Search Documents

By Reginald Dias

Mining equipment life may be extended through preventive maintenance and the proper application of quality lubricants. There are several practices mine operators should consider implementing to preserve their equipment. An exercise in review — Begin by reviewing original equipment manufacturer (OEM) recommendations regarding servicing and maintenance intervals for each part of the equipment, especially the engine. And the verdict is — If the manufacturer’s recommendations have been followed, good. If not, owners/operators should begin periodic service work on equipment, to help minimize equipment downtime and extend engine life.

Jan 1, 2004

Strategic planning in mining is an important value accretive process. One of the most important aspects during the planning phase is determining the correct mine and plant design. The traditional mine site design (mine, plant, stockpiles, dumps) develops a fixed system for one set of conditions or expected values. A robust design is a fixed system that is designed to deal with a large range of conditions without changing the system design. A flexible design changes the system dynamically in response to changes in uncertainties. It is hypothesised that a robust design generates less value than a flexible design as it fails to realise the value of actively managing the operation. One of the most critical aspects in creating strategic value from a project is embedded in the design of the system. A flexible design has components that allow the design of the system to change over time. An operational plan is proposed as a hybrid of a robust and flexible design. This paper seeks to compare these different design methodologies. An analysis of the same case study is undertaken to compare these approaches, showing an a traditional net present value (NPV) of $1678 M, robust design NPV of $1787 M and an operational plan NPV of $1867 M - an increase of $170 M.

Dec 6, 2010

By John A. Herbst, Alexander Potapov, Xiangjun Qiu

"High Fidelity Simulation is a name applied to the use of first principles modeling tools including Discrete Element Modeling (DEM), Computational Fluid Dynamics (CFD) and Discrete Grain Breakage (DGB) to mathematically describe and study processing systems. Over the past few years, significant advances have been made in High Fidelity Simulation applications, particularly as many mineral processors have been drawn to the study and use of DEM of grinding mills for optimization purposes. This presentation provides an introduction to High Fidelity Simulation, with an emphasis on DEM. It will include insights into current applications of these tools including the optimal design (wear and throughput) of mill lining systems and media selection, the analysis and design (flow and efficiency) of the back-end of grate discharge mills. Advantages of full mill simulations versus individual sub-process simulations will be demonstrated for a SAG mill with different discharge system designs.INTRODUCTIONHigh Fidelity Simulation is providing mineral processors with the opportunity to analyze the behavior of mineral processing equipment from a fundamental or microscale point of view. In the past complex phenomena such as tumbling mill grinding had to be analyzed using black box tools such as residence time distributions for transport and classification functions for passage of particles through grates; while breakage had to be analyzed using PBM models who derived their form from theory but required direct measurement of kinetics. Today with the help of DEM, CFD and DGB these can be analyzed at a very fundamental level.The key element of DEM simulation is the application of Newton’s laws of motion to individual objects or discrete elements. Using this simulation method one can describe the position, velocity (both translational and rotational) of all objects and the transfer of momentum to other objects (Mishra and Rajamani, 1992; Cleary, 1998; Nordell et al, 2001)."

Jan 1, 2003

By R. K. Dunham, D. J. Reddish, X. L. Yao

Paper presented at the conference: Risk assessment in the extractive industries, held in Exeter, UK, 23-24 March 1994, and first published London: IMM, 1994, preprint volume, 10pp., 10 refs. The integrated approach combines a powerful ground movement prediction program with a knowledge-based expert system. ESDAS (Expert Structural Damage Assessment System) was developed to evaluate mining subsidence damage in the form of risk and in terms of the three vital contributing components (mining factors, site factors and structural factors). Using a certainty factor risk assessment technique, the system can be used to predict the likely damage to a particular structure subjected to mining subsidence. A previously developed powerful ground movement prediction program, SWIFT (Subsidence With Influence Function Techniques), has been combined with the expert system to allow the mining factor to be more accurately determined in a broader range of mining layout. Since SWIFT can be calibrated to any particular coal field using local subsidence data, it is believed that the integrated system could be used in any coal field worldwide for the assessment and control of mining subsidence damage risks

