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By E. Piesch, M. Urban, G. M. Hassib

INTRODUCTION In radon dosimetry diffusion chambers with passive [a]-detectors are now in current use to investigate the long-term accumulated indoor exposure of radon and daughters. For the diffusion chamber developed at Karlsruhe the electrochemical etching technique (ECE) was applied to reveal [a]-particles in polycarbonate plastic detectors. Compared to conventional etching, the main advantages of the ECE are the large track diameter, simple track counting in a single field of about 1 cm2, stability of the latent tracks to humidity and temperature and ability for a long-term accumulation up to 1 year. The electrochemical etching system was designed to etch in one run about 101 foils by using a 200 W high voltage generator. The commercial available radon dosimeter system is applied for a country wide program of measuring radon in dwellings. Because of an increasing interest of radon monitoring in mines, environmental monitoring and personnel dosimetry the properties of several track etch detectors have been studied. In the comparative study, Makrofol E, LR 115 and CR 39 were used in the diffusion chamber to investigate the etching techniques, the relative efficiency, the measurable [a]-energy range, and the counting statistic for the measurement of radon concentration. THE KARLSRUHE DIFFUSION CHAMBER The design of the Karlsruhe diffusion chamber is presented in Fig. 1. The upper part of the chamber is closed by a fibreglass filter to separate radon from aerosols, heavy dust particles and radon decay products. Inside the diffusion chamber [a]-particles from radon and daughters are detected by two passive radon detectors, one on the bottom of the chamber and the other in front of the filter. With the fibreglass filter applied the diffusion time is about 1 minute for radon. Therefore, also short-term variations in the radon concentration are recorded by the track detector. Mainly because of the short halflife of thoron (56 s) only about 7 % of the thoron concentration is expected in the diffusion chamber. Radon monitoring provides the estimation of the long-term accumulated mean value of the radon concentration with a lowest detectable concentration of 0.1 pCi/1 after 3 months accumulation by using polycarbonate track etch detectors, an electrochemical etching technique and track counting in a single field of 1 cm2. The diffusion chamber was optimized for the polycarbonate track detector with respect to chamber geometry and detector position [1]. Table 1 presents data for 3 different diffusion chamber designs. The radon sensitivity of the diffusion chamber depends on the [a]-energy discrimination and the angular response of the [a]-track detector. The difference between foil No 2 and foil No 1 can be explained by an additional plate-out effect of radon daughters on foil No 3. The high sensitivity of foil No 3 compared to that of foil No 2 is caused by an increase of the effective volume and the effective area for [a]-particle from radon and from plated-out decay products, respectively. Additional experiments have been performed in order to investigate the electrostatic properties of the plastic material and the properties of the diffusion filter [1]. The properties of bare a-detectors were compared with those inside the diffusion chamber. In contrast to laboratory results, dust particles deposited on the detector surface or in the environment of the detector obviously affect the reproducibility of the bare detector significantly. After 4 months exposure in dwellings the scatter of 10 dosimeters exposed in the same room exceeds a factor of 3 compared to 15 % for the diffusion chamber. COMPARATIVE STUDY OF TRACK ETCH DETECTORS Detector types and evaluation technique In the comparative study the properties of the following plastic track etch detectors have been applied: - LR 115 from Kodak Pathé, France, is a red dyed cellulose nitrate layer of 13 µm thickness on a 100 µm thick polyester support. The holes appears as bright spots in a dark red background. In an optical microscope counting of through etched [a]-tracks which must penetrate the detector layer - CR 39 from Pershore, England, is an ally1 diglycol carbonate plastic of about 300 m thickness. The normal etched [a]-tracks are counted by an optical microscope and the ECE [a]-tracks by a microfiche reader.

