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By María Virginia Ramírez, Alejandro Alarcón, Alea Reyes

Reactive grounds (presence of FeS2, CuFeS2) can create hazards in a mine; misfires to premature deflagration or detonation of loaded blast holes. This occurs because some minerals can react to ANFObased explosives. Due to a high potential event that occurred in The Mine in 2013, The Mine and the Explosive Provider (“The Company”) are conducting a soil characterization of the areas containing reactive sulfides. This study was planned along with The Mine and it is being developed by a multidisciplinary team.

Jan 1, 2018

By R. Bridge

Mining companies are progressively finding themselves having to develop operations for more complex, deeper ore bodies, which require the use of more complicated mining and mineral processing methods. This coupled with the generally increasing trend of higher capital and operational costs have led to a need in the industry for improving ore body knowledge, mining and mineral processing. Geometallurgy is a relatively new concept that can link the three aspects, and when used effectively it is a method that can produce the necessary information for designing and building operations for reliable and optimum performance. Geometallurgy not only involves the integration of geological, mining, and metallurgical fields, but it can also be expanded to include environmental and economic information to produce a block model that can be used to obtain the best outcome in terms of plant response and plant sustainability. The geometallurgical program should not end once the block model has been populated. A detailed geometallurgical approach should be applied to all stages of the operation encompassing sample selection, through to equipment sizing and production forecasting. It can also become a useful optimisation tool thereby allowing the operation to be proactive rather than reactive against changes in the ore characteristics. With the development of metallurgical performance predictors it is possible to quantify how the ore will behave in the process plant in terms of throughput, recoveries, reagent consumption, etc. Therefore, in terms of responsible mining and sustainable resource development, a geometallurgical approach to operations is the logical step for plant development. In this paper we describe the state of the technology with respect to the application of geometallurgical modeling and its utilisation in the fields of design, forecasting and optimisation of mining operations.

Aug 1, 2013

By R. J. Boyd

SUMMARY The productivity of drill and blast methods of mining in hard rock is limited by the cyclic nature of the operation, and a plateau of performance has been reached, even with the most advanced equipment developments. Higher mine operating costs and lower metal prices have more than ever generated the need for breaking through these productivity barriers. After initial field testing The Robbins Company has designed and manufactured, on a joint venture basis with Mount Isa Mines, Ltd., Australia, a prototype "Mobile Miner" for continuous cutting of hard rock. This paper describes the cutting concept, the initial application of a completed 1,156 m (3792 ft.) long 14% decline, actual performance and delay analysis, developmental modifications, anticipated performances of a fully developed machine, and possible future applications. Sincere appreciation is expressed to the management of Mount Isa Mines, Ltd., for allowing access to the data used in this paper. The views expressed here are those of the author and not necessarily those of Mount Isa Mines, Ltd. INTRODUCTION A paper titled, "Design and Development of a Mobile Mining Machine", was presented by J.P. Kindsvater at the RETC, New York, in 1985. This paper described the evaluation of a test fixture in an andesite quarry near Seattle, followed by design, construction and

Jan 1, 1987

By A. F. Usov

The paper is concerned with an analysis of the experience gained in development of special electro-technical installations applied in electric-pulse destruction of materials. A principle scheme of an electric electric-pulse installation is given, and electric circuit variants of its blocks made on various element bases are discussed. Also assessed are some ideas to further improve the technical and economic characteristics of the equipment.

Jan 1, 2014

By Per Hedvall, Jan-Eric Ståhl

"The main objective of this study is to introduce the new Sandvik’s production cost-model within Crushing & Screening (C&S) technology. So far, there have been different ways of determining different production costs in the industry, however, the previously published and presented methods have not been very efficient in calculating the costs per product and metric ton. Accordingly, the current study has been planned and started in collaboration with Lund University to provide an accurate and easy to implement cost estimation program to determine the costs for crushing and screening plants worldwide.The proposed model has been adapted to fit the C&S processes of different rocks/ores fractions. The result is presented as cost per ton of the end product(s).Within this paper the cost estimation results for 3 different crushing and screening plants are presented based on the information obtained from the following sources: a) documents at Sandvik SRP, b) Sandvik’s crushing & screening internal/external machines/plants data and information, c) literature studies, including the use of Sandvik’s internal/external simulation and software programs, d), visiting the crushing and screening plants ,e) interviews, information systems’ data, and, f) testing and observations by ourselves.In order to improve the level of accuracy and the validity of the attained results, simplistic Monte-Carlo simulations have been used, where needed. The achieved results, so far, have proven the reliability of the model. The calculated cost estimations have shown an accuracy over 80% when they compared with real cost data obtained from plant practices.The current cost calculation model, will offer the possibility of:•,Calculating the production costs in proposed and/or existing C&S plant.•,Making detailed cost analyses for the end product(s) in proposed and/or existing C&S plants.•,Determining the profitability of each finished product when it’s required.•,Cost optimization by potentially cutting the cost for part of C&S plant with an existing plant practice"