Dec 1, 1995

By M. A. Reyes, L. Yan

Heat and humidity buildup withn refuge alternatives (RAs) may expose occupants to physiological hazards such as heat stress. The Mine Safety and Health Administration (MSHA) regulations require RAs in underground coal mines to provide a lifesustaining environment for miners trapped underground when escape is impossible. RAs are required to sustain life for 96 h while maintaining an apparent temperature (AT) below 95 °F (35 °C). The National Institute for Occupational Safety and Health (NIOSH) tested a 10-person tent-type RA, a 23-person tent-type RA, and a 6-person metal-type RA in its underground coal mine facilities to investigate the thermal environment over a 96-h period. The test results showed that mine air and mine strata temperatures surrounding an RA occupied by simulated miners (SMs) increased over the 96-h test period. The test results suggest that RA manufacturers should consider this increase in temperatures when calculating and evaluating RA components during surface and laboratory tests. The findings can equip stakeholders with additional considerations for calculating the interior heat and humidity temperature profiles for occupied RAs not tested in situ.

Using a cylindrical hydrocyclone with a long vortex finder as the separator, a batch sizer was developed for the fast comparative sizing of the coarse solids normally encountered in mineral pulps.Operating times as short as 2 or 3 min gave separations ranging from 16 mesh down to the subsieve sizes.Reproducibility was good and sensitivity was adequate for most applications.

Jan 1, 1968

By Roderic A. Ellman

The new Woodrow Wilson Bridge (WWB) will replace the existing bridge over the Potomac River to connect Alexandria, Virginia to Prince Georges County, Maryland. The new WWB will extend approximately 1.1 miles across the river, with a 367-ft long bascule span in the main river channel where the water depth is about 36 ft. The subsurface soil profile consists of up to 50 ft of a soft organic silty clay layer that is very vulnerable to scour, underlain by a deep deposit of hard sandy clay. Foundation construction in the Potomac River required the use of cofferdams to allow structural concrete work to be performed in the dry. This paper will the present the types of cofferdams used to construct the foundations for the WWB replacement project. The bridge is primarily comprised of fixed spans in relatively shallow water and a bascule span over a navigation channel in relatively deep water. Foundation construction included the installation of 48? to 72? open end steel pipe piles and cast-in-place concrete pile caps. To achieve the desired bridge appearance, pile caps were required to extend below the water surface and below the existing river bottom in shallow water locations. Conventional steel sheet pile cofferdams with tremie concrete seal were used to construct fixed span, shallow water piers. Selection of deep water bascule span foundation cofferdams was governed by several factors including contraction scour, environmental considerations and cost. Potomac River cofferdams, i.e., relatively shallow depth cofferdams that are supported by the foundation piling were selected. This cofferdam system provided a shallow profile which minimized contraction scour and the amount of filling in the river. Design issues include load selection and cofferdam stability in very soft alluvial soils. Construction issues include erection sequence, tremie concrete mix design and placement procedures.

