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By W. W. Krech, T. E. Perkins

As fractures are propagated through rocks, energy is absorbed near the extending crack tip. Apparent surface energies for several rocks have been measured by cleavage under dynamic con-ditions. At nominal crack velocities from 0.5 to 500 in (min, measurements showed that fractures propagated in discrete jumps. Calculated surface energies and moduli were relatively insensitive to nominal rate of cleavage. in another set of experiments, rocks were cleaved under high confining stresses. The rocks were submerged in low leak-off fluids which formed a filter cake on the freshly cleaved surfaces (similar to the hydraulic lracturing process). Apparent surface energies were increased substantially as the surrounding fluid pressure was increased. Moduli in bending increased significantly upon application of the first 1,000 psi but were insensitive to stress level at greater pressures. INTRODUCTION For almost 20 years, hydraulic fracturing processes have been utilized effectively to stimulate oil and gas wells. During this period, some process improvements have resulted from studies of fracture orientation, mechanics of fracturing, areas generated, conductivities of cracks, etc. Yet many questions remain concerning the conditions and pressures needed during fracture propagation. In this paper we will report additional studies of the mechanics of fracture extension. It was shown previously3 that large rock samples could be cleaved under controlled conditions so as to measure the apparent surface energy (that amount of energy absorbed per unit area of new surface created). In this paper we consider the effects of two additional factors on surface energies, viz.: (1) effect of cleavage rate and (2) effect of confining stress level. THEORY Cleavage experiments were conducted on rock samples similar to that illustrated in Fig. 1. Blocks of rock several inches wide, 2- to 3-in. thick, and up to 3 ft in length were grooved longitudinally with shallow guide slots. A crack was initiated and allowed to extend along the web as the top of the rock specimen was pulled (or pushed) apart. Auxiliary equipment permits the measurement of (1) force applied at the top, (2) separation at the top and (3) crack length. (Further experimental details will be given in the next section.) The rock beams created by the crack are considered ton be cantilever beams. The deflection (or separation of the rock beams) at any point is calculated 4,5 by the beam Eq. 1.

Jan 1, 1967

By Qingwei Wang

Heavy metal-containing wastewater from hydrometallurgical processes of lead-zinc was treated by biologics in a 200 m3/h industrial scale experiment. The result shows that Zn concentration declined from 50.28 mg/L~240.81 mg/L to 0.21 mg/L~1.98 mg/L, Pb from 1.00 mg/L~13.47 mg/L to 0.083 mg/L~0.71 mg/L, Cu from 0.24 mg/L~2.38 mg/L to 0.059 mg/L~0.40 mg/L, Cd from 2.12 mg/L~23.47 mg/L to 0.011 mg/L~0.071 mg/L and As from 0.50 mg/L~6.00 mg/L to 0.005 mg/L~0.10 mg/L. The concentrations of the above heavy metals in the treated water were lower than that in Integrated Wastewater Discharge Standard (GB8978~1996) in China. Furthermore, the treated wastewater was recycled and reused in smelter plant. Zinc content in hydrolytic sludge reached up to 34.04%, which indicates that this sludge can be used to recover valuable metals.

Jan 1, 2010

By Gordon M. Matheson, Douglas A. Anderson, David K. Miller

"Traditionally, analysis of vibrations from blasting has been focused on peak particle velocity fordetermining the likelihood of both annoyance and damage. The US Bureau of Mines, in RI 8507,indicated the importance of frequency in vibration. Methods of controlling the vibration by reducingthe vibration concentrated in certain frequency bands using delays have been successful over the past decade."

Jan 1, 1997

By D. Hopkins, D. Türler, R. D. Giauque, W. B. Davis, M. Karaca

In a highly collaborative research and development project with mining and university partners, sensors and data-analysis tools are being developed for rock-mass characterization and real-time measurement of mineral content. Determining mineralogy prior to mucking in an open-pit mine is important for routing the material to the appropriate processing stream. A possible alternative to lab assay of dust and cuttings obtained from drill holes is continuous on-line sampling and real-time x-ray fluorescence (XRF) spectroscopy. Results presented demonstrate that statistical analyses combined with XRF data can be employed to identify minerals and, possibly, different rock types. The objective is to create a detailed three-dimensional mineralogical map in real time that would improve downstream process efficiency.

