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By B. C. Bhowmick, B. B. Dhar

Central system of ventilation, adopted almost universally in coal mines of India and elsewhere in the world, has often proved deficent in providing a cost effective solution to the acute ventilation problems of remote workings in many mines. Loss of air due to leakage through a number of stoppings, doors etc. and accumulation of heat and moisture by intake air on its way to a working through long and circuitous route are the main unavoidable reasons for low efficiency of the system, sluggish and oppressive ventilation of workings. Multi-zonal ventilation system using large diameter bore holes for feeding fresh air in the mine close to a working has been proposed as a viable economic alternative. The method promises to provide congenial environment at working faces without resorting to air conditioning or use of booster fan. Optimum location and diameter of bore holes as well as general design procedure have been dealt in the paper. Finally, the technical as well as economic advantages of the method over the conventional design have been highlighted with the help of a case study where ventilation system of an extensive shallow mine in Central India has been redesigned according to the old and the new concepts. The methodology is general enough for adoption elsewhere in other mines under similar circumstances.

Jan 1, 1993

By Lars Söderberg, Eric Sandström, Per G. Broman

INTRODUCTION Boliden Mineral AB currently mines sulfide ores in 18 mines and processes them in eight concentrators. Most ores are typically complex. Gold consti¬tutes a considerable part of the value of the ore reserves. The value of total production in 1984, distributed by different metals is shown in the pie chart below. Traditionally, gold has been recovered as a byproduct, or coproduct, along with silver in floated copper and lead concen¬trates. Gold-price trends over the past decade have prompted comprehensive efforts by Boliden to increase the recovery of gold in concentration processes. Gravimetric recovery of gold in the grinding circuit is one method that has led to quick results. This method supplements tradi¬tional recovery processes based on flotation. The development of a feasible circuit, and the results obtained by its application in the central concentrator at Boliden, in the northern Swedish province of Västerbotten, are reported below. GOLD MINERALOGY IN BOLIDEN ORES The gold content in Boliden Mineral's ores is primarily in the form of alloys with the elements silver and mercury. A minor quantity appears in an unalloyed form.

Jan 1, 1986

By Ronald I. Fuller

Core Laboratories, a division of Western Atlas International, maintains laboratories in all energy-producing areas of the United States, as well as in many foreign countries. Central to laboratory operations has been the incorporation of computers and computer software. Core has developed a mu1tiuser Laboratory Information Management System (LIMS) , which is currently installed in numerous company sites in the U.S., and is now undergoing installation in Canada. In addition, Core has provided custom soft ware to contract laboratories which Core operates on behalf of mining firms. The software development was done under the direction of the author in Denver, Colorado, and Casper, Wyoming. The intent of this paper is to pass some of the practical experience gained by our efforts on to those who wish to utilize computers more fully in the laboratory setting. The product of analytical laboratories is numbers. Nothing else comes from our work. We deal in information about samples. It is then reasonable to assume that the computer would be central to a laboratory operation. The hard part is to initially define what kind of computer the lab operation needs. The choices today can be very complex, and almost every hardware salesman is full of bad advice. Even the people in your own information services department may hold divided opinions. Since the advent of the personal computer, we have lived with a polarized data processing community. The PC boys consider their machines equal to any challenge, while the "save the mainframe" crowd view the PCs as limited toys that are only good for the things that clutter up a real computer. Management tends to lean toward whatever costs the least.

Jan 1, 1989

By G. B. Misra

Heat transfer in partially wet mine airways has been the subject of study for quite some time. Of the available models some are quite empirical while some involve highly complicated computation. Models developed by Amano, Mizuta and Hiramatsu and Banerjee and Chernyak as well as that modified by Misra were evaluated for prediction of the rise in temperature and humidity (mixing ratio ) of partially wet mine airways at four different levels in the Mosaboni Mine of Hindustan Copper Ltd. Measurements of barometric pressure, virgin-rock temperature and changes in dry- and wet-bulb temperatures along a certain length of airway were made. The rise in dry-bulb temperature and mixing ratio of air over the sections were calculated using the three models. The study reveals that calculated values of temperature and moisture content agree within possible rage of experimental error with all the three models in case of three levels with low wetness factor, but the agreement was poor for the relatively more wet airway on the 30th level. Errors in the estimation of fw to the tune of 0.025 can lead to fair error up to 0.94 K in the estimated temperature while alternative ways of estimating the heat transfer coefficient [] can introduce errors up to 1.45 K.

