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By Nobuzwe Makhotla, Sasha Boskovic, Steve Hearn

"Mineral separation efficiency in flotation depends, to an extent, on the type of frother used. Huntsman develops and manufactures unique frothers which are suited for mineral processing applications. This paper discusses the Huntsman approach to understanding the industry’s flotation frother requirements to optimise frother selection and introduce the Huntsman’s POLYFROTH® frother range. Specific case studies where the frothers are used are discussed. INTRODUCTION Froth flotation is a process of using bubbles to separate minerals based on their relative affinity for water. Bubbles are induced in the slurry through aeration. Chemistry is used to aid the flotation process and chemical reagents are added to enhance the separation process. The flotation reagents include frothers, collectors, surface modifiers and pH regulators that control physical and chemical conditions of solid, air and liquid phases, respectively. As described by Harris (1976), the key effect is that of bubble size control by way of preservation of the generated bubble size, which is attributed to the coalescence inhibition by the presence of the frother on the bubble surface. Following this, the frother must stabilize the froth phase. Frothers are also added to create optimal conditions for bubble creation and stability by decreasing the surface tension of the water. Depressants may be added, depending on the ore treated, to assist the hydrophilic particles to stay in the water phase. Clay particles may need to be dispersed to prevent them from attaching to the bubbles. Hydrophobic particles attach to the bubbles and are carried to the surface of the slurry where froth is formed. It is important for these bubbles to have the mobility to carry the mineral to the launder where the concentrate is collected. Types of Frothers There are generally three main groups of frothers used in froth flotation. Alcohol Type These frothers have a molecular structure that usually includes 5 to 8 carbon atoms in a hydrocarbon chain and their solubility in water is limited. Methyl isobutyl carbinol (MIBC) belongs to this category and is widely used in the industry. The weaker alcohol-type frothers are more selective and typically suited to finer particles. There are three sub-categories under this group: aliphatic, cyclic and aromatic alcohols."

Jan 1, 2015

Minerals are fundamental to the U.S. economy, contributing to the real gross domestic product (GDP) at several levels?mining, processing and manufacturing finished products. The estimated growth rate for the real GDP of the United States was 2.1 percent and the nominal GDP was about $13.8 trillion in 2007 (Table 1). The prime interest rate decreased to 7.25 percent in December from 8.25 percent at the beginning of 2007, reflecting actions taken by the Federal Reserve Board to counter financial difficulties surrounding subprime mort-gages. Delinquencies on subprime mortgages increased throughout the year, affecting not only the delinquent home owners but also financial instruments invested in mortgage-backed securities. The average contract mortgage rate for the purchase of previously occupied homes in the United States was 6.35 percent in November; a slight decrease from 6.37 percent in January but still greater than 5.34 percent reported in July 2003, the lowest rate in the past five years. With the tightening of credit, the seasonally adjusted annualized rate for new privately owned housing starts declined 27 percent from December 2006 to November 2007. The loss in the residential market was balanced by a 9-percent increase in nonresidential construction between January and August 2007, during which slight increases occurred in nearly all

Jan 1, 2008

The Hill 50 Gold Mine is situated at Boogardie, 3 miles on a bearing of 295 degrees from; Mount Magnet township. Mount Magnet lies 300 miles north-north-east of Perth, Western Australia (Fig. 1).The older workings of the mine may be identified with those of Sirdar, Gold Mining Lease 696M The Sirdar had been worked before 1902 though no records remain, and irom 1903 to 1912 about a thousana tons at a grade of 6' 2 dwt. was extracted annually; by the end of 1918 6,225 oz. of gold had been obtained from the milling of 17,852 tons of ore. In view of these yields, and the length and width of the lode, this mine was early recognized as one of the most promising in the district. From 1919 to 1924 the ground,including G.M.L. 1282M, was held as Mt. Zion G.M.L. 1183M.The Hill 50 Gold Mine N.L. company took up the workings as Hill 50 G.M.L. 1282M in 1934 and have continued operations to the date of writing. To the end of 1956 the Hill 50 Gold Mine had yielded 982,106 tons of ore for a return of 448,'602 fine oz. of gold.The mine has been described by: J utson (1915), Feldtmann (1920), Johnson (1949), and Finucane (1953). Finucane (1953) details the mine structure to a depth of 414 ft. The author was able to examine the mine to a depth of 1305 ft. Detailed main level mapping to the 1060 level and a detailed surface examination have revealed aspects of the structure which were previously obscure.