Jan 1, 2013

M.S. Azun I have many objections to the content of the author's paper. Before discussing it, however, I would like to repeat the property of semivariogram function. Second order stationary properties of regionalized variables (ReV's) such as semivariogram function y(h) are perfectly known in geostatistics. Also, the kriging equations in the language of mathematical statistics using second order stationary properties are well understood. However, the way to use the sample (estimated) semivariogram function in any one of the kriging procedures is vague. The sample semivariogram function is given as follows: [ ] where N is the total number of samples, Xi is the sample value at the i - th location, Xi+h is the sample value at the i + h - th location, and h is the distance among the samples. An estimation variance of sample semivariogram function of first lag is smaller than that of higher order lag. The theoretical semivariogram function reaches the variance of samples asymptotically. But this is not easily observable because of the larger variation involved in the estimate of semivariogram function. In general, an estimation procedure is done for h = 0, 1, 2, up to the greatest integer less than N/2, even though sample semivariogram function can be computable through N-1. After estimating semivariogram function, the critical question of how to model sample semivariogram function arises. As seen in the above equation, sample semivariogram function is discrete and can be smoothed by the model being selected. Therefore, modeling of sample semivariogram function is the most important step in geostatistics. It not only smoothes a discrete function but also affects the results of the kriging procedure. When the only aim is to model the semivariogram function, which is the basic point of the author's paper, one can employ any fitting techniques, such as curve fitting, or any arbitrary functions, which are called submodels in the paper. The term "arbitrary function" is used rather than "submodel" because there is no basic understanding of developing them. The author suggests that the sum of those submodels can also be used for the modeling of sample semivariogram function. The combination of any arbitrary functions brings many problems instead of giving an insight of the domain structure considered. The author used two arbitrary functions and the nugget effect in response to sample semivariogram function (Fig. 10). For the same example, he stated that the parameters involved in the mixed arbitrary function model can be accepted when the discrepancy between sample semivariogram function and the model is small visually. For verifying the fitting behavior of any selected model, one should not be contented with the visual satisfactory. Some statistical measure such as goodness of fit has to be used. The author's practice is no more than an exercise in curve fitting without any fundamental understanding or conceptualization of the underlying physical mechanism. Furthermore, the selection of any model is not an easy task if the purpose is the search for the "best" response to the observed second order properties of ReV's. I suggest that the Markovian model (Azun, 1983), on the basis of a theoretical understanding of underlying mechanism, which gives more information about the occurrence of regionalized variables, is used to respond all properties of ReV's. There are a lot of problems for modeling of one-dimensional sample semivariogram function. Thus, it is not appropriate to go to higher order dimensional sample semivariogram function modeling. In the meantime, I would recommend that one can connect the values of standardized sample semivariogram function rather than simple values of semivariogram function in the two-dimensional estimation. The standardized values can be computed in dividing the semivariogram function value by the number of sample pairs involved in each lag regardless of the directions. In conclusion, geostatistics is an interdisciplinary area in mining that uses the principles of mathematical statistics. Thus, it should not violate any probabilistic and statistical rules. When Matheron was developing the theory of geostatistical study in the early years of geostatistics, many mining people had a reservation accepting the geostatistical tools. However, this does not mean that we, the geostatisticians, might try to convince those people using some "strange" tools or rules as some authors implied (Baafi and Kim, 1984). Instead, we have to develop and explain the geostatistical tools staying only in the framework of statistical concepts and properties. References Azun, M.S., 1983, "Stochastic Process Modeling of Spatially Distributed Geostatistical Data," Columbia University, Ph.D. Thesis. Baafi, E.Y., and Kim, Y.C., 1984, "Discussion - Comparison of Different Ore Reserve Estimation Methods Using Conditional Simulation," Mining Engineering, Vol. 36, No. 3, p. 280. Reply by J.M. Rendu The interactive method proposed by Rendu allows practitioners to develop semivariogram models that take into account not only the numerical information obtained by sampling, but also highly significant additional information that often cannot be quantified. The geology of the deposit - including hypotheses concerning its genesis, sampling methods, assaying methods, and mathematical methods used to calculate the semivariograms - all have an influence on the numerical results obtained and on how these results should be interpreted. If all the information concerning the spatial distribution of values in a mineral deposit was contained in the sample values, it could be argued that statistical techniques alone would produce optimum models. However, this is rarely, if ever, the case. Methods that allow the user to take into account his experience and his geologic understanding of the deposit should not be rejected for the sake of theoretical statistical purity.

Jan 11, 1985

The Bulli Seam, New South Wales, comprises medium to low volatile bituminous coal, generally of coking quality. It is worked over an area embracing 300 square miles.Variations in several factors are found.1. The seam is somewhat disturbed and dissected by various structural features.2. This structure, and present topography, have resulted in depths of cover from very shallow to approaching 2,000 ft in the presently worked areas.3. Wide variations of seam thickness occur.4. Gradations of rank occur from place to place.5. Variations in seam gas content and wide variations in seam gas composition are experienced.6. Variations in coal strength occur.These factors may contribute to the occurrence of stress and gas phenomena in mining exploitation.INTRODUCTIONThe Bulli Seam, the most extensively worked seam in Australia, is the uppermost seam of the Illawarra Coal Measures, which comprise the southern portion of the Sydney Coal Basin. Generally, the rank of the seam and its assemblage of types make it ideal for the production of hard metallurgical coke. The thickness and relatively flat dips render the seam suited to mechanized bord and pillar mining, and this method is used almost without exception. At the north-eastern corner of the field, stress and gas phenomena have occurred during mining.Various data have been assembled on physical, chemical and geological conditions of the seam which may influence the occurrence of stress and gas phenomena. This material is presented in an attempt to explain the location of such phenomena to date, and to enable variations in conditions to be considered when future possibilities are being assessed.

