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By Brian Ulrich

The majority of individuals involved in the mining industry can appreciate and under-stand that mining is an activity that is necessary to satisfy the very basic needs of society, and to assist in accommodating our ever-changing world. As the expression goes, ?if it can?t be grown, it has to be mined.? And at this point in time, society has granted the mining industry the right to go about the business of mining, with the general anticipation that the work will be carried out without causing undue harm to the environment or populations in and around the mining operation. The term ?sustainable development? is gaining momentum as a popular concept, and indeed it has become something of a catch-all phrase, but it is important that the idea behind the term is not cast aside as a nonsense buzz word, as it simply is an indication that development (e.g. mining) can be satisfactorily carried out with an eye toward stewardship of the environment and society. On Feb. 19, 2010, a round-table discussion (Roundtable 2010) on ?Strides Toward Sustainability in Mining? was hosted by Knight Piésold and Co. (Knight Piésold) at the Red Lion Inn and Casino in Elko, NV. Knight Piésold had local representatives (Bryan Ulrich and Steve Boyce), as well as representatives from other office locations (Cynthia Parnow and Rick Damiani from Denver, CO, and Rick Frechette from Tucson, AZ) to help facilitate the discussion. The meeting played host to 30 attendees from five states. Attendees included personnel from nine mining properties and various corporate offices. The majority of participants were people who are directly involved with environmental work on a day-to-day basis. Others were project managers whose jobs involve some level of environmental focus.

Jan 1, 2010

By L. A. Forsyth

"SINCE I received and accepted your invitation to present to this meeting a paper on A Canadian Integrated Coal and Steel Industry, I have given the subject a great deal of intensive study.Two conclusions have emerged from my considerations: first, that the subject should be dealt with by a person having a firm grasp of its technical aspects; and second, that it is a subject which requires expert analysis of the complicated problems it presents in pure economics.A third conclusion inevitably results from the two just mentioned -namely, that the mantle of the prophet which has been draped up-on my shoulders is too large for me to wear, because I am neither a practical nor a theoretical coal and steel man; and I am not an economist.With the warning that I have discovered, and am keenly conscious of, the inadequacy of my background for the task, I shall attempt to place before you those aspects of my subject which appear to high-light it from a layman's point of view.In the first place, in .order to avoid confusion as between my audience and myself, some definition of terms may be required.As I interpret it I am discussing -a coal and steel industry, using the last word in the generic and not the unit sense, self-sufficient in the provision of all its needs from within the geographical limits of Canada.Now, I start with the proposition that, in the very broadest aspects of such a concept, the Corporation of which I happen to be the executive head meets my definition as a combination of operations resulting in one fully integrated unit of a coal and steel industry."

Jan 1, 1952

By V. Sheikhzadeh, M. Saghaeian, R. Hejazi, A. Abazarpoor

The research aimed to compare the chemical analysis (K, Na, Cl) of Iranian concentrate plants, which are the main source of materials corrosion in the pelletizing plants. Cl alongside alkaline elements (especially K) may cause corrosion and plug in the grate plates and other involved equipment. Therefore, it is tried in the processing plants to remove impurities from the concentrate to prevent potential problems in pelletizing and iron/steel making processes. Part of these impurities are existed in the nature of ores and others are sourced in the processing water. Various samples from the largest Iranian concentrate plants including Chadormalu, Gol-e-Gohar, Jalal-Abad and Sechahun were prepared to investigate the possibility of alkaline problems for each samples. The amount of Cl, K and Na of Chadormalu sample was obviously low and therefore no alkaline problem is expected. The Cl content of Gol-e-Gohar sample was high (980 ppm) while amount of K was less (0.008 Wt. %). Due to low content of K, most of Cl will release as Cl2 or HCl and so problems caused by KCl plugging would not be a problem. The amount of Cl in Sechahun case was nearly same as Jalal-Abad (400-600 ppm), higher than Chadormalu and less than Gol-e-Gohar samples. However, the K content was higher than all samples (0.04 Wt. %). Therefore, the amount of evaporated K would be 2-4 times more than other samples. Since the amount of Cl and K is simultaneously higher than usual iron ores, therefore alkaline problems may be a serious prevention factor for the continuous operation of this plant. In order to solve this problem some counter-measures is suggested and discussed including cleaning system, partial dust enriched with KCl removal and variation in the materials type of involved equipment.

