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Laboratory and pilot plant investigations aimed at recovering gold as an electroformed sheet from gold eluate and gold leach solutions and slurries are discussed. The electrolytic test work undertaken makes use of high surface area electrodes, in particular nickel-chrome foam metal and activated carbon, as well as ultrasonic activation. The process involves initial gold electrowinning (or adsorption onto activated carbon), followed by gold electroforming, both operations being carried out in a specially designed reactor. The pilot plant work mainly involved the treatment of gold eluate solutions from a South African gold mine containing 600 mg/L Au: some tests were also carried out on gold leach solutions containing 6 mg/L Au. In the former case, very efficient gold extraction onto the foam metal cathode was achieved using electrolysis combined with ultrasonics. The polarity of the gold-loaded cathode was then reversed and, using a replacement electroforming electrolyte, gold was electroformed in situ onto a polished stainless steel mandrel, from which gold sheet was subsequently removed. In the case of leach solutions, pilot plant tests confirmed laboratory findings that in the presence of calcium (resulting from the lime used during the leaching process) no electrowinning is possible. Laboratory tests showed, however, that when sodium (in the form of NaOH or Na2CO3) is added to the leach solution, electrowinning can indeed take place. Alternatively, if a special activated carbon electrode is used (without current), the non-ionic calcium aurocyanide complex is adsorbed on to the activated carbon. When a gold-loaded activated carbon electrode is made anodic in a gold electroforming electrolyte, gold electroforming is feasible, although the efficiency is very low. The possible implications of these developments for gold recovery are further examined.

Jan 1, 2007

By S. L. Crouch

The general term "coal mine burp" refers to the sudden and violent failure of in situ coal. Coal bumps occur in most countries where coal is worked by underground methods, and are related to both geological factors and mining tech¬niques. Although no single set of circumstances is solely responsible for causing coal bumps, it is generally agreed that at least one of five conditions is necessary in order for then to occur: 1,2,3,4 (1) the depth of cover exceeds 500-ft., (2) the overlying strata are relatively strong and stiff, (3) the coal is structurally strong, (4) the floor does not heave readily, and (5) the mining method produces high stresses over a large area of the seam. Except for the last, these conditions relate to geological factors that are impractical to control. Consequently, methods of controlling or minimizing the occurrence of coal bumps usually are concerned with mining techniques. Coal bumps have been successfully controlled by both longwall and 'yielding pillar' mining systems 4. The longwall system is particularly effective in controlling bumps, but does not eliminate them completely, especially in strong coal seams being worked at comparatively great depths, say in excess of 2000-ft.5. Under such conditions, auger drilling or water infusion often prove helpful 5,6. These techniques are used to destress or otherwise alter the mechanical properties of the coal in an attempt to shift the peak "abutment pressure" away from the immediate vicinity of the face. Under 'normal' conditions, however, it can be expected that the coal near the face will be crushed under the prevailing high stress conditions and that the peak abutment pressure will automatically be shifted into the solid coal. In this context, coal mine bumps can be characterized as unstable releases of energy associated with successive yielding of portions of the coal seam with progressive mining. Longwall and yielding pillar mining systems are effective in controlling coal bumps because they ordinarily do not allow the zone of peak abutment pressure to become 'surrounded' by destressed coal.

