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By R. J. Hundermark, L. R. Nelson

The critical importance of tap-hole design and management to furnace performance and longevity is explored through examining some of the specific matte, metal and slag tapping requirements of non-ferrous copper blister and matte converting and smelting, ferroalloys smelting and ironmaking systems. Process conditions and productivity requirements and their influence on tapping are reviewed for these different pyrometallurgical systems. Some critical aspects of the evolution of tap-hole design to meet the diverging process and tapping duties are examined. Differences and similarities in tapping practices and tap-hole management are reviewed. Finally core aspects of tap-hole equipment and maintenance are identified that are considered important to securing improved tap-hole performance and life, so pivotal to superior furnace smelting performance.

Jan 1, 2014

By Jacob Chacko

The Izmit Bay bridge, a 3-km-long suspension bridge crossing of Izmit Bay, Turkey is planned to be constructed in one of the most seismically active places in the world. The site, which has the potential to experience significant earthquakes associated with the relative motion accommodated on the North Anatolian Fault, is underlain by deep deposits of soft soils, and areas of unstable and liquefiable soils. Characterizing the seismotectonic setting, foundation soil conditions, potential fault locations, as well as other geohazards was a critical component for the project concessionaire to finance the project and obtain meaningful bids for bridge design and construction. Given the Build Operate Transfer (BOT) funding mechanism, executing this work in the least possible time was critical to the concessionaire?s financing scheme. Fugro was retained to provide geotechnical, geological, and seismological evaluations for the project region, and to generate data for contractors to develop reliable designs and bids. The uncertainties in these data made it difficult for the BOT concessionaire to finance the project and tender Bridge design and construction. The investment in an early and comprehensive site characterization program to evaluate and quantify those uncertainties allowed the concessionaire to save schedule, provide a robust bid basis to bridge contractors, and persuade banks to finance what was perceived to be a relatively high risk project.

Jan 1, 2011

By John Kinneen, Sunghoon Choi, Arne Fareth, Edward S. Barboe, Kyle R. Ott

A new water treatment plant is to be constructed for a portion of the water supply system of New York City. The project includes construction of new water conveyance tunnels crossing perpendicular and sub-parallel to the existing pressurized water tunnel at two locations. A study was conducted to evaluate the impact of new tunnel construction on stability of the existing tunnel and hydrojacking potential in the surrounding rock mass. This paper introduces a practical approach to evaluate tunnel interaction, expressed in terms of rock-liner interaction, stress-induced stability and hydrojacking failures. A simple method to evaluate hydraulic and mechanical properties of concrete liners and jointed rock mass is also presented.

Jan 1, 2007

By K. Lundholm, A. E. Mäkinen

"Ore grades are declining and getting more complex around the world which not only complicate the ore processing but also produce new type of requirements to manage the produce waste streams. One specifically problematic and increasingly identified element in waste streams produced in mining and metallurgy is arsenic.Arsenic is a compound that has no significant market value, but that needs to be removed from ores, concentrates and other process streams because of environmental or process technical reasons. One example of a removal process is partial roasting of high-As sulfide concentrates, originally developed by Outotec. In this process the arsenic is volatilized in the gas phase and thus separated from the solid material, i.e. the calcine. If the arsenic is recovered by wet methods the process gas is quenched and all arsenic needs to be stabilized in the effluent treatment plant.Outotec has developed ferric arsenate precipitation as a method to produce stabile arsenic residues from wet gas cleaning effluents. Iron based precipitates, when correctly produced, can meet typical landfill criteria measured with different types of leaching methods meant for characterizing the arsenic dissolution behavior from the precipitates.In this paper partial roasting of sulfide concentrates with arsenic volatilization in combination with ferric arsenate precipitation is discussed from the perspective of producing wastes that can meet the stability requirements set by common leaching tests methods, TCLP and CEN. These leaching test methods set the normative landfill requirements for most operations generating arsenic containing wastes. A typical flow sheet of Outotec® Ferric arsenate process is discussed with results showing the importance of correct process control and sequence on producing arsenic containing waste that can meet the landfill disposal requirements."

