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By Gui Hua Wang, Xin Chang, Zhong Ying Han, Yuan Fang Cheng

"According to the geometrical characteristics of triangular meshes, Triangular Mesh Split Model (TMSM) based on a finite element method is proposed to simulate cracks propagation of fractured rock. With TMSM, stress intensity factors at the tip of cracks are obtained by far-field contour integral. Meanwhile, vector cross multiplication is adopted to fix the cracking unit, and maximum circumferential stress criterion is used to determine the crack propagation angle. Then crack dynamic propagation simulation is realized through local mesh split or node movement at crack tip. With this method, the crack can split apart a unit or extend along the mesh boundary, so the crack could extend along an arbitrary path and is not restricted by the initial mesh. The applicability of the mesh split algorithm is verified by the crack propagation examples of wing crack and multi-fractured rock mass with holes. The results show that this method not only has higher accuracy of fracture parameters calculation, but also can accurately simulate the crack initiation and propagation of rock under complex stress state such as tension, compression and shear. In addition, the far contour integral is introduced to determine the crack tip stress intensity factor and there is no need to reconstruct a singular element at the crack tip or to intensify the meshes. Compared with the existing mesh reconstruction algorithm, this method significantly improves the computational efficiency.INTRODUCTIONGenerally, rock is neither the full continuum, nor entirely discrete body, but rich in geological defects, such as joints and cracks. A large amount of geotechnical engineering practice shows that most fracture of rock is closely related to the internal joints, cracks and crack expansion (Horii et al., 1985; Wong et al., 1998). Although the classical theory of fracture mechanics established the theoretical foundation of crack initiation, propagation, so far it is still extremely difficult to characterize the propagation of airfoil-typed crack and the interference problem of multiple cracks. Up to now, the micromechanics mechanism research of crack propagation of fractured rocks has still been a hot research topic of rock fracture mechanics."

Jan 1, 2015

By Orid A

A fast, non-contact technique for measuring sizes of rock fragments on a conveyor belt is presented. An image processing technique called active stereopsis is used which makes use of a light stripe projected on to the surface of the fragments on the conveyor belt. A CCD TV camera is used to capture the shape of the distorted light stripe. the video image of this shape is then processed by a computer program so that the 3D profile of the surface can be obtained by triangulation. The sizes of the rock fragments are then calculated from this profile. The speed of the technique is improved by calibrating the light stripe system before measurement begins so that the profile of the fragment surface can then be measured using simple geometry. The technique is fast and highly parallel so that it is able to operate in real time.

Jan 1, 1990

The Hall-Hoult process is likely to be the dominant method of aluminium production for the remainder of the century. The characteristics of the operation of a modern smelter are described and attention drawn to their disabilities which are due chiefly to the small production capacity of individual cells.The principal components of the Hall-H6roult cell - the electrolyte, the anode and the cathode - are discussed in order to identify the problems of scale-up. The factors influencing current efficiency and energy consumption are analysed and lead to the conclusion that the greatest potential for energy saving lies in reducing the anode to cathode distance (ACD).The most promising direction for major change is in the application of a new titanium diboride - carbon composite for coating of the surface of the cathode carbon. It improves the wetting of the carbon by aluminium and should permit the use of sloping cathodes and anodes. The deep metal pad would thereby be eliminated and, in the absence of magnetic perturbations, the ACD could be substantially decreased.The construction and testing of a full-size "Low Energy Cell" is scheduled for early 1986 and is expected to reduce energy consumption in aluminium production by about 15%.

