Search Documents

By H. Nazeri, T. G. Rozgonyi

Many industries when volumes of the solid materials are large invariably relay upon the gravity to induce solids to flow out of storage, through channels and reactors. In mining industry ore pass’s requirements to less energy (only gravity) have made them very popular both in underground and open pit mines. This paper discusses the major findings of research on 2D Discrete Element Method simulation of gravity flow of ore in ore passes. Results show that ore characteristics, ore pass configuration can significantly affect loads (static, dynamic) on the gate assembly and creation of hang-ups.

Jan 1, 2003

By F. W. Bloecher, A. M. Gaudin

H. H. Kellogg—There is one point that the author has failed to emphasize sufficiently in his paper. What is commonly called the equilibrium contact-angle (the author's "maximum contact-angle") can have only one value on a smooth, flat, homogeneous surface under a given set of conditions. The equilibrium contact-angle is defined, for such a system, as the angle between the solid-liquid and liquid-gas interfaces, measured through the liquid. The value of the equilibrium contact-angle is uniquely determined by the value of the interfacial energies of the three intersecting interfaces and is independent of other forces in the system. When the liquid-gas interface intersects the solid at an edge—as was the case for all the experiments reported in this paper—the orientation of the solid-liquid interface is indeterminate or varies through 90" for a right-angle edge. Mr. Morris has called the angle between the horizontal and the liquid-gas interface for this edge condition a "static contact-angle." I feel that this term is unnecessarily misleading. In the first place, "static contact-angle" sounds too much like "equilibrium contact-angle." In the second place, the magnitude of the "static contact-angle," which I would prefer to call the "supporting angle," is determined by the forces in the system other than those derived from the interfacial energies, hence "contact angle" is misleading. If Mr. Morris had said that the "supporting-angle" is variable and depends on the weight of the particle and size of the bubble and that it has a maximum possible value equal to the equilibrium contact-angle, his discussion would have been more accurate. T. M. Morris (author's reply)—Mr. Kellogg puts forth a reasonable criticism of some of the terminology used in the paper. I agree that the term "static contact angle" may be misleading. Substitution of the term "supporting angle" or "vector angle" may be more suitable. F. X. Tartaron—In this paper the author presents a very interesting mathematical development of the forces present when a mineral particle adheres to an air bubble. Excellent concordance is obtained between mathematical formulation and experimental results. It is the writer's understanding that when the mineral surface presented to an air bubble is greater than the area of contact, the maximum contact angle is obtained. However, this contact angle represents distortion of the bubble, the normal shape of which is spherical or in cross-section, circular. This distortion produces a force that acts in opposition to the force of adhesion between the bubble and particle. Hence, at maximum contact angle, the force of adhesion between bubble and particle is at a minimum for static conditions. However, when the size of bubble is increased, the size of particle remaining the same (and all other conditions remaining the same), the contact angle decreases, the distortion of the bubble decreases and the force in opposition to adherence of bubble and particle also decreases. Thus, there is stronger attachment between bubble and particle. When this situation is applied to actual flotation conditions, it is doubtful that it has any significance. The reason is that the bubbles are normally so much larger than the particles, that in substantially all cases, it is probable that negligible distortion of the bubble takes place. In table IV, the author makes computations for bubbles from 0.50 to 2 mm diam. This is from 0.02 in. to 0.08 in. Certainly the bubbles generated in a flotation machine are far larger than this. The surfaces of the author's bubbles range from 0.79 to 12.6 sq mm. The area of contact of the glass rod (0.15 mm diam) is 0.017 sq mm. Thus, ratio of bubble surface to mineral area of contact ranges from 47 to 741 in round numbers. If we take a %-in. diam bubble and a 65-mesh (0.208 mm) particle of cubical shape, the ratio of bubble surface to mineral area of contact is 2931. Mineral particles do not readily become attached to air bubbles. Taggart has shown that in pneumatic flotation machines collector-coated particles are only temporarily attached to bubbles. They keep falling off and down in the froth but at a delayed rate as compared with gangue. Spedden and Hannan's motion pictures confirm the difficulty of attaching particles to air bubbles. In the agitation froth process, according to Taggart, air is precipitated from the water selectively on to the collector-coated particles and these