Jan 1, 1973

By Stephen R. Grano, Jon Glatthaar, Philippe Steinier, Christopher J. Greet

"The importance of the oxygen content of sulphide mineral pulps in determining which reactions occur, and their subsequent influence on flotation behaviour is grossly underestimated in most operating concentrators. While pH is routinely monitored, Eh and dissolved oxygen measurements are obtained infrequently. However, dissolved oxygen measurements in conjunction with other pulp chemical parameters (i.e. pH, Eh, and EDTA extractable metal ion analysis), can provide valuable insight into where and what type of reactions are occurring within a circuit. Unfortunately, these readings yield “instantaneous” measurements of the pulp chemical parameters.What is needed is a means of establishing how reactive a pulp is, and how this reactivity changes as components of the system are manipulated. Oxygen demand provides an opportunity to do this. Several attempts at measuring the oxygen demand of a pulp have been made in the past with varying degrees of success. Most notable among these are Noranda and BOC Gases.Learning from these experiences, Magotteaux have developed the MagO2 ® demand vessel to measure the oxygen demand of mineral pulps. This paper described the apparatus, and through a case study on Broken Hill lead/zinc ore demonstrates how the MagO2 ® demand vessel is used.INTRODUCTIONThe role of oxygen in flotation is complex. While a considerable body of work exists demonstrating the strong involvement of oxygen in the interactions between sulphide minerals and collector (Gaudin and Finkelstein, 1965; Gaudin, 1974; Woods, 1984; Laajalehto, Nowak and Suoninen, 1993), the presence of oxygen can also affect the oxidation state of sulphide and non-sulphide minerals, which can impact on their flotation behaviour. Further, sulphide mineral oxidation is related to their oxygen demand (Spira and Rosenblum, 1994)."

Jan 1, 2004

By W. J. Wuest, M. J. DeMarco, J. R. Koehler

Yield-pillar-based gate-road designs often fail to provide mine operators with adequate ground control. This is because of the unknowing m is employment of "critically" sized pillars. A "critical” pillar is one that is too large to either yield nonviolently or to yield before the roof and floor sustain permanent damage and is too small to support full abutment loads. To demonstrate the critical pillar concept, afield study of a tapering gate road was conducted by the US Bureau of Mines at the Sunnyside Coal Mines, Sunnyside, UT. Extreme pillar stresses and associated coal bumps characterize the response to first panel mining of a 16.8-m (55.1-ft) wide critical design. Significantly lower pillar stresses, early yielding of the pillar and adjacent panel rib, and an absence of coal bumps suggest that a narrower 12.2-m (40-ft) wide design more closely approaches proper yield pillar dimensions. A probe hole in several 10.6-m (34.8-ft) wide pillars revealed low stress levels and substantial pillar and panel rib yielding prior to abutment onset, indicating a properly functioning yield pillar design.

Jan 1, 1997

By Tooth MA

Mining, metallurgical and engineering consultants have made a considerable contribution to mining industry development in Australia. Expertise has been developed locally to a high level during the last decade which has contributed to the success of many recent mining projects. The services available'cover the whole spectrum from the evaluation of ore reserves, through feasibility study and financial evaluation to design, project management and commissioning. Using these services effectively and economically is an objective which client and consultant both must pursue but which is not always achieved. This paper discusses some aspects of the use of consultants which the experience of the authors has shown to be of prime Importance

Jan 1, 1975

By Luo Yang

A one-dimensional wave equation based algorithm for estimation of shaft and toe resistance of driven piles using High Strain Testing (HST) data is presented. The pile is represented by a uniform elastic bar, while the soil around the pile is assumed as a homogenized isotropic medium, and Smith model is adopted to represent soil-pile interaction in the wave equation analysis. In most cases, the displacement of pile particles along pile shaft is greater than recoverable soil deformation (i.e., soil quake in Smith model). Therefore, static shaft resistance could be reasonably assumed to be totally mobilized during pile driving. Smith damping factor is used to account for combined dynamic and rate effect. Force and velocity time histories measured at the pile head are used as input boundary conditions in an analytical solution of the one-dimensional wave equation. As a result, two unknown parameters, static shaft resistance and Smith damping factor, can be incorporated into the one-dimensional wave equation and determined analytically for the time duration prior to the first downward wave reaching the pile toe. Then, soil resistance and Smith damping factor at pile toe can be further determined. The advantage of the proposed analysis technique is that the Smith damping factor and the static soil resistance can be directly determined based on the closed-form solution of the one-dimensional wave equation, which is computationally efficient. Numerical examples are given to illustrate the use of the proposed method to determine the pertinent Smith model constants and the static resistances.