Jan 1, 1985

By William M. Barret

In order properly to evaluate the data related to geomagnetic surveys, it is highly desirable to have all the available information concerning the magnetic properties of the involved media. This is true of surface as well as subsurface formations and becomes of increasing importance as advancement in instrumental and interpretative technique permits the analysis of relatively slight magnetic reflections of buried masses. Since the magnitude and areal distribution of the usually complex resultant magnetic field at the surface of the earth is a function of the susceptibility1 of the involved matter, it necessarily follows that susceptibility determinations will afford valuable data for geophysical correlation. The present method was developed to meet the need for routine analysis of specimens in the geomagnetic laboratory where it was felt that general utility, ruggedness, ease of manipulation and reproducibility of results were of greater importance than extreme sensitivity. Electric Circuits The electric circuits are illustrated diagrammatically in Fig. 1. Current from the battery, B, passes through the variable resistance R1, reversing switch S1, double-break key K1 to switches S2 and S3. From S2 it flows through variable resistance R2, ammeter A2, to the primary coils of the fixed mutual inductance Mf and variable mutual inductance M,. . From S3 it passes through variable resistance R3, ammeter As, to the primary winding of the fixed mutual inductance MI, which is designed to receive the test sample. The ballistic galvanometer2 or fluxmeter3 G is connected in the circuit containing the double-break key

Jan 1, 1932

By Milton E. Wadsworth, Edward M. Eyring

Better understanding of solid surfaces and their associated adsorption products is of both academic and practical value. The study of detergents and their behavior in cleaning surfaces is fundamentally related to the nature of the products adsorbed and their ability to compete for certain surfaces. Similarly in flotation, the nature of the adsorbate before and after adsorption is basic to clear understanding of the process. The recently developed pellet technique employing infrared spectroscopy provides a powerful tool for the study of solid surfaces. Absorption bands, which are infrared-active, may be observed for adsorbed products. Also any changes in the surface substrate that occur as a result of adsorption may be detected by means of differential spectra

May 1, 1956

By Henry B. Smith, S. Paul Lindau

ThREe years ago it was decided by the management to granulate the matte that is produced in the smelter of the St. Joseph Lead Co. at Hereulaneum, Mo., thereby doing away with a large amount of labor in handling the matte and in subsequent crushing. On Mar. 1, 1915, the granulator was put in operation and up to Jan. 1, 1916, 18,735 tons had been granulated. The four blast furnaces have a daily output of about 280 tons of pig lead and 100 tons of matte assaying about 11.0 per cent. Pb. It is expected that projected improvements in roasting methods will eliminate more sulphur from the charge, and cut down the matte-fall to about one-half of the present figure. The blast furnaces are tapped into movable forehearths or settlers, 6 ft. by 4 ft. by 22 in., the slag overflowing into 27-cu. ft. slag cars which are hauled to the dump by electric locomotives. Previous to the adoption of granulation, the matte was tapped from the forehearths into small slag pots which were dumped after cooling. The matte cakes were broken with sledges, and transported to the crushing plant for fine crushing and screening. Here the matte was reduced to 1/4-in. size before being fed to the roaster bins. A Wedge and a Holthoff mechanical furnace are used for preroasting before sintering on the Dwight and Lloyd machines. The matte is returned to the furnaces as an iron flux until the gradually accumulating copper content reaches about 7 per cent., after which it is put aside to be concentrated in a small copper blast furnace, the resultant high-grade matte being sold. When the matte does not settle readily from the slag, two settling devices are often used, the second one being a large catch-pot, which gathers any matte that may overflow from the forehearth, the slag then overflowing from the catch-pot into the slag cars. When full of matte, the catch-pot is removed, allowed to cool, and the contents broken and crushed. a With the present plan of granulating, the matte is tapped into 6-cu. ft. iron ladles. These are transported to the granulating plant by a 5-ton

Jan 1, 1917

In mid-1998 Atlas Copco Rock Drills AB introduced the first member of a new family of drill rigs. This new family, Rocket Boomer L1C/L2C/L3C, is based on modern computer technology and also on what is characterised as information technology. The design of the drill rigs are modularised both in hardware as in the software. This means that the functionality of the drill rigs is upgradable step by step. Added upon the basic drill rig functions are the new options as ABC Regular (known also as Contour Control), ABC Total, drillplan generator and communication products. The main objectives of these functions are to facilitate real quality drilling.

