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By Bernie W. Martin, Jesus Schabib

The East Side Access (ESA) Project in New York will be the largest tunneling project ever undertaken by a US railroad. The objective of the ESA project is to connect the Long Island Rail Road (LIRR) Main Line and Port Washington Line in Queens to Grand Central Terminal in Manhattan. The Project is divided into two distinctive segments: Manhattan and Queens. The Queens segment is subdivided into two major components; cut and cover tunnel construction and bored tunnels. The bored tunnels in Queens consist of five tunnels driven from a launch shaft and traverse a railway storage yard, Sunnyside Yard and terminate under the multitrack mainlines of Amtrak and LIRR at portals in the heart of Harold Interlocking where1200 trains pass every day. The soil consists of remnants of glacial till moraines and of outwash and till deposits of inter layered gravel and fines, with the occasional boulders and cobbles and with a high ground water table. It is anticipated that a Pressurized Face Machine, either slurry or Earth Pressure Balance equipped with roller disks to mine the boulders encountered as well as the mixed face, will be used to mine the tunnels. One pass reinforced concrete gasket bolted liner will be used. The cut and cover construction consists of an approximately 21.3 m (70 feet) deep excavation supported by slurry walls and jet grout columns. The slurry walls, in combination with overlapping jet grouted columns, are installed to top of rock forming a closed bathtub to control external groundwater drawdown. Maintaining the groundwater level near its original elevation is of paramount importance in order to prevent undesirable settlements and migration of groundwater that could be contaminated. Mitigation measures to prevent the migration of nearby plums are contemplated for all types of tunneling and excavation work in this site of the ESA project.

Jan 1, 2001

By B. Weyerman

U. S. Steel's Oak Grove Mine experienced several top hinge failures on their caving shields. It was determined that all the caving shields needed to be replaced with new caving shields before more thilures occurred. The cost and amount of time needed for several scenarios of caving shield change outs were compared. This paper discusses how Oak Grove Mine decided to and did change 126 caving shields in six specially designed jig stations underground during a longwall move using their own UMWA employees.

Jan 1, 2001

In exploiting the ultra-deep, narrow reef ore bodies of the Witwatersrand, the ventilation and cooling systems within the stopes play a critical role because of high concentrations of active workers. This paper examines the heat, ventilation and cooling effects of a number of different stoping layouts for narrow reef mining in ultra-deep operations in very hot rock. The stope ventilation and cooling needs are driven primarily by the difference between the air temperature and that of the rock front being excavated. These needs depend on the face utilization, geometry, face advance (rate and direction), layout, backfill, use of water and machinery1,2,3. Detailed studies of different stoping configurations have been undertaken for mining operations extending to depths of 5000m below surface, where virgin rock temperatures approach 70°C. Extensive work has been completed with regard to evaluating ventilation and cooling requirements to maintain air reject temperatures of 28°C wet-bulb and better. This knowledge is being used to determine overall cooling requirements, reduce operational costs and maximize the efficiency of cooling systems. These issues are important when considering both the local and regional air conditioning systems and the most effective application of in-stope chilled water.

Jan 1, 2001

By T J. Scanlon

Heavy minerals recovered from recently discovered deposits in the Murray Basin are proving to be somewhat more difficult to process into saleable ilmenite products than ilmenites from existing operations. This is due to the nature of the gangue minerals present, the impurities in the valuable minerals and the size distribution of the mineral assemblages. Ilmenite product quality, in particular, can be adversely affected by any of these factors. Over the past two years the authors have been involved in assessing the potential to manufacture ilmenite products from a variety of mineral sand deposits in the Murray Basin. The steps undertaken to define the potential products and develop suitable flowsheets have evolved in parallel to the exploration efforts, in cooperation with companies undertaking exploration in the Murray Basin. A combination of an understanding of detailed mineralogy, application of magnetic fractionation and modification of magnetic susceptibility of the ilmenites has in all cases, been successful in improving ilmenite product quality. The targeting of particular ilmenites to specific downstream processes for TiO2 pigment manufacture is the most challenging aspect of this development.