Jan 1, 2018

By S. H. Ash

[On December 2, 1932, the Governor of California called upon the representatives of the mining industry of the State to attend a meeting at Sacramento to discuss ways and means of assisting is relieving some of its perplexing and extremely distressing problems, particularly the mounting cost of accidents which faces the industry with an industrial insurance rate for classification of $11.85 per $100 of pay roll, effective January 1, 1033. The significance of this fact is at once apparent when it is realized that the classification rates per $100 of pay roll for mining have steadily increased for some time, as follows: $3.91 in 1924, $5.54 in 1925 and 1926, $8.04 in 1927, $8.53 in 1928, $9.05 in 1929, $9.42 in 1930, $10.54 in 1931, $10.99 in 1952, and $11.85 in 1133. In other words, the cost rates have acre than doubled, wile statistics indicate that the accident rates nave shown an entirely different trend. At the meeting mentioned, one of the management officials sounded an effective keynote when he declared that a spade should be called: a spade. The perplexing problems of any industry can be approached best and remedies applied if that policy is kept to the front. It is appropriate to mention that high accident rates and a decrease in wages in recent years have unquestionably accounted in part for a unit cost rate, on a pay-roll basis; it also is well to explain that the policy years3 1926 to 1930, inclusive, are the years on which the accident-cost experience for 193: is based. That accident rates :lave not undergone the expected beneficial chance in California's experience is apparent in the words of a Bureau of Mines report:4]

Jan 1, 1933

By M. S. Davis

The Tek Process can produce masonry products such as bricks, roof or wall tiles, and block from virtually any inorganic waste. In the process the aggregate raw materials, portland cement, water and common chemicals are first mixed together; then mechanically subjected to several thousand pound pressure per square inch. This causes a novel chemical reaction between the cement, chemicals and water; producing the "patented" Tek adhesive binder which holds the aggregate together in a stone-like mix. Simultaneously, the desired product shape is formed. The building modules can have strengths of 8000 p.s.i. (pounds per square inch) with completely sound aggregates utilizing air curing for a period of 28 days. With most aggregates, 3000 p.s.i. is achieved within 24 hours. Eventual strengths usually exceed 5000 p.s.i. with almost any raw material. Water absorption ranges from 5-7.5 percent. Both absorption and strength figures are superior to the most rigid of any and all A.S.T.M. specifications for the highest quality bricks. In most locations, the product (when brick shaped is called Tekbrik) can be produced significantly more economically than can comparable grades of clay or other bricks, be- cause almost any inorganic waste materials or pollutant can be used as a raw material. The process results in a lower manufacturing cost as compared to clay bricks; fuel cost to operate a clay kiln represents a substantial portion of the total cost. Capital expenditure for a Tek plant also is lower due to the large investment in clay kilns. Transportation savings also are important, clay brick factories must be very large because the kilns are uneconomical unless they are large. Most bricks are manufactured at the sites of clay deposits in relatively uninhabited areas. The cost of transportation to the job site represents a considerable percentage of the selling price.

Jan 1, 1974

By T. C. Vogt

Earlier we described the uranium mineralogy of an areally broad sampling of Crownpoint ore, including the characterization of organic carbonaceous material associated with the uranium mineral. (1) We also reported on the leaching behavior of Crownpoint ores with a mild alkaline leaching system, oxygen (02)-sodium bicarbonate (NaHC03). (2) There was a wide range of leaching responses, with samples from some areas leaching at a slow rate with low uranium recovery. Evidence indicates that in these samples the organic material is intimately associated with the uranium mineral and shields it to some extent from contact by the leachate. (1,2) One method to obtain faster leach rates and higher recoveries is to use a chemically severe leaching system such as sodium hypochlorite (NaOCI) as an oxidant. (3) The use of sulfuric acid (H2SO4) and an oxidant for leaching ore in surface milling operations is widely practiced to effect high recovery of uranium (U308) from the ore. (4,5,6) The U308 is mobilized as the disulfate complex, U02(S04)224-, or possibly, the trisulfate complex, U02(S04)34-, is the soluble species. (7) Sulfuric acid leachate formulations were used in the first in-situ leaching operation in the Shirley Basin in Wyoming. (8) More recently H2S04 formulations have been used in the Rocky Mountain Energy field tests in the Powder River Basin (Bear Creek) and in the Teapot forma¬tion at Nine Mile Lake site near Casper. (9,10) Laboratory studies related to the use of H2SO4 for in-situ leaching have been reported (11-17) and Yan has .reported packed column leach studies on Crownpoint ore using H2504 and oxidant. (18)