Jan 1, 2006

By A. H. Morris, W. Harrison

1. INTRODUCTION Roadheaders have a shadowy origin - probably in Eastern Europe - but were introduced to Europe and the West by the importation of a Russian PK3 machine by the National Coal Board in 1961. A number of features rendered this type of machine an attractive tool for coal mine operators: its flexibility of operation, its combined cutting and loading ability, the opportunity it provided of making any shape of roadway, as well as its ability to cut some rocks. Encouraged and sponsored by the National Coal Board, the development of roadheaders was taken up in Great Britain, notably by Anderson Strathclyde and Dosco; in Europe, predominantly in numerical terms by Voest Alpine and Paurat. Over the 24 years since the importation of the first PK3, evolutionary development has taken place to the extent that machines are now available in many forms up to 120 tons in weight. Machine design has altered, partly as a result of increased power requirements and partly in line with the use of a ripping or a co-axial head. However, the basic concept remains: a boom containing a motor and transmission gear, with a driven cutting head at its extremity and capable of universal movement urged by hydraulic rams mounted on the boom turret and on the machine deck. Generally, the turret, hydraulic powerpack and all other necessary equipment are mounted on a chassis, which contains a discharge conveyor, the whole being carried on caterpillar tracks so that a complete machine entity is provided. Figure 1 shows how the weight, power and - non-proportionally - the cutting ability of machines have increased over the years. From

Jan 1, 1985

By Joel Moskowitz

A new office complex is being constructed within 25m of the Hudson River in New Jersey. The project, about 140 m by 100 m, will include 4 basements under the entire footprint. The perimeter was to be secured by a 0.8 m thick diaphragm wall, laterally supported by high capacity tieback anchors to rock. Columns were to be supported on footings or piers to rock at a nominal bearing pressure of 3.8 MPa at depths up to 17m. Although some variation in rock quality was observed in borings, a substantial vertical seam of weathered and/or decomposed rock, 1 to 2 meters wide by as much as 8 meters deep, was encountered during construction necessitating field redesign. In some locations the seam dipped below more competent rock. Footings were redesigned for support on drilled caissons, or soft rock was excavated and replaced with concrete necessitating a reduction in bearing pressure of the footings by one half.

Jan 1, 2002

By Fumihiko Sumiya, Yuji Ogata, Masahiro Seto, Yukio Kato, Yuji Wada, Kunihisa Utsuyama, Yoshikazu Hirosaki

It is well known that emulsion explosives can be dead-pressed especially in underground blasting. Voids in emulsion explosives will affect such malfunction of explosives. To clarify the factors that affect the dead-pressing phenomena, the characteristics of the pressure wave propagation in emulsion explosives were investigated. Three types of microballoons .or microbubbles, glass microballoons(GMB), resin microballoons(RMB) and chemical gas bubbles, were used as sensitizers for emulsion explosives. The pressure profiles inside the explosives were measured to determine the effects of the microballoons or microbubbles contained. The underwater explosion test and the large-scale drop hammer test were carried out to load the explosives with a dynamic pressure and a quasi-dynamic pressure respectively. In the underwater explosion test, the pressure profiles in the emulsion explosives were measured by a piezo-electric pressure gauge inserted to the center of the explosive cartridge which had a diameter of 30mm. In the large-scale drop hammer test, the same type of pressure gauge was placed at the bottom of the explosives. From these experiments, the following results were obtained ; A) The pressure profiles in the sample explosives sensitized by RMB or chemical gases were sharp, while in the sample explosives sensitized by GMB the profile was broad. B) The peak pressure levels in the sample explosives sensitized by RMB or chemical gases were twice as high as that in the sample explosives sensitized by GMB in the underwater explosion test. However in the large-scale drop hammer test, the amplification of the peak pressure is low compared with in the underwater explosion test. C) The impulse value was independent of the types of the microballoons or microbubbles in both tests. It was concluded that the type of the microballoons or microbubbles significantly influenced the characteristics of the pressure wave propagation in emulsion explosives.

