Search Documents

By S. Ragab

The objective of flotation models is to predict the recovery rate of minerals from a flotation cell. In this paper a CFD?based flotation models is presented. The model uses first order rate equation, and the collision frequency is estimated using Abrahamson [1] model with input from CFD two-phase simulations. Spatial distributions of dissipation rate and air volume fraction (also called void fraction) are determined by the two-phase hydrodynamic simulations. Knowing these parameters throughout the machine is essential in understanding the effectiveness of different components (rotor, stator or disperser, jets) on the flotation efficiency. Not only the average pulp recovery rate can be estimated but also the regions of high/low recovery rate can be identified. The CFD-based flotation model presented here can be used to determine the dependence of recovery rate constant at any locality within the pulp on particle diameter, particle specific gravity, contact angle, and surface tension.

Jan 1, 2012

By W. A. Wood, H. M. Bendler

Cylindrical fatigue specimens of OFHC* copper were subjected to alternating torsion while under axial tension. The superimposed tension strongly influenced the fatigue life of the specimens as well as causing characteristic changes in the structure of the fissures that form and develop throughout the life of the specimen. A further effect of the superimposed tension is a continuous extension of the specimen throughout its life in a manner formally similar to creep at elevated temperatures. RECENTLY, studies of the structural changes leading to fracture of metals by fatigue have been made by a technique which reveals, in section, the lattice distortion arising from slip movements inside the metal and the disturbances built up by these slip movements at the metal surface.1'2 According to this approach, fatigue develops as follows: a) fine slip movements concentrate in bands, producing little strain-hardening and thus permitting abnormal totals of plastic strain before fracture and, therefore, abnormal amounts of lattice distortion along each slip band; b) both forward and backward slip movements occur in each band which, according to their distribution across the band, may build up surface disturbances that include sharp notches; c) these notches early in the life of a specimen penetrate the distorted slip zones and transform them into deep, fine fissures; d) the fissures on continued cycling locally saturate the metal and cause local collapse in the form of a microcrack. Thus, the significant consequence of fatigue or cyclic

Jan 1, 1962

By Christian Neumann, Josef Arnold, Albin Reinhart

The Channel Tunnel Rail Link (CTRL) is the most significant railway infrastructure development project in the United Kingdom since the construction of the Channel Tunnel between France and England. The key element of this project is the 2-mile-long(3.2-km) North Downs Tunnel, which will be the largest and deepest twin-track railway tunnel ever constructed in the United Kingdom. This paper describes the contractual agreement, the design and construction (excavation and lining) of a twin-track rail tunnel with a 166-m 2 face excavated through chalk using the New Austrian Tunnelling Method (NATM). The importance of collaborating with a tunnel contractor/designer who not only is expert in the New Austrian Tunnelling Method, but who was also responsible for the design and installation of the primary lining, will be highlighted in this paper. This paper will also deal with the benefits of partnering in tunnel design and construction, as well as the resultant added values of mechanizing conventional tunnelling methods (Value Engineering).

Jan 1, 2001

By Paul. D. Merica

I LIKE to look upon the award this year also as a recognition of the importance of metallic materials of construction to the engineer and of the active progress which I believe is continually being made in almost all branches of that field today. It has been said that metals are the material backbone of industry and technology. Well in that case, I suppose we metallurgists are industry's bonesetters. And it is possibly not inappropriate that we should occasionally give some atten¬tion to those bony structures of our industrial activities upon which engineers in other fields hang their manifold and striking creations. What is going on in the field of metals development? Well, in the first

Jan 1, 1938

By Bernhard Leist, William D. Leech, Johann Kröyer, Holger Evers

Landsvirkjun—the national electric power company of Iceland—is building the Kárahnjúkar Hydroelectric Project in eastern Iceland. Two glacial river systems will be dammed and channeled through a series of tunnels into a 690 MW underground powerhouse. The Project has a total of 73 km of tunnels to be excavated of which mosthave been completed. From three access adits, three large diameter (7.2 m to 7.6 m),main-beam, gripper-type, Tunnel Boring Machines (TBMs) are being used to complete50-km of the waterway tunnel. Using the TBMs was a first in Iceland to excavate the complex Icelandic basalt formations, which consist of inclined layers of hard basaltic flows with weaker scoriaceous and sedimentary interbeds. Faults, fissures and dykes that frequently cross the lava flows posed both geologic and hydrogeologic difficulties to the TBM tunneling. This paper describes the extreme challenges that the men and equipment had to endure to complete the tunneling, including the harsh winter weather on the surface and the cold, abundant ground water inflows within the tunnels.