Jan 1, 1981

By Steve Kral

In recent years, junior mining companies, mostly listed in Canada, have taken a beating in the finance markets. Simply put, potential investors have been leery of sinking millions into exploration and mining projects due to volatile commodities prices and an uncertain regulatory climate in developed and developing countries. The 2014 edition of the Prospectors and Developers Association of Canada (PDAC), however, seemed to be a bit different for some juniors. Equity valuations have improved and metals prices appear to be stabilizing. So, for some of the stronger junior companies, there is some hope. Merger and acquisition (M&A) activity is picking up and, believe it or not, companies are raising some capital. Billed as the largest annual mining meeting in North America, the PDAC conference attracted more than 25,000 mining and exploration professionals from around the world. Organizers were anticipating attendance to break the 30,000 mark. But, given the state of the exploration end of the mining business, 25,000 is still a respectable number. Junior companies that are in the project feasibility stage, or have made promising discoveries that stand a good chance of proceeding to production, are being looked at by potential investors. Those are the survivors of the last three years of dismal M&A activity. On the other side are the juniors that are still around ? and there are plenty of juniors that were at the PDAC last year but have since disappeared ? but have little or no working capital. One analyst calculated that there are about 850 companies with less than $200,000 in working capital and about 600 with negative working capital. This will likely result in fewer junior mining and exploration companies as the year progresses but the ones that remain should be stronger.

By S. A. Willis

For the past several months 1 have been considering the functions of this Society and its reasons for continuance. The fact that it is now sixty years old indicates that it must have been of value and we all know that it has contributed much that was worthwhile to Nova Scotia and the Maritime Provinces. The question arises: "What is the future of the Society, and how might its activities be altered to suit present-day activities and to be of even greater value?" Let us analyse the various activities in which we are interested and determine which, if any, are of more value than others. First of all, at least once a year we have a two-day convention which constitutes a holiday for the members and their wives. This has always been well planned and has been much enjoyed. Second, there are many social and business contacts made during the meetings and interim meetings. These certainly tend toward better relations and co-operation between the various people concerned. Mine operators meet other mine operators, engineers, people from the education fields, Department of Mines, and so forth. Various sales contacts are made at these meetings which can be of value and use to both the Company selling and the customer. Third, and of greatest importance in any conference, is the exchange of ideas by the members and by authorities from outside, and the presentation of slides and drawings, or actual visits to operations. It is upon this phase that 1 wish to elaborate. These papers are not only presented to our meetings but are generally published in the C.I.M. Bulletin so that members throughout the Dominion have access to them. Many important papers describing new phases of operations have originated through our Society.

Jan 1, 1947

By D. W. Scott

Ontario has a diverse industrial mineral resource base including abundant resources of structural industrial minerals such as sand and gravel, crushed stone, building stone, clay, shale, limestone and dolostone. These resources are used in the production of aggregates, brick, metallurgical stone, fillers, lime, cement and other construction materials. The majority of the operations are in deposits of Paleozoic and Quaternary age in southern Ontario, close to the major markets. Province-wide, there were over 140 million metric tonnes of aggregates produced in 1985, approximately 115 million tonnes of which was produced in southern Ontario with the remainder being largely from Crown land in northern Ontario. The structural industrial minerals account for over 80% of the value of total industrial mineral production, with the remaining 20% of the value king accounted for by the non-structural minerals being led by salt which is produced in southwestern Ontario. A host of other non-structural industrial minerals are known but production is currently restricted to calcite, gypsum, quartz, talc, nepheline syenite and by-product metallurgical sulphur products (Fig. 1). Location and Market Area Major production is in the area closest to the large markets of urbanized southern Ontario and the northeastern and north-central United States. In general, with the abundant variety and widespread resources of industrial minerals and the large population within 400 miles of most deposits, the market offers great potential. Ontario's 9 million population accounts for about 35% of the entire gross domestic product of Canada of $476.361 billion dollars in 1985. This equates to about 113 of the nation's buying power being within a 200 km (125 miles) radius of Toronto. This major concentration of industrial and economic activity has resulted in a well developed industrial minerals industry fulfilling most of the structural industrial minerals demand in Ontario, as well as a subsidiary demand in neighbouring provinces and states.