Jan 1, 2001

"Many industrial processes involve materials that are subject to temperature change and thermal stress. Examples range from the casting of large metallic products to the cooling and reliability of small electronic components. Thermally induced stress is a major concern as it can lead to material damage and product failure. Material properties, thermal and mechanical, and process conditions such as the size and location of a feeder in metals casting, or the power dissipation in a computer chip, will govern the magnitude of these stresses. Temperature may also be influenced by fluid flow, for example, the airflow over a computer chip in a laptop will govern the rate of heat extraction, hence the temperature gradients in the chip and the evolving thermal stresses.This paper provides details on the governing equations for heat transfer (temperature) and solid mechanics (stress), their degree of coupling, and the numerical techniques used to solve them. Three examples are discussed to illustrate the use thermomechanical modelling. These also provide an insight into the degree of coupling required between the equations. The first example, involves thermal cycling of electronic components where a prescribed temperature field is applied. As temperature is known, this example only requires the solution of the stress equation. The second example also involves the modelling of an electronic component where the temperature field is also calculated. In both of these examples, the stress calculation is dependent on the temperature field, but the temperature calculation is not dependent of the solution of the stress equation (one-way coupling). The final example provides details on modelling the metals casting process. Both the temperature and stress equations are solved but, unlike the previous two examples, in this case the temperature field is dependent on the results from the stress calculation (two-way coupling)."

Jan 1, 2001

By Gordon Revey

The challenge of managing blasting risk, types of risk, public perception, and a system for managing risk were covered in the first part of this article in the May/June 2000 issue of the Journal of Explosives Engineering. This final part of this two-part series provides a method for identifying specific blasting risks and reviews the importance of community relations.

Jan 1, 2001

By S. Lähteenmäki, P. Koivistoinen, J. Levanaho

Semi Autogenous Grinding (SAG) circuit is the most common grinding circuit to day. In Europe and South Africa fully autogenous (AG) circuits are also popular. SAG circuit has a lower capital cost and simple operation. SAG circuit requires the use of grinding balls, which increases operating costs and decreases availability. An AG circuit may produce a higher Net Present Value to the investment. The AG circuit is more complex to design and operate. However, operating experience from AG circuits illustrates that an AG circuit can be as trouble free as a SAG circuit with the benefit of lower operating cost.

Jan 1, 2001

By Chris Larsen, Ian Orford, Mike Cooper

"An autogenous grinding circuit was commissioned at the Brunswick concentrator in October 1998. The autogenous grinding circuit replaced existing surface crushing plants, fine ore storage, rod and primary ball mills. The 8.54m diameter x 4.27m long (EGL) AN1 mill is driven by a bidirectional variable speed 6.3MW ABB wound rotor motor with Slip Energy Recovery (SER) drive. The AG mill was subsequently converted to SAG operation in May 1999 for a number of reasons. The mill is operated in closed circuit with horizontally inclined 660mm diameter cyclones to produce a circuit product P80 of 85 microns. Extensive test work and JKSimMet design modeling resulted in a production circuit operating closely within design expectations.The circuit is highly instrumented and controlled via a hybrid Programmable Logic Controller (PLC-5) and Fisher PROVOX Distributed Control System (DCS) that is in communication with the property information highway. An expert control system (Gensym G2) is used for control of the SAG mill load.Engineering and construction were completed in 28 months from the time of management approval for the project. The Brunswick AG/SAG mill circuit was commissioned on schedule at the $M 23.5 forecast budget."

Jan 1, 2001

David Wolach RMCI PRESIDENT 2001-2002 on behalf of the RMCMI Board of Directors and Officers of The Rocky Mountain Coal Mining Institute cordially invites you and your family to attend the 98th Regular Meeting and Convention to be held June 30 thru July 2, 2002 Breckenridge, Colorado

Jan 1, 2001

By Raymond Chenier

British Columbia (BC) is Canada’s most western province. The landscape in BC is amongst the most beautiful and pristine in the world. Along with its beauty come vast mountain ranges, coastal rain forests, swamplands, deep river valleys, and almost every type of landscape imaginable. These all have, or at one time had, logging roads constructed. Some of these areas should never have had roads constructed due to poor drainage and unstable slopes, but some of the roads could be considered engineering masterpieces. To navigate a vehicle the size of an off-road logging truck down the side of a mountain with an 80°h side slope or greater can be a hair-raising experience. Not to mention coastal rains and/or high elevation blizzards. These factors collectively make logging BC’s most hazardous occupation. People are seriously hurt, sometimes even killed everyday.