Jan 1, 1960

The term geochemistry - chcmbtry' of the earth - is almost limitless in its implied subject, but of recent years a major trend of research in this field has been towards economic application in the search for mineral deposits, and in particular for those of some ofthe less common elements for which a demand now exists.Geochemistry is in a state of slow transition from a purely descriptive subject to a fundamental science concerned with the relationships that exist between the distribution of the elements in the earth's crust and the physical characteristics of the atoms of those elements. The progress achieved promises a set of basic principles which will relate the atomic characteristics of an element to the physico-chemical conditions that make for its dispersion or concentration. This means that, given a geological map of an areasufficiently detailed for the physico-chemical conditions existing in past geological eras to be deduced, there is the possibility that the relative distribution throughout that area of any element present, and its likely mode of occurrence, could be predicted from a consideration of its atomic characteristics.Since the atomic characteristics of the elements are becoming increasingly well defined by physical research, the attainment of this ideal of prediction depends upon:(a) the strengthening of geochemical theory; and(b) the development of petrological and mineralogical methods of assessing the conditions of temperature and pressure prevailing in geological formations at various stages in their history.The other prime requirement is a d.etailed geological map - a requirement that is all too often lacking.The fact that there has been very little "geochemical approach" to problems of economic geology in Australia should not be taken to mean that there is little point in trying to develop such an approach here in as active and as rigidly scientific a manner as possible. The degree of success that has attended the attempts so far made, to which reference is made below, suggests the reverse, particularly in view of the relatively slight cost involved if the investigations were properly organised on a centralised basis. There are three aspects of geochemistry that are directly applicable to the search for economic minerals.(a) The classic technique of the prospector can be made more sensitive and reliable by the use of modern equipment coupled with the application of geochemical theory to geological and structural data. The case of the rare alkali elements (see below) is givenhere as an illustration of the way in which the distribution of elements can be predicted from the first principles of geochemistry, thereby replacing the prospector's dependence on his "sixth sense" that enabled him to suggest that a certain area of formation was"favourable" for the occurrence of a certain type of mineral deposit.At its best, this sixth sense amounted to an almost subconscious correlation of all relevant associations and typical occurrences of the particular mineral experienced by the prospector during his...

Jan 1, 1950

By M. A. Trevits, T. A. Gray, L. M. Crayne, P. Glogowski

Mine seals can he remotely constructed in underground coal mines through vertical boreholes when direct access to a fire is impossible or considered to he too dangerous. This method has great merit because the boreholes can be drilled to specific mine areas, and the seals can be positioned close to a fire zone. The technology however can be largely ineffective if the constructed seals do not provide of effective barriers to airflow or if they cannot he used to impound water and other inert materials. Unfortunately, no viable alternatives exists to sealing the entire mine to the ground surface. Full-scale remote mine seal construction research is being conducted at the National Institute for Occupational Safety and Health (NIOSH) Lake Lynn Laboratory (LLL). Under this effort. Howard Concrete Pumping Company and GAI Consultants Inc. have joined forces to evaluate a potentially significant improvement to the current state of the art. This paper covers the development o f novel technology or rewrote mine seal construction, the evaluation of rite materials used, the construction practice and the Fellow-up testing.

By David J. Mack

A SURVEY and critical appraisal of published information about Young's modulus was originally made by the writer because of a complete lack of information about this very important quantity in works on mechanics, physical metallurgy, physics, and other sciences. It was felt that a comprehensive summary of such information about Young's modulus might be of general interest and may suggest new problems or lines of attack on other problems that involve E. Hence this paper has been prepared even though it is only a review, with no new ideas or experimental data. The references are only those used in assembling the paper. No attempt was made to compile a complete bibliography on the subject of Young's modulus. CALCULATION OF YOUNG'S MODULUS FROM THEORETICAL OR EMPIRICAL CONSIDERATIONS Many attempts have been made to compute E from theoretical considerations. The earliest calculations were probably those of Tomlenson (1883) and Southerland (1891), but Fessenden 41,42 made extensive calculations a few years later and arrived at the relationship: [2E = 78. 101 (_L V] where V is the atomic volume. In 1923, Peczalski,43 working from the same stand-point but with more information available on atomic structure, arrived at an identical relationship, which he expressed as: [E=B(m) 2] where B is a constant of value about 8 • 10 7, p is density and m is atomic weight; the atomic volume, of course, being m/p. Portevin44 immediately pointed out that while the equations of Fessenden and Peczalski were true of the common metals, they gave low values for the refractory metals with high moduli (Fig. I). He showed (Fig. 2) that much better concordance was obtained by means of an empirical equation of the form: [E _ KT'Vb] where K is a constant; T the absolute melting point; V, atomic volume, and a and b constants of value approximately I and 2 respectively. This constant K in the Portevin equation is not necessarily the same for all elements, as shown by Thompson.45 Other equations for E based upon theoretical considerations have been derived by Honda and Yamada49 and Lasareff. 50 The most recent calculations of elastic moduli based upon quantum mechanics are probably those of Fuchs.46-48 He extended the method of Wigner and Seitz for calculating the lattice energy and compressibility of monovalent metals and computed the elastic constants of lithium,

