Search Documents

By Donald E. Ralston, V. Rajaram, Michael N. Greeley, John W. Peters, Terry J. Laverty, F. S. Kendorski, Peter G. Chamberlain, J. Brent Hiskey, William C. Larson

Preliminary figures from the US Mine Safety and Health Administration show 801 underground metal mines and 490 surface metal mines, at the end of 1981, up from 663 and 383, respectively, in 1980. Preliminary MASH figures also show 207 underground nonmetal mines and 1070 surface nonmetal mines at the end of 1981, compared with 167 and 1092, respectively, last year. In addition, preliminary MASH figures show there were 14,676 mineral extraction operations on the surface and 3845 underground at the end of 1981, versus 14,951 and 3675, respectively, for last year. The number of mines, then, in three of four categories increased significantly, while having a lower net total of just 2% in the other category. And the number of underground extraction operations increased nearly 5% for the year, while surface operations were down less than 2%. But despite operations totals that mostly held their own or showed significant increases, it was a tough year for the nation's mining industry. The nonferrous segment of the industry had a bad year and 1982 may be no better, according to Business Week (Jan. 11, 1982), which adds that a turnaround is impossible unless the general economy recovers. Even then, with diminishing markets and overcapacity plaguing its products, the mining industry's condition "will be far from robust," the magazine says. The basic problem is that nonferrous metals-aluminum, copper, lead, molybdenum, nickel, and zinc-are tied to the most troubled sectors of the US economy. As recently as 1979, for example, more than 40% of all aluminum shipments went to the construction and transportation industries. Last year, these markets were down to 35% of aluminum shipments. And molybdenum sales to steel producers dropped by nearly 15% last year. Moreover, nonferrous products ended 1981 at disastrously low prices. Molybdenum oxide sold at $8.77/kg ($3.98/lb), half its $17.63/kg ($8/lb) price earlier in 1981 and aluminum was listed at $1.08/kg ($0.49/lb), compared with $1.54/kg ($0.70/lb) a year earlier. The Comex price of copper was $1.54/ kg ($0.70/lb), down from $3.11/kg ($1.41/lb) in early 1980, in real terms the worst copper price in 30 years. Lower prices led operators to cut their output and increase layoffs, shut down mines, and defer capital spending projects. In December, Duval Corp., a Pennzoil Co. subsidiary, shut all four of its US copper mines until March. Aluminum Co. of America had laid off 7.3% of its work force, shut nine of its 38 smelting lines, and entered 1982 operating at only 68% of capacity. Inco Ltd., the Free World's largest nickel producer, lost money in 1981, an estimated $11 million, for the first time since 1932. And, like Falconbridge Nickel Mines and other major nickel producers, had cut back on nickel production and was operating at only 63% of capacity (Forbes, Feb. 15, 1982). Amax, the country's largest molybdenum producer, had cut production by 20%. And Hanna Mining Co. sold lead for $5.07/kg ($2.30/lb), about $1.54/kg ($0.70/lb) below what it cost to produce. Another problem is that copper companies in the next few years must come to terms with problems of aging smelters. Some companies are simply closing them. In 1980, Anaconda closed its 75-year-old Butte, MT, smelter and is shipping concentrates to Japan, rather than modifying the smelter to meet environmental requirements. And oth Phelps Dodge Corp. and Asarco Inc. have antiquated smelters on which they will have to make decisions. The most troubled metal in 1982, Business Week said, will be molybdenum, with no real recovery in sight until the mid-1980s. High molybdenum prices in the late 1970s, caused in part by shortages, triggered overexpansion that will take years for the US market to soak up. On a more upbeat note, 1981 mergers might help stabilize the industry by providing funds for mining companies. Standard Oil Co. (Ohio) said it plans to spend $7 billion on Kennecott during the next 10 years for modernization and expansion. And Atlantic Richfield Co. said it will spend $500 million on Anaconda Copper Co. during the next five years. Another positive note was sounded by T. H. Adams of the United Banks of Colorado Inc. He said he expects the mining industry to experience moderate growth in 1982, led by "interest rate sensitive" demand from energy, electronics, and defense markets. And mining will be helped by "weak, but improved" construction and auto markets. The mining industry will be operating in an economy stronger than 1981, but still relatively sluggish by postwar standards, Adams predicted. Iron Ore Estimated US iron ore production in 1981 was 75.2 Mt (74 million long tons), up 6% from 70.7 Mt (69.6 million long tons) in 1980, though down from the 87.1 Mt (85.7 million long tons) produced in 1979. The mine value of usable iron produced from domestic mines was estimated at $3 billion. US iron ore was produced by 28 companies operating 35 mines, 26 concentration plants, and 16 pelletizing plants. The mines included 34 open pits and one underground mine. Byproduct ore recovered from copper- and titanium-mining operations accounted for less than 1% of total iron ore production. Fifteen mines operated by nine companies accounted for 94% of total