Jan 1, 2002

By M Carter

The Great South Basin is located beneath the northwest part of the Campbell Plateau, a+broad, nearly level, triangular shaped submarine platform, southeast of the South Island of New Zealand. It encompasses an area of 77 700 square kilometres and contains a sequence of Cretaceous to Tertiary sedimentary rocks which are up to 6000 metres thick near the centre of the basin (Shirley, 1983). The western boundary of the basin is adjacent to the steep Aucklands Slope. In the+ north it merges with the Canterbury Basin and to the south onlaps against the Pukaki Rise, a basement high. The eastern margin of the basin is bounded by the northeast - southwest trending steep linear Antipodes Scarp. In the extreme south the Antipodes Scarp curves westward and joins the north trending Aucklands Slope. The Campbell Plateau is dominated by tensional tectonics. The Antipodes Scarp represents a major region of transcurrent faulting initiated by Cretaceous rotation within the Campbell Plateau. Later movements are associated with the Alpine Fault of the South Island (Sandford, 1980; Anderton, Holloway, Engstrom, Ahmad and Chong, 1982).

Jan 1, 1983

By R. E. Wilmot

The problem of corrosion of reinforcement in concrete structures is internationally recognized and represents the single biggest expenditure in the preservation of steel reinforced concrete structures. While the corrosion protection of the reinforcing steel is no substitute for design and the placement of good quality concrete, it does provide for a viable and economical extension of structural integrity and service life in the day-to-day and practical environment in which concrete structures are constructed. The mechanism of corrosion attack and consequent deterioration of reinforced concrete structures is well understood and documented. New structures can be designed and built to withstand corrosion. However, due to short-term economic restraints, many new reinforced concrete structures continue to suffer as a result of corrosion damage, which results from the corrosion of the steel reinforcing. This paper explores the economic and practical benefits offered by the application of hot dip galvanizing as a viable means of protecting reinforcing steel concrete structures. The paper also discusses technical misconceptions that exist about application and performance provided by the use of hot dip galvanized reinforcing steel.

Jan 1, 2007

By J. W. Joubert, R. C. W. Webber-Youngman, M. D. Budeba

"SynopsisCost estimation for surface coal mines is a critical practice that affects both profitability and competitiveness. New mines require these costs to be estimated using available information before a project begins. The competitive advantage of a new mine depends on it being both efficient and cost-effective. Low-cost producing mines have a higher chance of survival in a low-price environment than do high-cost producers. The competitiveness and profitability of a coal mine is based on the costs of production and the supply position on the cost curve. There is no single method of cost estimation, and the available methods consider only one or a few variables, leaving out multiple variables that could significantly affect the estimation of mine costs. Mining companies are thus searching extensively for a method that will increase accuracy in the estimation and evaluation of mining projectsThis paper highlights the shortcomings of the available approaches and proposes a data envelopment analysis method to develop a frontier for effective surface coal mines, and the use of a parametric method for modelling the costs and productivity of new mines to ensure effective competitiveness. The models will extend the capability of estimation and the accuracy of estimates using the efficient decision-making units, by considering the optimal mine-specific and external variables affecting costs.IntroductionCoal contributes 25% of the world’s primary energy needs, after fuel oil, which contributes 35%. The world energy demand, estimated over the period 1990 to 2030, is expanding at a cumulative annual growth rate (CAGR) of 1.7% (Schernikau, 2010, p. 14). This emphasizes the need for enhancing the production of existing mines, as well as opening new mines in order to increase the supply of coal."

Jan 1, 2015

By Thomas Novak, Sampurna Arya

Controlling dust generation and keeping it below permissible limits to meet federal dust standards at the working face of a roomand-pillar coal mine is a challenge for a mine operator. With the recent changes in federal dust regulations requiring lower worker exposure, maintaining compliance has become increasingly difficult. The current most effective practice of dust control at a continuous miner face in an underground mine is the use of a flooded-bed scrubber. A study carried out by the National Institute for Occupational Safety and Health (NIOSH) indicated that a flooded-bed scrubber could achieve cleaning efficiencies between 58 and 90%. But, the operation of such a system is maintenance intensive. The flooded-bed scrubber screen becomes clogged with dust particles and requires frequent cleaning to maintain performance. However, the dust control issue is not solely a mining industry problem. Other industries face similar issues. The University of Kentucky collaborated with Toyota Motor Manufacturing on the development of a novel wet scrubber, called the vortecone scrubber, for capturing oversprayed paint particles in automotive paint booths. The vortecone scrubber achieved a cleaning efficiency of 99% and required minimal maintenance. This study aims to assess the ability of this vortecone scrubber to capture respirable dust in an underground coal mine. The paper presents the results of computational fluid dynamics (CFD) modeling of this vortecone scrubber. It discusses the effects of air quantity and dust particle size on the performance of the scrubber.