Jan 1, 2014

By David W. Tongue

This report describes the engineering work leading to the design of an underground coal mine piping system to transport approximately 2,000,000 cubic feet per day of methane gas to the surface from degasification holes drilled horizontally into the coalbed in existing coal mines. Safety instrumentation for detection of gas leaks and provisions for automatic emergency shutdown are included in the design. It also includes specifications for a safe system of handling gas, water, and drill cuttings during drilling of the horizontal holes and recommendations for compressor and metering facilities at the surface. The main pipeline is recommended to be constructed of polyethylene plastic pipe joined by a butt fusion method while lateral lines and separator and meter piping at the horizontal holes are recommended to be screwed steel piping. The materials used are to be resistant to the forces of impact exerted by falling rock. The pipelines are to be suspended from the ceiling with pipe hangers. All steel components are protected from chemical corrosion by applying protective coatings and the vertical casing to the surface is protected from electrolytic corrosion by a rectifier station. Methane gas detectors monitor the mine atmosphere to detect the presence of gas leaks and a pneumatic plastic tubing line provides for control of the safety shutdown system. Both the recommended design and the required construction procedures are in compliance with the applicable Federal codes for coal mine safety.

Jan 1, 2012

By J. J. Forbes

This publication is a revision of the first of a series of four Miners' Circulars originally prepared and issued in 19'29 for use in a course of training designed to prepare mine officials to organize men for rescue and recovery operations. These circulars were revised in 1937 and 1938 and again in 1948. This circular (Miners' Circular 33) discusses mine gases and methods for detecting them. The second of this series (Miners' Circular 34) gives instruction in Bureau of Mines methods of sampling and analysis of mine gases; the third (Miners' Circular 35) describes methods and equipment used for protection against mine gases; and the fourth (Miners' Circular 36) explains procedures used in sealing and unsealing mine fires and in recovery operations after mine fires or mine explosions.

Jan 1, 1954

By P. Walford, C. Mealin, D. Good

"The geology of the Ore Fault Ni-Cu deposit has been reinterpreted in the light of recent studies of the geology of the Neoarchean Bird River Sill Complex and the occurrence of economic Ni-Cu and Zn-Cu-Ag mineralization. The Ni-Cu sulfides are hosted by the lower of two parallel NNW-trending and moderately W-dipping mafic-ultramafic intrusions related to the Bird River Sill Complex. The bod¬ies intruded a bimodal volcanic suite consisting of weakly deformed mafic flows and felsic pyroclastic rocks. The mafic volcanic rocks are geochemically related to the MORB-type rocks of the Lamprey Falls Formation, and the felsic volcanic rocks are related to arc-type rocks of the Peterson Creek Formation. The original pyroxene- and olivine-dominated mineralogy of the sills has been replaced by variable ser¬pentine-amphibole-talc-carbonate assemblages.The Ni-Cu sulfide assemblage exhibits textures and geochemical signatures typical of orthomagmatic sulfide mineralization. The sulfide minerals are associated with cumulate layers of magnetic ferrochromite that range in thickness from a few to tens of centimeters. A later event of Zn-Cu-Ag sulfide mineralization associated with quartz veining and garnet-chlorite alteration along a fault that strikes north, dips vertically, and cuts all rock types. The mineralized fault is cut by the NE-trending Peterson Creek shear zone. Where the Ni-Cu and Zn-Cu-Ag mineralized zones intersect, remnant magmatic features such as amphibolite or cumulate ferrochromite bands occur within quartz veins or local chlorite alteration. The mixed zones contain a very unusual polymetallic assemblage of Ni, Cu, Zn, Ag, and platinum group elements (PGE)."

Jan 1, 2009

By Northcutt Ely

This volume summarizes mining and petroleum legislation in 30 jurisdictions of the Western Hemisphere. Within these jurisdictions, primary attention is given to requirements that must be met in each country for acquisition of rights to permit development of mineral resources. Coverage includes: First, identification of the controlling laws or statutes governing minerals acquisition and reference to the administrative authority; second, analysis of the laws governing mines and quarries and their products; and third, analysis of laws applicable to natural gas, petroleum, and related materials. Where pertinent, sections dealing with historical background or administration have been added. In countries where minerals are subject to control of States or Provinces, those areas are considered separately from the central government.

Jan 1, 1970

By Gábor Csicsovszki

We have developed a novel method - at the laboratory scale - comprising an ion-exchange separation and a membrane-electrolysis step for the purpose of zero-waste regeneration of spent HCl pickling liquors originating from hot-dip galvanizing of common steels. It is aimed at the parallel regeneration of HCl and iron. Experiments revealed that iron can be electrodeposited at high current efficiencies by maintaining the following conditions: 0.04-0.08 M HCl, 500-1000 A/m2, 20°C and stationary electrolyte in a conventional cell. Zinc in the solution did not disturb the deposition of iron, however it contaminated the product and it poisons the anion-exchange membrane required to tackle acidity during electrolysis. For a preliminary separation, anion-exchange tests were carried out to produce pure iron solutions. Beyond the equilibrium studies, column experiments were carried out showing that low flow rates of the loading solution and the ~1.5 M HCl eluent are essential for separation.

