Search Documents

By Claudio Asioli

"The project’s goal was to construct the Al Ghazala Intercontinental, a multi-use development in the bay area of Tripoli overlooking the Mediterranean Sea. The site of the project is located approximately 500 ft (150 m) from the Mediterranean coast, near the Al Ghazala roundabout in the town center of Tripoli, Libya. The investor of the project was Magna Properties Group, Ltd. – Libya, the main contractor was Man Enterprise S.A.L., and the design and construction management was performed by Dar Al-Handasah Engineering. Trevi S.p.A. was contracted to perform the design and construction of the anchored diaphragm walls and dewatering systems for the excavation of a two-level basement car park, which extends across the full footprint of the site.The site was approximately 640 ft by 230 ft (195 m by 70 m) in plan and nearly flat. The groundwater level typically varies from about 11 ft to 23 ft (3.4 m to 7.0 m) above mean sea level. To construct the required raft foundation, it was necessary to excavate the area down to El. -15.7 ft to -26.3 ft (-4.8 m to -8.0 m), which resulted in an excavation depth ranging from about 27 ft to 39 ft (8.3 m to 12.0 m) below the existing ground surface. Subsurface ConditionsThe subsurface site investigation was performed in three phases by Al-Tamier Engineering Consulting Bureau. During Phase 1, a preliminary investigation was undertaken during the early stages of the project to obtain information about the general stratigraphy and groundwater level at the site. Phase 2 was performed to obtain subsurface information and design parameters, and Phase 3 was performed as a supplementary ground investigation to investigate unexpected ground conditions identified during Phase 2. In total, 14 boreholes were drilled to depths ranging from about 80 ft to 180 ft (24 to 55 m). The generalized subsurface profile is quite heterogeneous, and is predominantly composed of sand with silt and gravel that is underlain by limestone, calcarenite and claystone."

Jan 1, 2017

By Raul Prebisch

Como última parte del análisis sobre la realidad latinoamericana, el presente texto señala el estrangulamiento o crisis del desarrollo, las disparidades sobre la demanda y sus efectos sobre el desarrollo económico, el fin de la etapa fácil de la política sustitutiva, la industrialización hacia adentro y las exportaciones, la reciprocidad implícita en los grandes centros, la necesidad de rebajar los aranceles, la expansión del comercio mundial y la debilidad congénita de la periferia y la relación de precios del intercambio.

Jul 1, 1964

By Dale S. Preece

INTRODUCTION In 1975 Congress passed the Energy Conservation Act to establish a U. S. Strategic Petroleum Reserve (SPR) with a capacity of 750 million barrels of crude oil. The most economic storage medium was determined to be salt caverns leached in salt domes in Louisiana and Texas. Salt caverns existed at several sites when the reserve was created. These were obtained by the U. S. Department of Energy (DOE) and used to initiate SPR oil storage. In order to meet the storage capacity approved by Congress, new caverns also had to be leached. To support the resulting design effort, finite element computer programs have been used to determine the creep closure and structural stability of salt caverns Using site specific material properties including creep models, elastic moduli and fracture data, the finite element analyses have replaced earlier empirical approaches to cavern design. This report presents results of such finite element analyses to determine the best cavern roof shape and the minimum pillar to diameter ratio, P/D. These numerical predictions indicate that the current cavern design is safe. FINITE ELEMENT AND MATERIAL MODELING The finite element program used in this study has existed for approximately four years. Its theoritical basis (Key, et al, 1980) and application are well documented It was originally developed to predict the creep around mined openings In bedded rock salt for the Waste Isolation Pilot Plant (WIPP) The program was tested by modeling the creep of salt around a drift and by comparing the results with the predictions of eight other structural computer codes (Morgan, et al, 1981) Since then the program has had continual use for calculations to support the WIPP (Miller, et al, 1982) For about two years the

Jan 1, 1984

By P. A. Rona

The first hydrothermal mineral deposits found at a seafloor spreading center were discovered in the Red Sea by multi-national research vessels between 1963 and 1965. At that time, the deposits were considered a special case related to continental rifting and an early stage of opening of an ocean basin. Since that time, examples of almost all major varieties of volcanic- and sediment-hosted hydrothermal deposits associated with basaltic rocks in the geologic record have been found at present spreading centers. Review of over 100 hydrothermal mineral occurrences presently known at oceanic ridges and rifts indicates that a range of deposit sizes from small to large (> 1 x 106 tonnes) occurs at all seafloor spreading rates. However, larger deposits but fewer per unit length of spreading axis appear to form at slow- than at intermediate- to fast-spreading centers based on available data. Larger deposits are more common in sediment-hosted than in volcanic-hosted settings regardless of spreading rate. A spectrum of hydrothermal deposit varieties (stratiform, stockwork and disseminated sulfides; various forms of sulfate, carbonate, silicate, oxide and hydroxide deposits) occurs in almost all of the tectonic settings. High-intensity, ore-forming, subseafloor, hydrothermal convection systems that conserve heat and mass and concentrate hydrothermal precipitates are extremely localized by anomalous physical and chemical conditions relative to nearly ubiquitous low-intensity hydrothermal activity at and flanking seafloor spreading axes at all spreading rates. Two distinct shapes of volcanic-hosted