Jan 1, 1951

By N. Nikolaeva, A. Romashev, T. Aleksandrova

Energetic characteristics identify energy consumption for destruction of prills and kinetic characteristics rate formation of finished size grade in the course of destruction and identify crushing and grinding equipment capacity. And if screen sizing or classification processes are applied in the cycle of ore preparation, then the use of characteristics of separation to size – separating characteristics – is required for theoretical description. Separating characteristics have a lower profile for ore preparation but, nevertheless, they have to be taken into account especially for balance and design calculations of crushing and grinding circuits. In most cases there are impregnations of minerals which vary widely in energy consumption and destruction kinetics and thus polyminerality must be considered as one of priority factor. Raw materials which passed through crushing and grinding processes can be assessed numerically by functions of fractional composition of two types: differential distribution function y ( €) and assay function B( c ) . A set of experiments on grinding of crushed raw materials at different time (up to various sizes) was conducted to analyze effect of grinding size of carbonaceous overburden on function y € and B ( c) as well as to justify the possibility of preconcentration of raw materials at the stage of ore preparation. Analysis of metals distribution per size grades showed that metals are concentrated in size grades of less than 0.315 mm (which is equivalent of cut point for this type of raw material), however, there is no overgrinding and oversludging of material, and enriched product for its further processing can be excluded with the help of classification. The stage of size segregation was tested as a method of preconcentration of raw materials for optimization of ore preparation and further separation.

Jan 1, 2018

By M. S. Tsai

Recovery of uranium from wet-process phosphoric acid is a newly developed source of uranium. Many processes have been developed but the OPAP (octylphenyl acid phosphate) process is still the valuable one because the OPAP reagent compound has the high extraction ,power and cheap cost. The OPAP process was already studied by murthy(1) in 1970 and its complete process flow sheet was first fulfilled by F.T. Hurst(2) in 1974. WCFC(3) (western Co-op Fertilizer Ltd.) in cooperation with ESI (Earth Science Inc.) set up the OPAP uranium recovery pilot plant in Canada in 1978. We have studied the OPAP process since 1974 and first improved the OPAP extractant by proper adjustment of the DOPAP/MOPAP mole ratio with CH3OH-H20 method, resulting in shortening the phase separation time and avoiding the precipitation occurrence in our process. Second, we utilize the reduction and oxidation occurring by DC power supply on either side of the membrane to achieve the extraction and stripping at the same time. An improved OPAP process in which high recovery yield of uranium and acid uncontaminated by iron has been developed in our laboratory.