Jan 1, 2006

By K. G. Wheeland, J. E. Dutrizac, M. Wasserlauf, A. A. Condy

Numerous processes for the treatment of thiosalts in base metal milling effluents have been examined in the past decade. Flowsheets for thirteen processes are outlined, and cost estimates are presented for a base case of a 720 mi/h effluent flow containing 1400 mg/L thiosalts. The processes are ranked on the basis of Numerous processes for the treatment of thiosalts in base metal milling effluents have been examined in the past decade. Flowsheets for thirteen processes are outlined, and cost estimates are presented for a base case of a 720 mi/h effluent flow containing 1400 mg/L thiosalts. The processes are ranked on the basis of

Jan 1, 1988

By MacDonald B. Johnson, Douglass P. Bacon

"W ith the advance of science, rise of public interest in environmental matters, and continuing erosion of air quality, federal and state regulators are demanding an increasing complex array of data concerning emissions produced by burning and detonating energetic materials. The U.S. Department of Defense, one of the world’s largest consumers of energetic materials, now must characterize combustion products resulting from open burning/open detonation disposal operations. The catch-all phrase “below detection limits” no longer satisfies the regulators who nowwant testing to delve into the ppt level for volatile organic compounds and ppt level for semivolatile organic compounds."

Jan 1, 1995

By A. Pratt

Portland cement is primarily used to solidify backfill in underground mine workings and it represents a major cost in mining operations. CANMET-MMSL has invented an alternative binder technology that does not contain any amount of Portland cement and is made using waste materials, such as development rock and smelter slag. The technology has been successfully tested with many types of base metal and ferrous slag. Research conducted in collaboration with several mining operations in Canada has shown that the CANMET-MMSL binder has considerable potential as a replacement for Portland cement in mine backfill. An integral part of the overall mining operation, backfill is used for two main purposes: safety and environmental remediation. Depending on the mining method used, backfill provides a working surface, stabilizes stope and pillar walls, as well as the surrounding rock mass, and controls caving of stope backs. There are several benefits associated with the replacement of Portland cement in backfill, including reductions in (i) the footprint by placement of slag waste underground, (ii) the environmental effects and long term liability resulting from disposal and containment of slag waste on surface such as acid rock drainage, (iii) GHG as a result of reduced Portland cement usage (the production of 1 ton of Portland cement produces 1 ton of GHG), and (iv) the significant costs associated with reduced Portland cement usage.

May 1, 2010

By WILLETT G. MILLERS

GENERAL RECEPTION COMMITTEE.-Willett G. Miller, Chairman; F. G. B. Alan, Hon. Frank Cochrane, Eugene Coste, Thomas W. Gibson, Cyril W. Knight, J. C. Murray, 0. N. Scott, Alan Sullivan, J. B. Tyrrell, J. W. Wells, A. B. Willis. COBALT RECEPTION COMMITTEE.-Arthur A. Cole, Chairman; Will. Ask with, R. W. Brigstocke, Robt. Bryce, Fred Coombs, M. I. Culbert, I. R. Drummond, J. W. Evans, A. Ferland, F. N. Flynn, E. L. Fraleck, S. R. Heakes, Joseph Houston, D. L. Jemmett, I. R. Jones, Major Leckie, Capt. Jack Leckie, R. W. Leonard, W. H. Linney, Alexander Longwell, Frank Loring, Murdock McLeod, John Martin, D. B. Rochester, W. E. Running. COBALT RECEPTION COMMITTEE (Ladies).-Mrs. A. A. Cole, Mrs. A. Edwards, Mrs. R. Jennings, Mrs. S. H. Logan, Mrs. A. Longwell, Mrs. H. F. Marsh, Mrs. J. Smith. SUDBURY LOCAL COMMITTEE.-Mayor L. O'Connor, Chairman; S. Fournier, Secretary; A. H. Beath, W. J. Bell, F. B. Bennett, D. M. Brodie, J. S. Buchanan, F. C. Busby, Wm. Chalmers, R. Dorsett, W. A. Evans, John Frawley, J. S. Gill, A. B. Gordon, J. G. Henry, T. N. Kilpatrick, Major Leckie, Chas. McCrea, John McLeod, Wm. McVittie, R. Martin, R. S. Mitchell, J. H. Morin, J. A. Orr, James Purvis (President Board of Trade), C. R. Reid, Major Smith, W. W. Stull, J. F. Templeton, S. E. Wright. The first session, held in the Banquet Hall of the King Edward Hotel, was called to order Tuesday, July 23, 1907, at 2.30 p.m., President John Hays Hammond presiding. Prof. Willett G. Miller, chairman of the General Committee, introduced Alderman J. J. Graham, who, in behalf of the City of Toronto, extended a hearty welcome to the members and guests of the Institute. To this welcome, President Hammond replied in a few well-chosen and hearty remarks. In the hall in which the session was held there was exhibited a fine, full-length, life-size portrait of Dr. Rossiter W. Raymond, in 1871 Vice-President and acting President, in 1872, 1873 and 1874 the elected President, in 1876 and 1877 Vice-President, in 1883, by appointment of the Council, and for the last 24 years by annual election, Secretary, of the Institute. Dr. James Douglas, of New York, N. Y., on behalf of numer-