Jan 1, 2001

By Lindsay Wade, Peter Dare-Bryan

Benches in surface mines often contain known areas of ore and known areas of waste, which must be mined selectively. When rock is blasted it not only fragments but is also physically, and non-uniformly, moved. Risks therefore exist of ore being lost if treated as waste and of mill feed being diluted by waste. Both possibilities carry serious fmancial implications.

Jan 1, 2001

By D N. B Skinner, R L. Brathwaite, M S. Rattenbury

The Institute of Geological and Nuclear Sciences Ltd has carried out a mineral resource assessment of the Coromandel region, one of the most mineral-rich regions of New Zealand. The assessment focussed on metallic minerals and clays, because these are the main commodities that have potential for increased production and export from the region (and from New Zealand).   Three steps were used in the assessment: 1) development of mineral deposit models, 2) comparison of the models with regional geology, structure, geochemistry and past mineral production to estimate the number of undiscovered mineral deposits, and 3) application of grade-tonnage models to determine the quantity and value of the known and undiscovered resources. In step 1, descriptive and grade-tonnage mineral deposit models were developed for 11 different types of mineral deposits: ò     Low-sulphidation andesite-hosted epithermal Au-Ag ò     Low-sulphidation rhyolite-hosted epithermal Au-Ag ò     High-sulphidation quartz-alunite epithermal Au ò     Porphyry Cu-Au-Mo ò     Andesite-hosted polymetallic veins adjacent to mineralised porphyry stocks ò     Zn-Pb-Ag skarn ò     Cu-Ag skarn ò     Hot spring Hg ò     Shoreline placer Ti ò     Rhyolite-hosted halloysite clay ò     Volcanic-related kaolinite clay   Step 2 was aided by a geographic information system (GIS) assembled from a number of digital spatial data sets including: a digital elevation model, an aeromagnetic map (from open file mining company data), a geological map (from the GNS QMAP project), location of areas of hydrothermal alteration, locations of mineral deposits (from the GERM database), stream sediment geochemical analyses (from the REGCHEM database), and a lineament map derived from satellite remote sensing data and the digital elevation model.   Based on May 2001 commodity prices, potential resources estimated for the 11 mineral deposit and grade-tonnage models total NZ$22 806 million for the metallic minerals, NZ$1000 million for halloysite clay deposits and NZ$57 million for kaolinite clay deposits.

Jan 1, 2001

By Richard W. Hanford

The geotechnical construction industry generally considers soil mixing to be defined as an in situ ground improvement or treatment method by which a dry or wet reagent is introduced into the ground and is blended with the soil by mechanical or rotary mixing tools. This results in relatively homogenous mixtures whose engineering properties are improved and are greater than the soil properties before mixing. Reagents usually include cement, but may also include processed clay such as bentonite, when a reduction in hydraulic conductivity is desired, or other proprietary chemicals when chemical stabilization is the objective. Mixing may be either shallow or deep. Shallow Mixing is the term arbitrarily used for treatment of soils within the upper 30 feet; Deep Mixing denotes treatment below 30 feet to the depth limits of the equipment. Mixing equipment may consist of single or multiple-shaft tools having cutting and mixing blades of many different configurations. To avoid using proprietary nomenclature, reference to Shallow Mixing Methods (SMM) and Deep Mixing Methods (DMM) are the preferred terms. Although originally developed and patented in the United States in 1956, in situ construction using various soil mixing methods is more prevalent in Japan and the Scandinavian countries. Reintroduced into the United States from Japan in 1986 for ground improvement and liquefaction mitigation at Jackson Lake Dam, Wyoming, acceptance of soil mixing methods has been gradual but slow. Applications typically include:

