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By Yuji Yamashita, Kazuyoshi Kamimura, Tsuyoshi Takahashi, Naoya Matayoshi

"The CDM-LODIC method (cement deep mixing - low displacement and control) method enables ground displacement to be reduced by removing an amount of soil equivalent to that of injected cement slurry and the volume of the plunged mixing tool, which causes a certain degree of ground displacement. Since the CDM-LODIC method was developed in 1985, it has been applied to over 930 sites and the accumulated volume of stabilized soil has now reached 7.6 million cubic meters.In the CDM method, the number of blade rotations per unit depth in the ground when the mixing blades are withdrawn is considered a construction item. The blade rotation number depends on the degree of mixing between the cement slurry and the ground Some field tests were performed based on the degree of mixing between the cement slurry and the ground. In these tests, a new concept of evaluating the blade rotation number when the screw rod penetrates to a given depth without injecting cement slurry has contributed to the degree of mixing. Furthermore, a correlation exists between the coefficient of efficiency of soil removal and the cement slurry admixture rate. In this paper, we discus the data collected in those field tests and present some application examples.OUTLINE OF CDM-LODIC METHODThe injection of cement slurry may cause some ground displacement during Cement Deep Mixing (CDM). In recent years, due to an increased demand for ground improvement work in urban areas, there is increased concern that buildings near any CDM site may be adversely affected. The deep mixing method which reduces displacement due to mixing (CDM-LODIC method) enables ground displacement to be minimized by removing an amount of soil equivalent to the injected cement slurry and the volume of the mixing tool, which itself causes some ground displacement. When the construction site is near other structures, regardless of whether on or under the ground, the CDM-LODIC method can be used in order to minimize any ground displacement. There are considered to be two main causes of ground displacement as shown in Figure 1. Displacement A indicates ground displacement caused by the volume of the inserted mixing tool during the penetration stage and displacement B indicates ground displacement caused by the volume of the injected stabilizing agent. Thus, by removing soil equivalent to the volume of the inserted mixing tool and the injected stabilizing agent, ground displacement can theoretically be minimized. Figure 2 shows the amount of observed ground displacement in the cases of CDM and CDM-LODIC at an actual site. These case studies indicate that ground displacement can be reduced by removing the soil."

Jan 1, 2015

By Shahid Islam, Lucian Bogdan

There is a rapid expansion of world’s infrastructure and simultaneously existing infrastructure is aging. The maintenance of infrastructures has been of particular concern to the engineering community. Monitoring and evaluating the structures have become more significant than ever. Ground anchor is an important part of the structure where it is installed. Unfortunately there are limited testing methods available to assess the force in the pre-stressing steel. High cost, complicated equipment and limitation of space often prevent these methods from being implemented. DYNA Force sensors have been developed to measure the force in the pre-stressing steel during construction and at any time during the lifetime of the structure. These sensors make use of the magneto-elastic properties of ferrous materials. A readout unit is designed to magnetically energize the steel through the sensor and measure the response of the steel to the process. The readout unit then converts the response into a direct force reading. They can be used for bare, epoxy- coated, galvanized and greased-sheathed steel in the bonded, un-bonded, grouted or un-grouted length of the tendon. It measures the force of the steel element at the location where it is installed and can be recorded manually, automatically, or remotely. The sensor is robust, requires no maintenance and it is expected to have a similar service life to that of the surrounding structure. Sensors have received attention in terms of accuracy, performance, ease in installation, durability, and cost effectiveness. Sensor readings provide a second measurement, in conjunction with the jack pressure gauge, of the post tensioning force during initial testing procedure for ground anchors. This paper describes its application in tie-back and tie-down anchors and force monitoring of retaining walls, bridge abutment and dams where the data were collected manually, automated and remotely. INTRODUCTION Our infrastructure is expanding and the existing infrastructure is aging. Some structures are expensive to maintain and some occasionally fail. There is a large demand for implementing health monitoring of structures. Many tie-backs, retaining walls, dams and other geotechnical structures are post-tensioned and many of them need repair using a post-tensioned system. On many occasions during construction and service life of the structure, it is useful to know the force in the post-tensioning and anchor system. Many piles and drilled shafts are designed using reinforcing steel and the compressive forces in reinforcement are unknown. Although there are many methods to measure the tendon force, most of them are cumbersome, expensive, and the accuracy varies depending on the method used.

