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In constructing a financial model of a project significant effort is expended on capital and operating cost estimation, commodity price forecasts, and choice of discount rates while uncertainty in the primary input, the reserve, is often completely overlooked. The aim of this paper is to highlight the impact of uncertainty in the resource/reserve estimation process on the assessment of the financial performance of a project. Four qualitative processes have an impact on resource/reserve uncertainty. These stages are: 1.Ore definition 2.Geological interpretation 3.Resource estimation 4.Ore reserve estimation and mine planning. Each stage contains a number of tasks that may be considered as key performance activities (KPAs). Optimizing the manner in which these KPAs are completed can remove a great deal of uncertainty and error from the resource/reserve process. Examination of these KPAs within a company can also provide an insight to the quality of the information underlying the project. This will allow the company to identify any shortcomings in the data and to assess the resulting risks (Gilfillan, 1998). A hypothetical financial model based on a gold operation has been used to estimate the potential effect of resource/reserve uncertainty on revenue. Monte Carlo simulation has been employed to simulate a number of hypothetical scenarios: 1.a base case scenario which assumes no major errors or biases, but contains realistic margins for uncertainty that would exist in any project where work is being completed to the limit of best endeavours 2.a poor sampling scenario which assumes poor sampling practice and lack of understanding of sample preparation 3.a poor resource estimation scenario which assumes poor modelling and inappropriate choice of interpolation technique, and 4. a ?typical? scenario which represents a project where the majority of KPAs are not performed as best as they could be. The results show that realistic uncertainty ranges can generate changes in the estimate of potential revenue of plus or minus 30%.Therefore, it is important to allow for errors in these processes in any financial analysis or feasibility study. It is recommended that, when building a financial model, are view of relevant resource/reserve KPAs be carried out and appropriate ranges for uncertainty be applied to provide a range of potential outcomes. These outcomes can then be factored into the detailed cash flow analysis in order to ensure that technical uncertainty is built into financial decisions.

Jan 1, 1999

By Gregory Abramov

Borehole Mining (BHM), a remotely-operated waterjet mining method (Figure 1), has recently achieved two major milestones. It was, for the first time, applied to the extraction of manganese ore and at temperatures below freezing. The 1St stage is a demonstration test that is now underway just north of Emily, Minnesota, where the manganese ore is located 100-160m below the surface and its reserves are estimated to be in excess of 500,000 tons. The deposit was discovered over 60 years ago but, due to the fragile and sensitive nature of this Land of 10,000 Lakes (nickname for the State of Minnesota) and strong environmental restrictions, the iron/manganese reserves were deemed unrecoverable and remained untouched until late 2010 when permission for a single-hole demo-test was issued by the local Department of Natural Resources.

Jan 1, 2011

By Axel Preusse

On the basis of the Law on Financing Hard Coal Mining dated 28 December 2007, the subsidized German hard coal mining industry will be shut down to the end of the year 2018 in a socially acceptable manner; in 2012 this decision will be reassessed. Even after the abandonment of all mining activities subsequent burdens are inevitable. In this paper, the possible long-term effects resulting from a mining industry history, which is spanning more than 200 years, and their possible consequences are pointed out, in particular in connection with the abandonment of mine water drainage measures which is economically meaningful in the long term. According to the decision situation as it presents itself today, this point in time will be far beyond 2018. In preparation for this, an action framework is to be developed in areas possibly affected.

Jan 1, 2008

By Raj Mutharasan

The phenomena of gas-molten metal reactions for the production of metal matrix composites consist typically of a combination of one or more gas transport steps and a liquid gas reaction step. Reaction products include such strength enhancers, grain refiners, or high thermal conductivity phases as TiC, AIN, SIC, Si3N4, TiN in aluminum alloys. Nitrides, carbides and oxides can be produced at various volume fractions and in fairly fine sizes (500 am to 5 um) in laboratory melts by Reactive Gas Injection method (RGI). Gas injection methodology to produce the reinforcements is attractive because it can potentially be scaled to production scales in excess of 10,000 kg/h. For continuous production, the reactant molten metal can be continuously fed into the .crucible where the reactive gas is injected. The molten metal phase reactant may also be involved in a controlling transport step, depending on its concentration and viscosity. It is well known that the reaction product reinforcement size and shape of these phases have significant impact on the physical, mechanical and thermal properties. The current state of knowledge is unable to predict the kinetics and growth of solid reaction products obtained. The primary goal is to develop a fundamental framework for the understanding and prediction of the particle size in such reaction systems. In addition, the role of gas transport, liquid hydrodynamics and decomposition are important issues. A reaction-transport model is being developed using a reaction, transport, and thermodynamic framework, both at macro and at atomistic level to assess gas - liquid interactions.