Jan 1, 2007

By Harry Sutcliffe

THE PROBLEM Two and a half years have gone by since the December, 1976 Civil Engineering article on subway costs caused such a furore. What has happened in this interval? Even after discounting the crushing inflation rate, costs are still increasing, and there is no sign of a turndown, even in the rate of increase. Some steps outlined in the article have been taken. In April this year, the first D.O.T.-sponsored Peer Review Group, made up of managers of other transit properties, met in Boston to review MBTA's $500 million Red Line Extension-Northwest for cost effectiveness. While the impact of a review at the end of the design phase, with substantial segments under contract, cannot be as effective as a review early in the design phase, it is nevertheless a start. This first meeting will be followed by a review of Boston's Orange Line relocation, the final design for which is just underway. In the industry at large two facts are evident: 1. We are failing to reduce underground construction costs. 2. Underground construction is in danger of pricing itself out of the market place. It has always been a greater challenge to design a Chevvy than to design a Cadillac, but it is the Chevvy we need today. Much attention has been focussed in the past on engineering design in the narrow sense: areas such as ground loading conditions and concrete design. This paper will attempt to make the case that costs in urban underground construction are primarily outside the area of structural

Jan 1, 1979

By Anthony J. Konya, Calvin J. Konya

Mine sites and construction projects have faced problems with blasting a smooth back wall. This lead to safety concerns with slope stability and rock falls from the walls. Decades ago Dr. Calvin Konya began a special type of blasting called “Precision Presplitting”. This form of presplitting used relatively light loads based on the rock type being blasted. The explosive loads were estimated for each rock type and adjusted as blasting progressed. This current research project also determined a new equation for prediction of the ground vibration from one type of presplitting and compared it to vibration from production blasting.

Jan 1, 2016

By Roxana Barrantes Huamán

El presente texto describe la geología económica del depósito aurífero Alpacay ubicado en Arequipa, Perú. El depósito Alpacay es un típico depósito mesotermal, filoniano que es explotado por la Cía Minera Yanaquihua, donde el mineral es procesado en una planta de cianuración, gravimetría y flotación. Costa. Asímismo, se realiza en la Franja Aurífera Nazca-Ocoña que alberga innumerables minas y depósitos en vetas angostas como Arirahua, San Juan de Chorunga, Chalhuane, Las Clavelinas, María Eugenia, entre otros. La alteración es básicamente argílica en la vecindad de las vetas y propilítica hacia el exterior.

Sep 12, 2011

By E. R. Maize

This report is the second of a series on roof movement in coal mines. The first (R. I. 3355)4/ dealt with convergence of roof and floor and movement of the surface accompanying and following extraction in a mechanized mine in which retreat of rib lines was rapid. The studies reported herein were made in a mine in which all the coal is loaded by hand, and movement of the rib lines was much slower in consequence. In choosing a site for this work, it was decided that the mine selected should have natural conditions akin to those of the first study and entirely different methods of working. To this end a cooperative agreement was made with the Crucible Fuel Co. through W. J. Whitaker, secretary, for conducting the work in the company's Crucible mine, operating in the Pittsburgh bed in Greene County, Pa. This paper gives an account of the methods used in the investigation, excerpts from the data obtained, and such generalizations as can be made.

Jan 1, 1939

By R. H. T. Garnett

N.B. This paper provoked much (positive!) discussion in later issues, with responses from the author (and thanks also for the many private contributions he had received) - see under Garnett R.H.T. Expanded version of a paper originally presented at the Alluvial mining conference, London, 11-13 November 1991 and published in Alluvial mining, Barking: Elsevier Applied Science for IMM, 1991, p.115-156. The usual measure of performance in gold and tin dredging is the R/E factor. It compares actual production or recovered grade for a given period with that estimated from the original sampling. The factor is a multiple of four component factors, each ideally approaching 1.00. The factors are concerned with estimation, selection, excavation and treatment. The estimation factor reflects the errors involved in determining the grade and depth of single drill-holes or pits. An optimum selection factor is achieved by a higher drilling density. The excavation factor is affected by failure of the dredge to excavate the total volume contained within its course. The required dredge throughput rate influences not only the success in digging recovery but also the treatment factor. No two alluvial deposits are the same, but, in general, the greatest divergence from 1.00 is invariably demonstrated by the estimation factor. A major divergence in one of the other factors may also be the cause of the R/E factor being significantly different from 1.00. The component factors are examined in detail and historical trends in R/E factors are discussed