Jan 5, 1982

By Joel L. Morrison

The preparation of coal-water slurry fuel (CWSF) has the potential to be a commercially viable technology for the coal industry. The technology base required to prepare stable CWSF using grinding circuits has been developed over the past decade and is now being applied to the preparation of CWSF from wet coal fines which are generated during coal beneficiation. When preparing CWSF, the optimum CWSF formulation must be determined to ensure that the fuel will be stable while having acceptable atomization and combustion properties, and the production run must be monitored closely to ensure that the CWSF quality is maintained. This paper describes the CWSF formulation process, CWSF preparation circuits, and some of typical problems encountered in, and solutions to, the transportation and storage of CWSF.

Jan 1, 1993

By Yoginder P. Chugh

Most mines are large producing 0-25 mmt annually. The coal is mine.) at depths ranging from .0-150 m 120-500 ft mining at 300 m .(,1000 ft) depth is anticipated in the future. Single and multiple seams ranging from 3-12 m 10-40 ft) in thickness are mined. Most overburden is unconsolidated and consists of sands, and sandy or silty clays. The stripping ratio (volume of overburden to volume of coal mined) varies from 3-L. The overburden and coal is mined in benches 8-12 m -(24-40ft) high; the high-wall angle is about 45 degrees. Bucket wheel and bucket chain excavators are commonly utilized for overburden and coal removal, Some of the large overburden stripping machines nave capacities. Ranging from 4400-10,000 bank cu ( 6000-14,000 BC) per hour. The overburden from the upper benches is transported around the pit using the trains and belt conveyors. It is deposited in the spoils using large stacker-conveyor systems capable of handling 2550-7300 cu m/hour (7500-10,000 cu yds/hour). The overburden from the bottom two or three benches is transported across the pit using the conveyor bridges which are computer controlled. Conveyor bridges capable of handling overburden up to 60 m (200 ft) high are currently in use; a 60 a (20e ft) high conveyor bridge has a capacity of 85 x 10 cu ( 118 x 10 cu yd) annually. The coal is loaded in the trains directly and shipped to power plants or coke oven plants.

Jan 1, 1980

By Isa Nozari, Asghar Azizi

The extraction of copper from sulfate leaching liquor was investigated using Acorga M5640 commercial extractant in kerosene diluent. The effects of important factors such as the extractant concentration, contact time, liquor pH, and temperature were examined on the separation factor Cu/Fe and the extraction efficiency of copper. The results indicated that nearly 92.32% copper was extracted from the leach liquor at 10% (v/v) Acorga M5640 concentration, 1:1 aqueous/organic phase ratio, 20 min contact time, pH 2.5, and 25 °C temperature. Also, the further increase in the values determined had no positive impact on the extraction of copper. Under these conditions, the separation factor Cu/Fe was obtained about 29.64. The extraction mechanism was studied applying the plot of log(D) – 2 pH against log [extractant] and it proved the association of two moles of Acorga M5640 for the extraction of one mole of copper. McCabe–Thiele diagram was constructed and a single-step extraction process was found to obtain themaximumextraction. Additionally, thermodynamic datawere investigated and the extraction process was endothermic and non-spontaneous at 298 K (ΔH = 27.05 and ΔG = 15.52 kJ mol−1). Moreover, the loaded organic phase was stripped and 80.94% copper was recovered after 20 min using 10% sulfuric acid concentration.