Jan 1, 1989

By Gavin K. W. Freeman

The efficient separation of cobalt from nickel is a fundamental objective in the refining of cobalt. Based on recent experience at the Corefco refinery in Fort Saskatchewan, the identification of a novel process for the selective precipitation of cobalt from aqueous ammonia leach liquors is described. The addition of calcium sulphate, CaSO4.2H2O (gypsum), to an aqueous solution containing cobalt(III) hexammine sulphate, [Co(NH3)6]2(SO4)3, will result in the precipitation of a sparingly soluble double salt having the stoichiometry, [Co(NH3)6]2(SO4)3.2CaSO4.xH2O, where x = 4 or 6. Leach residues, which may contain a significant quantity of cobalt associated with the cobalt calcium double salt, can be washed with process solutions that contain ammonium carbonate. After contact with ammonium carbonate, the cobalt is recovered into solution, while the calcium is re-precipitated as the insoluble carbonate. The simplicity of this elemental separation and its high selectivity for cobalt, as well as the demonstrated usefulness in improving cobalt recoveries, are the basis for the potential applications of this process.

Jan 1, 2003

By Kenneth Eltschlager

The Surface Mining Control and Reclamation Act of 1977 requires that blasting be conducted so as to prevent injury to people and damage to public or private property. The three adverse effects are flyrock, ground vibrations and airblast. Blasting close to people frequently results in complaints of annoyance or damage. Federal and State personnel are responsible for evaluating the validity of the complaint. The elements to be evaluated include: reviewing blast logs, inspecting the mine, inspecting the house, measuring ground, air and structure vibrations, and predicting vibration levels. Computer spreadsheets, with their graphical capabilities, will be used to show how data can be cross tabulated to verify data accuracy. Complete statistical analyses of vibrations require more powerful software to make vibration predictions. Once all available data are gathered and verified, a decision on the complaint can be made.

Jan 1, 2001

By B. Markovic

Performance of mineral filler particles in ceramic applications can be enhanced markedly by adsorbing polymers of optimum molecular structure and dosage. In a recent work by Chen and Somasundaran (1997), a novel scheme of controlled polymer adsorption was used to produce nanocomposites of unique core-shell designs. Towards this purpose, adsorption and desorption behavior of selected polyacrylic acids (PAA) on three minerals; alumina, titania, and silicon carbide, was examined as a function of relevant parameters. Adsorption of P AA was found to depend on polymer molecular weight, pH, as well as solids loading. Specifically, the adsorption density was found to increase with increase in polymer molecular weight for non-porous alumina while it was found to decrease in the case of porous alumina. This is attributed to the inaccessibility of the pores to the larger polymers. An unexpected finding was the change in the adsorption density of PAA with solids loadings. PAA adsorbs on silicon carbide only at low pH values when the particles have very low surface charge suggesting that the adsorption in this case is controlled by electrostatic forces. Using polyacrylic acid as bridging agent between the alumina fillers (core) and nanosize alumina or titania particles (shells), controlled layer by layer deposition of nanoparticle on the core particle surface could be obtained.

Jan 1, 1997

By R. J. Gochin, M. A. Diaz

A modified Hallimond tube is described which allows the determination of the ultimate recovery R and the flotation rate constant k in a single, continuous experiment. The range of fine particles which can be satisfactorily floated with the modified apparatus can be extended by increasing the length of the bottom part of the tube. Findings suggest that pyrite and arsenopyrite can be separated in alkaline suspension using the so-called F series of collectors. Lime was found to act as a depressant. The collectors operate under pH and dosage control and do not require other depressants. Collectors used in the study were thio-amine (a cationic surfactant) and alkyl propionamide (a non-ionic surfactant)