Jan 1, 1981

The VoD of non-ideal explosives depends on the charge diameter and the thickness, strength and sound velocity of the confiner. VoD measurements are made to evaluate explosives for development, quality control and prediction of field performance. In testing, the container is part of the explosive system and affects the measured VoD. Pipe testing in cardboard tubes delivers the best guide to unconfined critical diameter and minimum VoD range, but the thickness of the pipes affects the result close to critical diameter, even in emulsions. PVC pipes are not good for unconfined test work because they provide relatively strong confinement. Care must be taken to select pipes with constant relative pipe area across the range of diameters. Where pipes are used to evaluate the effect of confinement, the ratio of the wall thickness relative to the thickness of the detonation driving zone in the explosive needs to exceed 0.5 to create full confinement and the ratio of the detonation velocity to the confiner wave speed must be considered. Estimates for critical thicknesses are provided from Non-Ideal detonation models. The relationship between confinement modulus and VoD is discussed and indexes are suggested for quantifying the explosive performance.

Jan 1, 2007

By Anat Deepatana

Bioleaching of nickel laterite ores is the extraction technology based on the use of heterotrophic micro-organisms and their organic acid products to dissolve metals from oxide minerals. This study examined the chemical leaching kinetics of limonite and nontronite ores with metabolites including citric, lactic and malic acids. The leaching process was found to follow the chemically controlled model. The leaching kinetics was found to be significantly influenced by the acid strength or dissociation of acids in solution. Although increasing the acid strength increased the rates of leaching, this trend was not indefinite. An optimal acid concentration that defined the fastest leaching rates was identified for each acid. The amenabilities of the minerals hosting the nickel and cobalt in limonite and nontronite to organic acid leaching were also established.

Jan 1, 2006

By [D. N. ] Naresh

During different activities pile installation like pile boring, concreting etc., it is likely that various problems, depending up on site condition may be encountered. There are possibilities that some of the activities if not correctly followed may affect the pile capacity. This paper describes few problems encountered during pile execution at different sites and presents the remedial measures undertaken to overcome them.

Jan 1, 1996

By John A. Kost

Previous work performed under Contract H0220003 suggested that the mean incombustible content could be obtained with fewer samples and smaller samples without greatly increasing the sampling error. Under Modification No. 4 additional surveys were made in twelve coal mines, representing six states. Same 2,500 samples were collected, analyzed for incombustible content, and statistically evaluated. The earlier findings were substantiated.

Jan 1, 1975

Many sampling standards arrive at a value for the prescribed sample mass by assuming a specific relation between the sample mass and the relative standard deviation of the fundamental error and assigning a value to the tolerated coefficient of variation. In order to obtain an equation that provides a relation between the minimum sample mass and the particle properties, many different models for the drawing of a sample have been developed. Here, a model for the drawing of a sample is proposed which can be considered to be a generalisation of the model used in GyÆs sampling theory. Using simulations, it is illustrated that the generalised model can lead to a better correspondence with actual sampling processes.

Jan 1, 2005

Coal Preparation Research at Turkish Coal Enterprises (TKI)

Sep 13, 2010

By Charles L. Kimbell

The year 1977 generally was a year of growth in overall world mineral industry activity, although there were downturns in major elements of the world's iron and steel industries. The sharp upturns in market economy nation activities that were noted in 1976, following the reduced performance levels of 1975, were moderated, and in the centrally planned economy nations, overall mineral industry activity apparently continued to increase, but at a pace in keeping with that of 1916 rather than at the higher rates of the earlier 1976's. Noteworthy during the year, if only in a negative sense, was the inability of world powers to reach any significant agreement on issues relating to deep seabed mining. Interest from a commercial viewpoint centered around deposits or so-called manganese nodules. These materials, which indeed are chiefly manganese in terms of their content on a quantitative basis, really were of commercial interest primarily far their copper, nickel, and cobalt content. Participants at the Third United Nations Law of the Sea Conference looked into seabed mining rights, but reached no mutually agreeable decisions.

Jan 1, 1981

By K. L. Paciorek

The primary objective of this program was to determine the toxic fume and fire hazard of materials used in the construction of mine stoppings and in the sealing and reinforcing of mine ribs and roofs. The materials investigated were: silicone, phenolic, and isocyanate-based rigid foams, as well as epoxy and acrylate mine sealants. Of the rigid foams tested, the X-156 urethane foam presented the greatest toxic hazard based on toxic load values hydrogen chloride was the main toxic species evolved by this foam. In 'lone of the isocyanate-based compositions was hydrogen cyanide the major component, but its contribution increased with temperature. The FS-24 urethane and Celotex Max-Seal isocyanurate foams had the lowest toxic load values, although these two foams have different applications for in-mine use. Of the two mine sealants tested, the latex /acrylic coating presented the greater toxic hazard with acetic acid being the main toxic species evolved.