Jan 1, 1987

By James J. Scott

Dynamic rock anchors are interior fixtures developed by the author which promise to be a revolutionary development in the field of ground control. The fixtures are designed to be placed in the ground with modern roof bolting equipment, such as the type used in the American coal mining industry. They are composed of a plastic form- able anchor tube which serves to fasten a buttress deformed rod which is thrust and turned into the plastic and in turn clamps the roof plate to the rock surface. Plastic tubes 10 to 16 inches in length provide sufficient anchorage to exceed the yield strength of steel rods 5/8, 3/4 or' 7/8 inches in diameter. This paper presents field testing and early work done on the device over the last seven years. Results of pull tests, creep tests, laboratory testing in concrete, and field testing under natural rock conditions demonstrate the uniqueness and effectiveness of this new support system. A second development which uses the dynamic rock anchor in conjunction with a resin cartridge to provide a stiffer anchorage system is also discussed. These products will be manufactured and marketed by Ingerso-11-Rand Co. under the trademark of DYNA-ROK and DYNA-ROK PLUS anchors.

Jan 1, 1989

By Allan M. Hale

Taconite tailings reclamation, especially the stabilization of tailings ponds, .dams, and slopes, can be effectively accomplished through the use of appropriate vegetation. Utilizing vegetation provides both aesthetic and ecological enhancement of a site while at the same time protecting tailings structures against wind and water erosion. Generally, the methods and techniques for establishing vegetation are well known; however, there are many site-specific factors that can alter a particular reclamation approach. Those factors include slope gradient, tailings material size, solar exposure, and physical and chemical properties of tailings. In addition to the site-specific factors, variations in climate, geography, and physiography of a region can have a pervasive influence on the success or failure of a revegetation program. Both the site-specific and regional factors control reclamation planning in such areas as plant variety selection, methods and times of plants establishment, maintenance techniques, and subsequent monitoring methods. As a result of this multifactor relationship, it is important to establish a data base that identifies both the site-specific and location conditions in order to tailor the reclamation plan to the specific area. When an appropriate data base has been collected, detailing the various site-specific and regional factors that will influence a revegetation program (in the absence of previous testing), it is very beneficial to apply experimental techniques to develop the reclamation plan for a specific site. The reclamation plan for a specific site may include several techniques adapted for the differences found within the specific site as the result of topographic or other influences. Considering this, the Reserve Mining Company and Dames & Moore undertook to develop a successful reclamation plan based on a detailed test plot program conducted at the Mile Post 7 location.

Jan 1, 1980

By Brett P. Spigarelli

"To meet the growing need for CO2 capture and storage technology, Michigan Technological University is studying CO2 capture using alkali-based solvents. The objective of the present study was to find a way to increase the absorption rate of CO2 into an alkali solution without reducing the absorption capacity of the solution. One approach to increasing absorption rate is to use a surfactant to chemically alter the gas bubble size. The surfactant chosen for the study was a neutral-charge polypropylene glycol methyl ether (PPGME) with a molecular weight of 200. Experiments were conducted to study the absorption rate of CO2 at varying surfactant concentrations. Results showed that as the concentration of PPGME increased in solution, the absorption rate also increased. The CO2 absorption rate increased from 3.45 x 10-3 mol/min CO2 at 0g/L PPGME to 3.92 x 10-3 mol/min CO2 at 0.48 g/L PPGME. This amounted to a 14% increase in the CO2 absorption rate with no decrease in the absorption capacity of the solution. IntroductionChemical absorption using an amine solvent is currently the most mature carbon capture and storage technology available. Amines are advantageous in that they have a fast CO2 absorption rate, which leads to a high CO2 removal efficiency. However, amine absorption has some considerable drawbacks, such as high energy requirements, high equipment corrosion rates, amine degradation in the presence of oxygen, high waste generation and a large increase in plant footprint if new equipment is constructed (Herzog and Golomb, 2004; D’Alessandro et al., 2010). Due to these drawbacks, Michigan Technological University (MTU) is studying CO2 absorption using alkali-based solvents, which address the above disadvantages of amine solvents."