Sep 1, 1907

By R. V. Higgins

The Bureau of Mines investigated the use of electronic computers for obtaining more information about relative permeabilities of reservoir rock to oil and water. It was found that there are many possible combinations of relative permeability curves that will result in virtually the same recovery versus injection) but they require different times and rates to recover the oil even with different mobility ratios. Permeability curves obtained by the use of non-viscous oil and employed for calculating the waterfloods of viscous oils can lead to serious inaccuracies. For viscous oils) the wettability characteristics in the middle portion of the permeability curve affect recovery nearly as much as other portions of the curve; this) however) is not true for non-viscous oils in water-wet reservoir rock.

Jan 1, 1967

By B. Unver

Effective strata control is a prerequisite for maintaining an efficient mining operation. If the strata in the vicinity of an opening are not controlled effectively, it is impossible to perform a safe, efficient and economical operation. In this paper, the reasons and outcome of instability problems observed in roadways opened in clay and marl at the Bolu Colliery of Yeni Çeltek Establishment are investigated. Roadways under examination were located in a syncline causing high residual tectonic stresses. Factors affecting the instability have been studied thoroughly by examining geology and tectonics of the area, establishing convergence measuring stations to understand in situ behaviour of supports and laboratory tests to determine engineering properties of samples taken from nearby convergence measurement stations. As a conclusion, a new production strategy and a new support system are recommended to maintain stability.

Jan 1, 1999

By R. G. Warncke, J. H. East, D. Harrington

The mining industry of the United States has long been severely criti- cized because of its high rate of accident occurrence, not only as compared with other industries of the United States but also with the mining industries of other countries, particularly Europe. Statistics, often not strictly com- parable, indicate that the accident-frequency rate in all mining is currently about three times and the accident-severity rate is about seven times as great as the average for general industrial work in the United States. These fig- ures are by no means comforting to humanitarian mining men, irrespective of their status in the industry, and they constitute a challenge that certainly cannot continue to be ignored much longer. The picture becomes much darker when the above statistics are augmented with data indicating that on an exposure basis our mines (more particularly our coal mines) have accident rates two, three, or even more times as great as more or less similar mines in Europe, particularly England, Wales, Belgium, France, and Germany. The sting is alleviated to some extent by the knowledge that our coal mines produce about 4 to 5 times as much coal per man day as is produced in at least some European mines. However, all of these foreign acci- dent statistics should be analyzed carefully before we become very much con- cerned about them, because they are not strictly comparable, for several reasons, not the least of which is the fact that foreign methods of compiling or recording accident statistics often differ materially from ours. Moreover, foreign mining and other conditions are definitely dissimilar to ours in many phases, and numerous other factors affect the comparability of foreign mine- accident statistics with those of the United States. Unquestionably, it should also be taken into consideration that the accident rate of the 140,000,000 or more constituting the populace of the United States as a whole is much higher than that of any other major country in the world and is two, three, or more times the rate of the European countries that have more favor- able mine-accident rates than those of the United States (table 1). Moreover, it is significant that the mine-accident-severity rate of British mines is about six times the average accident-severity rate of the major industries of the British Isles, or but little more favorable than the comparable figures in the United States; namely, that mining has an accident severity rate about seven times the average of about 30 of the major industries of this country.

