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By R. J. Robbins

The mechanization of hard rock underground mines offers a large potential for reducing cost, improving efficiency, and increasing profitability. However, in spite of serious efforts by quite a number of equipment developers and mining company initiatives, the industry has achieved little real progress. The task is difficult and the blasting alternative to mechanical excavation is an effective and well-developed method, which continues to improve in spite of its inherent limitations. A large number of machines have been built and tried. Only a few developments have succeeded to make a major impact on underground hard rock mining. It is certain that hard rock mines would be laid out and designed quite differently if the mining engineers knew they had available continuous mechanical excavation machines. In the absence of the machines, mines will be designed for excavation by traditional methods. It is not easy to utilize mechanical excavation in a mine which is designed to operate with normal drill and blast excavation. This is certainly an impediment to machine development. But what if an ore body cannot be mined conventionally, simply because the mining company cannot get permits to satisfy the ever increasing strict EIS requirements of the general public and governmental agencies? This may provide the incentive necessary to develop the equipment that will be needed by a new mining method that will have almost no impact on the environment.

Jan 1, 2001

By J. P. Sancho, J. M. Duart, J. I. Verdeja, J. O. García

Following a short review of the history of rails used in the transport of passengers and goods, this paper describes the process for rail fabrication, rail structure, and properties, and summarizes the fatigue test curves carried out on rails used today. Also reported is the process for “continuous rail” production using aluminothermic welding via the introduction of weld metal in onsite casting, as a homogeneous melt. Weld characteristics of aluminothermic welding using different preheating procedures—fusion zone, heat-affected zone, microstructure, hardness, slow bend test, and fatigue test resistance (Wöhler curves)—are related to preheating and welding procedures of 700, 900, and 1,100 MPA rail grades. The Locati method is preferred over the staircase method for ascertaining the fatigue limit due to its simplicity. Macrographic and metallographic inspection of broken specimens reveals the reliability of welding techniques and the good metallurgical quality of welds.

Jan 1, 2007

By Meghan McGrath

Third generation advance high strength steels with microstructures of acicular ferrite and retained austenite were investigated and meet mechanical property goals. A good combination of strength and ductility were achieved with duplex ferrite and austenite microstructures where cementite formation was suppressed. Transformation induced plasticity (TRIP) behavior produced rapid work hardening. The mechanical properties of two hot-rolled steels with duplex microstructures were compared and had the following compositions: (1) Fe-0.14C-13.87Mn-1.42Si-3.51Al; and (2) Fe-0.06C-14.2Mn-1.85Si-2.38Al. These steels were cast, homogenized, and hot rolled at 900ºC to obtain a refined microstructure with ultimate tensile strengths and elongations to failure of 865 MPa and 39% and 1,217 MPa and 28%, respectively. The amount of metastable austenite in both compositions decreased after tensile testing from 58% and 28% to 6% and 0%, respectively. Microstructures were characterized using optical microscopy, scanning electron microscopy (SEM), and x-ray diffraction.

Jan 1, 2010

By M. V. Swain, N. Bristow, R. D. Dukino

During mining, crushing and handling the size of iron ore lumps decreases. Key factors in determining the amount and size of fines that are produced are the mechanical properties of the ore. In a continuation of earlier work on the same ores the mechanical properties of three Australian iron ores from Yandi, Koolan and Mt. Whaleback were determined. In particular, fracture toughness was investigated in greater detail by examining its relationship to crack length using the compact tension test. The elastic modulus and strength of the ores were also determined in flexure and compression. The results were interpreted using Weibull statistics, enabling the ores to be ranked according to strength and elastic modulus. These results, together with data on the mechanical response of the ores to stress and observations concerning the effect of mineralogy on cracking, provide a coherent understanding of the mechanisms involved when the ores fracture