Apr 1, 1995

By Ronald F. Balazik

[This Bureau of Mines study is intended to identify and evaluate potential effects of impending large-scale U. S. rail line closings (abandonment) on domestic nonfuel mineral industries. This is the first nationwide study of rail abandonment impacts focused on nonfuel minerals. The analyses presented is based principally on a survey of 200 rail freight records and on statistical tests that correlated 2,000 points in the Bureau's Mines Industry Location System (MILS) with 700 prospective abandonments throughout the United States. The conclusions derived from the analysis can be useful in evaluating proposed national rail abandonment policy rind legislation regarding nonfuel miner it shipping. Among these conclusions are the following: (1) Certain mineral materials (especially fertilizers) are likely to account for a large percentage of the rail traffic affected by abandonment in the next few years, but the total tonnage- involved will be small; (2) abandonment will adversely affect some mineral shippers, particularly local smart haulers; and (3 abandonment could significance reduce the opportunity to develop new resources or reopen defunct mining facilities. Despite these problems, however, the data examined in this study do not indicate that current abandonment trends will cause widespread disruption 01 domestic nonfuel mineral shipping.]

Jan 1, 1980

By Rajendra Singh

In India, pillar mining is contributing more than 90% of underground production which involves extraction of a part of coal from bords with pillars around as natural support in the development stage. #Liquidation of these pillars with splitting and stooking, broken nature of face during mining under complex geomining factors like massive roof, varying treatment of goaf and over or underlying workings result in high stresses and deformation in and around the neighbouring piilars, causing operational problem and hazards to mine safety. This paper suminarises the results of three case studies of depillaring under shallow depth with or without stowing. Assessment of nature and amount of mining induced stresses and deformation was done under these conditions, by insitu instrumentation and observation at three depillaring panels of Girmint. Samla and Lachhipur collieries of ECC at 54, 90 and 110 m depth cover respectively. The value of induced stresses and associated deformations was comparatively low in well caved and stowed waves, whereas for massive roof the roof fall followed overriding of pillars and stooks, with very high value of induced stresses and deformaton in absence of stowing. The stress in the centre and outer edges of the pillars changed with respect to depillaring face advance or splitting of pillars. The caving panel of Girmint colliery under weak coal measure formation, showed maximum induced stress in the pillar at 4 m distance from the face which was 1.2 times (16.6 kg/sq.cm) the preminlng stress of the area. The main roof fall over partially stowed goaf of Lachhipur colliery under massive roof strata caused overriding of pillar after crushing 39 stooks of 7.5 x 7.5 sq.m in rythmic sequence with development of 133lsq.cm maximum induced stress. Well stowed Waf of the same panel reduced this value of abutment stress to 2.3 times (65 kg/sq.cm.) body stress after 40 m further advance of the face from the crushed zone. The depillaring at Samla colliery even under massive roof strata induced low stress, equal to 0.8 times field stress only under the same condition with stowed goaf. The studies revealed the effectiveness of stowing in the goaf over loading of pillars and stooks.

Jan 1, 1990

By A. M. Riddle

GROWING out of the nation's most colorful era of railroad building, and with the vision of early pioneers who foresaw a great future for the Western Empire, the Colorado Fuel & Iron Corp. set as its objectives The establishment and building of colonies, towns, schools; industries such as coal mining, iron making and manufacturing works; canals and roads. This was the beginning of CF&I in the year 1872, and from this small western beginning has grown a company that has achieved national importance, ranking ninth in size in steel producing capacity, with over 22,000 employees and operating 14 plants in strategic locations throughout the United States.

Jan 11, 1953

By R. S. Archer

The proper representation of equilibria involving graphitic carbon in the constitutional diagram of the iron-carbon system is admittedly an unsolved problem, the complete solution of which will probably require the establishment of more experimental evidence than is at this time available. The object of this paper is to present the author's observations on some of the phenomena in question and his interpretation of this and other recorded evidence. The chief of the recently disputed questions upon which the author has experimental evidence concerns the occurrence of graphitization at temperatures below the Al point. In a paper1 presented at the September, 1919, meeting of this Institute, the following is found: "the results given would seem to indicate that the graphite eutectoid lies at a smaller value of carbon content than has been previously supposed. At least this is true unless there is either a marked formation of graphite eutectoid at these rates of cooling, or a decomposition of pearlite into graphite, both rather unlikely suppositions, but not impossible ones." In a discussion of this paper, H. A. Schwartz2 takes the position that the possibility of graphitization occurring below the A1 point is an open question, but that complete graphitization (to less than 0.10 per cent, combined carbon) commonly occurs above this temperature. Another opinion from the malleable castings industry is found in a recent paper3 by Touceda: "Also the carbide of iron can be broken up into its two soft constituents at the temperature referred to. This temperature is called the critical temperature, or critical range, and for air-furnace hard-iron castings it is in the vicinity of 1440" F. It is the