Jan 1, 2016

By A. Ebrahimabadi

Roadheaders are very versatile excavation machines used in tunnelling, mine development, and mine production for soft to medium strength rock formations. Performance prediction is an important factor for successful roadheader application and generally deals with machine selection, production rate and bit consumption. Among many different parameters, brittleness is also one of the material properties related to breakage characteristics and can be used as a cuttability parameter from a mechanical excavation point of view. The main objective of the research study is to contribute the brittleness of rock excavated to construct a new empirical equation for predicting the performance of roadheaders in different material and operational conditions. In this regard, a new performance prediction model for medium duty roadheaders based on a brittleness index (BI) is presented. In this study, rock mass brittleness index (RMBI) is defined in order to investigate the influence of BI on roadheader performance. RMBI is an index which can be used to relate the intact and rock mass characteristics to machine performance. Results demonstrated that RMBI is highly correlated to instantaneous cutting rate (ICR) (R²=0.94). Moreover, through the further analysis and normalization, the pick consumption index (PCI) was introduced as a parameter having a good relation with pick or bit consumption rates (PCR) (R²=0.79). Finally, the new predictive models for ICR and PCR showed very good correlations with the actual measured values. Keywords Performance prediction, roadheader, brittleness index, mechanical excavation.

Jan 1, 2011

By E. D. Gardner

An explosion occurred in a high-pressure compressed-air line in October, 1930, at an Arizona copper mine. The explosion was unusual, and nothing had teor. noted by the plant operators to indicate the possibility of such an occurrence. It is necessar The air is The mining company uses compressed-air locomotives to haul about 4,500 tons of ore per day from the stopos to the pockets at two hoisting shafts. The ore cars hold five tons each, and are pulled in trains of 30 cars. to charge the locomotive with compressed air at both ends of the trip. conveyed from the compressors at the surface to the distributing points unier roun in special high-pressure four inch steel pipe that was tested to withstand 2500 pounds per square inch before being installed. The air is delivered to the loco- motives at a pressure of 1000 pounds per square inch. There are no receivers in the system. The air for running the locomotives is compressed by one three-stage and two four-stage compressors which have capacities of 600 and 300 cubic feet per minute, respectively. These machines are operated by electric power, and are in an end of the main compressor building in which air is compressed to supply the air drills in the mine. Whenever the demand decreases, as at the noon hour, one or more of the Compressors are shut down. On this particular occasion, at the end of the noon hour, one of the operators was approaching the high-pressure compressors to start the two smaller machines that were not running, when the explosion took place under the floor a few fost ahead of him. The man was mocked down and received some superficial cuts and bruises, but was not seriously injured. The floor was torn , the side of the building blown out, and holes imo cited in the roof some twenty feet above. The explosion was immediately followed by a fire which was quickly put out by the plant operators with hand fire extinguishers. At the time of the explosion the 600 cubic foot compressor was running alone, and the pressure in the system at the machine registered 1040 pounds por square inch. On examination it was found that two 6-fout sections of pipe, about tan feet apart, were completely ruptured into twisted fragments; the rest of the pipe line, apparently, was not injured. The destroyed sections were in that part of the pipe near the large compressor and above the connection from the two smaller machines. It is not definitely mom what caused the explosion. Explosions in other compressed-air systems have taken place, and, although of rare occurrence, have caused loss of life. Such explosions are not confined to high-pressure installations and several have occurred at plants compressing air te one hundred pounds per square inch, or less. plosions of this nature are not to be confused with the rupturing of compressor cylinders from excessive air pressure caused by the discharge valve being closed.