Jan 1, 1945

By Sara Jane Boles

In recent years the demand for products of greater refractoriness has placed an ever-increasing emphasis on ceramic materials, including the metallic oxides. Magnesia (MgO) is one of the most important of these oxides, exhibiting, as it does, high electrical resistivity, high slag resistance, and a melting point of 2,800° C. However, magnesia has a tendency to hydrate in the presence of water and to volatilize above 1,500° C. in certain kiln atmospheres and has a comparatively low resistance to thermal shock. Because of these disadvantages, the previously listed advantages inherent in this material have been largely overlooked, and research on magnesia has lagged behind that on oxides such as alumina and zirconia. This bibliography has been prepared in an effort to present to Government and industry a comprehensive picture of the prospects for greater utilization of magnesia as a refractory material in future research. To provide as selective and accurate a collection as possible, the references included cover magnesia in a pure state, not as an additive or in combination with other materials. However, several references discuss the effect of minor impurities (less than 5 percent of the total) on the properties of magnesia, as these papers are considered to be of special importance. A few references to articles on forming techniques are also included, as they are valuable additions to the overall treatment of the subject. The processes used in obtaining and refining the raw materials are adequately covered in earlier publications and are excluded. A number of references are omitted as being of questionable value in enhancing the cumulative study of pure magnesia as an ultra-high-temperature refractory material.

Jan 1, 1962

In 1961, West Australian Petroleum's Eneabba No. 1 bore encountered 22 seams of coal totalling 40 ft in thickness between the depths of 6373 ft and 6441 ft. On analysis, this coal had a similar calorific value (8000-HOOO B.T.U./lb, assuming 20 per cent water) to the coal from the Collie Coalfield, Western Australia's only known area of commercially exploitable coal. Being buried to depths in excess of 6000 ft, the coal at Eneabba had developed weakly-coking properties, and thus, although much younger than the Permian coals of Collie, gave promise of being a major potential source of power for Western Australia.West Australian Petroleum undertook a programme of stratigraphic drilling and shallow test drilling to determine whether this coalhorizon persisted into the outcrop of the Lower Jurassic sediments in the Hill River district, 140 miles NNW. of Perth, and, if it was present, if the quality and quantity of the coal would warrant development of the deposits by open cutting. The coal horizon was identified in the near surface, but the poor quality of the coal and the complexity of the structure made development (in the area examined) uneconomic at the time.A strong seismic reflection in the Eneabba area occurs at the same depth as the Jurassic coals. This event originates within the upper beds of the Lower Jurassic and it is probable that the velocity contrast between the higher velocity siltstones and the very low velocity coals enhances this very strong, distinctive seismic reflection.This event can be followed on continuous seismic data over a large area of the northern Perth Basin, from 13 miles SE. of Dongara to 20 miles SW. of Coorow. It can be followed from a depth of 4000 ftnear Dongara to over 17,000 ft to the SE., so development of thisvast potential source of power will depend on the economics ofprocesses being developed for the production of power from theburning of coal seams in situ.INTRODUCTIONThe discovery of 22 seams of economically useable coaltotalling 40 ft in thickness in the Lower J urassic sedimentsof the Eneabba No. 1 bore (Fig. 1) led to the search forthese seams at economically workable depths. The Ministerfor Mines in Western Australia granted to West Australian1. Supervising Geologist, West Australian Petroleum Pty. Ltd.Manuscript received at The Institute, 25th May, 1964. and presented to the 1964Annual Conference.

