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By Edward L. Wilson, Keshavan Nair, Ranbir S. Sandhu

In planning and designing of underground excavations and construction, it is of considerable importance that the stresses and displacements in the rock mass subjected to arbitrary sequences of unloading and loading be within allowable limits. For determination of the stress and displacement fields, the usual approach is to treat the rock as an elastic material and to apply the principles of the theory of elasticity. However, analytic solutions are available only for a limited class of problems of simple geometry and idealized material properties. Nonhomogeneity and anisotropy of material coupled with complex geometrical configuration and initial stress fields that are almost always preexistent in rock masses at great depths, render the problem intractable by analytical methods. Approximate solution techniques using numerical procedures have, therefore, to be resorted to. The finite element method as applied to plane stress analysis was introduced by Clough.1 It has developed into a powerful tool for the analysis of various field problems in structural and continuum mechanics. The method is well documented in the literature2-6 and, therefore, its historical development will not be discussed here. Wilson's analysis of the plane stress/strain problem has found extensive use in the area of soil and rock mechanics including stresses around underground openings; stresses and displacements in dams, foundations, etc.7-11 In his analysis of the axisymmetric solid,3 Wilson proposed a procedure to allow for certain cases of nonlinear material properties. In this chapter, the develop-

Jan 1, 1972

By G. Velarde

Agglomeration has as main objective to form a uniform and highly permeable heap for leaching. An inaccurate dosage of moisture during agglomeration leads directly to poor agglomerate quality and segregation of particle sizes during stacking. This causes a heterogeneous distribution of the leach solution inside the heap which invisibly and practically permanently affects the recovery. Unfortunately, only when this becomes serious and the mineral contains an excess amount of fine particles and/or clays then the poor permeability of the pile becomes obvious. This paper is based on the experience of Minera Cerro Verde in the development and application of a quantitative method to control moisture during agglomeration. As the amount of fine particles/clays varies, the quantity of moisture has to be altered in real time. The measurement of agglomerate electrical conductivity is used for it. This concept is based on the sharp change seen in conductivity when the mineral passes its absorption limit. A liquid conductive film then begins to form over the surface of the particles, which leads to the formation of agglomerates through liquid bridges, which are also electrical bridges. Moisture is adjusted to reproduce a value of conductivity established previously and is the guiding parameter. Moreover, moisture amount added to reach this conductivity parameter provides information about the fines/clays relative content for best leaching management.

Jan 1, 2004

By Danqing Xu, A. W. Khair

"This paper presents a laboratory simulation of regrinding and resulting dust generation. An Automated Rotary Coal Cutting Simulator (ARCCS) was modified to conduct regrinding experiment. In order to estimate the effects of coal properties and operating parameters on regrinding and dust generation, an orthogonal fractional factorial experimental design was implemented in regrinding experiment. Marple personal cascade impactors, Series 290, were used to measure dust concentration during experiment. Three types of coal seams, namely, Waynesburg, Pittsburgh, and Lower Kittanning, were used to represent different coal properties. Experimental results and complete parametric analysis were presented.In a rotary cutting system, all the broken coal and part of the remaining coal from previous cutting cycles must be transported through part or entire circumference of the cutting drum. This transportation of already recovered coal through the cutting zone of rotary head makes it a rotary grinder. Some of the coal particles will be subjected to secondary fragmentation or regrinding in the process. The potential effect on dust generation by regrinding is significant because the cutting head utilizes kinetic energy to comminute recov¬ered coal material. The moving bits and bit blocks on the cutting head impact coal particles and transfer some of their kinetic energy to the particles. After obtaining kinetic energy, coal particles are free to impact one another and they also impact the coal seam or cutting head. During impact, high impact force and high internal stress concentration are created in the particles. Kinetic energy is transformed into strain energy. When stored strain energy exceeds allowable strain energy, the particles will break. A great amount of respirable dust will be generated due to impact failure. In reality, regrinding occurs at the same time as primary cutting. The particles to be ground are the result of primary cutting. Both primary cutting and regrinding produce dust. Therefore, it is impossible to separate regrinding from primary cutting. In order to study respirable dust generation by regrinding and analyze the influencing parameters, a laboratory approach was adopted. In this approach, it is possible to study the regrinding separating from primary cutting."