Jan 1, 1987

By S. Kelkar, H. Murphy, Z. Dash

Nearly 30 estimates of the minimum earth stress were obtained from hydraulic stimulation tests in 5 boreholes at depths varying from 0.6 to 4.3 km in jointed granitic rock near the Valles Caldera in New Mexico. This site is located within the transition between the Colorado Plateau and Basin and Range provinces. Stresses were determined from open hole hydraulic fracturing experiments conducted with water at pressures up to 48.3 MPa (surface). The virgin bottomhol e temperatures ranged up to 327°C. Pressure records show no evidence of rock breakdown, indicating injection into pre-existing joints. A typical pressure response consists of an early wellbore storage period followed by linear fracture flow, which then evolves into a steady pressure, fracture extension mode. Shut-in behavior is characterized by a sharp pressure drop followed by a more gradual decay. The minimum earth stress shows a general linear trend with depth, increasing with a gradient of 19 MPa/km. A low stress anomaly occurs from 2490 to 3100 m where the minimum stresses are as much as 28 MPa lower.

Jan 1, 1986

By N. S. Tanious

The accuracy of vibrating wire stress meters has been questioned by various users in the mining industry. During an in situ coal pillar study, a laboratory evaluation program was developed to determine whether stress meters could produce reliable measurements in coal. More than $0 stress meters were tested for accuracy, repeatability, effects of setting pressure, and the concept of using a single curve for interpreting the stress-meter data. The testing medium was lucite, a material with a modulus of elasticity very similar to coal. The evaluation demonstrated that the stress meters did provide repeatable measurements, but that accuracy was lacking when the recommended interpretation technique was used. Therefore, a new technique was developed that required all stress meters to be calibrated in the laboratory before use in the field. This new technique reduced the average error to typically less than 10% and, in the worst case, to below 15%.

Jan 1, 1988

By Agne Rustan

Most of the mines in Sweden are metal ore mines in hard rock and none of these mines are classed gassy because there is no methane emission. The risk of methane explosions in Swedish mines is therefore very small. Since the 1960?s, in Swedish mines, there has been a change from electric and pneumatic loaders and transport machines to diesel. Today in almost all Swedish underground mines diesels are used. One of the most common complaint from the underground mine- workers is the exhaust gases from the diesel-vehicles. This is a strong motive for attempts to assure a more comfortable environment. Another motive for a better efficiency of ventilation under ground is the increasing cost of energy for fans and for heating the air during winter. For the largest mine in Sweden, the Kiirunavaara Mine, 36% of the energy for ventilation is used for preheating the air during the seven months when the temperature is below zero. The air quantities used for ventilation are large. In table 1 a comparison of the ratio between yearly produced ore and waste rock and installed fresh 'air capacity is shown. [ ]

Jan 1, 1980

By Yixian Zhao

Although many ultimate pit limit design algorithms have been developed for the past one- quarter century, only the well known Lerchs-Grossmann's (LG) algorithm is capable of producing a truly optimum ultimate pit limit today. This paper presents a graph theory oriented algorithm for optimum ultimate pit limit design. This algorithm produces a true optimal solution and maximizes the total undiscounted net profit for a given 3-D block mine model. The algorithm performs much better than the well known LG algorithm, in terms of the reduction in computation time and computer memory requirements. More importantly the new algorithm is easier to understand and implement than the LG algorithm. Specifically, this paper discusses: 1) the computer representation of arcs and the rules of arc generations which dictate the formation of trees in the graph, 2) the mechanism of joint support and re-allocation, 3) the properties, the general procedures of the algorithm, and the suggested specific steps to implement the algorithm, 4) comparison between the new algorithm with LG algorithm, and 5) some experience in implementation of the algorithm and two case study results.