Jan 1, 1996

By S. A. Sadough vanini

In this paper, Stress-Strain-Temperature relations for Shape Memory Alloys are studied. Temperature effects on Shape Memory Alloys are different from those related to ordinary materials. In ordinary materials, elastic characteristics can be assumed to be constant in low temperature ranges, and only the deflection arising from temperature changes could be added to the elastic defection. As long as two phases of austenite and martensite could be present in Shape Memory Alloys simultaneously, elastic modulus follows temperature and temperature gradient. In continue a smart actuator is investigated considering a homogeneous cantilever beam. Beam bending is established by using shape memory wires. An initial strain is imposed to shape memory wires in a low temperature, and then, they are installed in the outer surface of the beam. Therefore, since the temperature is imposed in these wires and they cannot have free recovery strain, the compressive recovery stress will be produced in the outer surface. This will result in a deflection in axial direction of the beam. At first, beam deflection is calculated on the basis of theoretical relations and solving the relevant differential equations. Afterwards, experimental tests are performed on an elastomeric beam equipped with shape memory wires. When a voltage is applied, a temperature rise will occur in the wires; then, this temperature rise causes a deflection in the beam. Finally, the theoretical and experimental results? comparison indicates a good conformity. One capability of this actuator is its high flexibility, and by controlling the inlet current, the end-beam deflection can be controlled.

Oct 1, 2011

By Saeid Akhavan

Accumulative roll bonding (ARB) is a severe plastic deformation process for achieving ultrafine grains in metallic sheets without changing the sample dimensions. In this study, ARB process was carried out on 5083 aluminum alloy sheets up to 6 cycles. In this process, the surfaces of the strips to be joined are roughened and cleaned and then stacked. After stacking, the specimen is roll-bonded by rolling using a 50% reduction. The rolled specimen is cut into two halves, and the above-mentioned procedure is repeated for several times. Microstructural characterizations were analyzed by transmition electron microscopy (TEM). Tension and Vickers hardness tests were performed on produced sheets for evaluating their mechanical properties. In order to clarify the failure mode, fracture surfaces after tensile tests were observed by scanning electron microscopy (SEM). The results indicated that at the early stages of ARB process, grains were subdivided by deformation induced boundaries. After several ARB cycles, lamellar structure elongated in the rolling direction contains lamellar boundaries was formed. With increasing the strain, mean spacing of lamellar boundaries decreased. Finally, continuous recrystallization resulted in a microstructure covered with small recrystallized grains with an average diameter below 100 nm at the end of four cycle. The tensile strength and hardness of the 6 cycle ARB processed 5083 aluminum alloy sheet increased about two and three times of the initial values, respectively. Results indicated conformity between mechanical evolutions and microstructural changes during ARB process. Fracture surfaces observations showed that failure mode in ARB processed aluminum is shear ductile rupture with elongated small dimples.

