphasis on a general layout of facilities, a summary of subsurface conditions, and brief descriptions of actual construction activities for the six contracts where tunneling has been performed. All projects are being excavated with tunnel boring machines.

Jan 1, 1987

By S. Chander

The formation of surface films on pyrite has been studied through electrochemical techniques of cyclic voltametry and AC impedance measurements. The characteristics of the surface films depend upon the conditions of oxidation and the source of pyrite. At potentials near 0.0 V, some pyrites have large values of polarization resistance showing a certain degree of passivity. Some pyrites show more passivation than the others, however. On oxidation, metastable phases of Fe(OH2) and Fe(OH3) form which transform to more stable 3 phases on aging. The growth of surface films near the corrosion potential of pyrite follows a linear kinetics which is attributed to a chemical (or an electrochemical) reaction as the rate determining step. The surface film is considered to be a hydroxide or an oxide rather than sulfur because the later is expected to be limited to a monolayer in alkaline solutions. This study has also demonstrated that AC impedance measurements can be used to study the growth characteristics of films at mineral/ solution interfaces.

Jan 1, 1987

By Albert E. Ketler

The techniques for fire monitoring of conveyor belts in underground coal mines have been revolutionized by the advent of sensitive carbon monoxide sensors and computer monitoring systems. These new systems are rapidly replacing the previous thermal (fixed-point temperature) sensors that have been shown to be considerably less sensitive for early fire warning. CO is generally an excellent indicator of spontaneous combustion. However, the most recent non-flammable conveyor belt materials have been shown to "burn" with dense smoke, but without sufficiently high temperatures to produce much carbon monoxide. To cover this fire detection void, a smoke detector was developed to augment CO sensing for these new conveyor materials. However, computer monitoring provides the flexibility for handling this and other additional instrumentation as fire monitoring techniques evolve. CO, smoke and temperature sensing may eventually be advocated for complete fire monitoring.

Jan 1, 1987

By Peter M. Turcic

A Mine Safety and Health Administration (MSHA), National Institute for Occupational Safety and Health (NIOSH) and Bureau of Mines (BOM) interagency task group was established to assess the health and safety implications of the use of diesel-powered equipment in underground coal mines. The objective of the group was to conduct an assessment to identify areas of concern, to evaluate the adequacy of existing methods for addressing the identified concerns, and to recommend agency approaches for addressing inadequacies. The interagency group concluded its work in April 1986 and presented a report to the Assistant Secretary for Mine Safety and Health. The report included the conclusions reached by a group and recommendations for regulatory action by MSHA. This paper will present the methods and approaches used by the interagency task group and will discuss the findings, conclusions and recommendations of the group. The paper will attempt to meld together the technical and policy aspects of the issues involved with diesel equipment in coal mining.

Jan 1, 1987

By K. A. Brunk

This paper describes Newmont's research, operations, history and experience with pre-treatment of preg robbing carbonaceous ores. The chemistry, physics and kinetics of chlorine treatment are described. Present operations, control strategy and projected changes are discussed. Included is a summary of the adsorption of chlorine into pulps and off-gas scrubbing.

Jan 1, 1987

By Y. C. Kim, F. Szidarovsky

The technique of linear kriging as a grade estimation method of mining blocks is reason¬ably established in the mining industry. During the kriging process, negative kriging weights ([]i) are sometimes encountered. Due to negative kriging weights, negative block grades may be obtained in some extreme situations, which makes no practical sense. To guarantee nonnegative weights, an additional constraint is required in the kriging system of equations. Unfortunately, the nonnegative weight constraint results in a set of nonlinear system of equations. In this paper, a derivation of the resulting set of nonlinear equations is presented and a numerical algorithm is developed for the solution of the equations. Because the algorithm developed does not remove negative weights arbitrarily, optimal nonnegative weights are always guaranteed. Results obtained using the developed algorithm were compared with those using the standard linear kriging, in terms of computer, time and the estimation results. Both the computer time and the kriging variance were found to be higher with nonnegative constraint, as expected. However, some systematic pattern was observed in the kriged values (i.e., over-or underestimation) with or without the nonnegative constraint. The study also demonstrated when one should generally expect negative kriging weights in practice, and what practical impact the negative weights can have on the kriging estimates.