Feb 1, 1921

By Donald E. Meyer

High current-low voltage EB-gun evaporation in an oil-free ultra-high vacuum system was found to be necessary, though not sufficient, for stability (300°C, 106 v per on) of aluminium gate MOSFET's and MOS capacitors not stabilized by a phosphorous glaze. five characteristics of the equipment used: 1) Vacuum purification of the aluminum charge, 2) Ionization of the evaporant by the electron beam, 3) X-ray formation, 4) Residual gases during evaporation, and 5) Metal film structure were studied as Possibly significant in MOS fabrication. EVAPORATION of contact metals common to the semiconductor industry historically has been accomplished with oil diffusion pump systems and various resistance heated evaporant sources as dictated by the type of metal evaporated. To meet a need for greater reliability of semiconductor devices, other metallization methods were developed. A good example would be application of the moly-gold contact system to integrated circuits with deposition by RF or triode sputtering.' More recently, fabrication of stable metal-oxide-silicon devices and circuits has put new demands on metallization. The purity of the thin metal films composing MOS structures is critical, particularly at the metal-oxide interface, and ultra-high vacuum metallization using sputter-ion pumping and electron beam gun (EB-gun) evaporation are well suited for the task. At this laboratory aluminum has been the most common contact-gate metal for both MOS capacitors and MOSFET's. In the earliest work with MOS capacitors, aluminum was evaporated from wetted tungsten filaments using both diffusion pump and ion pump vacuum systems. In spite of clean oxide techniques these capacitors were unstable under bias-tempera-ture stressing. Only after a switch to EB evaporation of aluminum were stable capacitors produced. Using the same techniques it was possible to make MOSFET's with equivalent stability. Stability data for a discrete MOSFET is shown in Fig. 1. This is a "clean" oxide gate (no phosphorus stabilization or no etch back of a thicker gate) having a thickness of lOOO? thermally grown on the (111) plane. Gate length after diffusion was 0.24 mils, and the devices were hermetically sealed. Stressing conditions were 300°C and 106 v per cm applied alternately as a positive and negative field for 10 min, 50 min, and 4 hr for a total stress time of 10 hr. An initial shift in turn-on voltage of 0.1 v was detected for 10 min of positive bias. All evidence at this laboratory indicated that while EB-gun evaporation of ultra-high purity aluminum was not sufficient for 300°C stability, it did seem to be necessary. There may well then be something inherent in the EB-gun deposition used which enhanced stability, and probably no single factor existed but rather a series of factors. It is the purpose of this paper to report on some of the investigations carried out to learn more about EB-gun evaporation in ultra-high vacuum systems. EXPERIMENTAL DESCRIPTION The EB-gun was self accelerated, had a maximum power rating of 10 kw, and used a water-cooled copper crucible able to hold a 20-g aluminum charge. The electron beam was bent 180 deg and focused by an electromagnet which also provided movement of the beam across the crucible. Normal power conditions in this work were 9 kv and 300 to 600 mamp. The gun can be described as high-cur rent/low-voltage and was quite different in its mechanism of operation from EB-guns with much higher acceleration potentials. An oil-free vacuum system capable of 5 x 10- l0torr, a quartz crystal rate and thickness monitor and a quadruple mass spectrometer completed the evaporation system, Fig. 2. A typical evaporation cycle consisted of a 3 to 4 hr pumpdown to the upper l0-9 range and evaporation at l0? per sec with the pressure in the bell jar not rising above 1 x 10"7 torr. Thickness control was 5 pct or less and could be automatically monitored and controlled. Five phenomena associated with the EB evaporation and considered as possible contributors to Ma performance included a purification effect, ionization of evaporating aluminum, X-rays, constitution of vacuum ambient during evaporation, and film structure dependence upon evaporation rate. These phenomena are now discussed. Vacuum Purification. The design of the EB-gun permitted purification of the aluminum charge by vacuum outgassing. Particular features included an efficiently water-cooled copper hearth with a capacity of over 20 g of aluminum and the capability for sweeping the beam across the charge. Such capacity meant that aluminum had to be added only after about every fifth evaporation. A new charge was not required each evaporation as is necessary with filament evaporation. An oxide "scum" which appeared on the charge could be completely cleared from the top hemisphere of the charge by sweeping with the beam prior to opening the shutter. An indication of the purifying effect was obtained by a series of analytical measurements on incoming aluminum, after melting but with little vacuum out-gassing, after 30 min outgassing, and the evaporated film itself. Either a solids (spark source) mass spectrometer or an emission spectrometer were used for analyzing the aluminum charge. Analysis of the evapo-

Jan 1, 1970

By Marian Radetzki

The economic developments and industrial behavior patterns that led to a lasting excess capacity in the world non-ferrous metals industries from the aid-1970s are explored. Detailed attention is devoted to analyzing and defining crucial concepts like "capacity", "excess capacity", "capacity maintenance" and "investments". Empirical evidence of capacity utilization and capacity growth in the industries under study is provided. The coincidence of excess capacity and low prices on the one hand, and investments in capacity maintenance and capacity expansion, on the other, is seen as a consequence of substantial declines in the metal industries' investment and production costs during the period studied.