Jan 1, 1963

The labour question is one that has caused mine managers much thought and anxiety and is likely to continue to do so as long as human beings exist. The difficulty is to devise some arrangement whereby the interests of miner and mine ownerare identical. Mines cannot be worked without capital, and capital is no good without labour, yet, though both have the mine in common, their interests are not exactly the same. Some men are happy so long as they can scrape through by exerting themselves as little as possible, but capitalists do not work mines for charity, they want some return for their money.Where a large number of men are employed there are bound to be examples of all sorts, good and bad, and it is because one cannot depend on all, that different methods of employment have to be adopted. Which method is selected depends to a great extent on the labour market, local conditions, nature of the ore and the way in which it occurs.A big step towards success is obtained by securing the services of good bosses, not only those who know how work should be done, but men who have a knowledge of human nature. It is a big mistake to be too lenient with a man, also to be unnecessarily harsh. A good boss will always be sought out by good men who have worked under him before, or who have heard of him from others. By a good boss we do not mean one who employs two men where one would do, or who lets the men loaf...

Jan 1, 1901

By Gregory Yates

INTRODUCTION Project Description The Silver Line is a Bus Rapid Transit (BRT) Line and is Boston?s newest transit service. Silver Line Phase I extends along Washington Street entirely on the surface in priority bus lanes from Dudley Station in Roxbury through the South End and Chinatown neighborhoods to downtown Boston. The Phase I opened in July 2002. Silver Line Phase II consists of an underground transit tunnel from South Station to the South Boston Waterfront with underground stations at Courthouse and World Trade Center to Silver Line Way east of D Street. Phase II continues through the Ted Williams Tunnel to all the terminals at Logan Airport, and on the surface to the Boston Marine Industrial Park and City Point. Phase II opened in December 2004. Silver Line Phase III is a one mile tunnel connection to the existing Phase II tunnel in the vicinity of South Station and will eventually portal on Tremont Street just north of Marginal Road. After leaving the portal, the buses will use dedicated bus only lanes on the surface roadway network to connect to the Phase I service. Figure 1 shows the alignment of the Silver Line upon completion of the Phase III project.

About twelve months ago, owing to the increasing quantity of stone and dirt being drawn frQm the Victorian State Coal Mine due to the large amount of dead work below ground, cutting, faults, etc, and to the increasing quan#ty of banded coal beingworked, the writer was forced to consider the question of economy in handling the spoil at the surface. The method in operation at the time was to run out level dumps fro,m the, tipping floor of the heapstead, or brace, and to tip most of the skips of stone in tipplers at the ends of the dumps, the remainder of the skips being side-tipped to widen the dumps.The method, whilst quite satisfactory for dealing with a few skips of stone, was found to be costly as the dumps extended, and the number of skips to be dealt with increased from 300. to 400 per day of two shifts;. therefore, in order to expedite thework and cheapen its cost, the writer devised an improved method which may be qescribed as follows :-(1) The stone is tipped into a hopper car which holds about 10 skips(2) The hopper car is hauled up an inclined dump by means of an electric winch.(3) The spoil is dumped from the car forwards or to either side, as required.(4) The car is returned to the starting point for a further load.Plate I Fig. 1 gives an idea of the construction of the hopper car. In the illustration the car is in position for tipping to one side. The body of the car is supported on a ball race on the under carriage, and it can be swung round to tip in any required direction. The bottom of the hopper is extended to form a 4 ft. lip...