Jan 1, 1983

By Greg J. Hasenfus, Allison M. Haines, Joshua M. Silvis

The floodable volume of longwall gob can be of great importance in developing accurate coal mine operation plans, particularly for mine water management and environmental control strategies. Given the inaccessibility and difficulty in direct measurement of gob characteristics following gob recompression, hydrologic, geomechanical, and spatial data and principles were used to solve for the porosity and height of the residual gob using a mathematical model framework and bulking-based techniques. Based on this approach, gob porosity of Appalachian longwalls appears to be tighter than previously reported, ranging between 4.99 and 14.31%. Residual gob height, as normalized with respect to mine extraction height, ranges between 1.90 and 2.45. A novel, bedding-based bulking approach is ampliative with respect to existing roof caving and bulking fundamentals, as it has greater explanatory value compared with the traditional, lithologic-based bulking application. The efficacy of using the residual gob characteristics determined by the mathematical model and bedding-based bulking is examined using a causal comparative method, whereby time series prediction of historical groundwater rebound is compared with observed mine pool elevation data. Prediction accuracy is significantly improved using a prototype model to calculate void volume of longwall gob, specifically, the dependence of porosity of the gob material upon the longwall width to overburden depth ratio for movement basins of subcritical and critical panel widths. The potential implication of these findings toward hydrologic, geomechanical, and ventilation studies of longwall gob could be significant.

Aug 13, 2021

By M. Yavuz

Two different methods of fuzzy multiple criteria decision making have been proposed to solve the problem of mining method selection in the paper titled ?Mining method selection by multiple criteria decision making tool, by Bitarafan and Ataei. This problem is really important and also difficult to solve because of the need of handling many criteria simultaneously in the process of decision making. Bitarafan and Ataei have selected 15 criteria for the case study in their paper and those criteria have not been clustered/grouped yet. The number of selected criteria is only 15, although there are more criteria that should be handled in a real case, because they have used Saaty?s method in the section ?Fuzzy multiple attribute decision making? in their paper. Saaty?s method considers the pair wise comparison of criteria and uses random indexed which have already been derived and published. Available random indexes, however, have been derived for maximum 15 criteria so far.

Jan 1, 2007

By S. Klingmann, G. Blackwell

"Terrestrial photogrammetry has been used for many years to build three-dimensional pictures for analytical purposes. Photographs can include images from open pit mine walls, ground topography, mine buildings infrastructure or accident scenes. Analysis and co-ordinate estimation in early photogrammetric systems demanded the use of specialized and costly optical-mechanical stereocomparators. Few of these instruments could be interfaced with computers to provide databases, and all required trained personnel with good perspective vision to collect data.Digital photogrammetric software has replaced these older systems, and the digital video plotter (DVP) is a simple computerized system utilizing readily available PCs to quickly produce a stereoscopic model of any scene where an area of overlap exists in photographs taken from two different locations. Specialized cameras providing reference marks or grids on the photographs are still necessary for detailed analysis in three dimensions.This paper describes the application of DVP to the three-dimensional analysis of strike, dip and location of dominant fracture planes visible on an open pit wall slope, and the intersection of planar features which might reduce wall stability. Where reference survey points cannot be provided because access by personnel to the photographic scene is impossible for safety reasons, normal case terrestrial photogrammetry can provide the necessary control points for more complex aerial photogrammetry geometries.DVP recreates the geometry existing at the moment photographs are taken, providing the user with the ability to safely recreate, compare and analyze the structures determining the stability of open pit wall slopes."

Jan 1, 2003

By Albert Musschoot

The expanding applications of vibrating feeders for controlling the flow of bulk materials, and their adaptation for processing requirements, have developed considerable interest in stockpiling and reclaim systems. The general design of these units consists of a material transporting trough, or platform, driven by a vibratory force system. Design flexibility and variety is limited only by engineering ingenuity. The basic motion of the vibratory trough, or work member, is a controlled directional linear vibration that produces a material tossing or hopping action. Material travel speeds vary from 0 to about 30 m/min, depending on the combination of frequency, amplitude, and slope vibration angle.