By J. L. Potter

An inert-gas fusion technique was applied by the Bureau of Mines to the oxygen analysis of mixed-fluoride electrolytes used in electrowinning uranium and the rare-earth metals. Method development included: (1) Thermodynamic and experimental evaluation of the temperature required to quantitatively remove oxygen from a fluoride melt; (2) installation of a water and an acid trap to entrain the volatilized fluorides; (3) development of a suitable sample-preparation technique for the heterogeneous fluoride baths in which both pulverizing and pelletizing were necessary to achieve reproducible results; (4) comparison of platinum flux and dry crucible techniques, which showed that the use of platinum was not necessary. The accuracy of the method was evaluated by analyzing fluoride baths containing known amounts of oxygen added as the metal oxide. In the 0.05-to 0.5-percent range, the relative error was about ±5 percent.

Jan 1, 1962

By Don Dodds

Iron Mountain Mine Rehabilitation Project Brief History The Iron Mountain Mine is located in Northern California approximately 12 miles northwest of Redding. The ore body is a large, very dense pyritic intrusion, discovered in 1860, and initially minded for silver. The silver played out quickly and 34 years later the ore body was mined for copper. Copper mining was scheduled to cease in 1939, but WWII prolonged the closure. After WWII, the pyrite ore was mined to produce sulfuric acid. In 1949 when large amounts of cheaper sulfuric acid were being generated by the oil industry the underground mine shut down. Little was done with the site conditions until 1970 when the U.S. Bureau of Mines began monitoring the pH of the effluent. The initial pH readings were around 2.0. This was lower than anyone expected. Laboratory tests showed that when the ore from the mine was submerged in water, the pH of the water would stabilize above 4.0. However, the pH got steadily lower. In 1989 with the ph around 0.7, the U.S. Environmental Protection Agency (EPA) required the owner to build a capture and treatment facility. During this initial period, the majority of the effort was spent on the treatment plant. The relationship between the mine owner and the EPA was basically an adversarial relationship from the very beginning. In 2001, North Pacific Research was hired to upgrade the capture and control facility. The general layout of the Iron Mountain Mine is shown in Figure 1.

Resources and reserves are critical inputs into the determination of an operating mineÆs financial results and balance sheets, but how well understood is this fact. Do the investors, directors, accountants and geologists/engineers responsible for preparing or relying on relevant aspects of the end results properly understand the inputs and outputs and the associated risks that may be established. The first step is to understand how financial reports are impacted. The most obvious, and best known, impact is in the calculation of depreciation and amortisation charges against long term assets. In addition, however, there is a requirement to regularly determine whether asset book values are impaired û this is nearly always performed globally by the preparation of a discounted cashflow model for a mine which is usually based on a mine life as determined from the resource and reserve statement û the particular driver here is normally the short and long term production plans. A key aspect of the short term production plan is that it would normally not assume that the reserve and resource statement implies consistent grade, stripping ratios, etc. However, outside of the early years of a plan, more generic assumptions of these variables are often made in conjunction with the reserve and resource statement. Depending on the timeframe of the detailed production plans, this can have a large impact on a projectÆs net present value. Other financial balances that may also be impacted include restoration and rehabilitation provisions, retrenchment provisions and deferred or equalisation stripping accounts. The age old question of whether all reserves should be used or whether some or all of the resources should be included for financial reporting purposes has never been adequately resolved. It is our view that there should be no prescriptive answer to this question but judgement of all professionals involved in the process needs to be included. Furthermore, the company needs to be able to support their conclusions with well thought out and appropriate answers. This may not be in line with the approach that certain accounting standard setters may be proposing or taking, and this paper will outline the current status of global requirement and the likely future directions. Whether reserves or resources are utilised, does not change the key requirement that those preparing or using reserve and resource statements need to understand key aspects. For example: geologists/engineers do they know how reserves or resources will be used? have they imparted information on variability of key drivers such as grade or depth or dilution? do they know that major financial/business altering decisions may be made based on the analysis? accountants do they understand where the numbers have been derived from and the assumptions that may have been made in their determination? do they understand the degree of accuracy (or inaccuracy) that may exist particularly with resources)? do they understand the history of resource reconciliations and what it may mean for the future? directors do they understand the processes undertaken by the company to prepare the financial report and the interaction between the geologists/engineers and accountants? do they understand the potential sensitivity of results to the input variables? Financial reporting is extremely reliant on the use of the reserves and resources, however, the geologists/engineers, accountants and directors do not always understand the interactions between themselves which may lead to misleading public reporting. More education and communication between various parties is needed.