Jan 1, 2003

By John Floyd, Maria Rocha, Benjamin Cebrian

Wall control blasting is needed in most metal mining operations in terms of increasing mineral reserves and assuring the safety of the operation. This type of blasting has the goal to achieve a clean, stable rock wall in the shortest distance from a well fragmented, easy to excavate, blasted rock mass. This can be done with a variety of blasting techniques, all of which decrease the explosive energy towards the final wall. Each technique needs to suit the geology: modified production blasting, buffer blasting, pre-split and line drilling of empty holes. Pre-split is the most expensive technique, and allows final steeper bench face angles while modified production blasting is the least expensive but needs wider berms.

Jan 1, 2018

By A. I. Gorshkov, Y. A. Bogdanov, O. Y. Bogdanova

Abstract - Detailed crystal-chemical study of iron and manganese oxides and some other minerals from low-temperature hydrothermal deposits in a newly discovered inactive mound in the TAG hydrothermal field were used to determine the precipitation sequence of mineral phases during lowtemperature processes and their post-sedimentary transformations. Particles of primary sedimentary X-ray amorphous proto-ferrihydrite with high silica content were replaced in situ by nontronite, ferrihydrite, or goethite during alteration. Ferrihydrite is the only proto-hematite phase. The transformation of the iron minerals, related to change in the physicochemical environment, is an important characteristic of low-temperature hydrothermal processes. The occurrence of hydrogenetic Fe vernadite and Mn feroxyhyte in the uppermost part of low-temperature deposits and bottom sediments near the base of the mound is evidence for cessation of low-temperature hydrothermal processes. Among the investigated mineral phases, goethite, nontronite, and hematite are stable in reduced sediments only.

Jan 1, 1999

By G. L. Chierici

Starting from Muskat's theory of water and gas coning, maximum permissible oil production rates without water and/or free-gas production have been determined, in a broad range of reservoir and well parameters, using the potentiometric model technique. The main assumptions made are as follows: (1) the reservoir rock is homogeneeous (either isotropic or anisotropic); (2) the volume of the aquifer underlying the oil zone is very small, so that it does not contribute to reservoir energy; and (3) the gas cap expands at a very low rate, so that it can be assumed to be in quasi-static conditions. The results obtained are presented in the form of diagrams which can be used for solving two types of problems: (1) given the reservoir and fluids characteristics, as well as the position and length of the perforated interval, determine the maximum oil production rate without water and/or free-gas production; and (2) given the reservoir and fluids characteristics only, determine the position and length of the perforated interval which optimize the maximum permissible oil production rate, without water and/or free-gas production. INTRODUCTION In oil reservoirs where the oil-bearing formation is underlain by an aquifer which does not participate in the production mechanism, water-coning is a limiting factor to the flow rates of producing wells. Production rates are usually kept to a value that will prevent the water from entering the wells. The entry of water into a well lowers its productivity by increasing the weigbt of the fluid column; moreover, the separation of water from the effluent, at the surface, may constitute a very difficult problem in cases of heavy viscous oils. A similar situation is encountered in oil reservoirs with a gas cap overlying the oil-saturated zone; here a downward gas cone is induced by the flow of oil towards the producing wells. Production rates must be low enough to prevent the gas from being produced; producing gas from the gas cap would be a waste of energy. Of course, water-coning and gas-coning phenomena can occur at the same time in the same reservoir if the oil-producing formation is both overlain by a gas zone and underlain by a water zone. Due to its relevant practical importance, the mechanism of coning was studied by many people.2,3,5-8 Defining the conditions for getting the maximum water-free and/or gas-free oil production rate is a difficult problem, often encountered under one of the following aspects: 1. Predict the maximum flow rate that can be assigned to a completed well without the simultaneous production of water and/or free-gas. 2. Define the optimum length and position of the interval to be perforated in a well, in order to obtain the maximum water and gas-free production rate. A systematic study of these problems was made by means of the electrical analog technique. The results of this study are presented here, under the form of a set of curves providing solutions for the above stated problems. These curves are valid only for homogeneous forrnations, either isotropic or anisotropic. Should the formation be non-homogeneous (by horizontal or vertical variation of permeability, shale diaphragms, fractures, etc.), a specific potentiometric study would be required for each specific case. Especially when shale diaphragms of some radial extension are present, the critical rates observed are much larger than would be expected from the diagrams. STATEMENT OF THE PROBLEM In the present study the aquifer is supposed to be of such limited volume that it does not contribute to the energy of the reservoir. Moreover, the gas cap is supposed to expand at such a low rate that the potential gradient in the gas cap is negligible. Under static conditions water-oil and gas-oil interfaces (T1 and T2) are both horizontal. When the reservoir production starts, below each well these interfaces take a cone-like shape (Fig. 1) having as an axis the axis of the well. This shape results from the equilibrium between potential gradients in the oil zone and gravitational forces due to density differences between oil and water and between oil and gas. Assuming the oil-bearing formation to be homogeneous and the oil to be incompressible, the analysis of the problem (see Appendix) shows that the oil-water and gas-oil interfaces are stable only if the oil production rate of the well is not higher than the following values.