Jan 1, 2015

By Bronson Stringham

The close area! relationship of Cretaceous or later intrusive porphyries to larger hydrothermal deposits of Pb, Zn, Au, fig, Cu, Mo, Hg,, and U of similar age in the Basin Range Province, was statistically shown in a recent paper (Stringham1) During the past year this study has been expanded to cover p11 of the larger hydrothermal deposits of similar nature occurring in the entire western United States. The sandstone type uranium deposits of the Colorado Plateau and Wyoming have been excluded since considerable controversy exists regarding their origin. The close relationship between intrusives in general and hydrothermal ore deposits has long been-recognized, but the association involving intrusive porphyry only, was suggested in 1954 when Sales concluded that the formation of porphyry may be an intermediate stage of activity between the development of granitoid rock and certain types of copper deposits. However: he applied this concept to only a few copper deposits. The relationship appears to be true also for a great majority of the hydrothermal deposits of the other metals mentioned above of Cretaceous and later age, at least in the western United States. This situation then leads to the conclusion then when exploring for similar types of hydrothermal deposits of the metals considered one may feel reasonably sure that if an intrusive porphyry of considerable size is. not present he may be facing much greater risk of finding an ore body than if a prophyry were presents Since, there are many intrusive porphyritic rocks which do not seem to be associated with hydrothermal deposit, it is believed that some distinct value can come from the recognition of intrusive porphyry which might be barren as well as the intrusive prophyry which might be productive This paper deals with that problem.

Jan 1, 1960

By G. R. Hopkins

The average quantity of heat needed to refine a barrel of crude oil in 1934 was 638,000 B.t.u., or about as much heat energy as contained in 5 gallons of fuel.oil. Although the total heat utilized in 1934 was slightly above 1933, crude runs to stills increased 4 percent, hence the average requirement per barrel declined from 660,000 B.t.u. in 1933 to 638,000 B.t.u. in 1934 (see fig. 1). The average for 1934 constitutes a new record for firing efficiency, being just under the previous low of 1929. Heat consumption at refineries depends on many factors, of which the trends in yields of gasoline and lubricating oils are probably most important. The yield of gasoline is indicative of activity at cracking plants, which typo of plant utilizes more thou the average amount of heat per gallon of product. The yield of lubricating oils is indicative of the extent to which crude oil is refined; that is, it takes considerably more heat to refine a barrel of crude through lubricating oils than it does to separate only gasoline and kerosene. The yield of gasoline decreased from 43.7 percent in 1933 to 43.4 percent in 1934; on the other hand, the yield of gas oil and fuel oil increased. Although the yield of lubricating oils increased slightly in 1934 the theoretical increase in fuel requirements probably was offset by technical improvements, such as solvent refining. Although no outstanding technical developments of a fuel-saving nature were made in 1934, some progress undoubtedly was recorded. Heat exchangers, an effective fuel-saving device, wore enlarged, and some refiners now take off several cuts before the crude reaches the pipe stills. The total capacity of pipe stills increased 2.5 percent in 1934, and many of the less efficient shell stills were torn out.

Jan 1, 1935

By Dave Minney

The South African mines health and safety regulations require that mine management establish a quality management system for rock support material. Quality control of resin capsules used as a support medium in South Africa is specified under SA National Standards No 1534. Experience has shown that this specification, while addressing the chemical and physical aspects of the products, but does not address the required performance criteria. In order to address this shortcoming, the industry has put a lot of emphasis on short encapsulation pull tests, performed insitu, in the underground workings of the mine. This is also fraught with many shortcomings, particularly as regards site availability, cost and repeatability of results. To try and address these issues, the Department of Mechanical and Aeronautical Engineering at Pretoria University were approached to develop equipment and machinery that could produce reliable, repeatable results in a laboratory environment which reasonably simulates installation practice underground. The test method is based on the ASTM F432-95 Strength Index test, but modified to use push test rather than pull tests. The paper describes development of the test method and the preliminary results and findings of the work.

Jan 1, 2007

By Oliver Bowles

"Waste Granite in the Barre, Vermont, District: Waste in the great granite center at Barre, Vermont, consists of three types of material, the rough blocks rejected at the quarries on account of imperfections, the chips or spalls resulting from trimming and dressing at the cutting plants, and the granular and pulverized material from the dust collectors. The waste piles at the quarries of are immense proportions and constitute a serious handicap to quarrying in that they cover up good rock deposits, and are also so large that waste disposal becomes more and more expensive. The problem of utilization of such waste material is a topic of keen interest to all granite producers.Barre is not situated on a water route, and thus transportation costs prohibit the shipment of waste blocks for rip rap or ballast. Crushing plants use a small amount of this material for road construction, but aside from this, the waste is practically valueless.Investigators of waste utilization problems are awaiting with interest further information concerning an enterprise undertaken at Montpelier, Vermont, to utilize crushed granite for the production of brick similar to sand-lime brick. Granules of granite are mixed with lime, moulded, and hardened under steam Pressure, The brick produced are said to be of excellent quality for structural Purposes.There seems to be no logical reason why waste granite could not be utilized for the manufacture of building stone, and paving blocks, for many of the defects which condemn a stone for monumental purposes are not at all detrimental for building or street paving. F or the most part, monumental stone workers are not particularly interested in other branches of the granite in-dustry, and a combination of industries such as that suggested"