Jan 1, 2001

By M H. Randell, J B. Haines

The Honeymoon Uranium Project comprises the Honeymoon Deposit,Goulds Dam Deposit and Yarramba Prospect in the Southern Lake Fromeregion, South Australia. Both the Yarramba Prospect and HoneymoonDeposit (which includes Honeymoon and East Kalkaroo orebodies) arelocated in the Yarramba Palaeovalley. The Goulds Dam Deposit is about75 km north west of Honeymoon, in the Billeroo Palaeovalley. Exploration for sediment-hosted uranium began in the area in the late1960s, culminating in the discovery of Honeymoon and Goulds Dam inthe early 1970s. In 1982, a 25 L/s demonstration plant was built atHoneymoon to confirm suitability for in situ leaching. The project was put on hold in 1983 due to changes in government policy. Southern Cross Resources Australia Pty Ltd acquired the project in mid 1997. Roll-front deposits form from a migrating geochemical cell, anadvancing reduction-oxidation interface between oxygenateduranium-bearing groundwater and its reduced aquifer host. The source of metal is uranium-anomalous granites, which were eroded fromsurrounding ranges. The weathered granites and resultant sediments are stripped of uranium by oxidised groundwaters, to form solutions carrying uranyl carbonate complexes. The solutions percolate down-slope through permeable sand zones until contacting a reduced environment where uranium precipitates. Uranium mineralisation occurs interstitially between and as thin coatings on sand grains, usually in the form of uraninite or coffinite. The palaeovalleys (previously termed palaeochannels) are incised intounderlying Cambrian/Precambrian basement rocks and filled withsemi-consolidated, largely un-cemented, Tertiary sediments of the Eyre Formation. The late Palaeocene to middle Eocene Eyre Formation is the basal unit of the Tertiary succession in the Callabonna Sub-basin of the Lake Eyre Basin. Further to the north, the Lake Eyre Basin overlies the Jurassic-Cretaceous Eromanga Basin, which comprises much of the Great Australian Basin. Eyre Formation sediments are in turn overlain by the late Tertiary Namba Formation and terrestrial Quaternary units. At Honeymoon, the Eyre Formation includes immature, pyritic,carbonaceous sands and gravels interbedded with lignite andkaolinite-illite-montmorillonite clays. It was deposited by braidedstreams during epeirogenic uplift of the Olary Ranges, accompanied bysubsidence of the Lake Eyre Basin. The Eyre Formation comprises aconsistent stratigraphy of interbedded sand and clay units that arecontinuous over the Honeymoon Deposit but with local variationindicating some hydrological connection between aquifers.In the Honeymoon orebody, uranium occurs within coarse-grained,pyritic sands where the basal sand pinches out between overlyingcarbonaceous clay and the southern palaeovalley slope. Its characteristics are typical of the well-developed, planar limb of a roll-front uranium deposit. Zonal changes related to the reduction-oxidation interfaces across the deposit are readily observable. The orebody extends for nearly 1000 m along the valley margin, is 400 m wide at its maximum and averages about 6 m in thickness. The East Kalkaroo orebody also lies near the southern margin of theYarramba Palaeovalley. It extends discontinuously for approximately 3.5 km and averages 200 m width, with significant uranium present in the Middle as well as the Basal Member. The Billeroo Palaeovalley extends northward for 40 km sub-parallel tothe western side of the Benagerie Ridge, is up to 5 km wide and hasgently dipping banks. Eyre Formation within the palaeovalley isconcealed beneath 90 m of Quaternary and Namba cover, isapproximately 40 m thick, and is sub-divided into three upward-finingunits, which are remarkably similar to the Yarramba Palaeovalleysequence.