Apr 1, 1949

The fundamental features of the Cable Belt Conveyor are described. It consists of independent wire ropes which take the transmission load, and a special reinforced rubber belt which acts 'only as carrier of material. The first cable belt installation in Scotland is described briefly.A general description of this type of conveyor is followed by details of the rubber belt construction and the method of joining sections of belt. The drive unit, the tensioning arrangements and the power requirements are outlined.Applications of the cable belt conveyor are 'dealt with and its advantages summarized.INTRODUCTIONThe cable belt conveyor, as its name implies is a conveyor composed of steel wire ropes and a rubber belt, in which the ropes serve as transmission members, and the belt merely as a carrier of materials.Over the years it has been the ambition of engineers connected with the belt conveyor industry to develop a conveyor that would use the high tensile strength of wire ropes to transmit the stresses involved in the driving of large capacity belt conveyors. Different lines of approach have been adopted in the United States of America and in Britain. In the United States the method adopted was to introduce a large number of flexible steel cables into the rubber belt itself, in the form of a closely packed layer arranged across the full width of the belt. These small cables are packed in a nylon filled duck envelope which is incorporated in the rubber belt. This is commonly known as the steel corded conveyor belt. In Britain, a Scottish firm developed a rubber belt conveyor in which full advantage was taken of the high tensile features of wire rope, without embodying or moulding the wire rope into the rubber belt, so that the two wire ropes and the rubber...

Jan 1, 1957

By V. J. Sopuck, O. P. Lavin, Ian Nichol

"A major challenge of contemporary exploration geochemistry is the development of procedures that can locate blind mineralization or mineralization that sub-crops below a cover of transported overburden, the composition of which bears no relation to the underlying mineralization. Over the past few years, the possible existence of diagnostic geochemical features in the country rock associated with volcanogenic massive sulphide deposits has attracted increasing attention both on the local mine scale and on the regional scale. In the present investigation, the nature of the geochemistry of a number of Archean greenstone belts of the Canadian Shield is examined to determine the feasibility of distinguishing productive from non-productive areas of copper-zinc mineralization. The results indicate that productive areas are distinguishable from non-productive areas providing consideration is given to the effects of igneous differentiation on rock compositionIntroductionArchean massive sulphide deposits are an important source of copper and zinc, and to a lesser extent silver and gold, particularly in Canada. As in the case of most other forms of mineralization, there is a continual need to develop new techniques that will improve the chances of success in the search for these deposits. The majority of Archean areas in the northern latitudes are overlain by a variable cover of glacial overburden. Considerable progress has been made in the development of new geochemical exploration techniques for use in glaciated terrain, based on the detection of anomalous dispersion in the glacial overburden. In certain situations, however, as in the search for blind deposits or in areas covered by glaciolacustrine deposits, overburden geochemistry offers little hope for success. In the case of massive sulphide deposits, one possible solution may lie in the detection of anomalous geochemical signatures in the bedrock. Recognizing this possibility, attention has been directed to the investigation of the nature of lithogeochemical dispersion associated with massive sulphide deposits on both regional and local scales, to establish the potential of lithogeochemistry as an aid in the search for these deposits."

Jan 1, 1980

By M. I. Mthenjane

"BackgroundThe paper discusses post-mining land use however, the essence of the topic is the emotional motivation behind the decisions related to mining investment and development. Therefore this is not a typical SAIMM technical paper about the science and techniques of post-mining land use. There are already numerous papers written and conferences held on this aspect of post-mine land use; the science is well understood, but the evidence of the practical application of the (environmental, social, and economic) science is sparse. At a recent conference held in November 2017 on the theme of ‘Science, Business, Society Dialogue – linking science, society, business and policy for the sustainable use of abandoned mines in the SADC region’, it was demonstrated through the delivery of several papers on the possible viable options of post-mine land use. The conference was structured in nine sessions, covering the following relevant topics:? Sessions 1 and 2: Nature and magnitude of the problem: raising awareness? Sessions 3 and 4: International experiences in remediation: case studies? Sessions 5, 6 and, 7: Technological solutions: converting liabilities into assets? Session 8: Implementing solutions: social and legal aspects? Session 9: Wrap up, lessons learned: conference resolution.Summaries of the key outcomes of the sessions are available for reference.The aim of this paper, accompanied by the video speech, is to provide a visualization of the possibilities of post-mine land use. Mining contributes approximately 7% to South Africa’s GDP - this is the lowest it has ever been and is attributable to both a diversifying economy and to poor mining and investment policy which has resulted in reduced investment in the sector. The objective of the paper is to highlight the opportunities, for succeeding and diversifying economic activity following mining and mineral extraction which can continue to sustain the livelihoods and wellbeing of communities and societies beyond mining.During mining, very few alternative and local economies develop. Dependence on mining and its value chain prevails until mining ceases. This idea is conveyed in Figures 1a and b."