Jan 1, 2018

By Shuichiro Okada

Various efforts to reduce energy consumption and smelting cost are made at Tamano Smelter. Production of anode copper has been increased by about 30 % and energy requirement has been decreased about 50 % respectively. Challenges toward more higher goal are being continued. Details about the following are described in this paper. 1 Waste heat recovery Steam recovery at up-take of FSFE Heat recovery from waste gas of anode furnaces 2 Application of tonnage oxygen 3 Application of pulverized carbonaceous fuels to the flash smelting furnace with furnace electrodes ( FSFE ) 4 Application of computer control system to copper smelting 5 Improvement of the fugitive gas collecting system 6 Improvement of the mechanical tuyere puncher for the converter furnace

Jan 1, 1983

By J. W. Putman, N. J. Grant, D. S. Bloom

SEVERAL recent determinations of the melting S point of pure chromium have been reported which give values of 1845°C1; 1895°C,² 1930°C,³ 1860°C,' and 1890°C.5 because of this wide spread of values, it appeared desirable to make one additional attempt to obtain a more accurate, reliable figure. bloom and Grantx recently reported a phase transformation in chromium:.--- it was desired to check this, too, in the course of checking the melting point. To accomplish this, a much higher purity chromium was required. Electrolytic chromium containing about 0.5 pct 0 was crushed to a finer size and was then annealed in highly purified, dried hydrogen at 1375°C for 100 hr. This treatment produced chromium with about 0.008 pct 0, 0.002 pct N, and negligible carbon. The balance of the impurities was 0.3 pct Fe, 0.03 pct Si, 0.004 pct S, and less than 0.001 pct Mo. This chromium was melted in a stabilized zirconia crucible under pre-purified argon, using induction heating. Temperature measurements were made with annealed wolfram-molybdenum thermocouples and a Leeds and Northrup Speedomax Recording Potentiometer. The thermocouples were annealed for 1 min in hydrogen at a temperature of about 2400°C. Each leg of the thermocouple was immersed in an ice-water mixture using mechanical connectors to the lead wires. The thermocouple tip was immersed in the molten chromium in a zirconia protection tube which introduces an error of about 3°C as a temperature drop through the walls of the tube. The weight of chromium was about 183 g. The dimensions of the melt in the crucible were about 1.25 in. diam x 2 in. high. The tip of the thermocouple was held about ½ in. from the bottom of the crucible. Two new thermocouples were used with the above set-up giving the results shown in Table I. Since this chromium is purer than that used by Greenaway, Johnstone and McQuillan,' by Carlile et al.,4 and other investigators,²,3 it is believed to be the more accurate. Thermocouple aging effects which are believed responsible for the high value of 1930°C³ were avoided in this work. This value of 1903°C is correct to about ±10°C. The right hand column lists the temperature of the a ? ß transformation on heating and the ß ? a on cooling.3 A sample curve is shown in Fig. 1. The value so determined is 1840°C + 15°C. Fig. 1 gives adequate evidence that there is a transformation in chromium at high temperatures.' References 'H. T. Greenaway, S. T. M. Johnstone, and M. K. McQuillan: High Temperature Thermal Analysis USing the Tungsten-Molybdenum Thermocouple. Journal Inst. Metals (November 1951) 19, p. 109. ²J. W. Putman, R. D. Potter, and N. J. Grant: The Ternary System Chromium-Molybdenum-Iron. Trans. A.S.M. (1951) 43, p. 824. ³D. S. Bloom and N. J. Grant: Chromium-Nickel Phase Diagram. Trans. AIME (1951) 191, p. 1009; Journal of Metals (November 1951). ' S. J. Carlile, J. W. Christian, and W. Hume-Rothery: The Equilibrium Diagram of the System Chromium-Manganese. Journal Inst. Metals (1949) 76, p. 169. 5G. Grube and R. Knabe: Ztsch. Elektrochemie (1936) 42, p. 793.