Jan 1, 1965

By M. Quamrul Ahsan, Andrew Griffiths, Edward P. Jucevic

Heap leaching of precious metal ores using the cyanide process is extensively used in the Western U.S.A. for extracting gold. Consequently, the impact of cyanide in the spent heap is closely examined by environmental agencies and permitting authorities. Currently, many states require that all decomnissioned heaps be detoxified before abandonment. This paper describes a case study for detoxification of spent heaps at the ACH-Dayton Project using hydrogen peroxide. The chemistry of cyanide detoxification by hydrogen peroxide, together with simplicity of a detoxification operation, is discussed.

Jan 1, 1989

By J. J. Strohl, H. J. Schwellenbach

This paper relates the results obtained by decreasing the size of feed to a rod mill screen circuit. As would be expected, added production was gained and a finer grind with no tonnage loss was made possible. THE MacIntyre mill of the National Lead Co. has four parallel sections in which magnetic and gravity separations are made. Ore from a 5000-ton bin is fed by Hardinge constant weight feeders to a 6x12-ft open-end Marcy rod mill in each section. Rod mill discharge is bucket elevated to two 4x10-ft Tyrock screens whose oversize is returned to the rod mill. Screen undersize is pumped to Crockett separators for magnetite removal, and the Crockett tailings are sized and tabled to make an ilmenite concentrate. Minus 200-mesh material, overflowed by the Crockett and Dorrco sizers is thickened, de-slimed, and concentrated by flotation.' By 1948, the development of a successful slime flotation process and numerous improvements in the gravity circuit of the mill had increased the capacity of the available concentrating equipment. At the same time, improvements in the operating techniques of the dry crushing plant and improved feeding of the crusher by the mining department had appreciably increased the production rate per operating hour in that plant. Therefore, it was decided to take advantage of the added crusher capacity to produce a finer rod mill feed and in that way increase grinding capacity. At approximately the same time, finer screens were installed in the rod mill circuits to give finer grind and thus improve liberation of the magnetite and ilmenite from the gangue and from one another. Prior to the first part of 1948, a 3/4-in. limiting screen was used for sizing rod mill feed. The first reduction in crushing plant screen size was to 1/2 in. With this screen, the circulating load in the tertiary crushing circuit was too high and plant capacity dropped below a practical hourly rate. A 9/16-in.-sq opening screen, installed next, proved satisfac-