Jul 31, 2020

By E. J. Onuscheck

With passage of the Federal coal' Mine Health and Safety Act of 1969, many challenges have been directed to the industry's mining and safety engineers. The most critical challenge is that of ventilation. The language concerning ventilation in many sections of the Act could very well deprive or limit the mining engineer in planning the ventilation for new mines, since the Act requires federal approval of all ventilation plans. Dependent upon approval and of course application of the law, this could, due to economics, prohibit the opening of new mines in some cases. Petitions for modification of some mandatory standards relating to ventilation have already been filed under Section 301(c). It is quite possible that many of these standards may be modified.

Jan 1, 1970

By K. Awuah-Offei

The objective of asphalt mix design is to produce a mix with optimal performance using available aggregate stockpiles. Often, this process does not take into consideration aggregate plant stockpile inventories or the cost of aggregate in the mix. This is due to the lack of tools that enable the lab technician or the engineer to optimize the mix for good performance while reducing the cost of aggregate and managing the stockpile inventory levels. The Bailey method provides useful guidance on aggregate gradation selection for optimal performance. This work presents a linear programming model of the asphalt mix design problem. The algorithm is implemented in MATLAB as an Asphalt Mix Design Optimization (AMIDO) program. The program is successfully validated with real-life data. The results show that AMIDO can be used to successfully produce any mix design with known Bailey method ratios. Also, RAP can be included in a design easily by making use of the Bailey method ratios and AMIDO. This work improves the state-of-the-art in asphalt mix design for dense graded mixes and could potentially be modified for other mixes.

Jan 1, 2009

By R. C. Keaney

The metals industry is in complete chaos with mines being shut down, profits becoming non-existent, and continual losses to imports from other countries. Yet the raw material supplier to the glass industry has many opportunities to grow and to produce profits. Fortunately, the cost of most glass raw materials are low enough that competition from imports is not anywhere as critical as it is in the metal industries, such as copper, aluminum, lead, and others. But the glass raw material supplier must develop new products, both chemically and physically, to effectively compete in the future. The purpose of this paper is to point out generally where these opportunities exist and to suggest how they may be further developed. As the glass industry looks for energy saving materials, they look once again towards finer materials. A glass furnace is now approximately 40% efficient. Glass engineers are constantly striving for energy savings and it is well known that finer materials melt easier so that the manufacturer can operate his furnace either at lower temperatures for the same production or he can produce more material at the same temperature. The old 20 mesh sand specification is no longer sacred and as the mesh size for sand changes so do the specifications for all other raw materials used in the melting process. Highly instrumented glass furnaces can now measure quite accurately the energy needs to produce glass and can also measure the energy loss in each furnace. Glass technologists desire today a sand with a top size of 40 mesh while some would like to have the top at 60 mesh. This becomes more difficult to accomplish as a raw material supplier without .grinding. As you well know, grinding develops fines. Yet the same technologists will tell us that we can have nothing passing a 140 mesh screen. Therefore, we must develop processes which allows us to produce a finer screen size without increasing the amount of fines passing through the 140 mesh screen. To counteract this, different and changing industries are now demanding much finer products so possibly there will be markets for the fines which are currently separated out of the products. Methods that are practical and low cost must be found to develop different products with different screen specifications. What works for sand can be carried over to the other raw materials used in melting. Among the answers to finer products, of course, are pellets. Aglomeration or pelletizing has been looked at in the past and will be looked at in the future. Considerable work has been done in the glass container industry on this and must be carried out more extensively. By using aglomerated material or pellets, the glass producer will gain the benefits of melting fine materials without suffering from handling or dust problems. Pelletizing, particularly where using basic glass melting materials such as burned lime or sodium silicate, will not only produce a good pellets but will add desirable minerals to the glass batch.