Oct 1, 2011

By Madan Kumar Annam, Hari Krishna Y

"Basement construction is one of the challenging geotechnical concerns in the urban environment. Several types of retention systems are practiced to support the earth which is suitable for restricted access, rapid mobilization, fast excavation and cost-effective designs. A thorough understanding of geotechnical engineering as well as the structural mechanics is important for the earth retention systems. This paper discusses a project with various types of foundation solutions including monitoring of deflections during excavation stage of a retention system.A multi storeyed residential building (3B+Stilt+18F) in Chennai having structure foot print area of 1500 m2 has to be constructed on large diameter pile foundations and also to support the proposed basement excavation. Ground water table was encountered at about 6m below the existing ground level (EGL). In order to support heavy structural loads, large diameter bored cast-in-situ piles were chosen and installed. Further, complete retention system was economically designed and built, which includes installation of Contiguous Bored Piles (CBP) in combination of vertical grout columns behind CBP wall to seal the gap between the CB Piles, installation of inclined ground anchors, construction of capping beam, stressing and locking of installed ground anchors. A detailed monitoring program was in place and continuous monitoring of wall deflections is being measured at the time of publishing this paper. This paper describes the design and construction aspects adopted for foundation and retention system including the monitoring results during excavation stage of the project.INTRODUCTIONIn general, stage wise open excavation will be opted for basement construction where plenty of space is available. Due to urbanization and restricted space, open excavation became a difficult task nowadays. To overcome this problem, suitable retention system need to be selected to retain the soil mass. Selection of suitable retention system for multi-level basement excavation is a great challenge in geotechnical industry, especially when the proposed site is located within the minimum set back distance from the existing structures. This in turn calls for the advanced and innovative methods of retention system.Several earth retention systems such as Diaphragm Walls, Secant Pile Walls, CBP system, Soldier Pile Walls, Sheet Piles, Deep Soil Mixing (block walls) etc. with or without inclined ground anchors are being practiced worldwide. Considering the advantages and disadvantages of the available retention systems in practice locally and keeping in view of present site conditions, the developer has chosen CBP system with inclined ground anchors so that all foundation related works of the project will be handled in a single package. The main advantage of such packaged solution will ease the coordination between design consultants and foundation contractor resulting in faster construction of foundation works which in turn reflect savings in time and cost."

Jan 1, 2015

By Enver Alan

This Research & Development (R&D) study was conducted in the field of applied blasting engineering in Ethiopia, within the AKH Railway Project, which was built in Girena, within the boundaries of the province of Mersa, in the Basalt Quarry at km 346, Ashangi Formation, occured in Eocene geological time in the aphanitic trachibasalt.

Feb 1, 2020

By H. J. Heinen

This Bureau of Mines report reviews the recent developments in the heap leaching of gold ores with dilute cyanide solutions and the recovery of gold and associated silver from the pregnant effluents by a carbon adsorption-desorption method. Mineralogical considerations, experimental work, field studies, and commercial operations are described. Also presented are recent process advances developed by the Bureau, including the application of (1) alcohol additives to the conventional hot alkaline cyanide strip solution to enhance gold desorption from precious metal-laden activated carbon, and (2) Na2S precipitation of the silver from geld-silver cyanide solutions as a means of reducing the inventory of carbon required for precious-metal adsorption from heap leach effluents and for the production of low-silver bullion from activated carbon stripping solutions.

Jan 1, 1978

By J. B. Dyess

TARNISH films on some of the common metals (particularly on copper and silver) have been of much scientific and commercial concern for a long time, but before the development of the electrical method1 of measuring film thicknesses there was no satisfactory quantitative approach by which to study the separate parts of these complex films. This method has been adapted to the measurement of duplex (cuprous-cupric) oxide films on copper .2 In the present work it has been used to measure tarnish films on copper when they were mixtures of cuprous oxide and cuprous sulphide, and also when they contained cuprous oxide, cupric oxide and cuprous sulphide, each component part being measured at a different potential value. Oxide-coated copper specimens, prepared by heating copper in air at chosen temperatures for given periods, were exposed to moist hydrogen. sulphide in air to form the various oxide-sulphide films studied. The comparative resistances afforded by (1) different thicknesses of oxide films, and also (2) equal thicknesses of oxide and sulphide films, against severe attacks of hydrogen sulphide were measured. The electrical method requires that the time be observed for the cathodic reduction of each part of the film substance, and these respective time values multiplied by the constant current give the corresponding quantities of electricity expended. Then each millicoulomb per square centimeter represents a film thickness of T= MX10 8 2D X 96,494 X 103 (a) where M is weight of oxide (or sulphide) giving one gram-atom of oxygen (or sulphur) for cathodic reduction, D is density of the oxide (or sulphide) and t is the thickness in Angström units per millicoulomb per square centimeter. The value of t for cuprous sulphide (cubical) is 14.27, and is obtained by substituting 5.78 for D and 159.20 for M in equation a. Previous values2 of t for cuprous and cupric oxides (12.36 and 6.39, respectively) were used in the present work.