Jun 18, 1905

By Joseph Harrington

It is sufficiently correct to say that domestic solid fuel is universally hand fired and it is almost as correct to state that a very large proportion of hand-fired domestic fires are extremely inefficient and smoky. This is particularly true with raw bituminous coal for the fuel. The smokeless and efficient firing of domestic coal affords one of the most difficult problems confronting the combustion engineer. This is due to the universally constricted combustion space in the domestic furnace, the complete ignorance regarding the laws of combustion on the part of the average person, and the fact that the laws of efficient combustion are almost completely nullified under these conditions. It is well to familiarize ones self with these laws. These are: 1. The gradual introduction of the fuel to the furnace. 2. The admission and mixing of the right quantity of air with the coal gases. 3. A temperature high enough to permit complete combustion, and 4. A furnace space of volume sufficient to permit of the combustion gases and the oxygen getting together within the confines of the furnace. Even a casual inspection of the domestic heater will show that none of these essential things are present in proper degree, and this is the reason why the problem of domestic firing presents such difficulties. I have analyzed these conditions in a paper published by the Black Diamond, and which has already had wide distribution, so that I will not repeat the rather lengthy discussion in this paper. A survey of the entire field indicates very clearly that a reversal of existing methods and equipment must be had before any real improvement can be expected. It is my firm belief that in this instance above all others it is necessary to build the efficiency and smokelessness into the equipment in such a manner that its performance will be entirely independent of both skill and interest on the part of the operative. To attempt to educate every man, woman and child who periodically throws coal into a domestic furnace would be literally impossible. Much can be done, however, if we could teach the householder the simple essentials of alternate firing, which I have explained at length in the above mentioned paper. This would go a long way toward making the domestic furnace problem more satisfactory, as well as efficient and smokeless. Many will argue, and with good reason, that the domestic fuel should be prepared coke and with this I agree up to the limit imposed by the practical considerations of quantity production, price and the possibility of marketing the by-products. It will be obvious that if enough raw coal should be processed to provide all of the required domestic fuel that the amount of by-products recovered during the coking process would be so great that there would be little or no market at any price which would justify the manufacture of coke. If the by-products were wasted they would not only be a tremendous economic loss, but the price charged for the coke would probably be so high that the market would be limited, and this would defeat the very idea of the whole thing. Much can be done, however, in advancing the use of coke, but I believe that much more extensive and careful experimentization should be had in order to determine the right size and quality of coke for the various domestic furnaces. If coke were to be developed for extensive domestic consumption it is more than probable that the coking process should and could be stopped at a point where the volatile content of the coke would be sufficiently high to permit of prompt ignition and combustion in low draft installations. If the volatile content were from five to ten per cent a very different kind of coke would be produced from that which is now produced with perhaps one per cent of volatile. A skillful manipulation of this feature would make coke adaptable and satis-

Jan 1, 1925

By W. G. Pariseau

Joints may be taken into account when using numerical modeling as an aid to mine design by embedding joints in the model. When using the popular finite element method, say UT3PC, a pre-analysis step is necessary, Step 0. This step is for the computation of equivalent properties of a representative elementary volume of jointed rock (REV) in the model. This Step 0 is taken before Steps 1, 2 and 3 for specification of a rock properties file, generation of the mesh, and model analysis are taken. A brief explanation of equivalent properties and several examples aid in explaining the details of Step 0. Focus is on procedures, input files, and output to show ease of computation. Theoretical details are relegated to references (e.g. Pariseau 2022). Comparisons of safety factor distributions about example mine excavations with direct scaling from mine observations then offer some insights concerning equivalent properties, especially strengths.

Feb 1, 2023

By B Taylor

Although the underground mining environment is arguably safer now than at any time in history, as underground mining operations across the globe increase in-depth, magnitude, and complexity, protecting workers from harm becomes increasingly challenging. In deep, stressed, seismic mines the development face is one of the most hazardous work areas. The active face is usually the furthest extent of the underground workings, so ventilation can be difficult to maintain, exposing workers to high temperature and humidity while working on foot and doing manual labour. While mechanisation has made many tasks easier in modern times, the reality of underground mining is that development charge-up workers still spend long periods directly exposed hazards at the face. In 2019, Orica and Epiroc partnered to co-develop the world’s first fully mechanised development charging unit using fully wireless initiation, called Avatel™. Built on Epiroc’s M2 Boomer carrier platform, the system is designed to allow one person to charge a development face from the safety of a fully enclosed cabin, thereby reducing exposure to hazards at the face. The system was prototyped in Europe before entering commercial introduction in 2022. This paper reviews earlier attempts to mechanise underground charge-up and describes the development journey and engineering challenges of building a mechanised development charging machine.

