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By J W. Simmons, T H. Antoun

"Rock fragmentation is an important component of explosive mining and excavation techniques andis the culmination of a damage accumulation process dominated by crack propagation. During the past 20 years, improved computer modeling of this process has resulted in new and promising computational tools for improving explosive mining and excavation procedures. This paper discusses one of these new computational tools, a computer model called BFRACT."

Jan 1, 1995

By Kidd, Robert L.

INASMUCH as galena and sphalerite flotation concentrates are being produced that contain over 95 per cent galena or sphalerite, it is not unreasonable to believe that a flotation concentrate assaying at least 80 per cent of native gold can he secured provided the gold is free. As yet, little if any fundamental information has been published concerning the flotation of free gold either alone or in the presence of sulfides. So far, we are unable to make as complete a separation of gold from sulfide minerals by flotation as is possible in, the separation of one sulfide from another by this method. An introductory study of the flotation of several free gold ores has been made in our Utah laboratories. For this study three general types of gold ores were chosen, namely: (1) Quartzite containing 0.26 oz. gold per ton in which no base metals are present; (2) sulfide ore (2.04 oz. Au; 1.31 oz. AO containing pyrite as the only sulfide present and the gold free; and (3) oxidized ore (1.10 oz. Au; 0.70 oz. Ag) from an oxidized zone of the vein from which sulfide ore (No. 2) was taken; little sulfide iron was present.

Jan 1, 1932

Present roof bolting practices in the collieries of Australian Iron and Steel Pty. Ltd. are outlined. Roof support has been improved since introducing roof bolts and it is hoped to increase the reliability of the bolts still further.Expansion-shell, and split and wedge roof bolts five to eight feet long are placed by "Atlas Falcon" and "Fletcher" roof bolters. Both anchorage and tightening have presented some problems.Good panel supervision is required if systematic roof bolting is to be properly co-ordinated with coal production without unnecessary delay to either. Successful roof bolting can only be the product of conscientious men and supervisors who are all convinced of its value. A rigid operational code should be established early and maintained.INTRODUCTIONRoof bolting is a method of support which is permanent and reduces or eliminates the need for other support; The method was pioneered in America and was first experimentally investigated in Australian collieries at Elrington in 1949 (McKensey, 1953). Pneumatic installation methods were employed. Subsequently, a method of using standard hand-held electric coal drills was developed at John Darling Colliery (Horseman, 1954). Pneumatic roof bolting equipment was first operated in the collieries of Australian Ironand Steel Pty. Ltd (A.I. &. S.) in 1951. Since then various hydraulically operated mobile machines have been installed in Australian collieries and these, together with improved pneumatic equipment, form the two present basic methods of placing ,roof bolts. Roof bolt anchorage is achieved by either split and wedge or expansion-shell bolts.The two broad types of roof bolting are 1. consolidation of strata, and 2. suspension support.

Jan 1, 1961

By G. H. Lind

Research into the safe and economic extraction of underground coal pillars in the Witbank and Highveld coalfields of South Africa highlighted that future practices will have to consider pertinent risks associated with this least safe of all underground coal mining methods conducted in South Africa. To this end, a computer-based program called A-PEP (Analysis for Pillar Extraction Potential) was developed to assess three aspects of this mining practice, viz. risks associated with the physical attributes, operational risk attributes and economic attributes. This intelligent tool can thus be used when planning to conduct underground pillar extraction to ensure that all pertinent risk elements and legislative requirements are considered to conduct this mining method safely before a submission is made to the Department of Minerals and Energy. Keywords: operational risk management, mine planning, underground coal mining, pillar extraction.

Jan 1, 2003

By Edmund J. Cardoza

The paper describes the design, construction and quality control aspects of the installation of a cement-bentonite (CB) cut off wall to impede seepage through a flood control dike. Special emphasis is placed upon the development of a proper specification, distinguishing the CB method from the Soil-Bentonite technique. The importance of the pre-construction laboratory testing program and field quality control procedures is emphasized by the fact that the in-place properties and characteristics of the CB cut off may not be known until after a majority of the work is complete. Sections are included which describe the construction method, the specialty equipment and personnel requirements and the quality control/quality assurance aspects of the project.