Jan 1, 1982

By E. Miller, R. Geffken, K. L. Komarek

The thermodynamzc properties oJ liquid Cd-Sb alloys were investigated using the cell arrangement measurments were obtained every 2°C at a heating and cooling rate of 12°C per hr and at equilibrium every 2O0C frorn 500°C down through the stable liquidus. The S-shaped asCd US composition curve was used in the cotnposition regzon near Cd,Sb, to calculate a tempeerture-dependent inleraction coefficient from quasichemical theory. Rapid changes in a scd were observed at a transition temperature varying from 400" to 465°C depending on con/kosition. It could not be determined if the changes in aScd were discontinuous, but tlze composition dependeke of the magnitude of the change is indicative of a second-order phase transformation in the liquid. The values of the experimental changes in ASCd are in agreement with calculations from the slope of the transition temperature, using the concept that a second-ovdev phase transition occurs in liquid Cd-Sb alloys. II is suggested that the transformalion is associated with the formation of Cd4Sb3 molecules in the liquid. ThE structure of liquid alloys is the subject of many investigations. X-ray, resistivity, and thermody-namic data have been interpreted as indicating varying degrees of short-range order in the liquid in alloy systems forming inter metallic compounds. In general, the melting process is not a transition from an ordered to a completely disordered state, but some degree of order is retained in the liquid. Maximum ordering in the liquid state occurs close to the melting temperature of the compound and the arrangement of atoms becomes more random at higher temperatures. Of special interest in this respect is the Cd-Sb system. It is one of the few metallic systems which form both stable and metastable compounds when liquid alloys are cooled at normal rates. The stable system exhibits an intermetallic compound, CdSb, melting at 459"c.l A second compound, CdrSbs, has also been reported,' melting close to this temperature. The metastable system has one compound, CdsSbz, melting at 420"c.I Resistivity measurements on liquid Cd-Sb alloys close to the liquidus temperatures have been interpreted in terms of a complex ordering behavior which changes rapidly with increasing temperature.3 The resistivity-composition curve is characterized by two maxima corresponding in composition to CdSb and CdsSbz. The resistivity-temperature plots show sharp breaks for alloys in the composition range of 45 to 70 at. pct Cd on cooling through a transition temperature close to the stable liquidus. Fisher and phillips4 investigated the influence of temperature and composition on the viscosity of liquid CdSb alloys. The viscosity of some alloys increases sharply on supercooling below the stable liquidus. A maximum in the viscosity-composition curve occurs at the composition CdSb. The thermodynamic properties of liquid Cd-Sb alloys have been investigated by Seltz and ~e~itt' and Elliott and chipmane by the electromotive-force method and their results are in good agreement. However, these investigations were carried out at temperatures well above the liquidus temperatures of the alloys, and the temperature coefficients of the electromotive force, dE/dT, were obtained from experimental points for each alloy at a few temperatures considerably above the liquidus temperature. Scheil and ~aach' investigated the thermodynamic properties of this system by the dew point method in the temperature range from about 100°C above the stable liquidus down into the supercooled liquid region. They reported several anomalies, i.e., the activity of a melt on heating differed from that on cooling, and the activity increased sharply in the limited temperature interval immediately above the liquidus temperature of the stable alloy, followed by a sudden decrease below the liquidus. Values obtained on heating and cooling were not in agreement. A reinvesti-gation of a few alloys by Scheil and Kalkuhl' by the electromotive-force method failed to confirm these observations. The authors concluded that the anomalies were due to inhomogeneities in the starting alloys and they discarded their previous results. The present investigation was undertaken in order to obtain thermodynamic data close to the liquidus temperature and in the supercooled region where the anomalies were originally reported, employing the electro motive-force method. This method is quite precise and will most easily permit observations of small changes in activity and partial molar entropy with temperature. Measurements were taken every few degrees so that the dE/dT values could be calculated over the entire temperature range and small changes in the thermodynamic properties close to the liquidus temperature could be observed. I) EXPERIMENTAL PROCEDURE Specimens were prepared from 99.999+ pct Cd and Sb (Cominco). Surface oxide was removed by scraping and then melting the metals under vacuum and filtering through Pyrex wool. Appropriate amounts of the metals were weighed on an analytical balance to k0.1 mg, sealed in double Pyrex capsules under vacuum,

Jan 1, 1968

By S. E. Phillipson

The Late Miocene San Cristobal Ag-Zn-Pb deposit represents syngenetic and epigenetic mineralization with low- and high-sulfidation characteristics. Geology is characterized by barren dacitic ring fracture domes, mineralized resurgent rhyodacite domes, strongly altered and mineralized tuffaceous lacustrine sedimentary rocks, and an extensive crystal-lithic tuff debris apron. The ore body is hosted by intra-cauldron sedimentary rocks and breccias. Fluid inclusions suggest that silver, lead, and zinc were transported as chloride complexes and precipitated by cooling in veins from <5 wt. % NaCl eq. fluids at 170°-215° C. Silver associated with resurgent rhyodacite was transported as a chloride complex and precipitated by increased H2S activity or increased fluid pH.