Jan 1, 2001

By M. E. Rossi

Reconciliation of long-term, block-model reserves and mine production frequently shows significant discrepancies. This reconciliation can be done comparing the long-term, block-model reserves against a grade control model (a model based on blast holes or production data). In this article, this is called an Fl factor for tonnages, grade and ounces. This reconciliation should also be done by comparing the grade control model to the mill feed (or loaded to heaps) tonnages, grades and ounces (F2 factor). The long-term model usually contains blocks with dimensions larger than the size of the selective mining unit (SMU) of the operation. The smoothing effect of an estimator, such as kriging, will generally result in a grade-tonnage curve that does not match the grade-tonnage curve of the SMUs to be recovered. This problem is partly to blame for the reconciliation discrepancies found. In addition, in-pit perfect selection is impossible. Therefore, the grade-tonnage predictions based on blastholes also need to be assessed - considering unplanned dilution and the errors of estimation of the grade control model. This article focuses on using conditional simulations to assess the uncertainty of the predicted grade-tonnage curve in terms of minable reserves and in the framework of long-term mine planning. Quantifying the uncertainty in no uncertain terms is done in conjunction with a popular pit optimizer. It yields several possible minable reserves and several possible minable tonnages and grades, per pit shell or scheduled phase. This is a step further from the usual sensitivity analyses that are performed for deposit evaluation or development planning. Specifically, this approach takes into account the volume-variance relationship, the selectivity of the mining operation and the planned and unplanned dilution. It also carries the local uncertainty implicit in grade estimation into the mine design and mine planning phases. The estimation of recoverable reserves revolves around estimating the block distribution of metal grades from the drill hole information available, typically composites of a fixed length. Ideally, this estimation should accurately predict the ore sent to the processing facilities of an operation. Here are some definitions used in this article: ? Recoverable reserves are those where an attempt has been made to estimate the actual distribution of grades (usually by a block model) that would be found in the ground at the time of mining, relative to the mine equipment size and other operational characteristics of the mine SMU. In particular, it incorporates the effect of internal dilution for each block how the grade distribution changes in variability when comparing a composite grade distribution to the "mining unit" grade distribution. In geostatistical jargon, this is known as "change of support effect," or volume-variance effect. ? Minable reserves are those recoverable reserves defined by a mine plan. In an open-pit scenario, they would incorporate pit optimization in addition to the sequencing and scheduling of production through mine life. ? All other block model estimates from drill hole data that do not explicitly attempt to estimate or measure the volume-variance effect are called in situ. It can be argued that these models may be inappropriate tools for predicting the grade-tonnage curve of the material to be sent for processing (minable reserves). The purpose of estimating recoverable reserves can be thought of as estimating the appropriate amount of dilution that should be incorporated into the model so that it adequately predicts (long-term and on average) the grade-tonnage curve of the ore sent to the processing facilities (mean grades and ton-

Jan 1, 1999

By Max Roseler

THE CHAIRMAN (WILLIAM KELLY, Vulcan, Mich.).-Some 8 or 9 years ago I was at Daiquiri, only a. few miles east of Firmeza, where there are deposits of iron ore of the same general character. There is a great conical hill, perhaps 800 or 1,000 ft. in height and the ore deposit appears to be somewhat in a canoe shape on one side of the hill. The mining has been done by quarrying the ore in benches. These are called levels and to go to the 10th level it was necessary to take mules and ride to the top of the hill, which was to me an upside down arrangement of numbering levels and a novel method of entering and viewing a mine. A little copper ore can be seen in places, and not being a geologist I thought the deposit might possibly be a gossan, but none of the geologists who have written on the subject approve of this hypothesis and the great question seems to be what part, if any, the limestones have played in the origin of ore; whether these deposits are replacements of limestone and whether they are contact ,deposits between the limestone and the other rocks. Examinations have been made by many eminent geologists and the problem has been discussed vigorously on both sides. The deposits are exceedingly interesting from a commercial standpoint and although they have been studied for a number off years the origin of the ore is still a difficult and somewhat controversial question. J. T. SINGEWALD, JR., Baltimore, Md.-I have had the privilege of visiting these deposits and have been very much interested in this paper, of Dr. Roesler's; having been on the ground, I can easily appreciate the difficulties under which he labored in attempting to work out the geology of that region, and he certainly deserves considerable credit for the way in which he has deciphered the geological relations of the Firmeza district. There are several points in his paper 1 ,would like to discuss; first, in regard to the geological interpretations. His differs from previous interpretations in the relative age of the diorite and the granite, but you will note that Prof. Lindgren suggests the probability. that those two rocks are very closely of the same age, and Prof. Kemp actually suggests, although he does not-accept the idea, that the granite is probably later than the diorite, so that there seems to be no particular reason