Jan 1, 2001

By Deming Wang, R. A. Overfelt

"This paper presents a computer-aided heat transfer simulation method to predict the thermal characteristics of an alloy sample in a special furnace for directional solidification. A two-dimensional transient heat transfer by conduction combined with radiation is developed to calculate the energy exchange between a directional solidification furnace and the sample. Finite difference equations with control volumes are used to calculate the transient heat transfer. A special boundary control volume is used to combine heat conduction and radiation in the transient heat transfer. Heat radiation effects on the surfaces of the special control volumes with a changeable view factor during directional solidification processing are also represented. The simulation results are verified by measurable experimental data. Using the computer simulation model, many thermal properties of the directional solidified castings can be obtained, such as temperature distribution, solidification velocity, the shapes and positions of the liquid/solid interface and thermal gradient at the interfaces. These are very important to analyze microstructure of casting alloys, avoid casting defects and control casting quality. 1 IntroductionIn directional solidification (DS) processing of castings, the temperature distribution, the interface between liquid and solid zone, thermal gradient in the mushy (pasty) zone and solidification rates are very important factors to analyze the microstructure and the casting quality. These variables affect the orientation and size of dendrites, shapes of grains, solute segregation and deleterious casting defects, such as microporosity, freckles and segregation channels. In order to avoid the casting defects, the temperature distribution and thermal gradients of castings during directional solidification must be strictly controlled. However, the structure of furnaces used for directional solidification is often complex. Heat transfer and temperature distribution within a casting not only depend on furnace temperature but also on the thermal properties of the casting alloy, crucibles, retorts etc. A more accurate heat transfer analysis."

Jan 1, 2001

This paper examines the complex interplay of deposit characteristics, mining plans, tailings disposal techniques and rehabilitation requirements on planning for mineral sands operations. All component parts of this mining cycle are interdependent and cannot be evaluated in isolation when optimising a mineral sands operation. This is most evident when projects are large-scale or involve resources that contain complexities such as high slimes content, consolidated hard band materials, acid forming materials and radioactive materials. Projects located in environmentally sensitive areas add further to the need for more stringent planning. This paper describes the analysis techniques adopted by Hatch to evaluate mining and tailings placement options for a dredging and floating concentrator system. The principles and methods used in the analysis are applicable to any mining system involving the complexities listed above. The focus of this paper is on the reconstitution of mined material as tailings and the impact of this process on mining schedules and tailings construction and placement options.

Jan 1, 2001

By M. Irish, M. Jahraus

Accurate prediction of gold (or other metal) production from a heap leach operation is essential to the economic vitality of any such operation. However, this is also one of the most challenging issues facing managers of these facilities. Three approaches to modeling gold production from the Valley Leach Facility (VLF) at Anglogold’s Cripple Creek & Victor Gold Mining Company are presented. Evolution of these modeling methods has been necessary as ore heights and volumes have increased. In addition, the complex geometry of the VLF presents additional complications to production modeling, Comparison of actual and predicted gold production are presented

Jan 1, 2001

By D Nourry

Optimising the blast is a major issue in the blasting business. It generally means acting on the blasting pattern (drilling, charging, detonating) in order to get a given æresultÆ. This result may either be related to economic reasons, such as the fragmentation influencing productivity, or technical reasons, for example vibrations and projections. Within the frame of the EEC funded Brite-Euram project entitled æBlast-ControlÆ, involving academic research and applied expertise, a general methodology was developed to approach such a problem and currently applied to the industrial partners of the project and final end-users of the generated results. These partners are the limestone ALZO quarry of the CALCINOR group in the north of Spain and the dolomite DMD (Dolomies-de-Marche-les-Dames) quarry of the LHOIST group in the east of Belgium. A first part of the project, over 18 months, was dedicated to establishing a clear relationship between productivity of operations from drilling to primary crushing and the fragmentation resulting from the blast. Extensive monitoring of blasting, production performance and fragmentation data was carried out and automatically collected into a database on both quarries. As expected, it appeared that excessive amounts of fines or boulders were substantially reducing productivity and thus profitability of the operation. Furthermore, an æoptimalÆ fragmentation was assessed for the quarries to run at the best (high throughput, low cost). The second and last part, for the remaining 18 months, was then dedicated to adapting the blasting practice in order to orientate the fragmentation towards a æbetterÆ one. A very common problem normally addressed by any consultant. Nevertheless, the target was not limited to solving the problem for these two quarries, but also to develop a generic method to address this blasting adaptation process and to implement it into a computerised tool. At this stage, it is then obvious that portability of the method and the system are major qualities to be looked for. This paper is aimed to present how this method was developed, how the system was implemented and how it was finally used.