Jan 1, 1992

By G. E. McElroy

Ventilation-pressure surveys are required to determine the rates of pressure losses in various parts of mine-airway systems. These may be determined directly by differential pressure measurements or deduced from absolute pressure measurements, Despite the confusion caused by its inverted nonlinear scale, the altimeter has special application to pressure surveys in mines in which only small differences in elevation are involved, as is true for most of our large bituminous-coal mines in these, the judicious use of information obtained by pressure surveying can result in greatly improved working conditions as regards health and safety and, in many instances, can yield large financial returns. The main purposes of this report are to discuss methods of using altimeters for pressure surveys and to present the particular methods of making surveys and calculating the results of surveys used by the Mine Ventilation Section of the Bureau of Mines.

Jan 1, 1957

By Blanchard R

The discussion submitted by Drs. Stillwell and Edwards is at once helpful and gratifying to the authors. Their contribution deals with two phases of the problem-(I) an additional suggestion for the relative solubility of galena and marmatite, and (2) submission of an alternative explanation for the greater leaching of the Northern ore-body. With the first we agree in principle, and herewith present recent data which will help to substantiate the idea, though the mechanism is not believed to be as simple as indicated by Stillwell and Edwards. Concerning the second suggestion, the original explanation put forward. in the paper is held to fit the facts more closely.In view of the influence, as shown by Garrells' paper,in which the presence of Cl' ion may have upon the relative solubilities of lead and zinc, it is perhaps worth noting that Broken Hill mine water carries a higher content of Cl' than has been reported from many of the other lead-zinc districts.Since our paper was published, an analysis of water issuing from the newly-opened Northern ore-body on the 2,600-ft. level has been made (12/1/43). It is compared with that quoted in the original paper as follows:

Jan 1, 1943

By Holly J

The period following World War II has seen many changes in stoping techniques at The Great Boulder Gold Mine. The new methods resulted in improved unit production figures, and have given some relief from the rising worldwide cost spiral in the post war years.Significant production figures are shown graphically in...

Jan 1, 1956

By Tracy Brettmann, Will Bohlen

An innovative retaining wall design consisting of tangent drilled shafts with supplementary seal piles was used to limit continuing bank erosion along the Brazos River in Southeast Texas. The riverbank erosion had progressed to where it was threatening the stability of both the bridge abutment and corresponding approach embankment of the heavily travelled Highway 99 bridge at this location. A tangent pile design was selected because it was both much faster to install and more cost effective than a secant pile system. The design included both 5.5-ft and 10-ft diameter shafts with depths up to 130-ft and comprised both anchored and cantilevered sections. Supplementary seal shafts were also installed between the structural tangent drilled shafts to help plug any gaps between the tangent shafts. The plumbness and diameter of the shafts were tested using a sonic caliper to make sure the shafts were installed within the specified tolerance. The initial design had to be revised when a record flood from Hurricane Harvey impacted the site during construction. Introduction The Fort Bend Grand Parkway Toll Road Authority (Owner) needed to protect the north bridge abutment with a retaining wall system due to rapidly eroding conditions of the Brazos River banks within the 300- feet-right-of-way of the State Highway 99 Jodie Stavinoha Bridge. The extent of the local scour and erosion along the north bank of the Brazos River has caused concern for the structural integrity of the bridge. The magnitude of the erosion along the north bank at the location of the bridge has been measured at about 120 feet over three recent hydrologic flood events locally referred to as Memorial Day 2015, Memorial Day 2016, and Tax Day 2016. During construction, a new record flood level occurred due to Hurricane Harvey in August of 2017 that resulted in a portion of the retaining wall needing to be redesigned due to even more erosion occurring. The Brazos River is an actively eroding and meandering alluvial river plain that naturally meanders and migrates over time. The processes of bank erosion and meander migration were ongoing before the bridge was constructed and will continue in the future. These recurring major flood events, however, rapidly increased the rate of erosion in just a few years. Background. Due to the need to protect the bridge as soon as possible, the Owner selected a project team consisting of the designer, general contractor and specialty deep foundation contractor prior to final design to work together in developing a cost-effective design that could be implemented rapidly. The project team initially considered both a secant pile and tangent pile retaining wall system using drilled shafts. After reviewing various alternative designs, a tangent pile wall with seal piles was selected based on both cost effectiveness and speed of installation. The tangent pile with seal pile option was approximately 20 percent lower in cost and 50 percent faster to install.