Jan 1, 1918

By Tsunenobu Nozaki

"AbstractThe PRESS-IN METHOD is widely recognised as “an environmentally friendly piling method”. However, this characteristic is only one of the fundamental advantages of the method and this paper presents the most up-to-date capabilities of the method. Due to the evolution in recent years, the Press-in Method is now applicable to 2.5m thick retaining walls, over 50m deep foundations, overcoming rock conditions and confined construction conditions.The Press-in PrinciplesThe basis of the Press-in Method is simple. The Silent Piler presses a pre-formed displacement pile into the ground by static jacking force. The reaction for the Press-in Force is generated by gripping previously installed piles. As a pile is pressed into the ground, “A Pressure Bulb” is formed around the pile toe. Accordingly, higher bearing capacity can be generated compared to driven piles without disturbing the ground and producing any vibration. (A comparison of jacked, driven and bored piles in sand (2005), Deeks et al.)Applicable Pile ProfileThe Press-in Method is applicable to most of the steel piles available on global market i.e. U sheet pile in single form and pair, Z sheet pile, also in single and pair and Tubular Pile as described in Figure 2. Wall thickness of those piles can be 0.3m to 2.5m and moment of inertia of the wall ranges up to about nine million biquadratic cm per meter, which can deliver similar elastic modulus EI (kNm2/m) to 2.0m thick diaphragm walls and can be utilised for extremely deep excavations required in today’s construction industry"

Jan 1, 2014

By Erich J. Jacob

In the past 15 years the enforced improvement of the public traffic systems caused a boom in urban tunnel construction. In 1961 the City of Paris started to build the Express-Metro. Of the 47 km long double-track line crossing the city center, nearly 45 km are in operation since 1971. Still missing is here only an about 2.6 km long connecting stretch, which is under construction now. From 1963 to 1969 the 21.8 km long Victoria Line was built in London as extension of the existing network,. A little later, in the years 1965 to 1973, the City of Hamburg supplemented its subway network by the construction of a 16.8 km long line between the Boroughs of Billstedt and Stellingen. Also in 1965 the City o Munich started to build a subway system of 54 km f length. Thereof a stretch of 16.2 km could be taken into operation in 1972 shortly before the Olympic Games. These are only some of the better known projectsas examples of the activities in European cities. In nearly all cities with more than about ½ million inhabitants subsurface traffic lines were begun or supplemented. Furthermore, numerous undercuts or other subsurface structures were built. The Ij Tunnel in Amsterdam and the new Elbe Tunnel in Hamburg may be mentioned, both structures finding international attention.

Jan 1, 1976

By Anthony Treasure

El presente trabajo señala la aplicación de la tecnología EMEW® para la recuperación de metales preciosos a partir de soluciones cianuradas diluidas que contienen plata y oro. La tecnología consiste en un proceso de electroobtención que ha sido desarrollado específicamente para la recuperación de metales en una sola etapa a partir de soluciones, hasta concentraciones de metal muy bajas, de forma que recupera plata y oro a partir de soluciones de lixiviación. Asimismo, este sistema ofrece beneficios como: menor costo de capital, costo de operación, simplificación de proceso, bajo riesgo técnico, mayor recuperación de plata, así como pureza del producto.