Mar 29, 2023

By Courtney A. Young

All cyanide species are considered toxic and can be found predominantly in industrial effluents generated by metallurgical operations. For example, cyanide's strong affinity for metals makes it favorable as an agent for metal finishing and treatment and as a lixivant for metal leaching, particularly gold. These technologies are environmentally sound but require safeguards to prevent water contamination. Various methods of cyanide remediation by separation and destruction are available, but certain methods are more effective than others depending on the cyanide species being remediated. Photolytic destruction is regarded as the one technique that is independent of the cyanide species involved. The destruction of various cyanide species by several photolytic techniques has been investigated for the past few years. A literature survey suggests heterogeneous photocatalysis with anatase (TiO,) should behave similarly to homogeneous photolysis with hydrogen peroxide (H,O,) since proposed reaction mechanisms for both processes involve hydroxyl radicals. However, experimental evidence on a suite of cyanide species suggests otherwise. A new mechanism for the photocatalytic destruction of cyanides, especially SAD species, is therefore proposed.

Jan 1, 1998

By L. Klinger, T. Werber, LA Levin, A Katsman

"The process of catastrophic carburization known as ""metal dusting"", whereby a solid metallic material is converted into fine particles in a carburizing atmosphere, was analyzed. It was shown that this conversion is the result of plastic deformation and subsequent fracture accompanying diffusional phase formation in the near-surface layer. The process is controlled by internal stresses arising during phase transformation. Competition between stress generation and relaxation may result in the attaining the ultimate strength in the near-surface layer and its fracture. Such a mechanism of metal disintegration may occur in a certain temperature interval depending on the kinetic and geometrical parameters of the system - the diffusivities of the alloy's components, the ratio between specific volumes of the new and the old phases, and the ultimate plastic strain. The temperature interval for disintegration of carbon steel, the rate of disintegration, and the period of the disintegration cycle, were evaluated and compared with experimental data. IntroductionCatastrophic carburization, known as ""metal dusting"", consists in conversion of a solid metallic material into fine particles. The process occurs in a carburizing atmosphere at elevated temperatures. The corrosion product, usually named ""coke"", consists of metallic particles dispersed in a loose carbon matrix. Under industrial conditions metal dusting takes place, for example, in a gas mixture of CO and H2 or in hydrocarbon environments. Steels, nickel- and cobalt alloys are susceptible to this kind of wastage in the temperature range 400-800°.A mechanism of metal dusting in steels was proposed by Hochman [1] and later developed by Grabke and coworkers [2-5]. According to the proposed model, the process consists of the following reaction steps:"

Jan 1, 1996

By Fedotov Pavel

One of the efficient means of ore disintegration during the processing is its volume breakage in such machines as roller-presses. Up to date neither the ore disintegration mechanism in roller-presses nor the reasons of their high efficiency are thoroughly investigated. In this work, the mathematical model of Finite Element Method of bad material disintegration in roller-press is discussed. The mechanism of the interparticle ore disintegration is traced.

Sep 1, 2012

By W. H. Gauvin, N. J. Themelis

I N ADDITION to its practical importance in the beneficiation of iron ores and in direct-iron processes, the study of the reduction of iron oxides involves many aspects of challenging theoretical interest. The complexity of the reduction process combined with the fact that under different experimental conditions the controlling stage for the reaction may not necessarily be the same, has led experimenters in this field to a wide diversity of opinion regarding the reaction mecl1anism. As a rule, each investigation has been restricted to the study of one or two variables over a comparative]~• narrow range of experimental conditions, and consequently, it be-comes necessary to examine the significance of each published work in the light of the results of other experimenters in the field.