Jul 1, 2019

By S. Lolon

Spontaneous combustion in underground coal mines has become a serious problem particularly in the caved area (gob). Recent statistic has shown that approximately 17% of total 87 underground coal mine fires in the United States are attributed to spontaneous combustion (De Rosa, 2004). Spontaneous combustion results from a self-heating process in exothermic conditions. The accumulated heat, if not removed, is conducive to the rapid increase of temperature and may result in mine fires or explosions. It is well accepted that the interaction between oxygen and coal substances is the main cause for spontaneous combustion, while other factors such as pyrite, moisture, and bacteria play a secondary role to the self-heating of coal. Therefore, only coal oxidation is considered in this study. Coal oxidation occurs as coal comes into contact with air. This process involves complex phenomena in terms of heat transfer, chemical surface absorption, and energy balance related to inherent properties of coal (Wang et al., 2003). For simulation purpose, overall reactions can be simplified as suggested by Mitchell (1990): C + O2 CO2 + heat [65°- 94°C] (1) CO2 + C 2CO + heat [100°- 150°C] (2) Stoichiometric reactions (1) and (2) show that 2.66 grams of oxygen are required to oxidize 1.0 gram of carbon. Once the temperature exceeds 100°C, the reaction has little chance to stop. The crucial step in reducing spontaneous combustion risk is locating the ignition point of spontaneous combustion (hot spot). This information is useful in the effort of developing a preventive method effectively. In this study, this was conducted based on the best gathered information: ventilation surveys conducted in an existing longwall mine located in the western US; the laboratory experiments performed on a physical gob model; and the CFD models to investigate the flow behavior in the gob, the oxidation of coal, and heat transfer phenomena. The hot spot location is determined as a function of oxygen concentration and gob temperature. The critical values are the following: 5% (by volume) for oxygen and 100°C for gob temperature. CHARACTERISTICS OF GOB MATERIAL AND MODELS Permeability Concept Permeability is one of the key parameters in any study dealing with porous medium. This is determined by particle size and the ratio of void volume to the total volume (porosity) of porous medium. This relationship is known as the Carman-Kozeny equation (Scheidegger, 1957) and is given mathematically as [ ] where k* = theoretical specific permeability, m2 dm = the mean particle size, m n = porosity However, permeability tests with various particle sizes were carried out at the University of Utah?s ventilation model (Figure 1) to verify this relationship. These tests indicated a necessity to modify this theoretical relationship. A factor of 0.898 was obtained to make up the different between theoretical permeability and the experimental one. The modified version of (3) is given by: [ ] This equation is used to determine permeability of the simulated mine gob throughout the study. [ ] Mine Gob Material The gob is represented by zones filled with material of given size distribution. For physical measurements and CFD simulations, the material used were crushed rock and coal. Due to compaction, three different characteristics of gob material were used in the model: unconsolidated, semiconsolidated, and consolidated. In the real condition, the largest coal-rock particles are more likely to be located in the area behind the shields. This material is freshly broken and unconsolidated. The size of these broken particles is based on a study carried out by analyzing images taken from the area behind the shields in three coal mines in the United States (Pappas and Mark, 1993). The results have shown that the mean size of materials behind the shields is about 1.22 m. The permeability associated with this size was then obtained from (4) and permeability tests. This was 4.68 x10-7 m2. For semiconsolidated and consolidated zones, due to the lack of experimental data, these were determined through CFD simulations. These simulations were designed by assigning a permeability of 3.15 x 10-8 m2 for consolidated zone and 7.98 x 10-9 m2 to the other zone. The airflow pattern in the gob assigned with given permeabilities was expected to follow the experimental distribution (Brunner, 1985). The mean particle sizes for the semi-consolidated and consolidated zones were 0.02 and 0.006 m, respectively; smaller than those of the unconsolidated zone. Figure 2 shows the 3D view of permeability changes in the gob.

Jan 1, 2009