Jan 1, 2001

By J. R. Thoenen

In Progress Rerort 1,4/ a number of facto were demonstrated and conclusions drawn from experimental tests and records made during commercial blasting operations at a number of quarries. For example, the tests showed (1) that vibrations received on outcrops were of comparatively

Jan 1, 1938

By G. Laird, N. B. Gray, N. Lawson

"Photographic, video, laser, hot film and conductivity methods are used in the experimental study of gas-liquid flows. A discussion of their capabilities and limitations are given in this paper illustrating the wide range of phenomena that can be studied. Most of these methods are limited to physical models at room temperature with transparent fluids, although they can be extended for use with opaque and hot fluids. A number of these techniques have been used by the GKW CRC in studies on industrial plants and their usage is increasing although a number of technical difficulties still need to be overcome. An in-depth discussion of the laser doppler anemometry (LDA) and particle image velocimetry (PIV) methods is given with experimental results on the flow field of an air plume in water based on advanced development of the techniques and studies carried out at the GKW CRC. The LDA method provides high resolution data on the velocity profiles, while the PIV method provides an overall view of the complex flow structure occurring at the gas-liquid regions. These two methods complement each other in providing experimental data for validating numerical models and exploring the complexities of multi phase flows.IntroductionThe injection of gases into melts is an important operation in the metallurgical industry. It is used in converters, anode furnaces, blast furnaces, ladles, bath smelters, zinc fumers and many other smelting processes. In many of these processes, the gas is injected into a molten bath resulting in the formation of bubbles that promote reaction, mixing, alloying and heat transfer. The study of gas-liquid systems presents enormous challenges to the researcher due to the complexity of the mathematical and physical modelling which require innovative numerical and experimental skills."

Jan 1, 1996

By M. H. Kirchner

Trackless mining at Thabazimbi Mine by M. H. KIRCHNER*. Pr. Eng.. B.Sc.. B.Sc. (Elec. Eng.}(Stellenbosch). Dip. Mining (Pta.) Certain aspects ?f the&apos; methods used in the exploitation, by sub-level caving, of a wide, tabular, steeply dipping orebody are described, reference being made to the use of modern mechanized equipment. Statistics relating to production and labour, as well as some geological details, are given.

By J. B. Morrow, D. H. Davis

THERE are two general approaches to the problem of increasing profits from an operation. One is to lower expense; the other is to raise income. Mechanical preparation of coal may be used for either purpose but a prudent consideration of many details must precede any decision lest the results be negative instead of positive. It is quite possible that any net gain will result from a combination of the two. Since mechanically prepared coal invariably is a better product qualitatively than a hand-picked coal from the same mine, it is a reasonable expectation that the customer will be willing to increase the producer&apos;s income by paying a higher price. Or there may be the possibility that a combination of mechanical mining plus mechanical cleaning will give a lower over-all production cost for the coal in the railroad car. More likely, there will be found a combination of these two factors. From the customer&apos;s point of view, the competitive delivered cost per B.t.u. considered in relation to such incidental factors as dust nuisance, handling properties, ash disposal, and ash fusibility determines what he will pay. In-a bulk tonnage such as coal, freight is a very considerable part of the delivered fuel cost, and obviously freight paid on incombustible ash has no economic attractions. INCENTIVE FOR CLEANING Coal is prepared in four major ways: l (1) by screening or sizing, (2) by mixing or blending, (3) by cleaning, including hand picking and mechanical cleaning, (4) by dustless treatment. By a combination of any or all of these methods, coal can be prepared to standard specifications. It is easily possible to have good cleaning and still get a poor final product because of faulty screening or mixing, while it is possible to produce a very acceptable product from mediocre cleaning if the coal is well screened and mixed.