Jan 1, 1953

By Leonard Sugin

Recent changes in the field of ore and bulk commodity handling has forced a reevaluation of previously conceived notions. When vessels were small, and sources of raw material were reasonably close to areas of need, the role of the shipping terminal was of secondary importance. Now terminals must be built to take advantage of the economic benefits of the supercarriers. The shipping rates of the 80's will not be determined by the 60,000 DWT or even 150,000 ton capacity bulk carrier, but rather by the supercarriers in the 250,000 DWT class or larger. When the Suez Canal was closed, the shipping industry took a hard look at the economics of the large bulk carrier. Naval architects overcame the problems and successfully designed large supertankers, which today are plying the seas in excess of 350,000 DWT. Orders have been placed for tankers of 480,000 DWT. The shippers of dry bulk materials are now coming to similar conclusions about the economics of supercarriers. As of today, over 40 orders have been placed for vessels in the 250,000 DWT class, representing an investment of over 11/2 billion dollars, and many more are being considered. These vessels are being designed as combination ore/oil (0/0) or ore/bulk/oil (OBO's) carriers. The oil industry has seen the need for terminals which can accommodate these supertankers. The dry bulk shippers, and particularly ore shippers, must now act.

Jan 1, 1972

By C. Özgen Karacan

In longwall development mining of coal seams, planning, optimizing and providing adequate ventilation are very important steps to eliminate the accumulation of explosive methane-air mixtures in the working environment. Mine operators usually try to supply maximum ventilation air based on the capacity of the system and the predicted need underground. This approach is neither economical nor safer as ventilation capacity may decrease in time depending on various mining and coalbed parameters. Thus, it is important to develop better engineered approaches to optimize mine ventilation effectiveness and, therefore, to ensure a safer work environment. This study presents an approach using coalbed methane reservoir modeling and an artificial neural network (ANN) design for prediction and optimization of methane inflows and ventilation air requirements to maintain methane concentrations below statutory limits. A coalbed reservoir model of a three-entry development section, which is typical of Pittsburgh Coalbed mines in the Southwestern Pennsylvania section of Northern Appalachian Basin, was developed taking into account the presence and absence of shielding boreholes around the entries against methane inflow. In the model, grids were dynamically controlled to simulate the advance of mining for parametric simulations. Development and application of artificial neural networks as an optimization tool for ventilation requirements are introduced. Model predictions are used to develop, train, and test artificial neural networks to optimize ventilation requirements. The sensitivity and applications of proposed networks for predicting simulator data are presented and discussed. Results show that reservoir simulations and integrated ANN models can be practical and powerful tools for predicting methane emissions and optimization of ventilation air requirements.