Jan 1, 1986

By A. P. Wickland

The characteristic problems related to drilling a hole for evaluation of an orebody are generally quite similar, whether we're drilling a core hole, or a hole to obtain chip samples. The basic objective in each case is fundamentally an economic factor; to produce the maximum amount of usable information per hole at a reasonable footage price. The success of the drilled hole depends largely upon the amount of investigation and research spent on the prospective area and the ability to forecast the capable personnel needed plus the right kind of drills, ancillary equipment such as bits, muds and various additives necessary to make the drilling program successful. The driller is confronted with a wide variation of drilling problems due to the nature of subsurface conditions. Some of these problems are: overburden, which may consist of clays; sand; boulders; or glacial till. These surface conditions may exist up to 2,000 feet in depth and upon reaching bedrock, formations may consist of swelling shales, broken sandstones, and every conceivable rock-type, coupled with every known structural problem such as dips, faults, folds, etc., and to this added extras such as permafrost and/or ground water problems combine to increase the necessity why an understanding of the problems along with the proper reaction of the driller plus the formula to compensate for ground conditions is necessary to complete a drill hole. Since most geologists are familiar with diamond core drilling techniques, I would like to discuss other methods used in evaluating ore deposits.

Jan 1, 1973

By P. J. Suardini, T. E. Seppanen, M. J. Hanninen

In order to reduce the heat loading in the Tilden Mine kilns caused by burning coal, which in turn resulted in rapid and significant build-upon the kiln lining, internal carbon was added to the green ball prior to balling. Intensive laboratory testing led to three short-term full-scale plant tests that were successfully conducted. Appropriate environmental permits were obtained to allow Tilden to use internal carbon on a continuous basis. Findings concerning carbon addition rates, reductions in coal use, build-up reductions, fired pellet quality, and environmental issues will be discussed.

Jan 1, 2003

By R. H. Kuhlman

The purpose of this paper is to describe the roles of cement and concrete in construction in general and, more specifically, as construction materials of the Southeast. For purpose of this discussion, the Southeast will include the geographic area composed. of the following 13 states: Alabama, Arkansas, Florida, Georgia, Kentucky, Louisiana, Mississippi, North Carolina, South Carolina, Tennessee, Texas, Virginia and West Virginia. In one sense, cement by itself is not a construction material. It is a finely ground manufactured mineral product, usually gray in color. Cement is mixed with water and sand, gravel, crushed stone, or other aggregate to form concrete, the rock-like substance that is the most widely used construction material in the world. Because cement is seldom used by itself for construction but is usually a component of concrete, there is no such thing. as a "cement" sidewalk, a "cement" highway, or "cement" building. Neither is "portland" a brand name. It is a generic term used to describe any cement that hardens in the presence of water and is made to standard specifications .. For all practical construction purposes, therefore, all cement is "portland." The name "port-land" was selected by the English inventor of the product in 1824 because concrete made with his product resembled natural building stone quarried on Portland, an English island. Although portland cement is not the final material which finds its way into completed construction, as the principal component of the most widely used construction material in the world, the location and process of its manufacture warrant some discussion