Jan 1, 1939

By H. O. Harju

Inco acquired majority interest in the nickel laterite concessions in eastern Guatemala in 1960 and, through its subsidiary Exmibal, extensively explored the deposits until 1965 to define the site for project development on the north shore of Lake Izabal. This paper outlines the exploration methods used to evaluate the Guatemalan laterite deposits.

Jan 1, 1979

By E. J. Gleim

A list of permissible mine equipment, tested and approved by the Bureau of Mines previous to January 1, 1942, was published in Bureau of Mines Information Circular 7207.3/ The list of that date was complete as to equipment then available and in current use. Information Circular 7240,4/ published as a supplement thereto, listed equipment approved curing the calendar year 1943. The present list is another supplement covering approvals issued during the calendar year 1943. The items are numbered to indicate the consecutive order in which each type of machine or device was approved in its particular classification. Thus, Information Circular 7207 gave 19 drills and drilling machines on the Bureau's active list. No additional approvals were given in 1942, but the three issued in 1943 bring the total to 22. Item 102, under Loading Machines and Conveyors, also appeared in Information Circular 7207, and items 120 and 124 appeared in Information Circular 7240. These numbers are repeated here to show that approvals were granted during 1943 for additional voltages on machines previously listed for one voltage only. Equipment listed in these circulars is approved by the Bureau of Mines only when found upon inspection and test to comply with minimum standards of safety as outlined in schedules prepared on the basis of many years of experience in dealing with safety problems of the coal-mining industry. The use of such equipment in mines known to be gassy, as well as in those that may become so, is earnestly recommended in the interests of safety. This circular is published so that the industry may be kept

Jan 1, 1944

By A. J. MacKellar

The economic viability of any project is generally assessed on an evaluation of the total capital constructed costs along with operating costs, owner's costs and market conditions. This paper will be directed to the role that Cost Engineering plays in the development of the capital costs and the cost control techniques applied thereto.

Jan 1, 1975

By Robert E. Barieau

A list of 163 references to original experimental PVT data on helium is presented for the period 1895 to 1968. The list is complete as of the start of the Helium Centennial Year, 1968, to the best of the author's knowledge. Citations were keypunched for easy updating and are listed alphabetically by author.

Jan 1, 1968

By Willam R. Normark

During a series of dives with the submersible ALVIN in 1984, samples of massive sulfide were recovered from four vent sites. All sites occur within a linear, steep-walled cleft about 50 m wide and as much as 30 m deep. The cleft bisects the axial valley floor throughout the 15-km-long study area and appears to have been the source for the most recent volcanic eruptions in the valley. Three of the vent sites are defined by a set of discrete hydrothermal discharge zones; as many as eight have been identified over a distance of 500-800 m along the cleft floor. Sulfide deposits occur as individual and coalesced mounds, spires, and chimneys generally less than 3 m in height but a few might be as high as 10 m. The vents are also marked by extensive, yellow-to-amber ferruginous sediment and clots of bacterial matter. Some vents have extensive colonies of tube worms, gastropods, mollusks, and several predator species, such as crabs and squid. The fourth vent site has no visible discharge and consists mainly of "dead" spires and chimneys of massive sulfide. The massive sulfide samples collected with ALVIN are primarily sphalerite with minor marcasite, pyrite, pyrrhotite, isocubanite, chalcopyrite, wurtzite, and anhydrite. Bulk analyses of these chimney and spire samples show Zn contents approaching 60% by weight and significant enrichments in Ag and Cu. Vent fluids have the highest concentrations yet reported for Zn, Fe, and Mn. Thus, the Zn- and Ag-rich nature of massive sulfide from the southern Juan de Fuca Ridge study area