Jan 1, 2018

By D. Gendzwill, N. Martin

"In early 1987, the Patience Lake potash mine near Saskatoon, Saskatchewan, was closed due to uncontrollable floodingWater inflows were first encountered during routine mining in 1975 at the south boundary of the mine lease. Underground grouting and construction of bulkheads limited the flo but did not completely stop it. Subsequent seismic surveys showed that the mine had approached the edge of a large collapse structure in which the salt and potash had been partly dissolved and removed by groundwater.In 1986, the small flow into the mine started to grow. Despite renewed grouting, the flood increased and outstripped pump capacity. The grouting program temporarily slowed the inflow but was unable to stop it. Eventually, from seismic and drilling evidence, it became clear that the water source was an extensive system of vertical fractures which would be impossible to seal by drilling and grouting from underground. A new plan to install 14 bulkheads underground would have sealed the water source from the rest of the mine but the construction program could not be completed before rapidly increasing inflow threatened to fill the mine. The underground mine was closed and a new solution mine started in 1988."

Jan 1, 1996

Notwithstanding full concurrence with the dictum of a famous scientist that "definitions are the most accursed of all things on the face of the earth," in view of the considerable confusion which exists in jigging nomenclature, it is considered advisable to commence this paper with the following explanations of the terms which will be used throughout the text.Jig Bed. The whole layer of material lying on top of the jig screen.Ragging. The layer of denser material lying immediately above the jig screen, which is too coarse to pass through this screen and is confined horizontally by the cells of the top grid.Ore Column. The layer of ore pulp between the ragging and the top-water.Top Water. The water, carrying fine material in suspension, which flOiWS over the surface of the jig bed.Hutch Water. The water added to the jig below the screen. (Except for the water discharged with the hutch concentrate, the "hutch-water" eventually becomes "top-water.")Feed Water. The water in the ore pulp fed to the jig.(This water becomes part of the "top-water.")Pulsion. The period of the jigging cycle during which the water is moving upwards relative to the particles in the jig bed.

Jan 1, 1937

In the course of work being carried out in the Lubricants and Bearings Section of the Council lor Scientific and Industrial Research on the production of copper4ead 'bearings for 'use in aircraft, it has been found necessary to develop special metallographic methods. For proper control of the production of steel-backed copper-lead bearings it is necessary to adhere to rigidly controlled conditions, and it is essential that a method of examination be adopted which will readily detect actual defects or any variations in quality. Some defects can be observed with the naked eye, whilst others are detected by radiographic examination. This latter method is invaluable as a rapid, reliable test in the production of aircraft bearings, but it is necessary to observe the structure of the alloys under the microscope, both to be able to interpret the radiograph correctly and to determine what has occurred to the metal during and after solidification. The use of a sound metallographic technique is'particularly important in developmental work and research connected with these bearings.Polishing TechniqueCopper and lead are practically immiscible in the solid state, but whilst they are miscible only in certain limited proportions in the liquid state; consequently "alloys" of copper and lead consist of a mixture of the constituent metals. The metallographic difficulties are obvious. Copper is a relatively tough metal, although it readily scratches, whilst lead is extremely soft and easily deformed. It wouId be expected if any normal polishing technique were applied that the lead would be readily torn out of the surface being prepared, and, in addition, that the lead would tarnish very easily.Grange(2) has described a method by which these difficulties can be overcome. The method involves an etch-polish procedure using "chrome regia" as an etchant for the copper. The chrome regia was a solution of chromium trioxide and hydrochloric acid in water. This type of etchant has been adopted, but it was found necessary to make certain changes.The method now adopted in this laboratory is as follows: The specimen (which is usually mounted in bakelite) is wet ground in a series of successively finer Hydro-Durexsil emery papers down to 60.0· grit paper.The specimen is then etched in the chrome regis, etchant (the composition of this etchant will pe discussed later) for approximately five seconds.Most efficient etching is obtained by swabbing the surface of the specimen...

Jan 1, 1944

By R. Cao

Geostatistics was initially developed in the mining sector, but has been extended to other geoscience applications, including forestry, environmental science, soil science, and petroleum science and engineering. This paper presents methods, workflows, and pitfalls in using geostatistics for hydrocarbon resource modelling and evaluation. Examples are presented of indicator variogram analysis of categorical variables, lithofacies modelling by sequential indicator simulation and hierarchical workflow, porosity modelling by kriging and stochastic simulation, collocated cokriging for integrating seismic data, and collocated cosimulation for modelling porosity and permeability relationships. These methods together form a systematic approach that can be effectively used for modelling natural resources.