Jan 1, 1950

By Alan A. Campoli

"Pumpable crib support for longwall gates and ventilation bleeder entries is becoming more prevalent in United States coal mines (Figure 1). The pumpable crib selection and spacing design has been greatly refined by the full-scale testing conducted at the National Institute for Occupational Safety and Health (NIOSH) Mine Roof Simulator. The peak load on 24-, 27-, 30-, and 36- inch diameter J-Cribs is, on average, 300, 400, 450, and 650 kips, respectively. Standard J-Cribs have useful deformation of approximately 8 inches. The maximum useful deformation can be extended to 18–20 inches with an exterior reinforcement layer or an interior double wall, for all four J-Crib diameters. J-Crib diameter is primarily limited by a maximum 4.5:1 height-to-diameter aspect ratio. Spacing is controlled by immediate roof stability, anticipated pillar deformation, and roof bolting practice. Approximately 500,000 J-Cribs have been successfully placed in 18 different United States longwall coal mines. The selection and spacing of the J-Crib utilized to date is summarized for each mine.IntroductionLongwall productivity and safety depend on ground stability in gate and ventilation bleeder entries. Numerous support technologies have been developed and employed in United States longwall mines since the 1990s to replace traditional wooden cribbing. Many, if not all, of these technologies have been evaluated at the NIOSH Pittsburgh Research Laboratory since the mid-1990s (Mucho, et al., 1999). The NIOSH Mine Roof Simulator has a 3,000-kip vertical load and 24-inch displacement capacity, which has facilitated in-depth analysis of complex multimaterial support technologies like the pumpable crib. The extreme cost and human exposure risk associated with modern longwall mining prevent the trial and error development that would have been required absent the Mine Roof Simulator research. As a direct result of this research, pumpable cribs are becoming a major component of the standing support industry, providing the peak capacity and extended deformation characteristics necessary for successful gate and bleeder support. Recent research by Zhang, et al. (2012) and others have defined the required performance characteristics."

Jan 1, 2015

By John S. Jones, Ralph E. Brown

INTRODUCTION For more than a century, artificial ground freezing has been used for groundwater control and structural support for excavations. Most of the early uses of the freezing method were for sinking deep access shafts for mines and tunnels (1,2,3,4). More recently, ground freezing has increasingly been used for construction of large diameter cofferdams and soft-ground and mixed-face tunnels (5). Although ground freezing has been used in the past-for tunnels, it was invariably used as a last resort measure, where more conventional measures could not be used. The more recent freezing applications, however, have become increasingly cost competitive with more conventional techniques, and are now being included as part of the design concept (6,7,8,9,10,11,12). The purpose of this paper is to describe some of the more recent applications of ground freezing for tunnel construction. The paper begins with a brief description of the most commonly used freezing system, the Poetsch process. Recent tunneling projects utilizing ground freezing for structural support are then discussed. DESCRIPTION OF THE FREEZING METHOD The most commonly used freezing method is the Poetsch process, which was originally developed by F. H. Poetsch in the late 1800&apos;s. The system consists of a brine coolant, typically calcium chloride and water. Freezepipes are placed into boreholes or are

Jan 1, 1979

By I Wilkomirsky

The neutralization of S02 from copper smelter gases to produce calcium sulphate (anhydrite) is considered an attractive alternative to sulphuric acid production. To develop the required technology for the process, a three-stages fluidized bed reactor prototype was designed and operated using both high and low grade limestone and gases with 2, 8 and 12 vol -% S02. The results obtained shows that at 800°C and up to 8 vol-% S02 in the gases, the capture of S02 reaches near 99% with limestone conversion to anhydrite of 45 to 48%. A larger pilot plant is presently being built at the Codelco El Teniente-Caletones Smelter to demostrate the technology and to evaluate the economics of the process. Cu2007

Jan 1, 2007

By E. G. Dean

A method of top slicing has been devised at the Miami Copper Co.&apos;s mine at Miami, Aria., which differs radically in some ways from the customary methods of top slicing. The area of that section of the orebody in which top slicing is used is about 800 ft. square. The ore, while for the most part soft, is, nevertheless, considerably harder than the capping. The latter is siliceous, seldom containing any clay or other binding material, and breaks into fine particles so that it runs like sand if given the opportunity. Because of these facts, and because the ore is above the average grade of the mine ore, it has been mined by top slicing. Haulage levels are opened up 150 ft. apart, vertically, with two sub-levels between at 50-ft. intervals, to facilitate the putting up of ore chutes. These sublevels are used during slicing for distributing air in the ventilation system. On the haulage level the drifts are spaced on 50-ft. centers, and raises along these drifts are also spaced on 50-ft. centers, except the incline raises as hereafter noted. The raises are cribbed where necessary. Where the wear will be excessive, 1/4-in. iron plates are spiked to the top of every third set of cribbing, for its protection. When top slicing was first used, an attempt was made to carry a slicing face from fifty to several hundred feet long. Timber and other supplies were brought in through long drifts from an auxiliary shaft. Great difficulty was experienced in keeping these drifts open, the side pressure breaking the posts and the top weight breaking both caps and posts. Furthermore, the men could not work efficiently while these drifts were being repaired. The slicing faces advanced irregularly, due to varying conditions, and in many ways the results were not all that could be desired. It was then decided to divide the slicing area into blocks 200 ft. square and this was later changed to 250 ft. square. At the center of each block a two-compartment raise is put up as a supply raise, the compartments being 2 ft. 6 in. and 4 ft. by 4 ft. 4 in., the smaller being used as a manway. Station sets of 12 by 12 timber with