Jan 1, 1985

Microorganisms are finding more use in the mineral industry, with extensive research efforts being reported in 1991. Most of these research efforts were presented in two major meetings, the SME Annual Meeting in Denver (February, 1991) and the Engineering Foundation Conference about Mineral Bioprocessing in Santa Barbara (June 1991). In addition, several articles were published in the IMM Transactions, Minerals and Metallurgical Processing and Water, Air. and Solid Pollution Journal. The literature can be categorized as: • Review articles presenting an overview of the activities in the use of biotechnology in mineral processing. • Research efforts into genetic manipulation of microorganisms to perform a specified job. • Studies in bioleaching of metals from different types of ores. • Biotreatment of wastes from the mineral industry including acidic mine waters, uranium tailings, cyanide destruction, etc. • Investigations into the role of microorganisms in the energy materials, such as oil, coal, tar sands, oil shales, etc. Smith (Mineral Bioprocessing Conference) presented a review of research efforts as well as practical applications of biotechnology in the mineral industry. In another article, Smith et al. (Minerals Engineering) emphasized that extensive fundamentals and applied research work should be pursued to explore the fundamentals, potential and practicality of the various possible uses of microorganisms in mineral engineering.

Jan 1, 1992

By Rudolf E. Greuer

Introduction The Institution of Mining and Metallurgy and the Institution of Mining Engineers organized the Third International Mine Ventilation Congress held in Harrogate, England. Sixty-one papers were presented and about 300 participants registered. About 30% of the participants came from Great Britain, 20% from South Africa, and about 5% each came from Australia, Canada, China, France, US, and West Germany. The remainder of the participants came from 18 other countries. Eleven of the papers presented dealt with methane, three with diesel exhausts, four with dust, four with radioactivity, 18 with heat, and 15 dealt with main and auxiliary ventilation. Six of the papers dealt with mine fires, which is a boundary region between main ventilation and gas concerns. Ventilation Congress proceedings are available. See ME, December 1984, page 1687, New Books page. With CH4 and radioactivity topics, the Australians dominated since they are becoming large coal and uranium producers. With diesel exhausts, the most important problem in highly mechanized mines, the North Americans were prominent. The South Africans, working in 90% SiO2 in their gold deposits, were preeminent in presentations on dust. They also led in topics related to heat, joined by the West Germans whose mines are getting deeper. In main and auxiliary ventilation, Great Britain and West Germany provided the majority of contributions. Methane The large number of methods for the precalculation of CH4 liberation in longwall mining all contain three elements: gas content of the coal, gas emitting zone (or influence zone of face), and degree of gas emission. Determination of the gas content, commonly accomplished by taking coal samples, does not pose much difficulty. But this is not the case with the other two factors. Most existing approaches rely on rock mechanics observations. Some only rely on intuition or speculation. The West German coal mines conducted a large research project between 1977 and 1982, in which gas pressures around longwall faces were measured. Gas pressures and gas contents can be related. Therefore, influence zone and degree of gas emission can be determined simultaneously. The precalculation of CH4 liberation in room-and-pillar mining is simpler. Since foot and hanging walls remain essentially intact, gas pressure distribution and gas flow can be calculated using hydraulics equations. A key to these calculations is permeability. A group of Australian researchers reported that the permeabilities of rock under three dimensional stress differs from rock under destressed conditions. This fact was known, but no systematic observations existed. These were provided. Methane drainage has been practiced for more than 40 years. It is used with great success in longwall operations. Some of the West Germans think that methane drainage from the footwall is neglected. Under certain geological conditions, they claim this is as important as drainage from the hanging wall. A research project was presented in support of this claim. Considerable efforts have existed for more than 10 years to use methane drainage in room-and-pillar mining. A paper described the accomplishments of Consolidation Coal Co. Since coal and rock are not fractured as much as in longwall mining, gas transport takes place by the slow diffusion from micropores into the cleats. Then, it is transported by laminar flow along the cleats until a drainage borehole or the mine workings are reached. Boreholes about 300 m (1000 ft) long can reduce the gas content of a band of coal 100-m (330-ft) wide by 50% in one year. A paper from India described methane drainage from gob areas. A French paper reported that especially high methane concentrations can be drained from gob areas if the face ventilation is descensional. Methane buoyancy and ventilating pressures compensate each other, and little air dilution by leakage takes place. Another French paper described a newly developed gas and air velocity monitoring system making use of a microcomputer. Four papers on methane dealt with gas outbursts. Two Australian contributions described the problems encountered with CH,-CO2 mixtures and the attempts to solve them with drainage boreholes having 10 to 20-kPa (1.5 to 3-psi) suction pressures. A Hungarian paper described problems and attempts to reduce the risks of gas outbursts in Hungary. Prediction of gas outbursts in coal seams was the focus of an English paper. Observations show that they are frequent when coal, through its geological past, has become soft and brittle with a resulting increased desorption rate. An instrument for gravimetric de-