Jan 1, 1964

By L. Frost

Physical Conditions Great Britain The physical conditions in the mines investigated in Great Britain are similar to those found in the mines of the Dominion Steel and Coal Corporation, with the important difference that many of the coal seams visited were interspersed by a large number of heavy faults, making the development of a continuous face operation difficult, and in many cases the life of a unit development was exceptionally short, adding to unit cost; but in spite of these difficulties, a great deal has been accomplished in the application of mechanical loading units in a number of the mines in the areas visited. The coal-bearing measures, as in Nova Scotia, consist of shales and sandstones, and in some sections mussel bands overlie the coal seams making roof conditions difficult'. In several mines, the main roof consisted of weak shale bind, being held by a coal roof of varying thickness. This shale bind had a tendency to flow when the coal roof was broken. The floor, in some cases where cutter loaders were operated successfully, consisted of weak, flaky shales with very little resistance and a tendency to disintegrate into powder when broken. The depth of cover under which these mines were operating varied from 250 feet to 2,340 feet, with an average of 1,700 feet. The coal seams varied in height from 3 feet to 8 feet 6 inches, and the gradients from level to 33 per cent. The seams vary in hardness, but all-with the exception of one seam, the 'Morrison Busty'- presented a cutting problem similar to that found in Nova Scotia. The structure and cleavage of the coal was well defined and uniform. Some of the seams visited were gassy, ?but the temperature of the workings generally was not in excess of 70°F.

Jan 1, 1948

By Wilton Johnson

The Bureau of Mines study indicates that land utilized by the mining industry for mineral extraction and processing from 1930 through 1980 amounted to 5.7 million acres, or 0.25 percent of the land mass in the United States. Land reclaimed by the industry during the same period was 2.7 million acres, or 47 percent of the land utilized. Land use by the mining industry includes surface land used for excavation or mining, for waste from underground mining, and for wastes from milling or processing operations. Data on land use for disposal of overburden waste from surface coal mines and on areas affected by subsidence associated with underground mining are included for the period 1930-71 only. The 10 leading States in total land used for mining over the 51-year period were, in decreasing order, Pennsylvania, Kentucky, Ohio, Illinois, West Virginia, Florida, Indiana, California, Alabama, and Missouri. Seven mineral commodities accounting for 92 percent of land use are, in decreasing order, bituminous coal, sand and gravel, stone, phosphate rock, clay, copper, and iron ore, all predominately surface mined. Bituminous coal production was responsible for nearly half of the total area utilized. Reclamation of mined lands and waste disposal sites over the reporting period was largely on lands utilized in mining bituminous coal; 75 percent of the land used for bituminous coal production was reclaimed.

Jan 1, 1981

By F. F. Aplan

Mineral processing engineers have recorded an- other year of active research and development work. Most gratifying was the broadly based attendance at the Mineral Processing Fundamental (formerly Basic Science) Committee sessions at the 1968 Annual Meeting of the AIME. Because of the availability of good papers, the active discussion and the growing attendance, sessions have grown from one to three at the annual meeting. Prof. M. C. Fuerstenau of the University of Utah will chair the Mineral Processing Fundamentals Committee for the next two years and we may thus be assured of continued active leadership. The name change from "Basic Science Committee" to the more descriptive "Mineral Processing Fundamentals Committee" approved by the MBD executive council is a welcome improvement. Our profession continues to attract the interest and cooperation of those in other professional groups. The 1968 Engineering Foundation Particulate Matter Conference, under the chairmanship of John Karpinski of Bethlehem Steel, was devoted exclusively to comminution this year. It attracted conferees from five continents and served as a particularly stimulating source of interchange of knowledge from many technical fields. Next year's conference will be under the chairmanship of Professor L,. G. Austin of The Pennsylvania State University. This conference plus the Symposium on Wettability and Flotation to be held at the annual American Chemical Society meeting in Minneapolis in April indicates the success achieved in the inter-disciplinary approach to problems. Other evidence of this spirit of professional cooperation is the forth- coming book on Size Reduction edited by D. W. Fuerstenau. This is the outgrowth of an AIChE symposium on size reduction held in 1965.

Jan 2, 1969

By Y. K. Yen, J. D. Miller, C. L. Lin

The image-based On-line Particle Size Analyzer (OPSA)system has been developed at the University of Utah to measure particle size distributions under plant conditions where overlapped and segregated particles are being transported on a moving belt conveyor. Evaluation of the OPSA system at several plant sites has been completed. The results show a consistent agreement between the particle size distributions obtained from the OPSA system and those obtained from laboratory screen analysis of belt samples. These results and the stable performance of the OPSA system during the field tests suggest that continuous quality control of crushed products is possible using the OPSA system.