By Irving B. Cadoff, Ernest Levine

The fracture path in a Cu-4 pct Ag alloy wet with mercury was found to he dependent on the heat treatment used prior to tensile testing. Both quenched and slow-cooled alloys were embrittled by the mercury.. For quenched alloys, which were single -phase, the crack path was intergranular. Slowly cooled alloys, which contained precipitate platelets, exhibited transgranular fracture. By comparing stress-strain data for these alloys with similar data on mercury -embyittled solid-solution alloys, it was found that the role of the precipitate and that of the grain boundary in the fracture process were equivalent . THE fracture path which results when metals are strained in a liquid environment appears to be dependent upon the nature of the specific system. Mixed transgranular and intergranular cracking has been observed in the 2024 T4 aluminum alloy when wet with a Hg-Zn amalgam.' Transgranular fracture was induced in an A1-4 pct Cu alloy by masking off the grain boundaries from the liquid Hg-Zn amalgam.' The embrittlement of solid-solution alloys of copper in mercury results in intergranular fracture.' The effect of a precipitated phase on the fracture path in copper alloys is the subject of the present investigation. Cu-4 pct Ag was chosen so that its behavior could be compared with previous work on embrittlement of copper alloys. PROCEDURE High-purity copper (99.999 pct) was used as a base metal, along with 99.999 pct purity silver. Melting was carried out in graphite crucibles with manual agitation to get adequate mixing. The ingots were homogenized by means of vacuum annealing, chemically cleaned, and cold-rolled with intermediate vacuum anneals, to the desired thickness of 0.025 in. The rolled sheets were sheared to the final specimen size of 1 by 0.025 by 0.1 in. The specimens were then electropolished in phosphoric acid (concentrated) and heat-treated in an evacuated capsule at the solution temperature of 770°C. One batch was slow-cooled and the other quenched in water. The thermal etching which occurred during heat treatment was sufficient to permit grain boundary and precipitate delineation. Tensile tests were carried out in air and in mercury on a Table-Model Instron at a pulling speed of 0.2 in. per min. Wetting was accomplished by electro-polishing in phosphoric acid, rinsing in alcohol, and immersing in a pool of mercury. Once wet the coating was stable throughout the mechanical tests. In our studies it was found that wetting the surface or total immersion in mercury produced identical results. For convenience, the wetting technique was used for the experiments described. The crack pattern was observed directly on the surface by removing the mercury after testing. De-wetting was accomplished by flame heating the samples in a vacuum after testing and before observation of the surface. No etchant or polishing was used so as not to obscure the crack pattern on the surface. The mercury removal, however, resulted in a pitted surface but otherwise left the pertinent features visible. Photomicrographs were taken in this condition so as not to disturb the structure associated with the crack pattern. The average precipitate spacing was measured previous to coating the sample with mercury by use of an optical eyepiece micrometer. RESULTS The microstructure of the quenched specimens was single-phase while that of the slow-cooled specimens contained thin platelets of a second

Jan 1, 1964

Significantly increase the amount of fresh air that sweeps the face in front of a continuous mining ma-chine, in order to prevent methane gas buildup. Approach Water sprays are mounted along the sides of a continuous miner and behind the cutter head to help push ventilating air along the required path, and prevent its short circuiting. How It Works A continuous miner is fitted with two sets of water sprays, one of which is used at a time. The set of sprays shown in the diagram, helps move the ventilating air forward along the left side of the miner and across the cutter drum from left to right. That air is then drawn into the exhaust air passageway located along

Jan 1, 1978

By Y. M. Zhao

The dry coal preparation technology based on air dense medium fluidized bed is an innovative dry highly efficient technology of coal by introducing fluidization technology into beneficiation.. A modularized 40-60 tones/hr system (KZX-40) with an air dense medium fluidized bed separator was established. The construction cost of the modularized system is only 1/3 of the traditional wet heavy-medium coal preparation plant construction cost with the same capacity, and the consumption of dense medium can be reduced by 50%-60%. The footprint and volume of the system are decreased by 75% and by 89.81%, respectively. These facts show the improved intensity, efficiency and economy of modularized coal preparation technique. The modularized KZX-40 system can be used to separated 50-6 mm coal over a separation density range of 1.3-2.2g/cm3 depending on the variation of <1mm fine coal content. The separation efficiency of the system was investigated at low and high separation densities by float-sink experiments. The partition curve of the products at low separation density shows that the separation density (d) is 1.33g/cm3, and the probable error (E) value is 0.05g/cm3. Using 50-6mm coal with an ash content of 55.35% as feedstock, at a high separation density of 1.61g/cm3, the clean coal with an ash content of 14.67% and the tailing with an ash content of 71.26% are produced with an E value of 0.06g/cm3. It is clear that the modularized KZX-40 system is suitable for separating 50-6mm coal effectively. During the dry coal preparation process, the dust is removed by the bag collector and recycled back into the separator. So the system has the advantages to work without environmental pollution and water. The modularized system greatly reduces the construction and operating costs and decreases the area and volume required, compared with wet dense medium system. The system is applicable to the coals located in arid regions and also to the coals that tend to slime during wet separation. Keywords: modularized, KZX-40, fluidized bed, beneficiation