Jan 1, 2002

South Africa has joined the league of other major Western World countries by officially adopting its own code for public reporting of Mineral Resources and Mineral Reserves. The recently published South African Code for Reporting of Mineral Resources and Mineral Reserves (SAMREC Code or Code) (SAIMM 2000) is presented here in its local and global context. The main aspects of the Code are listed and elaborated upon. The Code has been written with the participation of the major South African stakeholders in the field including Government institutions, the legal confraternity and the mining industry. Relevant foreign organisations, such as the Australasian Joint Ore Reserves Committee (JORC) and the United Nations contributed to its compilation, and supported it. The Code thus enjoys endorsement both locally and, to a large extent, overseas. The Code is modelled on, and is 90 per cent compliant with, the Australasian Code for Reporting of Mineral Resources and Ore Reserves (JORC Code) (AusIMM, 1999). The paper also elaborates on the duties and responsibilities of Competent Persons signing off resource and reserve reports and on the new listing requirements of the Johannesburg Securities Exchange (JSE), formerly the Johannesburg Stock Exchange, which has officially adopted the Code.

Jan 1, 2002

By Michael A. Trevits

Since the promulgation of the MINER Act and the follow-up changes to the regulations governing mine seal construction and maintenance, mine operators must be acutely aware of the atmosphere in sealed mine areas and prepared to deploy control technologies when the conditions are warranted. On Site Gas Systems1 in Newington, Connecticut was awarded a contract by the National Institute for Occupational Safety and Health (NIOSH) to construct a novel in-mine nitrogen (N2) generation plant using pressure swing adsorption (PSA) technology. PSA technology utilizes carbon molecular sieve material and pressure to adsorb oxygen (O2) molecules while allowing N2 molecules to pass through the sieve material. The prototype PSA unit was tested at the NIOSH Safety Research Coal Mine (SRCM) where a 62,000 ft3 area of the mine was rendered inert during a series of two tests. The resultant data were then used to construct a CFD simulation of both injection tests. In addition, O2 depletion and gas leakage rates were quantified in the model and were compared to actual values. Once the model was calibrated, the sealed mine area was doubled and simulations were made with various injection rates and injection site locations to determine the impact on the time needed to render this area inert. This paper presents an overview of the PSA plant, the details of the gas injection tests and CFD modeling work.

Jan 1, 2010

By Junhwan Lee

Pipe piles can be either closed- or open-ended piles. Pile load capacity for a closed-ended pile consists of the shaft and base resistances, while, for an open-ended pile, it consists of shaft, soil plug, and annulus resistances. In order to investigate the pile load capacity of both closed- and open-ended piles, two field pile load tests were performed. For the open-ended pile, the fully instrumented double-walled system was used to separately measure all the components of the pile load capacity. The soils at the test site were predominantly granular soils with relative densities varying from loose to dense with increasing depth. The incremental filling ratio (IFR), which affects significantly the load capacity of open-ended piles, was also measured during pile driving. The test results indicated that the total load capacity of the closed-ended pile was higher that that of the open-ended pile, mostly due to the difference in shaft capacity. The shaft and base load capacities of the open-ended pile were 44% and 20% lower than the corresponding values for the closed-ended pile.

Jan 1, 2003

The nature of the specialty glass and ceramic business magnifies the dependency of the ultimate product on the unique properties of their raw materials used to make them. This dependency has implications in the management of risk in the supply process which requires a special procurement organization and program commitment to be successful. The Coming system of managing critical materials and factors in development of alternate new suppliers and products is discussed.

Jan 1, 1989

By Neal Lee, Braden T. Lusk, Brendan McCray

Determining the minimum amount of inert material that can be used between explosive columns is a complex problem. Using too little inert material can result in detonator/primer failure, either by sympathetic detonation of or failure to fire of the subsequent explosive column(s). Propagation type failure results when inert material length between charges is small enough that the subsequent (delayed) deck fires more or less instantly. In this situation, the primer, detonator, or bulk product is initiated by the shock wave from the earlier firing deck. This type of failure may be un-noticed until the vibration/airblast report is examined.