Jan 1, 1999

By Ralph M. Foecking

The disposal of the phosphate slimes produced by Florida beneficiation operations is perhaps the biggest single problem of the phosphate mining industry. This is an old problem which has not been solved and which is becoming increasingly severe. In a typical phosphate mining operation, the phosphate rock mined is initmately mixed with sand and clay, constituting what is known as matrix. During the beneficiation, the clay and other fine materials are separated usually at -150 mesh, and washed from the phosphate rock in a form of diluted slurry known as phosphate slimes. The quantity of slimes solids and their composition vary considerably with the location but usually represent from 25 to 35% of the ore mined. Because of the affinity that clays have for water, large volumes of water are required to separate the granular material in the matrix forming a dilute slime suspension (1.5 to 3% solids) of colloidal material, which settles very slowly, and thus requires immense impounding areas, which never becomes totally usable land. These ponds also contain about 25 to 35% of the total P205 values mined. The magnitude of the problem represented by the slimes can be appreciated better if we realize that there are around

Jan 1, 1971

By Maya Kamenetsky, Khoi Nguyen, Natalee Bonnici, Steve Walters, Claire McMahon, Julie Hunt, Ron Berry

"The analysis of meso- and micro-scale textural attributes has been undertaken on ore samples from the Ernest Henry iron oxide-copper-gold (IOCG) deposit in NW QLD. Quantified textural data including grain size, shape and mineral association have been extracted from classified images of core with the aim to better predict potential mineral processing behaviours such as comminution, liberation and flotation. Data have been extracted from images of intact core at meso- and micro-scales using high resolution continuous images collected using automated core-logger technology, SEM-based and optical microscopy platforms.The results of this study will show examples of quantified size, shape and mineral association data from meso- and micro-scale classified images. Analysis of the data shows that there are domains of variable grain size and mineral association that can potentially be related to crushing and liberation behaviour. The trends that are observed at the drill-core (meso-) scale are consistent with those at the micro-scale. The results from the micro-scale analysis show that the domains defined at the core-scale have clearly different chalcopyrite sizes and shapes as well as variable bulk mineralogy.INTRODUCTIONInnovations in technology have allowed automated extraction of information about mineral shape, grain size and mineral association, i.e., texture, from meso- and micro-scale images of intact rocks. The overall aim of this research is to investigate trends in quantified textural data that can potentially give an early view of processing parameters such as predicted grind size and liberation behaviour."

Jan 1, 2009

The National Institute for Occupational Safety and Health (NIOSH) conducted a study to determine the effectiveness of a filtered air delivery system to reduce respirable dust exposure to roof bolter operators in underground coal mines. When performing roof bolting operations, roof bolter operators may experience exposure to high levels of respirable dust during a working shift, especially when working downwind of the continuous mining machine. While drilling and installing roof bolts, this filtered air system supplies a clean curtain of air over the roof bolter operator by means of a plenum mounted beneath the canopy. This experimentally designed air curtain, adapted for roof bolting machines used in this study, is based upon previous design prototypes, computational fluid dynamics (CFD) simulations, and trial-and-error testing. Both prototype and final designs were tested in the full-scale mining galleries at the Office of Mine Safety and Health Research (OMSHR) in Pittsburgh before being taken underground for field testing. Test results of the system in both laboratory and field studies show reductions in operator exposure to respirable dust when the operator is positioned directly under the protected zone of the canopy.

Jan 1, 2012

By Prasenjit Basu

Drilled displacement piles are being increasingly used as foundation elements, particularly in projects requiring fast construction. Different types of drilled displacement (DD) piles are available in practice. DD piles are classified according to the drilling tool design and installation method. The capacity of a DD pile, depending on its type, is between the capacities of geometrically similar nondisplacement and full-displacement piles installed in the same soil profile. This paper provides an overview of the different types of DD piles and their installation techniques and describes three design methods used in practice. It also compares DD pile capacities obtained with these design methods for two different sites.