Jan 1, 1920

By A. B. Hooker, L. C. IlsLey

In lare-scal e blasting, it is customary to fire me.l'\Y shot.!:l simu1. taneously. The electric !atonators ara usually conneced in seies, ard are fired either from a power circuit or :from a blasting ma.chine with large capacity, operated by hand. "!hen :'::ri111; with a blasting ca.chine, trouble with missed shots has been freqi.,.ently e>:pert0nced.. Unit1:i:' thes ,:::rcu:ns tances, the shots that fail to fire are often a gr"up in the t.:E"nter r,f t>e series, Various explaz,.a.tions hs.ve been given as to the cause of the failurs. Tis paper covers a few tests made cy the electrical section of tl:.e Dti..'t'cau. cf Mines, wh;.r.;h may be helpful in understanding the -probable cuse of tl1e misfiring of c.:anter shots, Wh3tever th9 source ot the firir. current generator, magneto, or batter, the CUl"rent delivered th:·01.1.gh a shot-f:?·ing circu.it is determined by t.ae total resistance of ,;he clrcili +.; c:1nd all cure:it leaving th9 p,si tive terminal must return to tre negative te1-minal. If a. metallic circuit is well i1,.sul.:tted, praeti­ccl. l;1 a.ll of the t.'Urrent keepo within the circu.it; but in a. shot-!11·.irig ci.rc1li t, Nhere the ·.vires f:ll·e often 1n c.c,i.cact with the eru:"!ih as i11 wet holer., end whero the ins".lla.tion of the leg wires :i. inadecpa.te to prc·,ent lea.l.tage, the current ma.v tu.e v a.r ious pa the: thro-.. .. gh the nr r. earth.

Aug 1, 1922

By Harry Elkin

Control of coal dust has long been an important aspect in the conventional mining of coal; the main reasons being from a health and disaster standpoint. With the advent, of mechanized longwall mining, the control of dust has required more attention due to the high extraction rate common to most longwall systems. The purpose of this paper will be to describe the dust abatement activities of the longwall operation at Sunnyside. Kaiser-Steel Corporation has three mires located at Sunnyside, Utah, with a total production averaging 6,800 tons of clean coal per day. Of this 6,800 tons, 71 % is mined with continuous miners, the remaining 29% coming from one longwall unit located in No. 3 Mine. Our first longwall panel was started in November, 1961. In October, 1966, we started mining our seventh panel. The present panel is located in the Upper Sunnyside Seam which averages five feet in thickness, but does get as low as 51 inches. The seam pitches 5.5% in this vicinity. The roof is generally good and is comprised of 10 inches of shale cap rocs overlain with sandy shale and sandstone. The floor is sandy shale and is quite undulating in nature. The present panel is 3,800 feet in length with a face of 670 feet. The major equipment employed on our longwall unit is a 125 H.F. Anderton Shearer-Loader, British Jeffrey Diamond armored conveyors and a Dowty self-advancing-roof support system. The Anderton Shearer in use on our longwall unit has a 60" diameter x 27" cutting drum. During the shearing cycle, it traverses the face at 20 feet per minute with a cutting rate of 7.5 tons/minute.