Mar 1, 1992

By Eugene Frey

"INTRODUCTION The Good Fortune mine was sampled by an engineer of the Bureau of Mines in June 1944. Project 984 was set up under the strategic minerals program to make old workings accessible for this sampling program. Actual operations commenced June 1, 1944, and were completed June 30, 1944.The deposit was visited and discussed briefly by Sidney H. Ball 3/ of the Federal Geological Survey in the summer of 1906 and by H. M. Chance 4/ several times from 1887 to 1900.LOCATION AND ACCESSIBILITYThe Good Fortune mine is situated in the Hartville mining district in Platte County, Wyo., approximately 9 miles northwest of the town of Guernsey. The property is about 100 miles north of Cheyenne, Wyo. (fig. 1).ACKNOWLEDGMENTSIn its program of exploration of mineral deposits, the Bureau of Mines has as its primary objective more effective utilization of our mineral resources to the end that they make the greatest possible contribution to national security and economy. It is the policy of the Bureau to publish the facts developed by each exploratory project as soon as practicable after its conclusion. The Mining Branch, Lowell B. Moon, chief, conducts preliminary examinations, performs the actual exploratory work, and prepares the final report. The Metal¬lurgical Branch, O. C. Ralston, chief, analyzes samples and performs beneficiation tests."

Aug 1, 1947

By Edward L. Beutner, Robert M. Crump

Benson Mines low-grade iron ore reserve is a replacement deposit within the Grenville gneisses of the Adirondacks. The average grade of the crude ore is about 23 per cent iron. The iron minerals are principally magnetite and hematite disseminated throughout the gneisses as discrete grains about 1 mm in size. Both the ores that are beneficiated by magnetic means and the non-magnetic ores that are treated by a gravity method of concentration are found in stratigraphically different positions but are mined from one open pit, which is about 2.5 miles long and 800 feet wide and are treated separately. The gneisses are described and named according to the distinctive mineralogy of each. Recognition of the gneissic types permits the interpretation of the structure as a northward-plunging syncline overturned to the west. A large subsidiary anticline-syncline complex occurs on the east limb of the major syncline. Iron minerals in sufficient quantity to be considered ore are confined to areas where the footwall rock has been overturned to become the hanging wall.

Jan 1, 1968

By Roger J. Morrell

Disk-cutter experiments were performed on five rock types ranging in compressive strength from 9,000 psi to 27,000 psi. A specially constructed testing machine called a linear-cutter apparatus (LCA) was designed to load and traverse a free-rolling disk cutter across a sawed rock surface. The LCA was instrumented to measure the vertical and horizontal forces acting on the cutter during the run.. The ability of disk cutters to fragment rock was determined for both 60--degree and 90-degree cutting-edge angles, and relationships and regression equations were developed to predict cutter performance based on rock physical properties and applied forces,

Jan 1, 1970

By R. C. Woodhead

During past years the most difficult problem presented to the coal preparation engineer has been the cleaning of fine coal, The problem of handling fine coals is more involved than the coarser sizes, because the higher surface moisture contents complicate screening, and the larger percentages of fine near size material complicate separating problems. Low gravity high capacity specific gravity separations were not possible with equipment available at that time. Coal preparation engineers did develop machines that would effect a separation of the fines, however, to maintain a high efficiency, the point of separation had to be a relatively easy one. The more difficult separations were made in the coarse coal sections of the washeries, and the fines were generally cleaned at higher specific gravities in equipment such as tables, feldspar jigs, rheolaveurs, etc. Clean products from both processes were mixed, resulting in overall lower ash contents, During the last several years, however, we have been confronted with increasing demands ZGP more precise separations of finer coals to still further reduce ash contents. A study was begun and a program instigated to improve the cleaning of fine coal, The result of this endeavor was the development of the new cycloidal heavy medium cyclone.