Jan 1, 2001

By Donald Leroux, Ralph Dahlke, Dave Scott, Finch. James A., Cesar O. Gomez

"The efficiency of the flotation process depends on how effectively air is dispersed into small bubbles. Bubble surface area flux - the surface area of bubbles per unit time per unit cross-section area of a cell - is emerging as the parameter to characterize gas dispersion. One of the approaches proposed to measure bubble surface area flux in industrial cells is based on the measurement of two variables: gas velocity and gas holdup, using separate sensors. Plant testing of the gas velocity sensor gave evidence of a series of operational problems which may be necessary to correct before attempting to characterize gas dispersion. Problems such as uneven air distribution within a cell and along a bank, faulty air and slurry valves detected during attempts to redistribute air, and poor control of pulp level and gas flow became evident. Detection of these problems from gas velocity measurements is illustrated.INTRODUCTIONBubble surface area flux is considered a key variable in the optimization of flotation circuit performance (Gorain et al., 1997; 1998). The Mineral Processing Group at McGill University has devised and developed a method for estimating bubble surface area flux in industrial flotation cells (Finch et al., 1999). The method is based on measuring gas holdup and superficial gas velocity using two separate sensors and applying drift flux analysis to estimate bubble size (Dobby et al., 1988; Banisi and Finch, 1994). With bubble size and superficial gas velocity known bubble surface area flux can be calculated.This method was selected by Noranda to characterize gas dispersion in cells as part of a program to model and optimize flotation circuit performance. However, initial testing at Brunswick Mine with the gas velocity sensor provided some unexpected results indicating operational problems and equipment malfunctions that needed to be addressed before systematic measurement of gas dispersion could be initiated.The subject of this communication is to illustrate the detection of these problems from gas velocity measurements. The line 3 Zn Cleaner circuit comprising four stages of Denver DR cells was the main subject of analysis, including the effect of correcting these problems on the metallurgical performance of the Zn 3rd cleaner bank of ten DRl 00 cells."

Jan 1, 2001

By M. El Ganaoui, P. Bontoux

"A computational model to investigate solid/liquid phase change transitions for binary alloy under directional solidification is presented. Conservation equations are developed by using an homogeneous formulation. A second order accuracy method of time and space based on finite volume approximation has been evaluated by comparing results to spectral solution for time-dependent solutal convection developping in a melted alloy. For extended model to solid/liquid interface effects time amplification of solutal perturbation injected near the interface is described before considering solutal convection is melt.IntroductionThe enthalpy method gives a front fixing approach for energy equation without introducing coordinate transformation. The interfare position is recovered a posteriori [1]. A number of authors have extended this approach so as to include the convection phenomena within the two phase 'mushy region' [2, 3, 4, 5, 6].We have developed a time-dependent enthalpy-porosity formulation for directional solidification [4, 6, 8]. The interaction between solid and liquid phases is modelised by a Darcien type force in the phase change area. The behaviour of the melt is similar with the flow of an incompressible fluid in a porous medium. This force is proportional to the relative phase velocity. It corresponds to a damping force depending on the anisotropic permeability of the 'mushy zone'. The permeability depends on the liquid fraction and on the size of·solidification microstructures. An informative discussion of a new slant on the general approach of continuum mechanics needed to analyze the formation of mushy zone is given in [12]. The method is extended to the presence of species diffusion: the solutal Stefan condition which expresses the solute incorporation or rejection across the interface is accounted implicitly in a species equation valid in all the domain [14, 15]."

Jan 1, 2001

By Vaughan R. Voller

"Numerical methods for dealing with a temperature dependent conductivity are discussed. An approach based on a local application of a Kirchhoff transformation at the discrete level is presented. The application of this transformation - that does not require any inversion- is demonstrated on solving a two-dimensional test problem.IntroductionMuch is said in the recent literature on the modeling necessity of obtaining appropriate thermo-physical properties; in particular the requirement to account for properties that are ""strong"" functions of the depended variables, e.g., Temperature. Of course obtaining appropriate thermo-physical properties serves no purpose unless they can be accurately integrated into a discrete numerical calculation. The purpose of this paper is to examine how temperature dependent conductivities that exhibit discontinuities or rapid changes can be handled in a numerical code.The discussion will be made in the context of a control volume finite element method [1]. After a brief outline of control volume finite element fundamentals basic methods of dealing with discontinuous or rapidly changing thermal conductivity are discussed. This is followed by the presentation of the recently proposed local Kirchhoff method [2,3], The paper concludes with an investigation of the performance of the various conductivity schemes in solving two dimensional problems. This testing clearly shows the advantages (accuracy and implementation) in using the local Kirchhoff method."

Jan 1, 2001