Sep 1, 2012

By Wilson Blake

The occurrence of rock bursts in some deep mines throughout the world constitutes a severe operational hazard. In addition to endangering the safety of the miners, the rock-burst problem is a major factor in mining economically in deep mines because of the loss of production and expense owing to cleanup and repairs following a burst. Developing means of controlling or eliminating rock bursts has been the subject of intensive research for over 50 years. While much has been learned about the effects of rock bursts, little is known about their basic causes; hence, control measures have been at best only partially effective--attested to by the number and severity of bursts that continue to occur throughout the world each year. In the Coeur d&apos;Alene mining district of north Idaho, the rock-burst problem continues as the silver and lead veins persist at depth. These veins are presently being mined at greater than 7,000 feet below the surface and will be mined to some 10,000 feet in the future. The majority of rock bursts in this district occur in pillars. While pillar bursting has been essentially eliminated in some deep-mining districts by longwall techniques, modification or application of this technique to the thin, irregular, and near vertically dipping veins of the Coeur d&apos;Alene district has not been found to be practical. The creation of pillars is a consequence of the horizontal cut and fill mining method used. Figure 1 shows a vertical longitudinal projection of the silver vein at the Galena mine, illustrating the mining method. Stoping progresses between raises and is carried upward between levels. A horizontal pillar is created as a stope approaches a mined-out level. Recent broad-band micro seismic monitoring of rock-burst-prone stopes by the Bureau of Mines has shown that potential burst zones could be delineated weeks in advance of a burst and that a definite sequence of events took place prior to the occurrence of a pillar burst (1). Hence, time was available for control measures to be effected when a stope pillar reached a critical burst geometry.

Jan 1, 1971

By P. Geoffrey Feiss

The Piedmont province of the southern Appalachians is becoming the focus of interest for many exploration geologists. In the past, only those deposits with significant surface exposure have been exploited. Thus, few deposits have been found and relatively little exploration has been conducted in recent years. Modern geochemical and geophysical techniques can alleviate this problem of concentrating on exposed ore bodies by allowing us to "look through" the soil and saprolite to detect the presence of significant mineralization at depth. This paper will attempt to evaluate the feasibility and effectiveness of several geo¬chemical exploration techniques in the Piedmont, of Cabarrus and Stanly Counties, North Carolina. The area chosen for the study is shown in Figure 1, lying almost wholly within the Mt. Pleasant quadrangle, North Carolina. The area is on the eastern boundary between the Charlotte belt, a zone of plutonic and intermediate grade metamorphic rocks, and the Carolina Slate belt, a series of complexly interbedded volcanic and sedimentary rocks of predominantly low grade metamorphism. The area is now considered to be a 500 million year old active, continental margin.1 As is typical of most of the piedmont, outcrop is sparse. Figure 2 is a sketch map of the general geology of the area under study, showing the Charlotte belt rocks in the northwestern quadrant and slate belt rocks, to the east. Within the area are a number of old mines and prospects, the most famous of which are the Furniss and the Phoenix mines in Cabarrus County. All are reported to have contained Au and Cu. Ag and Pb were reported from some. A summary of the deposits is given in Table 1. Data used in this study are from three Master&apos;s theses conducted at the University of North Carolina at Chapel Hill. 3,3,6 In separate studies, well waters5, B-zone soils3, and vein and float quartz6 from the area described were sampled and analyzed. Each study concluded separately that geochemical anomalies in the vicinity of the ores justify use of that specific sample type in a geo-chemical exploration program. However, no comparative study of the methods has