Jan 1, 1985

By Robert B. Fulton

The objective of this chapter is to discuss the interrelationship between industrial minerals and chemical manufacturing. It is intended to supplement rather than duplicate the commodity chapters. Particular emphasis is given to the pertinent chemical element and to market factors. Condensing this broad subject into a few pages of this handbook permits treating only the most important elements derived from industrial minerals. Hydrocarbons, which quantitatively dominate as raw materials for the chemical industry, are omitted, as are the metallic elements and the minerals covered in other "use" chapters such as phosphorous, potassium, and nitrogen for fertilizers, and titanium dioxide for pigments. The remaining six elements of major importance are: boron, bromine, chlorine, fluorine, sodium, and sulfur. These elements are treated individually under separate headings. [Table 1] affords an overview of the main industrial minerals, the chemical products derived from them, and end uses of the products. Salt brines have particular importance as raw material sources for the chemical industry. Table 2 is a chart of the chemical compounds derived from four types of brines: (1) Owens Lake-type brines, which are sources of boron and sodium compounds; (2) Midland-type brines, from which bromine, iodine, and chlorides of calcium, magnesium, potassium, and sodium are derived; (3) Searles Lake-type brines, yielding boron, bromine, lithium, magnesium, potassium, and sodium compounds; and (4) Silver Peak- type brines, produced mainly for lithium. MARKET ATTRIBUTES Some of the important market traits common to industrial minerals used by the chemical industry are: 1. They are international commodities, such as fluorspar and sulfur, which largely move to foreign consumers. 2. Grade, and freedom from deleterious elements are important factors affecting their usability in chemical processes. An example is salt (NaCl) used in electrolysis where ultrapure evaporated salt is required to meet rigid specifications. 3. Purified products take on the characteristics of specialty items and command a distinctly higher price than the basic commodity from which they are derived. 4. In practically all cases, chemical users require some sort of cleaning or beneficiation of the naturally-occurring mineral to bring it to specification, and individual specifications may vary from user to user for essentially the same use. 5. In some instances it is necessary to strike a balance between what the vendor can supply and what the buyer requires, with the result that specifications have to be eased to afford the needed materials in marginal cases. 6. Because they tend to be bulk commodities, low cost for handling and transportation are important and such costs may limit the area from which a chemical user can draw his supply. 7. Shipments are usually in bulk and frequently in multiple-car, full-trainload or full-shipload lots to reduce transport costs, which in turn may require large terminal investment facilities. 8. Purchases are generally by contract of one year or longer term, with spot buying playing only a minor role. 9. Contract prices are usually fixed in short term commitments, but may vary according to assay, with premiums and penalties for content above or below the norm; however, general practice is for specifications to be fixed in the contract with minimums being set for the desired material and maximums for undesired elements. In longer term contracts, prices are often escalated on labor, fuel, and other vendor processing costs. 10. Suppliers of individual commodities to the chemical industry tend to be limited in number and are generally medium- to large-size producers that supply a few major consumers. 11. The bulk of the mineral volume is for basic chemical uses, sulfur suppliers to sulfuric acid producers and fluorspar for hydrofluoric acid producers being typical examples. These basic chemical products then are used for the production of other products. 12. Shortage of a supply of adequate quality leads consumers to seek substitutes. In the case of fluorspar, much work is being done on recovery of fluorine from phosphate rock. Success in the form of fluorosilicic acid and/or hydrofluoric acid production could, in time, affect the hydrofluoric acid chemical industry. 13. Markets tend to be characterized by cycles of shortage followed by oversupply, with attendant wide price fluctuations. 14. Baniers to trade can have an adverse effect on the necessary movement of industrial minerals used by the chemical industry in international trade. Antidumping laws, quotas, and tariffs can disrupt or dislocate normal markets. 15. Chemical industry consumers may back-integrate for security of supply or for favorable economics, sometimes by joint ownership and often with experienced mining partners.