Jan 1, 1951

By H. J. Schwellenbach, J. J. Strohl

This paper relates the results obtained by decreasing the size of feed to a rod mill screen circuit. As would be expected, added production was gained and a finer grind with no tonnage loss was made possible. THE MacIntyre mill of the National Lead Co. has four parallel sections in which magnetic and gravity separations are made. Ore from a 5000-ton bin is fed by Hardinge constant weight feeders to a 6x12-ft open-end Marcy rod mill in each section. Rod mill discharge is bucket elevated to two 4x10-ft Tyrock screens whose oversize is returned to the rod mill. Screen undersize is pumped to Crockett separators for magnetite removal, and the Crockett tailings are sized and tabled to make an ilmenite concentrate. Minus 200-mesh material, overflowed by the Crockett and Dorrco sizers is thickened, de-slimed, and concentrated by flotation.' By 1948, the development of a successful slime flotation process and numerous improvements in the gravity circuit of the mill had increased the capacity of the available concentrating equipment. At the same time, improvements in the operating techniques of the dry crushing plant and improved feeding of the crusher by the mining department had appreciably increased the production rate per operating hour in that plant. Therefore, it was decided to take advantage of the added crusher capacity to produce a finer rod mill feed and in that way increase grinding capacity. At approximately the same time, finer screens were installed in the rod mill circuits to give finer grind and thus improve liberation of the magnetite and ilmenite from the gangue and from one another. Prior to the first part of 1948, a 3/4-in. limiting screen was used for sizing rod mill feed. The first reduction in crushing plant screen size was to 1/2 in. With this screen, the circulating load in the tertiary crushing circuit was too high and plant capacity dropped below a practical hourly rate. A 9/16-in.-sq opening screen, installed next, proved satisfac-

Jan 1, 1951

By Bernie W. Martin, Jesus Schabib

The East Side Access (ESA) Project in New York will be the largest tunneling project ever undertaken by a US railroad. The objective of the ESA project is to connect the Long Island Rail Road (LIRR) Main Line and Port Washington Line in Queens to Grand Central Terminal in Manhattan. The Project is divided into two distinctive segments: Manhattan and Queens. The Queens segment is subdivided into two major components; cut and cover tunnel construction and bored tunnels. The bored tunnels in Queens consist of five tunnels driven from a launch shaft and traverse a railway storage yard, Sunnyside Yard and terminate under the multitrack mainlines of Amtrak and LIRR at portals in the heart of Harold Interlocking where1200 trains pass every day. The soil consists of remnants of glacial till moraines and of outwash and till deposits of inter layered gravel and fines, with the occasional boulders and cobbles and with a high ground water table. It is anticipated that a Pressurized Face Machine, either slurry or Earth Pressure Balance equipped with roller disks to mine the boulders encountered as well as the mixed face, will be used to mine the tunnels. One pass reinforced concrete gasket bolted liner will be used. The cut and cover construction consists of an approximately 21.3 m (70 feet) deep excavation supported by slurry walls and jet grout columns. The slurry walls, in combination with overlapping jet grouted columns, are installed to top of rock forming a closed bathtub to control external groundwater drawdown. Maintaining the groundwater level near its original elevation is of paramount importance in order to prevent undesirable settlements and migration of groundwater that could be contaminated. Mitigation measures to prevent the migration of nearby plums are contemplated for all types of tunneling and excavation work in this site of the ESA project.

Jan 1, 2001

By Shawn Healey

The Mineral Hill Mine, owned and operated by TVX Gold Inc., is located in the Beartooth Mountains, 5 miles north of Gardiner Montana, U.S.A., which is the north entrance of Yellowstone National Park. Mining is carried out underground using ramp attack cut and fill as well as room and pillar mining. The mine currently employs approximately 145 people and is producing 550 tons per day at a grade of around .21 oz/ton.