Jan 1, 1922

By R. S. Archer

The proper representation of equilibria involving graphitic carbon in the constitutional diagram of the iron-carbon system is admittedly an unsolved problem, the complete solution of which will probably require the establishment of more experimental evidence than is at this time available. The object of this paper is to present the author's observations on some of the phenomena in question and his interpretation of this and other recorded evidence. The chief of the recently disputed questions upon which the author has experimental evidence concerns the occurrence of graphitization at temperatures below the Al point. In a paper1 presented at the September, 1919, meeting of this Institute, the following is found: "the results given would seem to indicate that the graphite eutectoid lies at a smaller value of carbon content than has been previously supposed. At least this is true unless there is either a marked formation of graphite eutectoid at these rates of cooling, or a decomposition of pearlite into graphite, both rather unlikely suppositions, but not impossible ones." In a discussion of this paper, H. A. Schwartz2 takes the position that the possibility of graphitization occurring below the A1 point is an open question, but that complete graphitization (to less than 0.10 per cent, combined carbon) commonly occurs above this temperature. Another opinion from the malleable castings industry is found in a recent paper3 by Touceda: "Also the carbide of iron can be broken up into its two soft constituents at the temperature referred to. This temperature is called the critical temperature, or critical range, and for air-furnace hard-iron castings it is in the vicinity of 1440" F. It is the

Jan 1, 1922

By Jeremy Cawley, Horry Parker Jr., Clint Wilson

The 5180 m EPBM drive on the Lower Olentangy Tunnel (LOT) is predominantly within glacial overburden. To connect LOT with the existing OARS deep tunnel in limestone bedrock, the upper 15 m inside diameter Vine Street retrieval shaft telescopes down to 6.7 m in diameter and extends into the karstic Columbus Limestone to a depth of 51 m, where a 104 m SEM tunnel will connect to OARS shaft 6. Pre-excavation grouting was reuired prior to lower shaft excavation to reduce potentially high groundwater inows. This paper discusses the secant pile installation, grouting program, shaft excavation, and hydrogeologic observations.

Jun 23, 2024

By Al Campoli

The majority of the 100 million roof bolts installed each year in the United States are 5/8 inch deformed rebar fully grouted into a one inch borehole. Commonly referred to as B-Series or No. 5 bar, this system is proven effective and cost efficient in coal mines with average to above average roof conditions. One of the critical variables affecting resin bolt performance is the size of the resin annulus, calculated as the difference between the hole and bolt diameters. The optimum annulus has been proven to be '/4 inch, which provides for effective mixing of the two polyester resin components and incorporation of the plastic film packaging within the cured resin. Glove fingering occurs when the plastic film is forced against the borehole wall potentially interfering with the mechanical interlock of the resin and the rock mass. Glove fingering is not a problem with the optimum '/n inch annulus but has been know to occur with the B-Series 3/8 inch annulus. Laboratory testing correlated the degree of Glove fingering with resin formulation and the bolt head to shaft axes alignment. Glove fingering occurred over 45 % of the grouted length of standard B¬Series bolts. The newly formulated Eclipse B-Series resin when combined with a 1/8 inch offset between the bolt head and shaft axes reduced the glove fingering 70%. The Eclipse system allows the 3/8 inch B-Series annulus to achieve the positive mixing characteristics associated with the / inch optimal annulus systems.

Jan 1, 2002

By Peter F. Steidl

As part of the Bureau of Mines methane control program, the Upper Free-port coalbed was studied in Fayette County, Pa., where this coalbed lies about 650 feet below the Pittsburgh coalbed and contains the largest remaining reserves of any coalbed in the county. Its estimated recoverable reserves in Fayette County are between 670 and 800 million tons. Coal and overburden isopachs, structure and joint pattern maps, and a fence diagram were prepared using data from gas and oil exploration logs and coal outcrops. These maps will aid in determining the need and/or feasibility of degasifying the Upper Freeport coalbed in the study area. Much of the coalbed in this area is under 600 to 1,400 feet of overburden. By correlation with data from the Pittsburgh coalbed, the gas content at depths of this order is estimated to be between 140 to 300 cf/ton of coal.