Jan 1, 1987

By Howard L. Hartman

If I told you tonight at the outset that my prognastications for the future of mine ventilation were imparted to me by a palm reader or inspired by a vision, you'd dismiss what I had to say before I said it! If, on the other hand, I told you that my forecasts were the result of an elaborate computer model, derived from a complex algorithm, which in turn relied on finite element analysis -- and the entire projection confirmed by on-site experiments with a turbo hybrid-flow mine fan -- you'd sit up in anticipation and hang on my every word!! All of which places me in a terrible dilemma, because my predictions really lie somewhere in between. My intent is to talk to you out of my background of forty years in mine ventilation, looking ahead to conditions that I expect to prevail in the next fifteen years. You may be curious why I picked an unlikely time span of 55 years for my overview, and my response is that it bridges a career lifetime. "The last forty", of course, corresponds with the period of my professional employment since graduating with a B.S. and M.S. here at Penn State. "The next fifteen" bridges the period I expect (the Lord willing) to remain professionally active -- and coincidently brings us into the beginning of the 21st century. (I must confess to stacking the deck a bit: Since it's infinitely harder to look ahead than to look behind, I purposely minimized the forecast period and maximized the history! Besides, "forty" and "fifteen" have a nice phonetic ring, perfect 20/20 vision sums to "forty", etc., etc.). With these disclaimers, I'll invite you to join me now in a fast 55-year overview of mine ventilation, of necessity limited to a broad-brush treatment of the subject. (After all, this is an after-dinner talk, not a marathon!) In each- segment, I've selected the seven topics that seem to me of paramount importance: in the first part, seven accomplishments in retrospect, and in the last, seven expectations for the future. (The number "seven" needn't confound you, either: In the bible, it signifies "wholeness" or "completeness".))

Jan 1, 1987

By R. A. Seitz

Although the role of the collector has long been thought to play a predominant role in coal flotation, recent investigations by the authors show that the frother plays an equally important role. These investigations have included extensive testwork in several coal preparation plants and in the laboratory. The factors which were investigated include the absolute level of collector and frother addition, the ratio of frother to collector additions, the type of frother, and the particle size distribution of the feed. Results from this testwork reveal strong interactions between these factors as well as the necessity of considering these factors in order to optimize the reagent regime.

Jan 1, 1987

By Galyn Rippentropp, Finn Erik Overlie

INTRODUCTION The wet shotcreting system utilizing steelfiber microsilica shotcrete with remote controlled equipment (The Robocon System) was developed in Norway 7-8 years ago. Norway was the natural origin for this system due to several factors. Almost 30% of all underground hydro-power stations in the world are located here. These projects created a need for high productivity shotcreting rigs for the rock support work in the caverns and in the connecting tunnels. During the period of 1976-1980, more than 1000 miles of tunnels were completed in Norway. Secondly, the utilization of microsilica in concrete was also developed in Norway due to a concentration of the world's ferroalloy p ants there. Robocon has presently placed approximately 110,000 m (150,000 cu. yds.) of this superior shotcrete, and has consequently an extensive experience in the shotcreting method. During a relatively short period of time (1975-1980), Robocon had a change from hand-operated, dry-process shotcrete to remote-controlled, wet-process shotcreting, because of improved productivity, reduced rebound, safer and cleaner working conditions. The introduction of microsilica and water-reducing admixture made it possible to produce wet-process shotcrete of high strength.