Jan 1, 1962

By Saluja, Sunder S.

Man had to learn to break rocks as early as the Stone Age, when they formed his main source of raw material. He started with chipping and over the years has reached a stage where he can employ atomic blasts and break, with one blast, millions of tons of rock. In between these two extremes there have been several stages of development including fire setting, use of the expansion of water on freezing in chipped cracks in cold climates, the use of low or deflagrating explosive black powder in about the 17th century, the use of high explosives with the discovery of nitroglycerine in 1846 by Sobrero, followed by the monumental discoveries of the great Swedish scientist Alfred Nobel in the latter half of the nineteenth century.

Jan 1, 1968

By H. J. Chen

In recent years, it has been recognized that the high horizontal stress is an important factor that contributes to a cutter roof. When the immediate roof is thinly bedded, the presence of a high horizontal stress may first cause failure on the bedding planes or weak planes, and then a cutter roof develops as the individual stratum crushes and buckles progressively layer by layer. In this study, the stress distributions in the bedding planes of the immediate roof are analyzed for an entry-pillar system in the multiple longwall panels by using the finite element method. Then the roof failure is analyzed based on the rock failure criterion and the stress distributions.

Jan 1, 1998

By William C. Browning

An economic drilling programme is one which costs the !east in chemicals, equipment, and time. The basis for such a programme with rotary drilling techniques is a drilling fluid in which bentonites do not swell. This is recognized in the growing trend toward gyp and other inhibited mud systems. Therefore, even though the mechanism of thinner action is a subject of applied colloid ,chemistry, the understanding of this mechanism is of economic importance in controlling the flow properties of inhibited muds. In phosphate, or sodium tannate, conditioned muds that are relative-!y free of contaminating-electrolytes, the thinner, or dispersing agent, is adsor.bed, ?creating an electrical double layer about the clay particles. The mutual repulsion of these charged particles effects colloidal stabilization, or deflocculation of the suspended clays, as discussed by Norton and others. In inhibited muds, however, the electrolyte concentration in the filtrate is sufficient to collapse the double layer and flocculation of the mud solids occurs, as evidenced by increased viscosity and gel values. Chemicals to control the flow properties of inhibited muds, therefore, are vital to the successful use of these systems as it is not always economical to adjust flow properties by watering back. Flocculation of suspended particles, as indicated in the work of Vervey, Overbeek, and others, is due primarily to gravity-like, long-range Van der Waals forces. Prevention of flocculation may, therefore, be secured by the interposition of any barrier between the particles, the thickness of which approximates the extension of the Van der Waals at-traction. Organic polyelectrolytes, such as Kembreak, Rayf!o, and Q-Broxin, may act to increase the double layer charge when used in small amounts in fresh-water muds. More important, however, is the fact that in inhibited muds an increase in concentration of the polyelecholyte permits the formation of a condensed film adsorption layer of the polyelectrolyte about the clay particle. When this occurs, the extremely viscous condensed adsorption layer creates a mechanical. barrier that prevents flocculation of clays, even in the presence of inhibiting concentrations of elecholytes. Rheological evaluation of the degree of deflocculation, or colloidal stability, may be made by utilizing the known effects of particle inter-action and volume concentration on the flow properties of suspensions. Rheological evaluation should be supplemented by direct microscopic or ultra-microscopic observation.

Jan 1, 1958

Mechanism Responsible for Flocculation in Poly (N-Isopropylacrylamide) Temperature Responsive Dewatering - Attractive Interaction Forces Induced by Surface Hydrophobicity

Sep 13, 2010

By A. El-Midany

Dolomite impurities are increasing in the currently mined phosphate deposits in Florida. Several research efforts have been conducted in various laboratories around the globe to find methods to economically removing the dolomite. However, a universal and cost-effective process is not now in commercial use. In this paper, a new process for dolomite/apatite separation is presented. The differential solubility of dolomite in slightly acidic solution is utilized to generate micro CO2 bubbles at the dolomite/water interface. Particle (dolomite)/bubble aggregates float to the surface leaving phosphate concentrate with low MgO content. Interestingly, up to 6.0 mm particles can be floated by such micro-bubble/particle aggregates. Different surface-active agents were tested to stabilize the bubbles. Results of these tests are presented, and the mechanisms involved are discussed.