Jan 1, 1977

By -Ing. Alexander Dohmen, -Ing. Gunter Hagen

In order to improve the thermal environment in deep coal mines, two principles can be applied: firstly, the reduction of heat flow into the air stream, and secondly, cooling of the air current. First of all one should try to minimize the heat-flow rate into the air stream underground by the mining method itself. German coal mines prefer the caving system of advance longwall mining simultaneously on several levels with ascensional ventilation. The effects of descensional ventilation and different face ventilation layouts on the thermal environment are discussed, besides the effects of pneumatic and hydraulic stowing. Application of all mentioned possibilities together instead of today's common mining method would reduce the Basis Effective Temperature considerably. In the future, hydraulic haulage of the raw coal underground substituting belt conveying may be a mean to improve the thermal environment further on. If the working depth of a coal mine exceeds about 1 000 m, cooling of the air stream under-ground will be necessary in addition to the above- mentioned measures. Generally, in German coal mines different types of indirect-contact air coolers located nearby the face are used. Besides such so-called cooling coils, large-capacity spray coolers are used because they work more efficiently if a great cooling duty is demanded. Common designs of both air cooler types and their possible utilizations are demonstrated. Deep coal mines in the Federal Republic of Germany need up to 30 MW of total cooling capacity. Mostly, the needed chilled water is cooled by large-capacity refrigeration plants placed on surface, underground or in combination of the above locations nearby the shaft. Due to the increasing underground cooling demand, the distribution of the chilled water and the control of the air coolers become more important. The conception of a control system is discussed, which is based on the control of the single air coolers. All air coolers of a mine are controlled so as to optimize the supply water-flow rate with regard to the demanded cooling duty of the coolers. On the next upper level of the control system the whole chilled water network and finally the refrigeration plant is regulated. Present research work deals with the use of ice for cooling mines. There are some unsolved problems in this new cooling concept. Some aspects of making, transporting and storing ice are described. The use of ice may probably reduce the cooling costs of German collieries, which are at present approximately 4 DM per ton of saleable coal.

Jan 1, 1989

By Joachim Klein, Frank Reimann

Nodular-graphite cast iron (GGG) is a material similar to steel, and one which exhibits excellent properties, in particular for components exposed to pressure. GGG cast iron has been used in many cases when sinking mine shafts with conventional tubbing. With linings made of cast iron tubbings (the backfill concrete is not integrated into the calculations, and merely serves as bedding) the properties of the cast iron can be made full use of, provided the tubbing is made to the appropriate cross-section. Calculations have shown that better static values can be arrived at when using cross-sections other than those of tubbings made to conventional German standard. The cross-sectional design of the new types of shaft lining made from GGG is to be developed on these lines irrespective of the cast iron structure being only stressed component or its restistance function being combined with the one of concrete. GGG 50 is used for the first time to make the reinforcing inner liner of a main shaft currently sunk in Germany. The physical properties of nodular-graphite cast iron, strength and deformability, suggest that, in the future, its application will not be restricted to shaft support but also in tunneling. New moulding techniques with better three-dimensional modelling resulted in new tubbing designs as installed e.g. for the Hannover underground at present. Shield-driven tunnels have to withstand earth and water pressure, apart from axial machine loads. In this field time is money as well. Therefore easy handling and quick installation are necessary for successful, use. Last but not least, safety is of first-order importance for work in shaft sinking and tunneling. Cast iron lining systems, accordingly, are adequate systems, in particular for excavations underneath water for transport systems and for goods and passengers.

Jan 1, 1987

By John E. Young

United States Steel Corporation's Winifrede Mine is operated by Lynch District in the mountainous region of Eastern Kentucky. This region is characterized by narrow mountain ridges and precipitous slows which present both an opportunity and challenge in the design and selection of coal handling facilities for the movement of coal from the section belts to the railroad cars. The narrow finger ridges precluded use of underground haulage and, thereby, presented the opportunity to use high capacity equipment on the outside bench. The precipitous mountain slopes, steepest at the Winifrede seam horizon, presented a challenge to select a solution for lowering the coal approximately 1000 feet from the seam level to the valley floor railroad load-out point. It was evident from the start of planning that these two factors predominated; namely, rail haulage and coal lowering, and solutions to these would determine the final design of the Winifrede Mine coal handling facilities.

Jan 1, 1970

By Edward L. Vickers

When I was originally asked to give this talk, I had certain preconceived ideas of the mining industry's reaction to Operations Research. It seemed at the time to be a rather simple task to collect these ideas for presentation here today. Jotting down these notions, I became concerned that overexposure to this activity called OR perhaps had clouded my outlook on what was actually being done on a nation-wide scale. I felt, to have a better cross section, a questionnaire of current industrial activity was in order. I solicited the response of some 75 mining companies varying in sizes and operating characteristics, and I am pleased to report that the response was good. I received answers from 51. The questionnaire was intended to measure the degree to which their concerns were actually engaged in OR efforts. With all due respect to the people who were so gracious as to answer the questionnaire, I feel that there is a tremendous misconception as to the designed purpose of OR. This is not to imply that there are no active OR groups in the mining industry. But by in large, the majority of the companies sampled appear to be somewhat confused as to what OR really is.