Jan 1, 1917

By Karl Kuhnhenn

One substantial element of the NATM is to take into consideration the geotechnical rock behavior in the design of excavation and support methods. Even if this opinion is being shared increasingly, the stress analysis is not the sole criterion for a successful tunnel drive. By the beginning, the inventors of the NATM have clearly defined a number of principles which have kept their validity until now. The evaluation of different failure cases demonstrate how necessary the observance of these principles and their strict following during execution are besides the stress analysis. The great number of successfully excavated NATM tunnels are an impressive evidence for these principles.

Jan 1, 1995

By B. Ainsworth

The 1972 discovery of the Howards Pass lead-zinc deposit was the product of systematic regional geochemical surveys used to evaluate conceptual geological models for the metal-rich black shales of the Selwyn Basin. Motivation of personnel involved in all aspects of work was as critical a factor to the success as the existing corporate attitudes and infrastructure. Exploration programs were flexible but maintained a focus only on targets of sufficient economic potential to support operations in remote locations. Direct costs for the programs that lead to the discovery were in the order of $500,000 (Canadian 1972). Geological reserves today stand at over 500 Mt (511 million st) of 7% combined lead-zinc, containing a higher grade zone of nearly 10 Mt (11 million st) of 16% combined lead-zinc.

Jan 1, 1991

By Dan Michaelsen, Warwick Stewart

"PT Kaltim Prima Coal (KPC) is a large-scale truck and shovel operation mining thermal-coal in East Kalimantan, Indonesia. The operation produces 15 million tonnes of coal and mines over 120 million bank cubic metres of overburden annually. Approximately 35 percent of the waste rock is classified as potentially acid forming. Acid drainage must therefore be managed to prevent acid formation from spoil dumps and mined-out areas.KPC aims to prevent acid production in dumps by covering potentially acid forming spoils with materials identified as non acid-forming. The covers, built to engineering standards, minimise the flux of oxygen and water to pyritic spoils, thereby controlling the oxidation reaction, and reducing ARD discharge to negligible rates. Cover designs and cover materials vary according to stability, materials availability, equipment availability, and cost effectiveness. A modified field net acid generation (NAG) test procedure has been developed at KPC to identify and segregate overburden geochemical types. This paper discusses the ARD management strategies and operational procedures adopted by KPC to manage potentially acid forming waste rock. The development and field application of the NAG procedure at KPC is presented in a companion paper. Analytical"