Sep 1, 1991

By A. R. T. Denues

The Explosives Division of the Bureau of Mines, United States Department of the Interior, is investigating cushioned blasting at the Explosives Testing Station, Bruceton, Pa. The general interests of this investigation are practical and relate particularly to safety. The immediate concern is an application of cushioned blasting in coal mining In cushioned blasting, various means are employed to reduce the intensity of the application of energy in an explosive action in a borehole. The primary object is to increase the efficiency of the use of explosives.

Jan 1, 1940

In several of the States of Australia, mining on private property has been seriously hampered by the fact that large areas of land have been alienated from the Crown before the discovery of gold or other minerals. In Western Australia this difficultyhas only occurred to a small extent, and has largely been overcome by an act entituled "An Act to Permit Mining on Private Property, No. XXIX., 'October, 28th, 1898." Under this act, the holder of a miner's right can apply for a gold mining lease on private land; such applicant may treat privately with the owner of such land as to the amount of compensation to be paid for surface ,damage, or the case may be brought before the Warden who will assess the damages. Private land used as a garden, orchard, or vineyard is exempt from lease, unless the applicant has authority from the owner, or such lease is limited to a greater depth than 100 feet from the lowest part of the surface.No lease shall be granted of any mines under any private land in any municipality unless either the applicant has authority from the owner, or such lease is limited to a greater depth than two hundred feet from the lowest part of the surface.The same regulation applies to leases of private land on which any hospital, asylum, or public building is situated or under or within one hundred and fifty yards laterally of any...

Jan 1, 1901

Used in conjunction with geology and geophysics, geochemistry provides powerful exploration tools of special relevance to Australian environments. New methods are needed that will confront the forthcoming emphasis on locating concealed orebodies. Deep weathering is conducive to techniques using groundwaters or gaseous emanations as sample media. Increasing use is anticipated for isotope measurements and for recognition of country rock characteristics that denote proximity to mineralization. Improvements in the sensitivity, reliability and portability of analytical instruments will underpin the contributions of geochemical methods to future mineral exploration.

Jan 1, 1982

By Aminul Islam, Vinay M. Kumar

"About 100 Hectares of land reclamation over the very soft to soft marine clay at Uran Creek in Maharashtra is planned. The depth of marine clay varies from 10m to 24m as observed from the geotechnical investigation. The marine clay was treated with Pre-fabricated Vertical Drains (PVD’s) installed from the elevation of +5.5mCD (chart Datum) and preload/placement of surcharge. A Settlement of soft soil mud under the reclamation was monitored using magnetic extensometer (M) and ground settlement maker (S2). These instruments are installed after constructing working platform at around +5.5m CD. Based on the field instrumentation data, the consolidation parameters were adjusted to match the theoretical and actual settlement plot. The author called this approach as “Back analysis method”. The objective of this paper is to present a case study of instrumented preloading treatment for a thick marine clay deposit. The degree of consolidation in clay strata was determined from magnetic extensometer and ground settlement marker data. Authors also determined degree of consolidation as Asaoka method, Hyperbolic method and Back analysis method and compared the results.INTRODUCTIONExpansion of Container terminal with port buildings, rail container depot, roads and utility buildings at Jawaharlal Nehru Port Trust (JNPT) is planned over a reclaimed land of 100 hectares. Uran creek predominately consists of the estuarine deposit of very soft to soft marine clay. They are characterized by low shear strength, very low bearing capacity and exhibit large settlement when subjected to loading. The additional load causes the significant magnitude of consolidation settlement over a considerable period of time. Thus for development projects on top of soft soil, the postconstruction settlement would be of primary concern.To accelerate the consolidation pre-fabricated vertical drains (PVD) were used. Pre-loading procedure was adopted to minimize the post construction total and differential settlements. PVD’s were installed at 1.0m and 1.2m c/c triangular pattern. Locally available borrow material is used as a reclamation material. The reclamation material has been placed over the existing sea bed level by land based method/end tipping method and created the working platform. The level of working platform is decided based on the tide data and it has been selected such that work should be affected during highest high water level. The PVD has been installed from the working platform and subsequently all the field instruments have been installed from the same level. Five different types of field instruments are installed to monitor ground improvement works."