Jan 1, 1962

A dedicated tunnel construction version of the Caterpillar 328D LCR compact radius excavator is proving highly productive on the A9 Autoroute construction project near Visp, in Switzerland. It is the first machine of its kind to operate on a Swiss contract and uses a special dedicated front attachment designed and constructed by German Caterpillar dealer Zeppelin. The machine offers a powerful, stable and compact solution for tunneling contractors. A rear overhang of just 305 mm (12 in.) provides a tail swing radius of just 1.9 m (6.2 ft). The 328D LCR is ideal for the restricted working areas within a tunnel construction site. The machine is equipped with the wide tracks from the 330D L conventional crawler excavator, ensuring maximum stability when operating. In addition, the boom mounting has been moved further toward the center of the machine for the tunnel model, creating an increased lift capacity over the front end compared with a standard 325D L. The boom itself features a robust box section construction, with high-strength steels, additional supporting struts and reinforced bearings for maximum durability. All pins have hard-chromium plating for optimum protection against wear. Stick digging force is a powerful 134 kN, with up to 212 kN of bucket digging force available, for maximum penetration in blasted material. The 328D LCR is also equipped with a heavy-duty dozer blade as standard. This ensures outstanding stability when working and providing a useful secondary tool for clearing and leveling within the jobsite. Two 45° tilting mechanisms in the boom construction, allow the boom to be swung to 45° on either side of the machine. So the specially designed attachment linkage provides increased rollback for access to the roof of the tunnel. A Caterpillar CW45S mechanical quick-coupler allows rapid changes between specialist tunneling attachments, standard Caterpillar buckets and a range of Caterpillar work tools. The machine is powered by a Caterpillar C7 diesel engine. This six-cylinder EU Stage IIIA diesel motor [ ] offers 8 percent more power than its predecessor, with 140 kW (190 hp) available at just 1,800 rpm. Caterpillar?s ACERT combustion technology results in lower fuel consumption and reduced exhaust emissions. However, the tunnel machine is also equipped with a diesel particulate filter as standard, to further cut exhaust gases within the tunnel working. The 328D LCR is designed for use in transport tunnels of 6.8 m (22.3 ft) in height. With the tunneling boom in place, the machine has an operating weight of 42,540 kg (93,783 lbs), yet retains a transport height with the tunnel boom of just 3.9 m (12.8 ft). Transport width with 600 mm (23.6 in.) track shoes, is just 3.2 m (10.5 ft). On the A9 tunnel contract, the machine is being used by a consortium of Swiss and Austrian companies working for the canton of Valais? Routes Nationals Construction (RNC) department. The 31.8-km (19.7-mile) A9 Autoroute construction project will connect Sierre in the west and the town of Brig to the east. The tunnel that is bypassing the town of Visp is just one of a number along the mountainous route.

Jan 1, 2009

By M. Trim, Y. Sun, D. Tepavac, A. Kumar

Configuration of Rozelle Interchange Project’s ventilation system required design and construction of some of the largest and tallest underground civil caverns attempted in Australia. The paper focuses on the technical challenges of designing these caverns within a heterogeneous, generally weak sandstone under highstress conditions while providing a construction sequence that would align with the contractor’s preferred techniques and schedule. Various construction techniques were investigated, but ultimately an observational approach relying on a construction sequence and specialized instrumentation met both the designer’s and contractor’s requirements. Relevant data obtained from excavations and the construction monitoring program are presented within.