Jan 1, 1992

By Osvaldo Bascur, Laurent Garrigues, Nouna Kettaneh, Svante Wold

The chemical, oil, semiconductor, mining, and paper and pulp industries, as well as most other modern industries, are rapidly expanding the range of measurements used to characterize raw materials, process steps, intermediates, and final products. In addition, process variables such as temperature, pressure, and flow become more and more numerous, providing extra information on the state of the process. However, no matter how many sensors are added, the underlying sources of variations that drive the process behavior remain constant. On the other hand, the measuring frequency of these data has increased from once a day or once an hour to once, ten, or even hundred times a minute. This gives masses of data that are swelling in both directions (more variables and more observations). These data need to be properly stored, managed, and analyzed to provide diagnostics about the state of the process as well as an understanding of the relationships between different parts of the process and the product properties. Projection methods such as PCA (principal components analysis) and PLS (projection to latent structures) compress process data to informative summaries of the original variables. These can be shown on line, providing an efficient, graphically oriented suite of diagnostics regarding the "health" and performance of the process. The power of these methods is illustrated by two examples of industrial data in the mining industry.

Jan 1, 2000

By Kirk H. P. E. McDaniel, Mark T. Strever, Keith G. Jr. Wallace

This paper presents the design and installation of an underground ventilation remote monitoring and control system at the Waste Isolation Pilot Plant. This facility is designed to demonstrate safe underground disposal of U.S. defense generated transuranic nuclear waste. To improve the operability of the ventilation system, an underground remote monitoring and control system was designed and installed. The system consists of 15 air velocity sensors and 8 differential pressure sensors strategically located throughout the underground facility providing real-time data regarding the status of the ventilation system. In addition, a control system was installed on the main underground air regulators. The regulator control system gives indication of the regulator position and can be controlled either locally or remotely. The sensor output is displayed locally and at a central surface location through the site-wide Central Monitoring System (CMS). The CMS operator can review all sensor data and can remotely operate the main underground regulators. Furthermore, the Virtual Address Extension (VAX) network allows the ventilation engineer to retrieve real-time ventilation data on his personal computer located in his workstation. This paper describes the types of sensors selected, the installation of the instrumentation, and the initial operation of the remote monitoring system.

Jan 1, 1995

By Raj K. Rajamani, Poly K. Songfack

The slurry transport within the ball mill greatly influences the mill holdup, residence time, breakage rate, and hence the power draw and the particle size distribution of the mill product. However, residence-time distribution and holdup in industrial mills could not be predicted a priori. Indeed, it is impossible to determine the slurry loading in continuously operating mills by direct measurement, especially in industrial mills. In this paper, the slurry transport problem is solved using the principles of fluid mechanics. First, the motion of the ball charge and its expansion are predicted by a technique called discrete element method. Then the slurry flow through the porous ball charge is tackled with a fluid-flow technique called the marker and cell method. This may be the only numerical technique capable of tracking the slurry- free surface as it fluctuates with the motion of the ball charge. The result is a prediction of the slurry profile in both the radial and axial directions. Hence, it leads to the detailed description of slurry mass and ball charge within the mill. The model predictions are verified with pilot-scale experimental work. This novel approach based on the physics of fluid flow is devoid of any empiricism. It is shown that the holdup of industrial mills at a given feed percent solids can be predicted successfully.

Jan 1, 1995

By Jean-François Boucher, Ernest K. Yanful, Mei Lin Shelp, Lionel J. J. Catalan

Shallow water covers for preventing acid production in tailings are based on the principle of minimizing oxygen availability. Resuspension of material from the tailings bed may result in increased oxidation and metal releases since dissolved oxygen is at near saturation levels in the water cover. Resuspension can be caused by waves and currents strong enough to mobilize the surface of the tailings bed. Tailings resuspension was measured with sediment traps in the Upper Cell of the Heath Steele site near Mirarnichi, New Brunswick Canada. Although significant amounts of resuspended tailings were collected in all traps, analysis of resuspended solids and bed tailings suggests that for the observed wind conditions resuspension did not occur at locations where the water cover depth was greater or equal to 1.0 m. Currents were likely responsible for the transport of resuspended tailings from shallower areas to locations where the water cover was deeper than 1.0 m.