Jan 1, 1967

By S. Badr, R. Mendoza, M. U. Ozbay, M. D. G. Salamon

ABSTRACT: The use of coal pillars at depth is fraught with problems due roof control difficulties and the possible occurrence of coal or pillar bumps. In the USA the largest and most important application of pillars at depth is in longwalling, where chain pillars are the customary supports of the multiple entry developments. At first, the chain pillars were designed using conventional approaches, where the principle is that the strength of the pillar should exceed the load imposed on it. Such approach to design led to larger and larger pillars at great depths, but instead of eliminating, it tended to aggravate the roof control problems. Eventually the idea was born that small sized yielding pillars, which have proved to be successful elsewhere, might provide the answer to this pressing problem as well. The aim of this paper is to study the modes of pillar failure at great depths, using two solution methods. The first of these comprises some elementary solutions obtained with the aid of a simplified conceptualization of the rock mass. This model consists of a strain-softening coal seam sandwiched between two stratified masses. The second approach utilizes FLAC3D, which is a commercially available three-dimensional numerical modeling software package. To gain a better insight, both the strain-softening and ideally plastic Mohr-Coulomb constitutive laws embodied in FLAC3D were exploited. As expected, the width to height ratio of the pillar has proved to be the primary factor that determined the behavior of the pillars. Narrow pillars fail in a stable manner without the occurrence of instabilities. Intermediate w/h ratio pillars under the appropriate loading conditions, may fail suddenly and may even collapse totally. Squat pillars do show the potential for sudden, coal bump like side failure, but because the remaining large width of the inner core, the ruble around the pillar provides sufficient confinement so as to reestablish stability. Finally, the study revealed that the traditional Mohr-Coulomb law does not provide a useful insight into the failure of coal pillars. RESUME: L’utilisation des piliers de charbon dans les mines souterraines de grande profondeur occasionne des problèmes due aux difficultés de control de plafond et possibles fracture ou explosions au niveau des piliers. Aux Etats-Unies d’Amérique, l’utilisation des piliers dans les mines souterraines de charbon comme moyen de support est considèrees comme étant la plus grande et la plus importantes des méthodes utilisée dans le ‘’ longwalling method’’ ou une série des piliers sont disposé de manière à supporter les multiple entrées d’exploitation de charbon. En premier lieu, cette série des piliers étaient construit de manière conventionnelle avec un principe basé sur le fait que le poids exerce sur les piliers doit être inférieur a la force que ces piliers exerce sur le plafond. Ce principe a conduit a ce que le volume des piliers augmente au fur et à mesure que la profondeur au de la mine augmente. Malheureusement, au lieu de résoudre le problème de support, ce principe n’a fait qu’aggraver le problème de contrôle de plafond. Eventuellement une idée s’est dégagé allant du fait que les piliers endommagés de taille moyenne qui se sont avérés être efficaces ailleurs, pourraient fournir un indice à ce particulier problème. Le but de cette recherche est celui d’étudier les différent types de ruptures qu’un pilier peut occasionner lorsqu’il est utilisé a grande profondeur, tout en utilisant deux possible méthodes. La première d’entre elle comprend quelques solutions élémentaires obtenues avec l’aide d’une méthode simplifié et conceptuelle de la masse de la roche. Ce modèle consiste à prendre en sandwich la bande de minerais de charbon entre deux masses stratigraphiques sans pour autant endommager le plafond. La seconde méthode nécessite l’utilisation du ‘’ FLAC3D’’, qui est un logiciel commercialisé disposant d’un modèle numérique en 3 dimensions. Dans le but d’obtenir

Jan 1, 2003

By A. T. Coumbe

The first survey 3/ covering sales of liquefied petroleum gases was made in 1930 by the Bureau of Mines, which at the time was under the United States Department of Commerce. This original canvass covered national totals for 1922 through 1929, and most of the supply came from natural gasoline plants. The 1930 report showed approximate totals for butane and propane and for butane-propane mixtures and pentane grouped together. No attempt was made to breakdown the national sales by various uses until 1931, when the quantities for domestic or household consumption, gas manufacturing, and industrial requirements, including miscellaneous uses were indicated. As the market for these liquid petroleum gases expanded and as new uses came into importance, their respective quantities were shown separately in the annual survey. Sales for internal-combustion engine fuel and for raw material for chemical plants were first taken out of the industrial total in 1936. During World War II liquefied petroleum gases became important as feed stock diverted to synthetic rubber plants, and consequently the survey was broadened to cover this particular demand, beginning in 1944. Pentane was dropped from the survey after 1943, as, being liquid at atmospheric pressure, it is not considered as one of the liquefied petroleum gases and furthermore, the quantity reported made up less than 1 percent of the total sales. Thirteen producing companies reported to the Bureau in the first survey made in 1930, and in the 1952 canvass about 130 producers--petroleum refiners and natural gasoline companies--and about 1,300 dealers cooperated by filing schedules showing a breakdown of their sales. Their 1952 deliveries of approximately 4.5 billion gallons of liquefied petroleum gases were equivalent to about 3.4 billion gallons of gasoline or 3.1 billion gallons of distillate fuel oil.

Jan 1, 1954