Jan 1, 1964

By Frank S. McKenna, Myron A. Pugacz, Clarence E. Jackson

THE notched-bar impact test has proved worth while in certain applications as a test for control of the quality or the heat- . treatment of steel. In view of the serious thought that even so simple a test as the tensile test, has evoked during the past years, it is not surprising that the notched- bar impact test should have inspired much experimental work. The correlation of the great number of data has not been successful, although steady progress has been made toward a better understanding of this test. Progress has been made, especially, in the isolation of the effects of the many variables that control the results. The stress system imposed on a specimen with a notch is so complicated and un- predictable that no simple evaluation of the test has been possible. Because of this uncertainty, many engineers hesitate to use the notched-bar impact test, and this attitude may well continue until a better understanding of the effects of the variables in the test are available. Without doubt, any additional data that may be presented should be accompanied by as complete a description of the details of test as possible, so that it may be added to the general fund of information that is to serve as the basis for the theory of the notched-bar impact test. The many factors that may control the test results have been pointed out repeatedly. The importance of the effect of the type and dimensions of the specimen has been recognized. Most of the work reported by American investigators has been limited to small- size (Charpy) specimens tested as a simple beam; two types of notches (Fig. I) have been commonly used. Considerable data have also been presented by many investigators using a small specimen tested as a cantilever beam; this commonly being called the Izod test. Here, however, a shear component of stress makes the stress system even mare complex than that present in the simple beam type of test, hence a critical analysis is difficult. Much work has also been reported by investigators using the tension type of specimen. A second variable that must be con- trolled is the testing temperature. An indication that the tests were performed at room temperature is not sufficient, since in many steels a variation of a few degrees in the actual testing temperature may be sufficient to give an entirely different range of results. Other factors. such as the com- position and condition of the material being tested and the speed of test, should also be considered. Many investigators have contributed data and theoretical discussions on the problems encountered in notched-bar test-

Jan 1, 1944

By Constanza Bujes, Mark Jones, Graham Crook, Yansan Jamyanbaatar, Sedat Esen

Tracking ore characteristics such as grade and hardness from its original position into the material handling and processing stages remains one of the key challenges in open pit mining of hard rock deposits. The most efficient technique for rock fragmentation and separation of ore from waste is blasting, which induces changes in the grade distribution by displacing the in-situ ore into a diggable muck pile. Material movement defines the post-blast grade distribution, which is key to optimising the value of the ore and accounting for ore loss and dilution. Techniques to directly measure the displacement in open pit mining have been implemented routinely and have provided calibration and validation data for blast models to build upon. The JK Value-Based Ore Control blast movement model (JKVBOC) is the latest development of a series of research studies into blast movement and ore control at the Sustainable Minerals Institute of the University of Queensland. The blast model discretises the bench into blocks, defines the initial velocity of each block based on the blast design, confinement and explosive properties, and simulates the displacement using a physics engine. Calibration and validation of the model has been performed in open pit hard rock mines in Australasia in diverse confinement conditions. This paper describes the calibration and validation of the blast movement model against direct measurements of blast movement and final muck pile shape for a case study where the displacement of multiple shots was modelled for an open pit mine, with an analysis of the implications for ore loss and dilution. A key finding in this study is the need for further integration of this technology into the existing systems for ore control, and the potential for applications in tracking ore characteristics other than grade into process control.