Jan 1, 2009

By Li Qian

Mechanisms of bio-dephosphorization from iron ore was investigated in this Paper. The results show that there are two bio-dephosphorization ways from iron ore, the one is that Acidithiobacillus ferrooxidans directly derive phosphorus from the ore, the other is phosphorus is able to be leached acid produced during metabolizing of Acidithiobacillus ferrooxidans, and the latter is more important than the other. Adding suitable pyrite can enhance the bio- dephosphorization process through providing nourishment and producing acid directly due to S 3oxidized or indirectly due to Fe3 as oxidant. The potential varies in the range of 0.434~0.498V and pH is in the range of 2.5 ~ 1.25 during bio-leaching process. It can be founded that, according 2+to the E-pH graph of Fe-H2O system, Fe wouldn?t be oxidized under sterile system in this potential and pH ranges. It can be obviously concluded that the Acidithiobacillus ferrooxidans are 2+able to reduce the potential for the oxidization of Fe and make the oxidization occur in the above pH and potential zone, so the bio-leaching process can proceed. the investigation of E-pH graph of P-H2O system show that H3PO4 can exist steadily.

Jan 1, 2009

By D. Malovichko

Seismic events and pillar failures observed in two platinum mines in the Rustenburg area, South Africa, were investigated. We studied the sources of approximately 300 largest seismic events recorded in 2009. Moment tensors of these events were estimated from amplitudes and polarities of P- and S-waves. The inverted mechanisms contain isotropic implosive components in many instances. Analyses of uncertainty of the moment tensor solutions confirmed the significance of the implosive component in general. Several documented cases of pillar failure were considered in detail. For each of these a seismic moment tensor was calculated from an elastic stress model assuming an instant removal of a failed pillar. The geometries and magnitudes of the theoretical seismic moment tensors are in agreement with the observed (i.e. inverted from seismic data). The results indicate that either pillar failure or fracturing in the proximity of the reef (within a fraction of the dominant wavelength of seismic waves) are responsible for a significant portion of the large events recorded in these mines.

Jan 1, 2012

By D. Malovichko

Seismic events and pillar failures observed in two platinum mines in the Rustenburg area, South Africa, were investigated. We studied the sources of approximately 300 largest seismic events recorded in 2009. Moment tensors of these events were estimated from amplitudes and polarities of P- and S-waves. The inverted mechanisms contain isotropic implosive components in many instances. Analyses of uncertainty of the moment tensor solutions confirmed the significance of the implosive component in general. Several documented cases of pillar failure were considered in detail. For each of these a seismic moment tensor was calculated from an elastic stress model assuming an instant removal of a failed pillar. The geometries and magnitudes of the theoretical seismic moment tensors are in agreement with the observed (i.e. inverted from seismic data). The results indicate that either pillar failure or fracturing in the proximity of the reef (within a fraction of the dominant wavelength of seismic waves) are responsible for a significant portion of the large events recorded in these mines.

Jan 1, 2012

By Koichi Nishimura

Japan's coal reserves are estimated at 8,583 million tons (according to the materials on X World Energy Conference,. 1976). Japan is a long island country in the shape of an elongated cashew nut whose top is pointing to the north and its lower tip is pointing to the west. And her major coal fields are located in the two extreme far parts of Hokkaido in the north and Kyushu in the south. On the other hand, Japan's major industrial center are located in the central part of the country far from either coal-producing areas. This fact places coal a great geographical disadvantage in comparison with petroleum whose refining bases are concentrated on the coastal regions virtually next to major industrial centers.

Jan 1, 1982