Jan 1, 1977

By A. L. Engel

This report is a compilation of results of preliminary tests on scheelite (tungsten) ores and tailings. These investigations were made to assist in establishing satisfactory treatment methods for small-scale concentrator operations, or to indicate a. method for conserving previously lost mineral values in old tailings, if possible. A discussion of test procedures is included, as it was felt that this would add to understanding the results reported under the several projects. The treatment of scheelite ores has become more or less standardized. Important differences occur in textures of ores from various mining districts. However, and this must be considered when planning ore-dressing operations. In most of the present investigations, only a limited amount of work was done, usually just enough to answer a specific question in regard to a particular ore or concerning local conditions. Two methods of treatment included gravity concentration, magnetic separation, and flotation.

Jan 1, 1952

The National Institute of Occupational Safety and Health has classified diesel exhaust as a potential human carcinogen. Though standards for diesel particulate matter (DPM) in the work place have not been established, concern for the health of miners is prompting mine operators to consider methods for reducing worker exposure to diesel exhaust. Approach One of many methods for reducing DPM being investigated by the Bureau of Mines is the use of additives in diesel fuel to improve combustion. Research Results Three fuel additives have been tested in Caterpillar and Deutz diesel engines which are similar to types used in underground mines. One iron-based additive containing ferrous picrate had no effect on emissions. A second iron-based additive containing ferrocene reduced DPM between 5 and 45 pet depending on engine operating conditions. The 37-pct reduction for an 8-minute duty cycle, which includes a wide range of transient loads and speeds, is considered to represent in-mine performance.

Jan 1, 1990

By Patricio F. Mendez

This paper presents a formalism to automate portions of the traditional scaling procedure. This formalism, called here Order of Magnitude Scaling (OMS), captures essential components of the governing equations into a set of matrices and arrays amenable to computer implementation using standard linear algebra tools. This approach is valid and specially useful for large systems of multicoupled equations. The matrix approach proposed enables one to automate operations such as normalization, dominant balance, obtention of characteristic values, and check for self-consistency. Also, automation permits an exhaustive exploration of all possible balances and the discovery of unsuspected scaling laws. As an example, OMS is applied to the analysis of the viscous boundary layer with no external pressure gradient. The obtained scaling laws for boundary layer thickness and transverse velocity are the same as those obtained with traditional scaling, and in addition, a meaningful estimation for pressure variations within the boundary layer is obtained; this last estimation is typically not addressed in the manual analysis.

Jan 1, 2006

By Tao Cheng

Previous research and applications in construction resource optimization have focused on tracking the location of material and equipment. There is a lack of studies on automated monitoring of the interaction between workers and equipment for safety purposes. This paper presents a new approach for measuring the safety performance of construction personnel particularly when they work in very close proximity to moving equipment as well as static hazards such as chemical and flammable substances. A method of generating hazardous zones according to the geometric and kinematic characteristics of the considered hazard is introduced. The spatio-temporal relationships between the hazardous zones and workers? positioning data collected by real-time location sensing technology are automatically analyzed. This approach has been validated in a controlled test bed environment that simulates a construction site. Results indicate that worker?s safety performance of selected activities can be automatically and reliably measured using the developed approach. Furthermore, a heat map is generated for visualizing proximity related issues in the test bed using the computed results.