By John Greenawalt

IN view of the increasing importance of sintering in the beneficiation of iron ores preparatory to their reduction in the blast furnace, the writer believes the time is opportune for an up-to-date, though brief, discussion of the general principles of sintering, as well as a discussion of some of the recent improvements and mechanical developments that have been achieved in this industry, its present trend and future possibilities. Sintering may be defined as the agglomeration of fine mineral particles into a porous mass by incipient fusion caused by heat produced by com-bustion within the mass itself. Its first successful application, in connec-tion with the treatment of lead sulphide ores, was known as blast roasting. In this process the lead ore was given a preliminary roasting in a reverber-atory furnace, then the incandescent mass was placed in a pot with a grate and an updraft was applied. It was soon discovered that much better results were obtained by cooling the ore, moistening it, and placing it upon an incandescent layer of fuel previously placed upon a grate, and then applying the updraft blast of air until the charge was converted into a more or less agglomerated mass. The fuel was sulphur and the process one of desulphurization, which was the principal result desired. The application of downdraft to blast roasting brought about tremen-dous results; the principal one of which was that an air blast of high pressure could be passed through a layer of ore deposited on a grate, or on a grate covered by a layer of coarse porous material, without disturbing the particles of which the layer is composed. The air current is compelled to filter through the pores of the charge, whereas if the same pressure applied to the top surface of the charge with downdraft were applied to the bottom of the charge with updraft, the charge would be completely blown off the grate. Another result of reversing the draft was that a flame could readily be applied to the top surface of the charge for ignit-ing purposes.

Jan 1, 1938

By Osamu Taki

The development of new auger bits for soil cement column drilling equipment has made it possible to create a homogeneous mixture of soil and cement-reagent slurry. As a result, soil-cement columns are used for foundations of houses and buildings, with reliable results, as demonstrated by many field projects and laboratory tests. This paper presents and discusses construction techniques for soil-cement columns, characteristics of the soil-cement solid, quality control, bearing test results, and soil-cement foundation design procedures.

Jan 1, 1992

By G. L. Fitzpatrick

Future applications of seismic holography to "seismically transparent phase objects," such as rock inclusions, fracture zones, liquid-filled cavities, etc., will require techniques to improve the poor image contrast generally characteristic of these objects. Although conventional phase-contrast enhancement techniques could be used, these methods involve additional optical elements such as quarter-wave spatial filters. Owing to the anticipated practical difficulties of properly alining such optical devices and properly locating poorly defined image planes and filter planes, this approach is not considered to be well-suited to the case of seismic holograms and their laser reconstructions. Results similar to those achieved with spatial filters may be obtained without filters by specially processing the seismic hologram data. The new process, which is an extension of Gabor's subtraction holography, achieves an improvement in contrast by an interferometric technique. The process involves adding a ?before" hologram without an object present to a 90° phase-shifted "after" hologram with the object present. Then, the combination is reconstructed with a laser or by computer. Not only is the image contrast improved in such processed holograms, but the images are also phase-contoured. In general, the latter feature is not to be expected when conventional phase-contrast enhancement techniques are employed. The new technique is experimentally verified by examining computer-generated synthetic seismic holograms rather than by examining actual seismic field data. However, results of this study are directly applicable to real seismic data and should prove useful in future applications of seismic holography.

Jan 1, 1973

By J. C. Hawkins

Determining moisture content and rate of flow of a solid product make measurement and control of dryers unusually difficult. This paper de-scribes a method of accomplishing this with readily made air-temperature measurements. The system can cope with changes in feed moisture and feed rate. It does not measure solids temperature. The system's application to several typical rotary dryers is described, and control schemes using feedforward techniques are explained.

Jan 1, 1971

By Charles E. Munroe

At the outset of the war the uncontrolled production and possession of explosives obviously became a serious menace to the safety of persons and property and the successful conduct of military opera- tions. Even in the years immediately preceding the entrance of the United States into the Great War explosives were employed in attempts to wreck munitions plants as at Eddystone, Pa., or to inter- rupt transportation and conveyance by demolition of munition-laden cars as at Black Tom Island, N. Y., or by attacks on ships, bridges, and viaducts. Outrages with explosives, such as that which Holt inflicted on the Senate reception room, United States Capitol, were not infrequent, and often caused serious loss of life and injury to persons as well as destruction of property. The regular manufacturers of explosives were keenly alive to this menace and early took such steps as lay within their power to meet it as is shown by the following letter:

Jan 1, 1921

By M Furche, U Noell, C Grissemann, J A. Meima, T Graupner, A Romero-Baena

The mining residues at the abandoned copper mine site Pe±a de Hierro, located at the headwaters of the Rio Tinto, contribute substantially to the pollution of the river with high loads of Fe, As, Pb, Zn and Cu. The pH of the outflow ranges from 0.5 to 2.4 in the dry and wet season, respectively. One heap composed of alternating layers, which were deposited parallel to the slope, was investigated in detail. Unsorted blocky to fine materials including gossan material, pyritic volcanics, ashes from pyrite combustion and slate were observed here. The top of the heap has a gentle slope and a hill contouring channel-rip morphology. The initially rugged surface was smoothed by heavy rainfalls filling up the pores of the blocky material with fines. These fines are capable of storing the water for a prolonged time, providing an extended reaction time close to surface in a dry climate at extremely low pH conditions (one to four). All minerals, pyrite, mica, barite and even quartz (probably due to F released from dissolved mica) have been digested and silica gel precipitates have formed a stable and quasi impermeable 100 ¦m layer with very low porosity (<5 area per cent, estimated using scanning electron microscopy (SEM) imaging). The silica layer itself is covered by Fe-oxy-hydroxide (ie FeOOH) coating (10 ¦m) and seals a 1 - 5 mm thick stable hardpan. This hardpan covers the channels and part of the rips almost entirely, guiding the rainwater subhorizontally towards slopes and sinkholes. By geoelectrical measurements, a 3D-resistivity model of the internal structures and the bedrock relief underlying the heap was generated. Internal structures relate to lithological changes in a number of layers. Zones of low resistivity may be attributed to washed-in fines within the mega pore system, whilst zones of high resistivity close to the surface probably reflect the advanced stage of drying beneath aging hardpans. The water movement at the surface was investigated by an artificial precipitation experiment with monitoring of the subsequent changes in resistivities.

Jan 1, 2008

By Benoît Pinier, Jason Furtney, Gustavo Sampaio Lopes, Jorge Valencia, Johan Hawinkel

This paper describes a numerical modeling study on the effect of airdecking on vibrations, fragmentation, and movement in mining-related rock blasting. Practice has shown that air gaps reduce blast vibrations and damage while maintaining the required fragmentation and movement, yielding similar blast outcomes with less explosive mass per hole. Given that the premise of “replacing explosives with air” for better blast results is counterintuitive, this paper aims to shed light on the physical mechanisms and processes occurring in a blast with airdecks. It is hypothesized that airdecks are effective and beneficial because they load the rock at pressures lower than what is required to crush the rock. In the airdeck, the explosive gasses directly fracture rock and avoid energy loss due to crushing. In essence, the airgap allows similar outcomes in fragmentation and throw with less total explosive product, as the lower pressure gasses in the airdeck are still effective at breaking and moving the rock. This is distinct from only having less explosive and more stemming, as the stemming reduces the pressure more than an airdeck at the same position. This study uses the blastFoam software (for modeling of single and multiphase flows) to accurately calculate the pressure history throughout a blasthole and air gap. The pressure and gas loading are coupled to numerical models of vibration, fragmentation, and blast movement. Using this modeling technique, a suite of blast scenarios for typical configurations in a range of commodities is assessed with and without airdecks. Rock blasting practitioners have a responsibility to protect communities, infrastructure, and heritage — demystifying airdecks through a better understanding of the physics provides another tool in the blasting engineering toolkit to serve this goal.