Jan 1, 1996

By Michael G. Li

Prediction of acid rock drainage (ARD) for low-sulphide, low-neutralisation potential (LSLNP) mine wastes is methodologically different from that for normal sulphidic mining wastes. In this paper. LSLNP wastes are conveniently defined as those with S2 < 1% and ABA-NP2 < 20 kg CaCO3 eq/t. The distinctiveness of ARD prediction for LSLNP materials originates from their frequently low oxidation rates and is mainly attributable to two reasons. First, the utilisation efficiency of available carbonate neutralisation potential (CNP2) rapidly deteriorates when the sulphide oxidation rate per unit mass of waste drops below a certain level. Reducing the flushing rate of a waste has the same effect as increasing the oxidation rate. Second, silicate neutralisation becomes increasingly important as oxidation rates diminish, and can no longer be ignored in LSLNP materials as it often is for normal sulphidic mine wastes. In this paper, the effects of oxidation rate, pore gas CO2 partial pressure, and flushing rate on ARD prediction for LSLNP materials are theoretically demonstrated with the help of modelling using the computer program MINTEQA2. A new methodology for ARD prediction for LSLNP materials is presented in terms of a prediction procedure. Finally, a case study is given to validate some of theoretical aspects discussed and to illustrate the use of the newly proposed ARD prediction procedure.

Jan 1, 2000

By James E. Jr Hargroves

With the ever-increasing population growth and modern trend to urban development, the expansion of utilities is a stable, mad or, and constant source of income for many. Blasting is a "necessary evil" to the utility contractor. It can make or break even the most solvent. Housing development expansion and higher treatment of effluents are causing utilities to appear in more congested areas. This paper discusses some of the aspects of utility blasting in the State of Virginia. Consideration is given to bid procedures, pre-blast surveys, record-keeping and practical application.

Jan 1, 1977

By Freeman Bishop

Mercury is the latest ecological disaster. It was believed to be no pollution problem because it is heavier than water and expected to fall to the bottom of streams. But the Food and Drug Administration (FDA) found that mercury in a dozen states and several Canadian provinces was being ingested by fish. A Deadly Dose First to sound the alarm was Canada when a graduate student&apos;s research revealed that mercury contamination in Lake St. Clair had reached 1.4 pmm. which is almost three times the 0.5 ppm the FDA&apos;s allowable maximum.

Jan 1, 1970

By R. Venkateswar, G. C. Sresty

Size measurement is important in characterization of fine particles. Commonly employed size measurement techniques such as sieving, microscopy, and sedimentation are discussed in this paper. Operating principles, advantages and limitations of these techniques are discussed based on the published information and working knowledge with several of these instruments at the authors&apos; laboratories. A brief description of the recently developed equipment for fine particle characterization is also included. At the end of the paper, a rationale is presented for selection of the size analysis equipment based on specific requirements.

Jan 1, 1980

By T. F. Witherbee

Success in this operation is much promoted by adhering to a definite plan. Random work is of little account. In general, anything done that will enable the blast to pass through the obstruction, providing the melted products can be got away from the tuyeres, is all that is necessary. Hence the utility of high explosives in breaking up the chilled mass in the hearth. (This, by the way, should be done with the wind on, so as to prevent the filling of the tuyeres with the usual rush of cinder following the explosion.) If from any cause it is not expedient to use explosives, the simple but very effective instrument known as the kerosene or hydro-carbon blow-pipe can be depended upon to perforate the contents of a blastfurnace hearth to any extent required. It consists, as used in the Champlain district (first by Mr. Charles H. Foote), of several pieces of gas-pipe, liberally supplied with elbows (five in number) so as to be flexible; one end being connected to a tuyere-stock and the other brought to bear upon the place to be melted out. A 1/4-inch pipe leads from the last length, or blow-pipe proper, to a reservoir of kerosene or crude oil, set high enough to overcome the blast-pressure, This 1/4-inch pipe should have a valve conveniently located to regulate the flow of oil, and also another next to the reservoir. With a good hot blast and a surprisingly small quantity of oil, this apparatus will melt, burn or mechanically dislodge anything around a blast-furnace hearth excepting firebrick and water-cooled castings or plates. It may be helped by vigorous prodding with a suitable steel bar, to detach the fused but sometimes sticky material. A very good way to operate on a chilled hearth with it, is to open up a hole from a cinder- or iron-notch to the nose of the most convenient tuyere and then make a blow-pipe of the tuyere by turning

Jan 1, 1885