Jan 1, 1987

By K. P. Unrug, E. Thompson, S. Nandy

The method of coal pillar design involves primarily two aspects: the geometry of the pillar and the strength of the coal. However, the strength of the coal has to be emphasized with respect to the entire pillar dimension rather than isolated strength values of coal samples taken and measured from different locations. As of now, the presently applied pillar design systems do not specify clearly what the coal sample strength really represents. The intention of this paper is to introduce the concept of seam strength as opposed to the current practice of using coal strength as a prime design criteria in the formulation of pillar calculations. Seams are most often composed of multiple layers of coal, partings, and bone in various configurations, changing within the vertical section of the seam even in relatively close locations. The difference in strength between the weakest and strongest component of the coal seam could be as much as five times or more. An experimental approach based on multiple uniaxial compressive strength tests performed on coal samples from the Coalburg and Warfield seams from eastern Kentucky was undertaken. Analysis of the results led to the conclusion that for pillar dimension calculations, both the weighted mean of the seam strength and the strength of the weakest stratum should be considered, rather than the relatively vague aspect of coal strength. The design of pillar dimensions based on the aforemen¬tioned criteria should assure a more realistic design performance.

Jan 1, 1987

By L. G. Hagenbuch

Several factors need to come together in creating an integrate mining equipment dispatching system. At the hub of these factors ace the central dispatching formulas. This paper details the development of these central dispatching formulas and explores the combining of these formulas with other elements to create an integrated dispatching decision. WHY DISPATCHING? Truck dispatching implies and in reality should equate to mine equipment efficiency. Good truck dispatching will yield good mine equipment efficiency while poor truck dispatching will yield the alternative. Truck dispatching can either be automated through a computerized, process or it can be manual. Every mine with haul trucks has a truck dispatching system whether it is recognized or not. Even a system wherein the hauler operators determine where they are going for their next load is a truck dispatching system.

Jan 1, 1987

By T. M. Jones

This paper outlines the development of the theory of controlled district recirculation and indicates the advances in understanding and technology which have enabled a major change in established ventilation practice. An insight is presented into the possible future use of controlled district recirculation as acceptable practice in mine ventilation planning.

Jan 1, 1987

By G. M. Smith

Several significant past and present producers of high grade and bulk tonnage gold ore from southeastern California and southwestern Arizona can be empirically and genetically linked to regional peraluminous magmatism which occurred during the late Cretaceous and early Tertiary. Geological relationships and geochemical characteristics from the Fortuna Mine area will be described and compared to those of the Tumco Mines area. Each of these historical gold producers is viewed as a morphologic end member in otherwise genetically linked metallogeny. Cold-quartz veins at Fortuna can be directly linked to peraluminous pegmatites both physically and mineralogically. Silica-magnetite±spidote±garnet rock which occurs as relatively barren, discontinuous, foliation- parallel horizons at Fortuna, but as high grade gold ore at Tumco, is interpreted as replacement of calcareous units during the same episode of peraluminous magnatism responsible for the gold vein mineralization. Whole rock and trace element data from pagmatites and aplites of the Fortuna and Tumco areas, together with data from the Gunnery Range batholith of southwestern Arizona, indicate that the magma series (after Keith, 1984) responsible for the gold metallogeny is peraluminous calcic, and is quite rich in sodium.

Jan 1, 1987

By Kenneth R. Dickson, I. Michael Gowring

This paper describes the underground work associated with the North Fork Stanislaus River Hydroelectric Development currently being constructed by Sierra Constructors for the Calaveras County Water District in California under a turnkey contract. Sierra Constructors is a joint venture of the Guy F. Atkinson Construction Company (sponsor) of South San Francisco, and the Harrison Western Corporation of Denver. Notable features of this project include the exceptionally high performance achieved by the 5.5m diameter Robbins tunneling machine and the 675m deep shaft pilot hole which was successfully realigned using oilfield directional drilling techniques. Other features include 3.7m and 4.3m diameter machine-excavated tunnels and various conventionally excavated tunnels constructed over a wide geographical area and diverse climatic conditions.

Jan 1, 1987