Jan 1, 2010

By William B. Hughes

The rubber-sleeve core barrel was developed to improve core recovery from unconsolidated sands, where it is most difficult to obtain cores with conventional barrels. The use of a rubber-sleeve core retainer, together with other departures from clsual design, has required a considerable amount of testing to prove its op-erability. Tests run in shallow experimental holes and in drilling wells in the U. S. and Vemzuela have, to a large extent, proved the operation of the barrel. Internal mechanism troubles, such as sandbinding of the sleeve, have been largely overcome. Cores have been recovered from completely unconsolidated sands where conventional coring has almost been abandoned because of poor recovery. In addition to retaining the core until brought to the surface, the barrel gives a "packaged-ar-cut" core, which is coilverzient for handling and transportatiorz. In the initial work, drag blade cutters, roller cutters, and tungsten carbide insert cutters were usrd for cutting unconsolidated sands. Further bit head development is presently being conducted using diamond heads in unconsolidated sands where shaler, hard sands, and limestones are encountered in adjacent formations. Thir work should render the barrel capable of cratting and recovering most types of formations, possibly including broken and frac- tured fornlations. This development is being carried on in cooperation with a diamond bit manufacturer. INTRODUCTIO N For many years the oil industry has needed greater recovery of cores from unconsolidated formations. Conventional equipment has been used to core unconsolidated sands with little success. Specifically, a core barrel was needed which would recover unconsolidated sands in a condition that would give useful reservoir information. DEVELOPMENT OF 'THE RUBBER-SLEEVE CORE BARREL Basic Requirements of Unconsolidated Sand Corino The basic need was defined as a core barrel that would obtain a continuous unconsolidated core with sand grains in place as deposited in the formation. A preliminary survey of coring equipment and search of the literature pointed out the weaknesses of conventional core barrels. Laboratory tests using unconsolidated sand in a metal tube simulated actual sand movement into the core barrel during conventional coring. In conventional barrels the core sometimes crumbles and bridges, or fails under compressive column action, becomes oversize, and wedges against the walls of the inner barrel. The core barrel requirements established by the surveys and preliminary tests are as follows. 1. The core should be held to- gether as it is cut so it cannot crumble and bridge against the walls of the coring tool, care being taken not to permit damage from fluid circulation. 2. The core should be continuously supported as it is cut so it will not have to support itself in compression. 3. The core should be packaged in the barrel to retain an undisturbed condition during the trip out of the well. The packaging should be such that the core can be removed from the barrel and shipped to the core analysis laboratory without physical disturbance or alteration of fluid content by exposure to the atmosphere. Operation of the Rubber-Sleeve Core Barrel The rubber-sleeve core barrel (Fig. 1) meets the basic requirements for the recovery of unconsolidated sands.

By T. Tamagawa, N. S. Fu, I. Iwasaki, M. Kobayashi

A 3-stage fluidizing bed process of chlorination, selective oxidation and sulfur chloride conversion was tested for processing of a chalcopyrite concentrate. It was found that the use of excess oxygen was essential to a stable operation in the oxidation reactor. The oxygen-excess gas will inevitably cause the oxidation of the sulfide concentrate in the chlorination and sulfur chloride conversion reactors. A new flowsheet is proposed to separate the chlorination and the selective oxidation steps with separate flow paths of the fluidizing gases, thereby preventing the passage of oxygen-excess gas in the chlorination and sulfur chloride conversion reactors. The feasibility of the proposed flowsheet was demonstrated in a laboratory-scale fluidizing bed setup.

Jan 1, 2000

By A. M. Hefny, F. P. Siew, P. G. Ranjith

Fracture initiation and propagation, being one of the most intensive subjects in rock mechanics; contribute significantly to the deformation of jointed rock masses. An experimental study on fractured granitic rock was carried out to determine the peak strength of specimen under triaxial loading conditions. The commonly observed failure mode for rock specimens in this study was found to be the shearing of the plane of weakness. The minimum peak strength of fractured rock is observed when the joint orientation is approximately 70° to the horizontal axis. Based on experimental test data, an empirical expression was developed to accommodate the effect of joint orientation and joint trace length in estimating the peak strength of fractured rocks. The predicted values of peak strength using the proposed equation well agree with the experimental results carried out on singly fractured specimens under triaxial loading conditions. The threshold stress values of crack initiation and propagation depend on joint geometrical parameters, their degree of interconnectivity, as well as surrounding stresses on the fracture plane.

Jan 1, 2003

Very few of those occupied in pursuits other than mining have any conception of the extent of boring operations that have been carried out on the gold and coal fields of Victoria, or of the valuable and definite knowledge obtainable by such means. The subject comprises various branches, which it will be necessary to describe in detail. The three main divisions are The Administrative, which includes all financial work and general management. The Professional, dealing with topographical and geological work necessary before any scheme of boring can be laid out, the preparation of plans, the inspection of cores obtained from bore holes, the examination of diamonds, etc. The Mechanical Branch, dealing with the drilling machinery, setting of diamonds, maintenance of stores, etc. In 1877, the Goverpment of Victoria decided to assist in prospecting the mineral resources of the colony by the aid of diamond drill boring, and for that purpose, a vote of £5,000 was passed, with which were purchased three diamond dulls, an American type being adopted.

Jan 1, 1901