Sep 12, 2005

By S M. C Verryn, K Deysel

In heavy mineral sands ilmenite, rutile and zircon are present in economic concentrations. These minerals are important sources of Fe, Ti and Zr for various industrial uses. The beach sands of northern KwaZulu-Natal, along the Zululand Indian Ocean coastline in South Africa, have been mined for 30 years. The various processes involved in mining and processing these minerals have been controlled by time-consuming and labour-intensive analysis methods which, in some cases, can be replaced by X-ray powder diffraction (XRD)-Rietveld analysis. Heavy minerals are concentrated in the plant to produce a heavy mineral concentrate (HMC). The heavy mineral extraction plant is controlled and informed of the proportions of minerals in the HMC according to their magnetic susceptibility. The different fractions are called magnetic, paramagnetic and non-magnetic fractions and quality control is based on their magnetic fraction weights combined with X-ray fluorescence (XRF) elemental analysis. This current quality control process is very time consuming and labour intensive. We have aimed to show that we can, by XRD, identify and quantify all the minerals in the HMC and also in the magnetic separations. These results are then compared with results obtained by Mineral Liberation Analyser (MLA) as well as with the results from the physical separation. It was possible to detect all minerals present in the material by XRD and use the Rietveld method for a full bulk mineral quantification. A maximum of 15 minerals can be included in the Rietveld refinement due to computational restraints. Major minerals detected are rutile, ilmenite and zircon and minor minerals are quartz, epidote, anatase, amphibole, monazite, magnetite, titanite and augite. The XRD and MLA results correlate relatively well and detailed results will be presented for HMC and magnetic fraction samples. Small differences were observed for some minerals due to the different ways in which minerals are detected or due to preparation methods within each method. Rutile seems to be more abundant in the XRD analysis and the detection of Anatase is possible by XRD, but not MLA. Leucoxene (consisting of mainly microcrystalline anatase, rutile and titanite is not detectable by XRD since it is not a mineral, but ilmenite alteration phases are observed instead. There is, however, a correlation between anatase, titanite and rutile detected by XRD and leucoxene analysed by MLA.

Jan 1, 2008

By A. N. Holden, W. E. Seymour

DURING the last several years, the U-Zr system has been studied at many laboratories as one of the research programs sponsored by the Atomic Energy Commission. The equilibria in part of this system have been difficult to determine, although the phase diagram from 0 to 60 atomic pct Zr has been established with reasonable certainty. Existing diagrams of the system vary appreciably beyond 60 atomic pct Zr, particularly with regard to the existence of an intermediate phase. Most existing diagrams show a transformation or reaction horizontal near 600°C. In 1955, a collection of uranium phase diagrams' was prepared at the Battelle Memorial Institute and the U-Zr diagram in that collection contained a questionable region in the vicinity of 60 to 80 atomic pct Zr. Summer-Smith" has published a phase diagram of the system that shows no intermediate phase. Summer-Smith did his work with powders and found only the uranium and zirconium eutectoid mixture from X-ray patterns of material annealed below 600°C. Mueller3 at Argonne National Laboratory did similar work with filings, and he found that initially there was a pattern of an intermediate phase, but on long-time annealing

Jan 1, 1957

By John Wise

Significant movement to an existing slurry wall which serves as a retaining wall on 'O' Street in Southeast Washington, D.C. initiated the Department of Public Works for the District of Columbia to invite specialty contractors to propose a rehabilitation and stabilization for the failed slurry wall. Nicholson Construction Company proposed and was awarded a contract for the construction of an anchored precast lagging and soldier pile wall to be located approximately 4 feet in front of the existing structure with granular fill placed between the new and existing walls. Stabilization of the existing slurry wall also included drilling horizontal weep holes and demolishing the failed panels down to the existing ground surface. A new and improved drainage system was also constructed to increase the amount of water directed toward the existing storm sewer system running along 'O' Street. This paper provides a detailed account of these construction activities.

Jan 1, 2003

By D. R. Wilburn

This summary of international mineral exploration activities for the year 2007 draws upon available information from industry, literature and U.S. Geological Survey (USGS) specialists. The summary provides data on exploration budgets by region and mineral commodity, identifies significant mineral discoveries and areas of mineral exploration, discusses government programs affecting the mineral exploration industry and presents analysis of the mineral industry based upon these data. Two types of information are reported and analyzed in this annual review of international exploration for the year 2007: 1) budgetary statistics expressed in U.S. nominal dollars provided by Metals Economics Group (MEG) of Halifax, Nova Scotia, and 2) information on regional and site-specific exploration activities that took place in 2007 and compiled by the USGS.

Jan 1, 2008

By R. W. Stahl

Burning coal-mine refuse banks were surveyed in 15 States. The following characteristics were tabulated for 495 hanks: County; name, population, and distance of nearest town; size and status of bank; status and stage of fire; and topography. Ways of controlling fires were reviewed, the compacting and sealing method proving most satisfactory. Means for preventing refuse-bank fires by proper construction of banks are described.

Jan 1, 1964