Jan 1, 2017

By Liu Wei

In order to make clear the dissolving characteristic of the chrysocolla (CuSiO3?H2O) in the ammonia-ammonium chloride solution, a thermodynamic model of the chrysocolla (CuSiO3?H2O)-ammonia- ammonium chloride-water system is established using the exponential computation method based on both mass balance and charge balance equations. The equation group of the thermodynamic model is solved by the MATLAB Soft on PC. The condition which is favorable for dissolving high concentration of copper in solution is making out. The stable area of chrysocolla (CuSiO3?H2O) and the condition of chrysocolla (CuSiO3?H2O) converting to atacamite (Cu(OH)1.5Cl0.5) is also studied. A group of experiments are designed to validate the veracity of the results of the thermodynamic calculation.

Jan 1, 2010

By A. R. T. Denues

The Explosives Division of the Bureau of Mines, United States Department of the Interior, is investigating cushioned blasting at the Explosives Testing Station, Bruceton, Pa. The general interests of this investigation are practical and relate particularly to safety. The immediate concern is an application of cushioned blasting in coal mining. In cushioned blasting, various means are employed to reduce the intensity of the application of energy in an explosive action in a borehole. The primary object is to increase the efficiency of the use of explosives.

Jan 1, 1940

By R. A. Meister

The study on improving surface coat refuse disposal site inspections included surface inspections of 15 refuse disposal sites. Monthly aerial photos were taken of the sites and computer methods were used to determine elevation changes. Photogrammetric techniques that were used are described in detail. A comparison of the results of each of these inspection techniques is included. A detailed evaluation of the photogrammetric techniques was made and conclusions were drawn concerning the advantages and disadvantages of using aerial photography and photogrammetry as part of the inspection procedure. Operators' opinions of the aerial photography methods are included.

Jan 1, 1980

By Y. P. Chugh, J. Ma

Higher production, better safety standard, and potential for automation are some of the benefits of longwall mining. Today, longwall face advances at a faster rate exposing many diversified rock layers in a short period of time. It is now a serious challenge to cope with ground control problems such as roof falls, face and floor failure, and excessive shield loading as fast as possible to minimize production and monetary losses. In Illinois coal mines, the existence of weak floor strata blow the coal seam may pose additional problems related to floor heaving, shield base punching, and associated roof and face falls. In this study, the effects of weak floor on longwall ground control are analyzed using two-dimensional finite element models. A two-leg 635.6-ton (700-short-ton) yielding capacity shield is included in the models to evaluate the effects of different thickness and material properties of the weak floor. The study indicates that the thickness and material properties of weak floor have significant effects on shield loading, the distribution and intensity of front abutment stress, failure zones in the surrounding strata, roof-to-floor convergence, and floor punching by the shield base.

Jan 1, 2000

By O. Naiker, T. Riley

Keywords: Pyrometallurgy, furnace, Xstrata, ferrochromium, Premus Technology The presentation will give a basic overview of Xstrata Alloys. Included will be a brief history of the Alloys division as well as of each plant within the division. The Xstrata chrome plants utilise a wide variety of production processes, including Xstrata's Premus process, the Outokumpu process, and the conventional process. Xstrata?s Lion Project is underway, with commissioning expected in the third quarter of 2006. The new smelter will utilize Xstrata?s patented Premus process, and the competitiveness of the Premus process is discussed.

Jan 1, 2006

By H. M. Chikashi

Keywords: Pyrometallurgy, furnace, bath agitation, regression analysis, entrainment This paper presents the results of linear regression analysis of the influence that each component of slag has on the losses of copper in slag-cleaning-furnace slag. Data used for the analysis are actual plant data collected over the past two years of operation. Facts obtained from the study will be helpful for smelter management to control these components in the flash smelting furnace feed and slag, to levels which will enable better control of copper in slag, and smoother operation of the KCM slag-cleaning furnace.

Jan 1, 2011