Jan 1, 1994

By K. E. J. Rapperport, C. S. Hartley

The only slip system observed in zirconium crystals deformed at 77", 575", and 1075OK was (1010) [1210] with a critical resolved shear stress in tension of 1.0 kg per sq mm at 77°K; 0.2 kg per sq mm at 575 °K; and 0.02 kg per sq mm at 1075 OK. The active twin planes were {1012}, (1121}, (11221, and (11233) with varying temperature dependence. A detailed analysis for the slip direction using Laue spot asterism is appended. NeARLY all metals of the hexagonal close-packed structure exhibit basal slip, i. e.,(0002)<1120>- type slip. This is true of magnesium,&apos; zinc,&apos; cadmium,3 beryllium,4 titanium,= yttrium,6 and rhenium.Many of these such as titanium 5&apos;8-&apos;0beryllium,4&apos;" magnesium, and zinc13&apos;14 display other slip modes even at room temperature, and nearly all have been reported to slip on other systems under particular loading or temperature conditions of testing. As is shown in this paper, basal slip was not found at any of four test temperatures from 77" to 1075°K in hexagonal close-packed zirconium under the simple loading conditions of tension and compression, even though in one case the resolved shear stress on the inactive (0002) <llgO> system was twenty-five times higher than the critical resolved shear stress on the active (1010) [1210] system. This result is consistent with prior studies on the active deformation processes in zirconium deformed at room temperature. &apos;&apos;-I7 SPECIMEN PREPARATION A) Material—The zirconium used in this work was of two types: 1) as-deposited reactor grade crystal-bar, and 2) arc-melted and forged reactor grade crystal-bar. Typical chemical and spectrographic analyses of these materials as received, and after hydrogen removal and crystal growth are given in Ref. 17. Crystals of type 1) above have the letter prefix (A) and those of type 2) have the prefix (B) throughout this paper. B) Crystal Growth— he zirconium was machined into rectangular parallelepipeds about 0.2-in. scl in cross section and 2 in. iong. These were hand polished through 4/0 abrasive paper, electropolished, given a hydrogen removal anneal, and subjected to long-time anneals at 840 °C in vacuo to produce usable crystals.&apos;7 A second technique used to obtain large crystals was to cycle the samples two or three times between 1200" and 840°C, allowing them to remain at the higher temperature for about 4 hr and at the lower temperature for 5 days.17 These techniques yielded some grains which occupied the entire cross section of the bar and were as long as 3/4 in. C) Orientation Determination—After the growth of large crystals by thermal cycling, the samples were repolished with extreme care through 4/0 abrasive paper and electropolished. Metallographic examination after polishing showed the surfaces to be free of visible deformation traces. Standard Laue back-reflection X-ray techniques were used to find the crystallographic orientations of selected large grains with respect to a specimen face and edge. Fig. 1 shows the stereographic projections of the stress axes for the crystals used. The sharpness of the spots on the Laue photographs indicated that the crystals were of good quality. EXPERIMENTAL METHODS Nine crystals were deformed in tension at 77"K, nine in tension and five in compression at 300°K in previous tests,17 fifteen in tension at 575"K, and eleven in tension at 1075°K. All specimens were stressed by load increments. After a predetermined load was applied, the specimen was removed from the loading appratus and metallographically examined for deformation traces. An attempt was made to initially stress each bar so that some crystals slipped a small amount and others not at all. This was done to bracket the critical resolved shear stress. One bar of special orientation (B-11) was repolished and annealed at 1075°K for 1 hr after lower temperature deformation, before final deformation at 1075°K. In the other bars the loading by increments, followed by metallographic examination, was continued until the surface distortion would interfere with analysis, or until fracture. One example of a crystal pulled to fracture is shown in Fig. 2. This photograph shows a crystal (B-14C) which was pulled at 1075°K and failed by slip on two (10i0) planes. The approximate orientation of this crystal is illustrated in the figure. Specimens were deformed at 77°K in liquid nitrogen on a tensile machine using an insulated bucket with an internal hook to accept a clamped specimen.