Jan 1, 2000

By Kenneth R. Ware

I INTRODUCTION The Washington Metropolitan Area Transit Authorities (WMATA) rapid transit system (METRO), currently under construction, will have a total length of 98 miles. Forty-eight of these miles are underground and require either open cut excavations or tunnels. Despite stringent construction controls, it is inevitable that some ground settlement will occur adjacent to the deep open cut earth excavations and large diameter earth tunnels. It is therefore essential to underpin nearby important structures to prevent excessive differential settlements and Fig. 1 presents the METRO criteria for this underpinning. This paper describes the underpinning methods currently used on METRO and evaluates the effectiveness of each method. II DESCRIPTION OF SUBSURFACE STRATA The foundation materials in the Washington, D.C. area are extremely variable. Fig. 2 presents an idealized profile showing typical subsurface strata. The engineering properties of each stratum have been determined by extensive exploration and testing programs. Fill: Washington, D.C. fills consist of every variety of soil and rubble. They are not important to this study because no underpinning is founded on fill material. Terrace Deposits: Formed in outwash plains during the glacier period, these deposits are composed of random layers of either sand 1 The writings and opinions expressed herein are solely those of the author and do not necessarily reflect those of WMATA.

Jan 1, 1974

By Gregory A. Hope, Kym Watling, Matthew I. Jeffrey, Ronald Woods

Surface enhanced Raman Spectroscopy carried out in real time has been applied to identify surface species formed during gold leaching in chloride and thiosulfate media. Chloride ion is adsorbed prior to the gold dissolution potential, but its coverage is significantly diminished at the beginning of leaching. A gold chloride band is again observed when dissolution is rapid, together with bands characteristic of AuC14- ions in solution. With thiosulfate, a thin gold sulfide layer is formed slowly in the potential region where leaching occurs. At higher potentials, thiosulfate is oxidized to sulfur and sulfate, both products being identified by Raman spectroscopy.

Jan 1, 2005

By A. C. Burrow, R. P. King

A dynamic model that predicts the variation of carbon content with time in the argon-oxygen decarburization (AOD) process has been developed. The model recognizes three distinct zones in the AOD vessel: the tuyere region in which the blown oxygen reacts very rapidly with the metal components in the molten alloy; a region in which bubbles of inert gas and oxide drop lets rise through the molten alloy; and a zone in which the slag layer can interact with the molten alloy. The process is dynamically controlled by the rate at which dissolved oxygen, produced on the surface of rising oxide droplets, and dissolved carbon diffuse through the molten alloy to react at the surface of the rising bubbles. The rate at which carbon and oxygen react on the bubble surface is assumed to be intrinsically very fast. Predicted decarburization rates compare reasonably well with rates measured in the AOD vessel at Middleburg Steel and Alloys. The model has been developed primarily to allow development of a time-optimal blowing stategy for the AOD vessel.

Jan 1, 1990

By Ch. Apostolaki

Eighty samples from Roman wall paintings from ancient Corinth were studied by means of optical and scanning electron microscopy coupled to an energy dispersive analyzer, X-ray diffraction and image analysis techniques. The goals of the study were the identification of the exact nature of the pigments and the technical features of paint application (binding medium, adherence to plaster, thickness of the pigment layer), which would provide evidence about the painting technique (fresco or secco). The main plaster is calcitic with secondary calcite as a cement binder to the primary calcite grains. All pigments, except Egyptian Blue, were naturally occurring ochres or pigment minerals, such as limonite, goethite, hematite for yellow, brown and red hues, cinnabar for red hues and celadonite for green color. The presence of specific elements such as Ni and Cr or minerals such as olivine, in the yellow, brown and red pigments, gave an indication about the provenance of the original pigments, which seems to be from Cyprus. The black color was represented using charcoal. It seems, finally, that for the pigment application the fresco technique was used, while secco is also apparent.