Jan 4, 1917

By Wellington Pereira Inácio, Frederico Muylaert Margem, Artur Camposo Pereira, Sergio Neves

"Natural fibers are currently gaining attention as reinforcement of polymer composites for uses in engineering parts for automobile and building construction. In spite of environmental, economical and societal advantages, the natural lignocellulosic fibers are not as uniform in their dimension and properties as compared to synthetic. In recent works it was found that the variation in strength could be correlate to the equivalent diameters for several lignocellulosic fibers including the sisal fibers. In the present work an investigation on a possible correlation of the equivalent diameter with changes in density and elastic modulus was carried out. Precise measurements of the equivalent diameter, conducted in a profile projector, were correlated with the density and the elastic modulus by means of the Weibull statistic analysis. The results showed that an inverse correlation with the diameter also applies for both the density and the elastic modulus with a high degree of precision. SEM observation of the sisal fiber in structure and fracture aspects strongly indicate that defects and microfibril participation could be responsible for the inverse correlation.IntroductionAccording to Kalia [1], cellulose-based fibers are currently being pushed owing to their ""green"" image. Contrary to synthetic glass fiber, extensively used in our modem technology, these lignocellulosic fibers are renewable and can be incinerated at the end of the material's lifetime without adding pollution in the atmosphere moreover, the amount of CO2 released during incineration process is negligible as compared to the corresponding amount taken up by the plant throughout its lifetime. Even if an industrial processing equivalent of C02 release is added, the lignocellulosic fiber is considered neutral with respect to the emission of gases responsible for the global warming [2]."

Jan 1, 2012

By T. Kelly

The Cannon Mine is located in Chelan County, near Wenatchee, Washington, at the eastern foot of the Cascade Mountains. The mine is situated about two miles from the Columbia River, in the arid Columbia River Valley. Two hydroelectric dams provide electricity for the area, the Burlington Northern Railroad has a switch yard and loading facilities in Wenatchee. Approximately 25,000 people live in the area. The principal industry is fruit farming. Underground mining techniques are used to provide feed for a 2,000 tpd flotation concentrator at the site. The techniques are low- cost, high productivity methods which allow for a high extraction rate along with a high rate of recovery of the minable reserve.

Jan 1, 1986

By Watkins JR

Movements in the mineral trade cycle are almost invariably out of phase with the gradua- tion rate of mining engineers, metallurgists and geologists. This commonly leads to situations where graduates are scarce in "boom" periods and in free supply when the trade cycle is depressed. This problem reflects the difference in elasticity and flexibility between the educational and industrial environments. In the educational system the decision that brings students to graduation is made three to five years prior to the event. This is quite a lengthy period of time in terms of mineral trade cycles. By contrast, the mineral industry has far more elasticity in responding to short term fluctuations in mineral trade. The authors do not believe that the mis- match between the availability of skilled personnel and the manpower requirements of industry in the short term is intractable. Much is to be gained by more realistic and rational manpower forecasting combined with greater flexibility in the educational realm.

Jan 1, 1982

During the period 1979 thru 1982. Multi Mineral Corporation conducted a mining research program at the United StAtes Department of the Interior's Bureau vi Mines Oil Shale Mining Environmental Research Facility in the Central Piceance Creek Basin, Rio Blanco County, Colorado. The program consisted of mining, environmental and geotechnical research data and. the results are described in this report.