Dec 1, 2022

By A. L. Williamson, G. Savci

Hydrologic assessments of existing and proposed waste rock stockpiles (WRS) are typically required for application of operating and closure permits at mine sites. The results of these assessments can be used to determine the applicability of the state groundwater permit program requirements to the operation and closure of these stockpiles. The objective of this hydrologic assessment was to ascertain whether or not the WRS at the Ajo Mine have a reasonable probability of discharging potential pollutants to the underlying aquifer under the operational mine conditions. The hydrologic assessment was performed based on an evaluation of climatic data, prediction of the net infiltration rate through the WRS and prediction of additional hydrologic factors such as the time required to deplete available moisture storage in WRS. The predicted net infiltration rates ranging from 0.13 inches/year (1.1x10-8 cm/s) to 0.24 inches/year (1.9x10-8 cm/s) are below the threshold value of less than 10-7 cm/s recommended by Hutchison and Ellison (1992) as being characteristic of conditions that produce no or negligible quantities of seepage. In addition, the total time required to deplete available moisture storage within the Ajo Mine WRS and for any potential seepage from the WRS to reach the underlying aquifer is estimated to range from 260 years to 1,950 years. Collectively, the climatological and geotechnical investigations and the hydrologic predictions demonstrate that the WRS at the Ajo Mine hydrologically do not have a reasonable probability of discharging pollutants to the underlying aquifer. As a result of this prediction, the stockpile will not be regulated under the state groundwater permit program and operational and reclamation requirements will be limited to managing surface water runoff.

Jan 1, 2002

By Paul A. Rittenhouse

Its a pleasure to be with you this afternoon and to talk briefly on one of my favorite subjects -- the U.S. sulphur industry. As our Chairman mentioned, I have been associated with the sulphur industry either directly or indirectly for the last twenty years, both on the production side and as a consumer. Sulphur, while unseen and relatively unknown to most people, is like margarine ... that ubiquitous spread ... that is yellow and nearly omnipresent in the industrial world. It is because sulphur, in some form, is required in nearly all aspects of our economy that makes its study so interesting to me as a researcher. An analysis of the sulphur outlook requires examination of such industries as fertilizer, paints and pigments, copper and zinc, uranium, petroleum, chemicals, pulp and paper and textiles - just to name a few. Of course, because its use is so widespread and ever-changing it is difficult to develop and maintain a good understanding of the sulphur industry. It is also a problem to cover the industry in a short discussion and to project its really dynamic nature. Hut, if you will bear with me, I will attempt the task. First of all, let me say that sulphur today is a world commodity and to a large extent moves freely in world trade; nearly a third of the world's sulphur or something over 15 million tons in 1974 entered international trade. However, today our interest is in the current changing sulphur picture in the U.S., with particular emphasis on the western part of the country.

Jan 1, 1975

By Taehong Kim

An accurate and reliable prediction of Tunnel Boring Machine (TBM) performances, in terms of Rate of Penetration (ROP), utilization (U), and cutter wear rate, is a critical element in the successful planning and execution of mechanical tunneling project. Three open hard rock TBM projects were studied to establish possible trends and correlations between rock mass properties and machine performance. Based on this analysis and literature survey, three geological parameters, including RQD, RMR, and groundwater inflow rate, were identified as having the greatest impact on TBM utilization level. Rate of Penetration (ROP) and cutter wear rate were also correlated with fracture spacing, alpha angle, and Cerchar Abrasivity Index (CAI).

Jan 1, 2008

By M. Tapper

If one considers that prehistoric man's first house may have been a limestone cave, calcium carbonate may be the most timeless of all building materials. Fanciful history aside, CaCO3 has been used for countless applications in human habitats. After all, tine marble block and tiles have always been the hallmark of eloquents and style. Mortars and cements derived from limestone have held together the very blocks of our civilization. In modem times, synthetic polymers are blended with ground limestone to produce everything from pipe, floor tile, cultured marble and house siding. All of these miracles of our technology contain CacO3 of various sizes and in varying amounts. This paper will discuss some of the critical attributes of CaCO3 which make it suitable for the new building products that have helped increase our standard of living. The vehicle of discussion will be a residential, single family house.

Jan 1, 1993