Jan 1, 1989

By Walter G. Kutschke

Four significant soil nail wall projects in the eastern United States were recently completed with a combined area of 175,000 square feet of finished shotcrete surface. These projects required the use of innovative design and construction methods in order to address various challenges, including slide-prone back slope materials, perched water, highly erodible rock materials, curved wall alignments, very tight construction tolerances and unexpected subsurface conditions. Special focus is given to issues such as bench excavation, soil nail installation methods, shotcrete mix design, anticipated shotcrete quantities, shotcrete nozzlemen qualifications and weather conditions, in order to provide a lessons-learned database for future soil nail wall design and inspector considerations. These projects also underscore the importance of design engineer and soil nail wall contractor qualifications as well as effective communication with the owner.

Jan 1, 2007

By Shiou-Chuan Sun

Notwithstanding the fact that unsaturated fatty acids are used in preference to saturated acids for most flotation purposes, information regarding their collecting properties is sketchy. Keck, Eggleston, and Lowry1 reported in 1939 that the collecting power of fatty acids on hematite decreased in the order of oleic, lauric, myristic, palmitic, and caprylic acid. Keck and Jasberg2 described in the same year that "unsaturated oleic acid with 18 carbon atoms was a better collector than saturated stearic acid" for floating magnetite. Gaudin and Cole3 stated in 1953 that the double bonds of oleic and linoleic acid were not oxidized during the flotation of fluorite, whereas the double bonds of linolenic acid were measurably altered even after one single flotation step. In August, 1953, Hukki and Vartiainen4 concluded that the collecting power of palmitic, oleic, linoleic, and linolenic acids on ilmenite, magnetite, pyrite, and rutile increased with an increasing number of double bonds in the acid molecules. This was subsequently proved to be generally true for the flotation of mapganese5, phosphate6, and magnetite7. The above cited literature indicates that, prior to the present paper, only about ten minerals were tested with pure unsaturated fatty acids as collectors.

Jan 1, 1959

By Andreas Stieben, Pierre Lutomski, Wolfgang Bleck, Martin Fischer

"For steel investigation and development, exact knowledge about the microstructural state is required. The information gained from 2D images often can't properly reflect the real 3D microstructural properties. In order to gain reliable information for meaningful models, simulations and correlations, it is necessary to accompany standard metallography with 3D information, which, unfortunately, is very difficult to access. This article presents a procedure for serial sectioning in combination with light optical microscopy. Only standard metallographic tools are employed in combination with image manipulation freeware. 3D microstructural data were extracted from three multiphase steel grades and in two cases virtual 3D-models of microstructural phases were generated.Three Dimensions Of MicrostructuresSince the invention of steel, craftsmen, inventers and engineers tried to improve its properties and tailor them to the requirements of new developments. For systematic development and enhancement of steels, the capability to investigate its inner structure is highly important, because it represents the linchpin between material production and properties. By having an in-depth understanding how production conditions form the microstructure and also how the microstructural state determines the material properties, steel design can be drastically improved. With this knowledge, microstructures can be designed to provide target material properties and process conditions can be identified that form these structures. Due to the key role of microstructure, the capability to gain accurate information about it is indispensable. It is the task of metallography to access and extract descriptive quantitative microstructural data like fractions, sizes, shapes and distributions of the different constituents. The most commonly used investigation tool in metallography is the light optical microscope (LOM). Besides this tool, additional high resolution techniques like Scanning Electron Microscopy (SEM) or Transmission Electron Microscopy (TEM) have become increasingly important. With these and other available methods, extensive information on the microstructural state of a material can be gained. Unfortunately, most metallographic methods have a major loss of information systematically built in. Analyses of microstructures are usually performed on surfaces, i.e. on 2D areas that emerge by cutting through the 3D material structure. This means, a complete dimension of information is not taken into account. How serious this reduction of information is and how it can affect interpretation of structures is exemplarily demonstrated in figure 1, which displays the planar structure emerging from a random cut through a simple 3D structure. It is very difficult to deduce or even imagine the original spatial structure from which this projection emerged and it is impossible to reconstruct it with absolute certainty without further information. The image has emerged from a random cut through a 3D structure of stacked cubes that is displayed in figure 2. The area shown in figure I is outlined. Although artificially constructed, this example demonstrates how distorted and misleading the view on structures can become by ignoring a spatial dimension."