Aug 1, 2013

By Giorgio Höfer-Öllinger, Peter Pointner, Manfred Stadlober

"SUMMARY Investigations from tunnel face are part of risk mitigation measures during the excavation works. With the tunnel equipment, percussion drillings of up to 30-40m can be achieved. Core drillings are state of art method for investigation exceeding 50m. At Koralm base tunnel, up to 270m deep percussion drillings were performed with drilling rigs and accompanied by an intensive investigation program. These investigations consisted of monitoring during the drilling, field tests (with packer, using the preventer, borehole imaging) and in laboratory. Percussion drillings are cheaper and save time of interruption of the excavation progress. INTRODUCTION As part of a proper risk management, horizontal advance drillings during excavation of underground works can be seen as state of art and meet wide acceptance. Core drillings, deep and shallow percussion drillings can be differed. The selection of the type of drilling, meanwhile, causes intensive discussions. On the one hand, only a core drilling allows a direct investigation of the rock mass expected during later excavation works. On the other hand core drillings are expensive in both cost and time – if there is no excavation progress during the investigation measures – in construction time. Percussion drillings can be performed as rapid investigation measure with the excavation equipment (“Jumbo”) allowing two dimensional image of the ground around the cross section. There is some limitation concerning a reasonable depth of approximately 30m and a borehole diameter of 76mm. The applications of preventer, packer or borehole imaging are hardly applicable. By use of a drilling rig depths of percussion drillings of several hundred meters can be achieved relative easily and there is less limitation of the borehole diameter. Installation of a preventer is possible, as well as packer tests and borehole measurements (imaging, gyroscope, borehole geophysics). The gap of information between core and percussion drilling cannot be closed completely, but it can be reduced substantially and sufficiently by combination of an intensive program of measurements and analysis accompanying the investigation works."

Jan 1, 2016

By C. E. Lundin, D. T. Klodt

The binary alloy systems, Y-Ti, Y-Zr, and Y-Hf, have been investigated throughout their entire composition regions. There is no compound formation in any of the systems, and each system is characterized by a single eutectic reaction. The eutectic compositions and temperatures are as follows: A eutectoid reaction pct Y and 870°C occurs in the Y-Ti system, whereas a peritectoid reaction,: pct Y and 880°C occurs in the Y-Zr system. Peri-tectic-type reactions at temperatures above the eutectic levels are postulated for the yttrium and hafnium transfovmations. The development of the technology of yttrium has been given considerable attention during the past few years, and studies of binary phase equilibria have, of course, taken a prominent position in this development. In many respects yttrium, in the third group of metals of the periodic table, is similar to the adjacent group of metals, titanium, zirconium, and hafnium, and the knowledge of the phase relationships of yttrium with these metals is basic to their technology. MATERIALS AND EXPERIMENTAL PROCEDURES Materials. The metals for this investigation were supplied by the General Electric Co., Aircraft Nuclear Propulsion Department. The yttrium was in the form of an arc-melted ingot, and the other metals were in the form of high-purity, iodide-Process crystal bar. Table I lists the purities of these materials. Alloy Preparation. Melting was done by conventional techniques in a nonconsumable electrode arc furnace in an atmosphere of purified argon. Melting conditions for each binary system were the same. Each alloy button was inverted and remelted several times to assure homogeneity. Accurate weights of the charges and resultant alloy buttons were obtained to indicate deviations from intended compositions. No chemical analyses were obtained since melting weight losses were consistently in the range of 0.1 to 0.2 pct of the total weight. 10- or 20-g buttons for each 5.0 wt pct composition increment were melted to survey the three individual alloy systems. Additional alloys differing in composition by 1.0 or 0.1 wt pct increments were also melted to study selected regions of the systems. Metallograpllic Techniques. Standard metallo-graphic techniques were followed for mounting and rough grinding. Preliminary polishing was accomplished using 6-u diamond paste as an abrasive on a Metcloth Lap. Final polishing was done on a Microcloth-covered wheel using 1-u diamond abrasive paste. Purified kerosene was used as a lubricant for both polishing stages. • sothermal- Annealing. Alloys were sectioned for as-cast structlure examinations and then homogenized in preparation for isothermal-annealing treatments. Homo{:enization was accomplished by cold pressing the alloy buttons followed by 72-hr anneals at 1100c. The alloys were encapsulated in Vycor or quartz for the homogenization treatments or for isothermal anneals. Resistance-wound or resistance-element tube furnaces were used for the annealing treatments. The homogenized alloy buttons were cold rolled until cracking occurred or until a -in. specimen thickness was obtained. Small -in. square) specimens for the isothermal anneals were then sawed from the alloys. Each specimen was wrapped in tantalum foil before being sealed in the capsule. Temperatures during the anneals were controlled The time at temperature necessary to equilibrate the structures during the anneals was determined for each alloy system by holding triplicate specimens of alloys at a constant temperature for three different periotls. The specimens were quenched and examined microscopically to determine the number and amounts of phases present in the micro-structure as a function of time. Melting Studies. Eutectic temperatures of the three alloy systems were established from the results of incipient-melting studies conducted on as-cast alloys. Specimens to be melted were suspended on a tungsten wire inside a graphite cylinder placed in a glass vacuum chamber. An optical pyrometer was used to follow the temperature of the specimen as it was inductively heated in a high vacuum. The temperatures were corrected for emissivity losses by standardizing the pyrometer with known-melting-point metals. Accuracy of the temperature measurements is estimated to be + 10°C. The melting point of the yttrium was determined to be 1550°C by this technique. The invariant-temperature levels were also checked by an anneal-quench technique. This technique consists of annealing a series of