Jan 1, 2006

By Terry L. Logan, Arfon H. Jones, James C. Seccombe

Deeply buried coal seams [greater than 3000 ft (914 m)] are difficult and sometimes hazardous to test and complete due to coal sloughing, formation pressure anomalies and coal fine generation. Data collected while stimulating two deep coalbed methane wells located at the Gas Research Institute/Resource Enter¬prises, Inc. "Deep Coal Sean Project" test site in the Piceance Basin, Colorado, is presented in this paper. A single thick coal seam was completed openhole in each well. Core data, reservoir data, in-situ stress measurements, and pre-stimulation calibration test data were collected at the site to use in the design of the fracture stimulation treatments for both wells. A nitrogen foam fracture fluid treatment was selected for the first well and a linear gelled water for the second well. Treatment pressures were monitored with a downhole quartz pressure transducer. Atypically high treating pressures were observed, possibly indicating coal fines plugging at the fracture tip or increase in fluid viscosity caused by interaction of the generated coal fines with the fracturefl uid. In addition, a comprehensive fracture diagnostic effort was employed during the fracturing of the second well; namely, triaxial borehole seismic, seismic televiewer, hydraulic impedance monitoring, gamma ray log (in conjunction with radioactive additives in the sand), and temperature log. The results indicate a vertical fracture was created parallel to the face cleat as expected.

Jan 1, 1986

By John D. Gardner

This paper describes a process which finds the maximum worth of a mineral deposit. The procedure requires two phases. The first uses a microcomputer evaluation model to find the optimum design input, with minimum attention giving to actual mining constraints that might exist. The second phase runs the first-phase design parameters through a direct simulation model on a mainframe computer. In phase one, financial, economic, and geotechnical data are entered; and an idealized list of design parameters is output. The list includes optimum values for cutoff grade, mine life, mine size, paytons, paygrade, and payvalue. In addition, the model generates pro forma operating and cash flow statements and it indicates the maximum net present value (NPV) possible for the deposit along with the probability of that oc¬curring. The initial results imply perfect mining conditions. In phase two, when actual mining selectivity, sequence, and other practical design considerations are related in a direct simulation model to the optimum criteria found above, the maximum NPV invariably decreases. However, if it is still satisfactory (NPV greater than or equal to zero) then the maximum worth/ optimum design have probably been found in the first iteration. If, on the other hand, NPV is now unsatisfactory, then design compromises must be made and simulated, and the results rerun through the evaluation model. If several iterations fail to yield a positive NPV then the deposit is most likely unfeasible t for the forecast economic conditions used in phase one.

Jan 1, 1986

By Henry R. Tiedemann, Eugene H. Skinner, George E. Wickham

Improving the state-of-the-art of tunneling is a continuing challenge to those involved in underground construction. New methods and procedures are usually evolved over a relatively long period of time as compared to advancements in other types of construction. To a large extent this is probably due to the fact that tunneling deals with a material or medium - the rock structure - whose physical properties are not only extremely varied, but in many instances virtually unknown until time of penetration. This hovering of the unknown tends to make "non believers" of many and at best leads to a general reluctancy of accepting new ideas or procedures. The situation is further complicated by: 1) discrepancies in terminology and respective meanings as used by different disciplines to describe, define or evaluate pertinent factors and their relative effect on the tunneling process and 2) the fact that no two tunneling situations are identical with respect to either geological conditions or construction and contractual requirements. In spite of the above there have been many successfully completed tunnels which make it apparent that both the technical and practical expertise needed to develop or project improvements is available within the industry. It is with this in mind that the RSR concept was developed. BACKGROUND This paper presents the findings and results obtained from contin-

Jan 1, 1974

By D. Altizer, E. Thompson, K. F. Unrug

Because of frequent sudden changes in the geologic composition of strata, the extrapolation of rock properties obtained from core samples to the surrounding areas can cause problems. To address this issue, a method of rapid strength testing in situ using a borehole penetrometer is being developed. This method, as opposed to conventional laboratory testing, does not require rock samples to be retrieved and handled/machined before testing. Rock strengths are determined di¬rectly on the drill-hole wall. The latest development is a borehole penetrometer that requires only a 38.1-mm- (1.5-in.-) diam hole. The small diameter of the penetrometer body allows for the drilling of test holes with production mine equipment such as a roof bolter. The new penetrometer allows for the possibility of a broad application in coal mines, as well as in hard rock mines and tunneling. The principles of the apparatus are described and are illustrated with examples of its applications.

Jan 1, 2002