Jan 1, 1961

By J. A. Burkhardt

Field measurements and theoretical studies have been made of pressure surges—momentary variations in fluid pressure—produced by movement of pipe in mud-filled boreholes. Pressure measurements were recorded by five pressure gauges located at various positions in the borehole. An important positive pressure peak was found to occur as the casing moved with maximum velocity. Important negative peaks were found as the casing was lifted from the slips and as brakes were applied to stop pipe movement. A rigorously formulated theory has successfully predicted the sequence and magnitudes of these positive and negative surges and has established a basis for understanding how they occur. Both the measurements and theory indicate that the most important pressure surge is usually due to viscous drag of the flowing mud. The theory of viscous-drag pressure surges has been approximated by simplified graphs and calculation procedures to facilitate ready use in field operations. Comparison of measured results with those predicted by the simplified theory shows that the magnitude of this surge can be predicted accurately. INTRODUCTION It is widely recognized that raising or lowering pipe in a fluid-filled borehole produces momentary variations in fluid pressure, commonly called pressure surges. Both negative (or "swabbing") surges and positive (or "fracturing") surges may occur. In 1934, Cannon1 measured the negative surges and showed that they could be large enough to cause flow of formation fluids into the well-bore and, in extreme cases, lead to blowout conditions. Later, Coins2 measured the positive surges associated with lowering pipe. His results and subsequent field operations strikingly demonstrated that pressure surges could be an important factor in some cases of lost returns. In addition, although the evidence is less clear than in the case of blowouts and lost returns, other investigators 3, 4 feel that pressure surges probably play a part in many instances of minor gas cutting, salt-water flow and other hole trouble. The importance of pressure surges in drilling operations led naturally to attempts to explain the physical causes, nature and magnitude of the surges. Cardwell5 was the first to publish a theory which allowed the quantitative prediction of momentary pressure variations. He assumed that the drilling fluid was a 300-cp Newtonian fluid in turbulent flow. Most field muds have a considerably lower viscosity and are generally believed to be Bingham plastic in nature.6 However, card-well&apos;s results were useful because they were presented in a form convenient for field use and, in some cases, gave a reasonably accurate predicted value for the maximum pressure surge. Subsequently, Ormsby7 published a more comprehensive theory of pressure surges. He discussed both laminar and turbulent flow and considered the theory of mud-bypass devices for reducing pressure surges. As a consequence of his more rigorous approach, his results were more accurate but more complex and difficult to use. Further, both Ormsby and Cardwell considered only the pressure surge arising from viscous drag of the moving mud. Clark later published idealized graphs of surges and presented equations for predicting their magnitudes. In addition to pressure variations arising from viscous drag, he considered those caused by inertial effects. His theory was in this respect more complete than those of Cardwell and Ormsby, although he did not discuss pressures due to breaking of the gel. Furthermore, his equations, while not exceptionally complicated, were too complex for ready use at a drilling location. One difficulty common to all three theories is that none was tested rigorously by direct comparison with measured pressure surges. Their accuracy, therefore, could, not be demonstrated. Further, the two theories based on most realistic assumptions (Ormsby and Clark) required the solution of one or more rather complex algebraic equations. The research described in this paper was undertaken to supplement that described and to overcome some of the difficulties noted. It seemed obvious that a fully satisfactory study of pressure surges should encompass three main phases. 1. A valid theory useful in all field situations must be developed. This theory must be based upon realistic assumptions, must be formulated rigorously and should lead to clear concepts whereby the nature of pressure surges can be easily understood. 2. The theory, however complex and involved, ultimately must be presented in simplified form for convenient field use. This may involve extensive machine computations and the use of figures and empirical equations. 3. The accuracy of the simplified equations must be established by comparing measured pressure surges with those predicted by the theory. These must agree both in their characteristic nature and in magnitude. &apos;This means that careful measurements of surges occurring in actual field operations must be made.