Jan 1, 1977

By John D. Sullivan, Edwin J. Rogers, Chester R. Austin

THE problem of making a building unit combining the necessary physical and mechanical properties and good thermal insulation has been foremost in the minds of architects and ceramic and construction engineers for many years. This paper presents the results of studies on thermally expanding shales or clays to produce light-weight cellular products suitable for making building units. An expanded clay block suitable for building purposes should be large enough so that substantial savings may be effected in labor costs in laying the wall. The permeability should be low and it should have sufficiently good "dry-wall" characteristics to permit exposing the exterior surface to the elements, and to permit plastering directly the inside wall surface. The thermal conductivity should be low and the mechanical properties should be adequate. Obviously, a unit possessing satisfactory qualities for constructing an outside wall would be satisfactory for interior walls and for back-up purposes. The results of studies on bloating various shales or clays† and the properties of the expanded products are reported. In another paper1 basic factors involved in bloating of clays are discussed. Manufacturers of ceramic products, particularly structural clay, may encounter bloating of the ware during burning, and precautions must be followed to avoid this phenomenon. About 1927 the C. F. Burgess Laboratories, Madison, Wis., while carrying on an investigation for the American Face Brick Research Corporation, conceived the idea of intentionally bloating clay while holding it in a restrained condition, with the hope of producing a unitary cellular mass. Work was carried on until about 1931, when studies were terminated because of business conditions. These studies were continued later by The Western Brick Co., Danville, Ill., which developed a process of "inwardly expansive bloating." The major purpose of the latter investigation was to produce back-up tile to compete with concrete blocks made from Haydite or cinder aggregate. Haydite is a light-weight aggregate formed by heating certain clays or shales rapidly in a rotary kiln. While the investigations at the C. F. Burgess Laboratories or at Western Brick Co. were not carried far enough to lead to the commercial production of material for the construction of walls, particularly outside walls, they showed that certain clays could be thermally expanded and that it was possible to produce a material of low permeability with a large percentage of the total voids or cells closed. Commencing in 1939, the Ozark Chemical Co. sponsored a research program at Battelle Memorial Institute for the purpose of determining whether it is technically feasible to make thermally expanded building units, and specifically to get answers to the following questions:

Jan 1, 1942

By P. W. Jeran, M. C. Irani, D. H. Lawhead

The Beckley mine is one of five new mines in a heretofore unmined portion of the Beckley coalbed. The remoteness of these new mines from prior mining and their greater overburden preclude applying methane emission experience obtained in the old mines. Four sections of the Beckley mine were monitored. The data gathered show that variations in methane emission cannot be explained by variations in coal production. Although overburdens varied by as much as 30 pct, no correlation with methane emissions could be determined. The rib emissions increase with increased length of rib from a section advancing into virgin coal and do not decline over a prolonged idle period (32 days) whereas some decline has been measured for a section not mining into virgin coal. The indication is that degasification prior to mining will reduce the hazard of methane emissions in this area of the Beckley coalbed.

Jan 1, 1977

By Matthew Violot

Vale Canada?s Birchtree Mine, located in Thompson Manitoba, has been experiencing problems with hanging wall / footwall dilution, as well as sloughing off of adjacent stopes and temporary stope block backs. Birchtree Mine is interested in determining how time affects the stability of their open stope blocks. Many factors simultaneously influence open stope stability (rock mass quality, joint condition, stress condition). This makes it challenging to determine the influence of a single parameter such as exposure time or stand-up time. This study focuses on determining the effect of exposure time on open stope dilution and combines stress analysis and empirical based approaches.

Jun 1, 2012

By T. Lindstad, J. Kaczorowski

The Boudouard reactivity of single cokes produced from selected bituminous coals and commercial cokes has been investigated in a thermo gravimetric furnace. The effect of potassium as a catalyst for this reaction was studied, as it is known to accumulate in ferromanganese furnaces. A gaseous impregnation technique using K2CO3 as the potassium source was applied to impregnate the coke samples. The reactivity experiments were designed to simulate conditions occurring in an industrial furnace, as used for production of Mn-alloys. The coke particle size varied from 3.35 to 6.63 mm, while the temperature was maintained between 800- 1100oC with a gas composition from 50 to 75% CO2 in a CO/CO2 mixture. To determine the catalytic effect of potassium, the concentration varied from a fraction of a percent up to 15%wt. The results show that single chars vary significantly in reactivity, depending on the properties of the parent coal, while commercial cokes exhibit similar reaction rates. Temperature and partial pressure of CO2 have the strongest influence on the reactivity, while the influence of gas flow rate and coke particle size were found to be negligible. The catalytic studies revealed that the relative reactivity of non-impregnated samples are preserved after the impregnation, so the least reactive coke is still the least reactive after the impregnation for the whole range of potassium loads. Also, it has been confirmed that the Boudouard reactivity reaches a plateau at potassium concentration of 4%wt.

Jan 1, 2007