Jan 1, 1999

By Enrique Touceda

For a number of years prior to the world war, the firm of Geo. H. Thacher & Co., of Albany, N. Y., was engaged in the manufacture of marine and other gray-iron castings. At the outbreak of the war the firm decided to specialize in the manufacture of propeller wheels. It attacked the problem, therefore, from a foundry point of view, seeking to produce a casting that would be so accurate that no subsequent machining would be required on the blades, also from the point of view of the ship builder. There were two general methods of manufacture, the shortcomings of which have been freely acknowledged. In the sweep method, the nowel, or bottom half-mold, for each blade is swept up by a spindle beam and pitch race, while the top half-mold for each blade is built up individually. In the pattern method one individual blade, with the hub or hub portion, is mounted on a spindle and the individual blade mold formed, the pattern is then rotated on the spindle to the position for the next blade, etc. In rare cases wheels were made from a solid pattern. Owing to the cost of the pattern, its failure in many instances to be correctly made, and (when made of wood) its early and sure distortion the disadvantage of this pratctice is obvious, while metal patterns in most instances were prohibitive in cost. In these methods both green-sand and loam molding was practiced. The casting produced by either method can be considered only as a blank from which the propeller must be machined. The back surface of each blade must be chipped to the templet and through this procedure chipped to such accuracy as will be required for a static balance. Inasmuch as the work done by the machine tool is confined to the driving face of the blades, not only is perfection most difficult, but corrosion will be greater because of the removal of the dense skin of the casting and the local strains set up by the pneumatic tool in chipping. To produce a finished 9-ft. propeller for a Navy destroyer required from 8 to 21 days of foundry work and about the same length of time for the machining. Through the use of the Thacher process, only as many hours are required, besides it is possible to produce a finished casting in perfect conformity with any particular propeller-wheel design.

Jan 1, 1922

By David L. Borusiewicz, M. Suri Surendra

"Abstract Helical piles have been used as anchors and for supporting lightly loaded structures as a method of underpinning, etc in the past. Recently, helical piles are being used to support new structures because of their simple installation process using relatively light and mobile equipment. This paper presents the results of evaluation and design performed for the temporary support of existing piers during a bridge rehabilitation project.INTRODUCTIONThe helical screw foundation was invented and patented by Alexander Mitchell in England in 1833. He installed screw piles to support lighthouses in the tidal basins of England. Many applications in the earlier years in the USA were in North Carolina and in Florida to support lighthouses (in coastal plain deposits). A lighthouse of similar foundation design is still in use at Key Biscayne, Florida.In the USA, the helical piles were reintroduced as foundation elements for electrical transmission towers. Helical piles were also used for anchoring guys of self supported towers and as tie-backs for excavation support systems. Typically, helical piles are being used for supporting lightly loaded buildings and for underpinning buildings undergoing distress as a means of remediation. The helical piles are not commonly used in the transportation industry.HELICAL PILESHelical pile is a segmented deep foundation system with helical bearing plates welded to a central steel shaft. Load is transferred from the shaft to the soil through these bearing plates. Central steel shafts are available in either a square shaft (Type SS) or a round shaft (Type RS). The Type SS series are available in 38 mm to 57 mm square sizes. The Type RS series are available in 73 mm to 114 mm diameter sizes. Type SS-RS combinations are also available for compression applications in soil conditions where dense/hard soils must be penetrated with softer/loose soils above the bearing strata.The leading segment consists of a shaft with one or more helical plates that are welded to the shaft. The plates vary in diameter from 203 mm to 355.5 mm and have a thickness of 9.5 mm or 13.7 mm. Typically the plate diameter increases from the bottom of the shaft upward. A helical bearing plate or helix is one pitch of a screw thread. All helices, regardless of their diameter, have a standard 76 mm pitch. Being a true helical shape, the helices do not auger into the soil but rather screw into it with minimal soil disturbance. Helical plates are generally spaced a distance of two to three times the diameter of the plate directly below in order for them to function independently as individual bearing elements. A typical detail of helical pile is shown on Figure 1."

Jan 1, 2014

By L. C. Brichta

During a study of the Badger-Peacock area from October 1950 to June 1953, the Federal Geological Survey and the Federal Bureau of Mines completed nearly 98 miles of resistivity profiling and drilled 96 test holes aggregating 17,628 feet of bore, In addition, seismic profile measurements were made along 8 traverse lines for an aggregate length of about 16,600 feet. The geophysical surveys were conducted by the Geophysics Branch of the Geological Survey; the drilling was done by the Bureau of Mines. Electrical-resistivity measurements disclosed 21 low-resistivity anomalies and 1 high-resistivity anomaly. Correlation of the resistivity data with the geological information revealed by the drilling disclosed that the low-resistivity anomalies indicated either slumped shale deposits in limestone sinks or undisturbed deposits of shale lying in erosional depressions in the limestone. The high-resistivity anomaly indicated hard, undisturbed limestone at or near the surface.

Jan 1, 1958