Jan 1, 2016

By Chand F

The silver deposits of Rockvale near Armidale, N.S.W., occur in fissure veins in epi-Permian granite. The ore is fine grained, mineralogically complex, and contains twenty-seven different minerals including eleven silver minerals. The ore is characterized by a unique multiple unmixing from a sphalerite solvent. The following minerals have exsolved from solid solution in sphalerite: pyrrhotite, chalcopyrite, cubanite I, cubanite II (chalcopyrrhotite), valleriite, "brown" stannite, "olive" stannite, argentian tetrahedrite, pyrargyrite, and an unknown grey-white mineral. Several of these minerals derive from a second-stage unmixing, the immediate solvents of which are the products of earlier exsolutions.INTRODUCTIONSmall silver-rich base metal deposits occur at several localities near Armidale in the New England district of New South Wales. Chief among these are the Tulloch Mine and the Rockvale Mine at Rockvale, 27 miles SE. of Armidale, and the Tait's Gulley deposits some 15 miles NE. of Armidale.At Rockvale (Kenny, 1928), irregular lenses of lode material, principally quartz and calcite, occur along a zone of shearing in biotite granite and altered sediments. The orebodies had a maximum width of 6 ft but averaged 2 ft 6 in. The largest lens was 150 ft long and 50 ft high. The Rockvale deposits were worked for both arsenic and silver; 2,897 tons of arsenic were produced but no figures are available forsilver.Little is known of the Tait's Gulley deposits which occur in folded arenites containing small but rich veins of pyrargyrite with base metal sulphides.The sediments in these localities are possibly Silurian.

Jan 1, 1962

Differentiation of a basaltic (?) magma occurred in an active volcanic area during the late Miocene and Pliocene, and a change in the general mode of extrusion from fissure flow for the basalt to explosion for the andesite reflects an accompanying increasing magmatic viscosity. A caldera formed after the flow phase was completed and was filled with coarse agglomerate, much of which has a fused appearance. After an erosion interval its shape was modified and it became gradually deeper as repeated explosions from growing andesitic volcanoes caused large quantities of pyroclastic material to be deposited. At the close of this phase the floor abruptly collapsed when a, large block of the underlying crust was engulfed. The incompetent pyroclastics filling the caldera steepened in dip and the ensuing fractures were filled by the rising magma as dykes and sills and a chonolith formed below the caldera at a shallow depth. The ensuing activity reveals a further stage in differentiation and biotite is an important new ferromagnesian to be observed in the new rocks.Fracturing of the surrounding basalts was most intense in the rocks forming the periphery of the caldera where steeply and flatly dipping faults resulted from increasing horizontal pressure directed towards the caldera.Further differentiation resulted in the increased crystallization of orthoclase felspar, as evidenced by the numerous intrusives of trachy andesitic composition. Magmatic freezing caused mineralizers to accumulate at the top of the chonolith. These eventually escaped and auriferous pyrites, tellurides, quartz, and calcite were deposited in the surrounding rocks.The flatly dipping fractures are the most important and can be expected at various depths in a zone about 4,000 ft wide surrounding the caldera. Latest movement along these was controlled by magmatic consolidation rather than the shape of the caldera. Some flat faults were able to remain open during mineralization and acted as a feeder for the shallower fractures, thus limiting the depths to which the steeper dipping fractures were mineralized with the possible exception of one particular Nw.-striking lode (the Crown-Crescent).INTRODUCTIONThe gold deposits of the Tavua district were discovered in 1932 and from 1935 to June, 1961, 1,985,041 fine ounces of gold were produced from 4,202,504 tons of ore. Of the original three producers, only the Emperor remains active in the...

Jan 1, 1962

By Charles C. Boley

Using bench-and pilot-scale coking facilities, the Bureau of Mines produced experimental coke from blends of char with Sunnyside coal (high-volatile A bituminous) from Carbon County, Utah. At bench scale, additions of char made from lignite improved resultant cokes when concentrations of up to 60 pct were used in the blends. At pilot scale (500-pound movable-wall oven), four chars made by entrained-bed carbonization techniques from the parent Sunnyside coal and from a North Dakota lignite were used in two-component blends with the Sunnsyide coal. Chars from Sunnyside coal had volatile matter contents of 5.8, 9.8, and 16.0 pct, moisture-free basis; the char from the lignite had 16.6 pct. In twenty-five 500-pound tests, improvement in coke quality was observed from all blends at char concentrations to 17.5 pct. The best coke, produced from a concentration of 12.5 to 15 pct of S.8-pct volatile char, exhibited physical properties approaching those of an industrial coke produced from Sunnyside coal blended with three higher rank blending coals. Studies were also made of the effects on coke quality of char source, of particle size, of comparative use of char and of a blending coal, and of prolonged coal storage.

Jan 1, 1973

By Foster Fraas

The most important lithium resource in the United States is in the form of the feldspathoid mineral spodumene. This mineral has not been used to any important extent as a source of lithium salts or lithium metal, as other more easily decomposed minerals have b en available in sufficient quantity to supply the relatively small demand. The need for cheaper lithium salts for such promising new uses as air conditioning or dehumidification and of lithium feldspar for use in the glass and [ramic] trades has justified the recent work done by the Bureau of Mines on King available, through improved beneficiation and extractive processes, some of the lower grade but extensive spodumene deposits.

Jan 1, 1937