Jan 6, 1981

By Alberto Pacheco Pacheco

En el presente texto se analiza el fundamento de lógica fuzzy aplicada al control de molienda de minerales, la que nos permite simular el comportamiento humano en la operación molienda, con la que se plantea el algoritmo de control inteligente de molienda.

Sep 12, 2005

By J. Lux, B. Clermont

Magotteaux, with the co-operation of Anglo Platinum, has erected a fully instrumented pilot plant at Frank concentrator, which is being used to study the influence of a variety of grinding parameters. This paper will discuss only the influence of mill speed and pulp density on secondary stage grinding. A Ø0.82 x1 m open circuit mill was used with reclaimed Merensky tailings as feed. The conclusions apply to this pilot plant but further investigation needs to be done to verify whether the same trends will be applicable to a large industrial-scale mill.

Jan 1, 2004

By Richard D. Lang

Introduction Argyle is located in the Kimberley region in northwest Australia (Fig. 1). It is a significant diamond discovery by world standards and is the first major diamond find in Australia. The deposit consists of a pipe and associated alluvial deposits. Before the 1970s, diamonds were known to exist only sporadically in Australia. They have been found occasionally in association with gold deposits in Western Australia. There is a small deposit near Copeton in New South Wales. Some alluvial occurrences have also been found in Victoria, South Australia, and New South Wales. The first indicator minerals in the Kimberley region of Western Australia were discovered in January 1973. Production from the alluvial deposits at Argyle began in 1983. A $430-million construction program to develop a mine and treatment plant capable of producing 25 million carats per year was completed in December (1 carat = 0.2 grams). Ownership and management Participants in the project are known as the Argyle Diamond Mines Joint Venture. The group consists of CRA Ltd., 56.8%; Ashton Mining Ltd., 38.2%; and the Western Australian Diamond Trust (formerly Northern Mining Corp.), 5%. The project is managed by Argyle Diamond Mines Pty. Ltd., a wholly-owned subsidiary of CRA. Marketing is undertaken separately by the Western Australian Diamond Trust and by Argyle Diamond Sales Ltd. (for CRA and Ashton Mining groups). History Ownership of the Exploration Joint Venture has changed over the last 12 years as various parties changed their shareholdings. The original Kalumburu Joint Venture was formed in 1972 with five participants, each holding a 20% interest. By 1983, a number of ownership changes had occurred. The end result is that two original participants have sold out. CRA now holds a 56.8% share and the Ashton Mining Group holds 38.2%. CRA also assumed project management in January 1977. Table 1 demonstrates the long lead times involved in developing a project.

Jan 1, 1986

Jan 1, 1967

By Bobby Dupree

I remember a big problem with a seismograph in the winter two years ago. In response to a citizen’s complaint I placed a transducer near the corner of a two-story home. It was a pretty nice day for the winter months, the people were pleasant, and I had no problems digging a hole to place the transducer.

Jan 1, 2004

By Zhang Yaonian

This paper describes full-scale tests on ten large bored piles with grouted end conducted for three projects in the urban area of Fuzhou city. Test program included site investigation, pile installation and end grouting. The piles were instrumented with strain gages and load cells to determine load distribution in the piles. Test results showed that end grouting improves load-settlement performance of bored pile. End grouting significantly increases the shaft resistance near the pile end. The better the end condition, the greater the shaft resistance. The average shaft resistance of the bored piles with grouted end is much higher than that of piles without grouting.

Jan 1, 2004

By Valery M. Paretsky

The effect of the degree of nickel oxide reduction and the reaction gas composition on the furnace productivity has been estimated by computations and the established relationship is in good agreement with the practical data obtained in the process of electric smelting at the Severonickel smelter. An increase in the reduction degree within a range of =0.65 - 0.9 results in an increase in the furnace productivity by 19% to 37% and in a decrease in the unit electric power requirement by 16% to 27% depending on the reaction gas composition. The agreement between the computed and practical data has confirmed that the decisive factor for the process of treatment of reduced nickel oxide in an electric-arc furnace under the given conditions is the specific heat absorption, which is dependent on the nickel oxide reduction degree and the reaction gas composition.

Jan 1, 2005