Jan 1, 2014

By Duane A. Smith

They are gone now. Gone like that long ago generation that gave them birth. The Homestake Mine, nestled in the northern Black Hills, closed in 2001 after 125 years, the longest run of any major American gold mine. The Homestake Mining Co., which guided its destiny for those many years, is gone too. It merged with Barrick Gold. The Hearst family, which guided the early destiny of both, has long since gone beyond its mining heritage and into the national and even international spotlight. The mine and the company passed from the scene with as little fanfare as heralded their birth, amid the Black Hills gold rush of the 1870s. They both grew into American mining legends, as did the town they sired and nurtured, Lead. In a real sense, the mine and the company symbolized one of the last links to a vanished world and a mining era.

Jan 1, 2003

By Kevin Malone

Mercury, or quicksilver as it is often called, has many applications in modern technology. Used principally in electrical apparatus, industrial contol instruments, insecticides and fungicides, electrolytic preparation of chlorine and caustic soda, chemical processes, pharmaceuticals, and dental preparations, the liquid metal has unusual properties that make it a preferred material for many industrial uses. United States consumption of mercury during the past 40 years shows a rising trend. In all except 4 years, U.S. production has been less than the domestic requirement, and imports, principally from Spain, Italy, and Mexico, have supplied most of the deficit. After World War II, domestic output decreased rapidly until 1950, when it was the lowest in the 100 years covered by production records. Higher mercury prices since 1950 have reversed the decline in domestic output and reduced the gap between U.S. production and consumption. Domestic output in 1958 was the highest in peacetime since 1883; however, the nation still imported 28 percent of its mercury requirements from 1950 to 1960 the price of mercury was high as a result of industrial applications of the mercury cell, the impact of the cold war and the Korean war, and the Government stockpiling program. The stockpiling program, in effect, put a floor under mercury prices even though only 9,428 flasks of domestic mercury went into the stockpile under the original program which ran from July 1954 to December 31, 1957. Under an extension of the program, an additional 17,463 flasks was purchased.

Jan 1, 1962

By Frederick M. Fowkes

Dusts can be filtered out of air streams onto polymer surfaces by electrostatic trapping resulting from the spontaneous transfer of electrons upon contact between dust particles and the polymer surfaces. Such spontaneous contact electrification has been studied quantitatively in this contract with the aid of modern semiconductor charge-sensors with the aim of determining what basic principles govern the sign and magnitude of contact electrification. Information obtained by capacitance-voltage measurements of thin polymer films on silicon showed that charges as large as 4 x 1012 electrons per cm2 develop spontaneously, and that such a charge gives adhesional forces of 165 pounds per square inch (11 atmospheres). Direct measurement of dust polymer contact electrification, using silicon surface channel conductance sensors, also showed spontaneous charges of more than 1012 electrons per cm2. Some polymers can either donate or accept electrons. These included chlorinated polyethylene, chlorinated polypropylene, polyethylmethacrylate, and a copolymer of maleic anhydride with n-octadecylvinylether. Other polymers never accepted electrons but could donate electrons; these included polystyrene, pulychlorostyrune, polyvinylchloride, polyvinylacetate, a polycarbonate (Lexan), and cellulose tributyrate. Contact electrification studies were made with dusts (coal dust, a channel black, or a silica powder) contacting thin films of various polymers solvent-cast onto the semiconductor charge-sensor. Sometimes charging was instantaneous and sometimes slower, but in all but one case (coal dust on a copolymer of maleic anhydride with n-octadecylvinyl ether) the charge trunsfer was a donation of electrons by the polymer to the dust. Some

Jan 1, 1973

By E. O. Mixon, Jack D. Kennedy

INTRODUCTION This contract is the most northerly portion of the Metropolitan Sanitary District of Greater Chicago's Tunnel and Reservoir Plan. (TARP) The project begins at Addison Street in Chicago and proceeds northerly approximately ten miles to end at Wilmette Harbor and Lake Michigan. The project which consists of 2 work shafts, 32 drop shafts, 7.322 km (24,020 ft.) of 6.7 m (22 ft.) diameter circular rock tunnel, 8.458 km (27,750 ft.) of 9.2 m (30 ft.) diameter circular rock tunnel and miscellaneous rock bolting and grouting, was bid for a total cost of $63,140,480. The tunnel invert elevation varies from 65.5 m (215 ft.) to 77.4 m (254 ft.) below the ground surface, which places the tunnel in a rock formation of dolomite limestone. At the tunnel invert, the unconfined compressive strength of the limestone varies from 96 MPa (14,000 psi) to 152 MPa (22,000 psi). The 6.7 (22 ft.) diameter tunnel required the mining of 10.9 cu m. (14.2 cu yd.) of rock per lineal foot of tunnel while the 9.2 m (30 ft.) diameter tunnel required the mining of 20.1 cu m (26.3 cu yd.) of rock per lineal foot of tunnel. The total cubic meters of rock required to be excavated from both tunnels was 818,821 cu m (1,070,978 cu yd.). All of this will be mined by tunnel boring machines (TBM). These tunnels were not to be lined with concrete. The thirty two drop shafts have upper portions that are cylindrical in the overburden and rock sections. They were divided into two groups, depending on diameter, with a different construction method for each group. The first group consisted of twenty three of the