Jan 1, 1962

By Mark K. Larson

Calibration of LaModel for deep coal mines begins with adjustment of overburden stiffness for load transfer distance. This calibration determines whether mining induced stresses are concentrated in the immediate abutment of the gob, or spread over a wider area. In the absence of site information, an empirically-based estimate is often used. Where data is available, a recommended calibration procedure can be followed, as is done in this case study at a deep western longwall mine, with minor modifications and extensions. In this case, data sources included borehole pressure cells, flatjacks installed in series with support Cans, and observed changes in ground conditions. Calibration was based on the first detection of mining-induced stress from the advancing longwall. Detection was found to depend on the type and sensitivity of measurement. Borehole pressure cell data with a 20-psi-increase detection threshold were chosen as the standard, in accord with data used in deriving empirical relationships. Application of this standard produced a load transfer distance estimate roughly four times the empirical relationship developed by Peng and Chiang (1984). This is a significant deviation with important implications for panel design at this site. Data from flatjacks, ground condition observations, and borehole pressure cells with higher threshold values, were tightly clustered and show load transfer distances from two to four times empirical guidance. Ratios between various measurements can be used to adjust measurements to the standard (although they may depend on mine geology). Once established, ratios can be used to adjust estimates, say from support flatjacks or ground observations, to the standard, where borehole pressure cell data is not available.`

Jan 1, 2012

By R. E. Campbell

Uranium metal of improved purity was prepared by electrorefining commercial magnesium-reduced uranium in a molten sodium chloride-uranium trichloride electrolyte. The best operating conditions for the preparation of refined metal were established as follows: an electrolyte containing 8.7 to 13.3 weight-percent uranium; initial cathode current densities from 300 to 1,500 amp/sq ft; and a molten salt temperature of 860° C. Ingots produced from electrorefined uranium crystals prepared with these operating conditions were substantially free of metallic impurities. The only impurities in the refined and consolidated metal were present in low or undetectable amounts.

Jan 1, 1965

By J. Creamer

Pumping plays a major role across multiple process and facility applications in the mining world. Examples include: raw water supply, leach solutions, chemicals, dewatering, and mine drainage, and process water for metal recovery. Mining operations such as grinding, classifying, separating and concentrating minerals all have pumps at the heart of the operations Special purpose pumps such as dewatering, process water and slurry pumps are at the heart of many of these processes. Unfortunately the pumps themselves are often overlooked in terms of energy savings potential as they are often embedded into these sophisticated processes which are the ultimate operational focus.

Feb 23, 2014