Jan 1, 1983

By M. Kumral

One of the most significant elements in solving the co-kriging equations is the matrix solver. In this paper, the singular value decomposition (SVD) as an equation solver is proposed to solve the co-kriging matrices. Given that other equation solvers have various drawbacks, the SVD presents an alternative for solving the co-kriging matrices. The SVD is briefly discussed, and its performance is compared with the banded Gaussian elimination that is most frequently used in co-kriging matrices by means of case studies. In spite of the increase in the memory requirement, the SVD yields better results.

Jan 1, 2012

By Taehong Kim, Carl Pannuti, Nikolas Sokol, Walter Herrick

BACKGROUND This paper discusses work performed as part the rehabilitation of the gravity flow section of the New Croton Aqueduct (NCA) during an approximately two year period between 2004 and 2006. The goal of the project was to restore the gravity flow section of the NCA to optimal operating condition, extending the lifespan of this significant water supply for the New York City metropolitan area. Rehabilitation of the NCA was purposely scheduled before the completion of the new NCA Water Treatment Plant now under construction (Figure 1). The NCA is a 3.73 to 4.34 m (12.25 to 14.25 ft) diameter brick-lined circular andhorseshoe shaped water tunnel constructed between 1885 and 1891. The NCA conveys water for approximately 50 km (31 miles) by gravity and pressurized flow from the New Croton Reservoir in Westchester County, NY to distribution and reservoir points along its alignment, terminating at a distribution station at 135th Street and Convent Avenue in Manhattan, NY. Prominent features of the NCA include a large intake facility at New Croton Reservoir, 38.6 km (24 miles) of gravity flow horseshoe shaped aqueduct, 11.3 km (7 miles) of pressurized flow circular aqueduct, 2 siphons, and 36 open shafts and headhouse chambers which are used as sampling, access and blow-off locations. Until a partial inspection in 1982, the NCA had flowed continuously since its completion nearly 100 years prior. Flow tests have confirmed that the NCA can convey up to 12.7 m3/s (290 mgd) (Figure 2). Cover depths of NCA vary considerably, ranging from a few to hundreds of meters, typically of hard rock. Primarily mined using means conventional for the late1800s, construction of the NCA also employed cut and cover methods in several low-lying sections of the alignment, totaling approximately 1.6 km (1 mile). The NCA crosses through numerous lithologic changes, fault/shear zones and under several significant water bodies including the Pocantico, Saw Mill and Harlem Rivers and the Tarrytown Reservoir. The NCA passes under the Harlem River as a siphon at a depth of approximately 122 m (400 ft) below grade (Figure 3). Soon after construction the Aqueduct Commission Reports on the New Croton Aqueduct documented prominent defects such as large voids behind the lining. More recently, large-scale inspections of the gravity flow section performed during the 1990sand a 2004 inspection of portions of the pressurized sections of the NCA have revealed additional defects such as open and/or deteriorated masonry joints/cracks, leaks ranging from trickles to several liters per minute into and out of the NCA, missing bricks, formed openings, and in one place, a rupture through the liner with discernable

Jan 1, 2007

By Alexander Filimonov, Yury Bloshteyn

The development of a high-efficiency control system for mine ventilation is a complicated scientific and engineering problem. As a result of high-costs and difficult conditions involved in experiments for the development and investigation of mine ventilation systems, simulation is a critical task in cost reduction and productivity. The paper presents the description of a universal simulation model for controlled aerodynamic processes in an Underground ventilation Network (UVN). The high-efficiency programming tool to design and investigate mine ventilation control systems (MVCS) is also suggested.

Jan 1, 1991

Unplanned ore dilution can have severe impact on the economics of a mining operation. The paper discusses and distinguishes between controllable and natural parameters influencing ore dilution, and how it can be minimized in longitudinal mining systems of narrow vein orebodies. It is shown through data of surveyed stope profiles and numerical modelling that unplanned ore dilution is a function of stope design and construction, orebody geometry, and rock mass characteristics.

Jan 1, 2010