Jan 1, 1979

By D Craw, P Upton

"An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation. The Otago Schist belt of southern New Zealand hosts widespread orogenic gold deposits. Erosion of these orogenic gold deposits has led to the formation of numerous placer deposits distributed across and beyond the host schist belt. Numerical modelling of crustal scale deformation and geomorphic evolution has defined the key tectonic features that have controlled the severance of detrital gold deposits from their sources. Tectonic activity over the past 20 million years, during development of the modern Pacific-Australian plate boundary, has severed links between some placers and their sources. Detrital gold was transported south from the Otago Schist source region in two different river systems in the Miocene. Mesozoic orogenic gold deposits shed gold into rivers that flowed to the south. These rivers were terminated by the rise of north-west-trending basement ridges at the boundary between weak schist crust and strong greywacke crust, and the ridges were controlled by pre-existing faults at that rheological boundary. In contrast, rising mountains close to the developing plate boundary in the Miocene were the locus of new orogenic gold deposits hosted in extensional faults. These gold deposits were rapidly exhumed and contributed detrital gold to orogen-parallel Miocene rivers that flowed to the south-west. Pleistocene deformation on mainly north-west and north-east orientations, and associated river capture, has severed the links between these Miocene orogenic deposits and downstream detrital gold.CITATION:Craw, D and Upton, P, 2015. Tectonic severance of links between placer gold and its sources, southern New Zealand , in Proceedings PACRIM 2015 Congress, pp 541–544 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 18, 2015

By Christopher Haycocks, Lawrence P. Johnson, George M. Neall, James M. Townsend

No method of roof control yet devised has proven to be universally acceptable for the wide range of strata conditions experienced in U. S. coal mines. However, a relatively new innovation, the roof truss, has proven itself capable of preventing roof failures which both conventional and resin bolting could not. Presently, the economics of roof trusses are not favorable when compared to bolting due primarily to drilling and installation procedures, but this is expected to change with improved truss and equipment designs. To realize the full potential of this new method of roof control, design criteria are needed which can optimize the effect of the truss for varying strata conditions. A review of the literature reveals that some work has been conducted on the roof truss. Cambrell and Haynes1 (1970) showed that the roof truss is superior to angled roofbolts installed through a header. Sheorey, Verma, and Singh2 (1973) used statics to prove that the optimum angle of inclination should be greater than 45°. However, to date, no systematic attempt has been made to establish design criteria. In this paper, the problem was approached in three ways. First, model studies were performed to determine general trends of truss support as a function of a number of variables. This provided a better understanding of the support mechanism involved. Secondly, beam theory was employed to calculate the actual support capacity of a truss, realizing the many simplifications, assumptions, and shortcomings of this approach to such a complicated problem. Last, field testing will be utilized to test the hypotheses previously developed and provide hard data to further synthesize roof truss design criteria. Field testing has recently commenced and should be complete before mid 1977.

Jan 1, 1979

By Paul H. Atkinson

"Sampling in the mineral processing industry has always been a subject which has received considerable discussion. There have been many volumes written on theory, techniques and practical application of sampling. However, until recently, the companies were not completely aware of the potential savings available with properly designed sampling systems both to assist in pieces: control and final product values.Definition In our discussion today, we will define sampling as the operation of removing a part, convenient in quantity for analysis, from a whole, which is of much greater hulk, and removing it in such a way that the proportion and distribution of the quality to be tested, i.e. size of particle, moisture content, specific gravity content, mineral and chemical composition, are the same in both the sample and the whole.Application It has been well established that undetected errors can result in large economic losses, thus most firms depend upon some type of sampling and sample analysis as a control in their continuous processing of materials. Despite the large investment in facilities and personnel the ""analysis"" of a sample can be no more accurate or reliable than the sample on which it is being based. The importance of sampling is recognized by a great many but it is appreciated by only a few, largely because it is sometimes one of the items which is taken for granted."

Jan 1, 1976