Jan 21, 2025

By A. Ehsani

"Seas and oceans constitute about 70% of the earth’s surface. They contain an enormous stock of various mineral resources such as sedimentary (marine placers), massive sulfide ore deposits, manganese nodules and cobalt-rich ferromanganese crusts. Sea and ocean floor ore deposits could well contribute to the meeting of ever-rising demand for raw materials in the metal industry. In this regard, more research and development in science and technology appear to be required to ensure maximum benefit from the mineral resources of seas and oceans. Since the 1960s, a variety of mineral and metallurgical processes have been studied and developed to deal with marine ores and to extract metals such as gold, nickel, copper, cobalt, manganese, tin, platinum group metals (PGM), zirconium, thorium, etc.In marine environments, there are many parameters which can affect the selection of the mineral and metallurgical processes. These include the extent and grade of the deposit, mineralogical and chemical properties of the deposit, and physical properties of minerals present with particular reference to particle size distribution and mineral liberation size.In this paper, we briefly review the latest trends in processing and extraction of marine mineral resources. Mineral processing technology is mostly applied for recovery of precious metals i.e. gold and PGM, in particular, from marine placers. In general, pre-treatment (sizing, classification, dewatering), gravity concentration techniques (shaking tables, spirals, jigs, etc.,), flotation, magnetic, and electrostatic separation are the options for enrichment of marine placer ore deposits. In the case of massive sulfides, manganese nodules/cobalt-rich crusts, hydrometallurgical and pyrometallurgical methods (as proven technological methods) can be exploited for extraction of metals from concentrates after physical separation or directly from marine ores. The hydrometallurgical treatments involve acid (e.g., sulfurichydrochloric) and alkaline (e.g., ammonia) leaching with different reducing agents and pre-treatments such as roasting. Alternatively, pyrometallurgical treatments involve mostly smelting, chlorination and segregation processes."

Jan 1, 2016

By P. W. Bridgman

DURING the war, the Navy undertook the construction, under my direction, of an experimental gun embodying features designed to lessen the cost and time of production. These experiments were initiated after representations as to their, desirability had been offered by myself, by the Naval Consulting Board, and by the National Research Council. The first drawings were made in June, 1917, and the experiment was completed in November, 1918. For the sake of clearness it will pay to recapitulate briefly the fundamental idea of gun construction. It is well known that if a hollow cylinder is subjected to internal fluid pressure, the maximum stress occurs in the inside layers, the outer parts carrying much less than their due share of the stress. This inequality of stress is more pronounced the thicker the walls of the cylinder. If such a cylinder is pushed to the elastic limit, failure in elasticity will take place long before the outer layers have reached the limit of their capacity. Economical use of the material would demand, however, that all parts of the cylinder reach the limits of their capacity simultaneously. This may be brought about, at least in cylinders of not too great thickness, by producing in. the inner layers an initial compression, and in the outer layers an initial tension. The effect of internal pressure is at, first to relieve the compression of the inside layers, while increasing the tension of the outside layers. If the initial stresses are properly distributed, all parts of the cylinder will reach their elastic limits simultaneously, thus giving a cylinder of maximum strength for its weight. In gun construction as hitherto practiced, this initial distribution of stress is produced either by winding the inner tube with wire, a common English practice, or by shrinking hoops over the inner tube, which has been the standard American practice. Either process is long and expensive, particularly with the larger guns, 12- or 14-in., which require

Jan 2, 1920

By S. W. Nicholson, L. G. Woodruff, K. J. Schulz, W. E. Cannon

The 1.1 Ga Midcontinent rift of North America has many similarities to the geology of the Voisey's Bay region in Labrador and the geology of the Noril'sk region in Siberia. These similarities include the hosting of large volumes of sulfur- undersaturated and trace-element-enriched basalt, having igneous centers characterized by crustal contamination, being characterized by metal depletions in some mafic units (an indication of prior sulfide segregation) and having known occurrences of Ni-Cu sulfide mineralization. These similarities along with new geophysical data and refined models for Ni-Cu sulfide deposits suggest that the Midcontinent rift probably contains undiscovered Cu-Ni [±] PGE sulfide deposits, some of which could be the size and grade of a Voisey's Bay or Noril'sk deposit. In particular, intrusions and related feeder systems that occur in northern Michigan and Wisconsin, as well as to the southwest along the rift margin, deserve serious examination.

Jan 1, 1999

By S. A. Kenzap

Risk & Uncertainty ? Uncertainty about a situation can often indicate risk, which is the possibility of loss, damage, or any other undesirable event. Most people desire low risk, which would translate to a high probability of success, profit, or some form of gain. Risk = Likelihood x Consequence Risk is the possibility of loss, damage, or any other undesirable event.

Oct 1, 2010