Jan 1, 2012

By R. E. Brewer

Published investigations show that many different chemical reagents have been used in determining the constitution of coals , but only a few studies have been applied directly in evaluating the effects of such reagents on the carbonization products of coal , Most of the treatments have been so drastic that any permissible conclusions that may be drawn are inferential in respect to any favorable effects on the yields and composition of the usual carbonization products .

Sep 1, 1943

By Jon A. Hummer, Emanuele Cauda, George H. Schnakenberg, Aleksandar D. Bugarski, Samuel J. Janisko, Larry D. Patts

A series of engine/dynamometer tests was conducted to assess the effects of three types of uncatalyzed diesel particulate filters (DPFs), a diesel oxidation catalytic converter (DOC) and three types of high temperature disposable filter elements (HT DFEs) on the concentrations and size distribution of diesel aerosols and concentration of nitric oxides in underground mine air. Tests were conducted in the NIOSH Diesel Laboratory at the Lake Lynn Laboratory experimental mine, a facility developed to allow evaluation of these and other control technologies directly in an underground environment. The aforementioned technologies are evaluated by comparing the aerosol and gas measurements in the mine air 60 m downstream of the exhaust from a naturally aspirated, mechanically controlled engine fitted with the tested systems or muffler and operated at four steady-state engine speed and power modes. The tested DPF and HT DFE systems caused a 10-fold reduction in total mass concentrations of aerosols. The size distribution and number concentration measurements showed that all tested DPF systems and HT DFE elements effectively removed accumulation mode aerosols (D50>30 nm) for all test modes. An increase in peak number concentrations of nucleation mode (D50>30 nm) diesel aerosols is evident for some of tested DPF systems when engine was operated at high-load modes. The effects of uncatalyzed DPFs on nitric oxide (NO) and nitrogen dioxide (NO2) concentrations are found to be minor. A four-fold increase in percentages of NO2 in total nitrogen oxides (NOx) over baseline case was observed for the DOC when the engine was operated at high-load modes. The findings from this study should contribute to better understanding the potential for various control technologies to reduce exposure of underground miners to nano and ultrafine aerosols. In addition, detailed physical characterization of diesel aerosols made directly in occupational setting should foster a better understanding of the health risks associated with exposure to nano and ultrafine diesel aerosols.

By Solomons S. S, Tillmann V. H

The progress of longhole open stoping (LHOS) at Zinc Corporation Limited and New Broken Hill Consolidated Limited (ZC/NBIIC) is described together with the design of a novel sloped wall longhole stoping method which should allow the complete extraction of the orebody without the formation of pillars and with minimal dilution of the ore with sand fill.

Jan 1, 1981

By E. Mongilardi

The construction of large underground openings through cohesionless or weak cohesive soils and under the water table in particular, often requires a ground improvement to be done from the surface or ahead of the excavation face in tunnelling problems. To this purpose various injection procedures have been used in the past and new outstanding techniques have been developed recently, such as "jet-grouting", extending the feasibility range. The paper presents a review of basic principles and practical design criteria with particular reference to the newest trends of development. Case histories have been selected within the experience of specialist contractor Rodio Co. showing the variety of problems solved by manifold grouting procedures and layouts, in widely different soils ranging from the sandy-gravelly alluvia of Milan to the soft marine clays of Singapore.

Jan 1, 2010

By M. Sagheer

An 8.5-km (5-mile) conveyor has gone into operation in western Turkey to eco¬nomically transport crushed lignite from the mine area to a power plant. This conveyor has replaced trucks as the principal mode of transporting the lignite. One principal element of Turkish govern¬ment policy is the country's commitment to increase electricity supplies for mining and other industries. Lignite is an important source of electric power supply in Turkey. Production was about 48 Mt (53 million st) in 1987, amounting to more than 20% of the total power supply in Turkey. In the western Anatolia supply network, it plays a major role for power generation. Deposits are located in the Soma region of western Turkey. The lignite is of low quality, deposits are scattered, and the terrain is dif¬ficult and hilly. These conditions demand an economical and technically feasible method of transporting the raw material from mining areas to the central thermal power plant. The Soma power plant is located about 120 km (75 miles) northeast of Izmir, near the coast of Aegean Sea. An overland conveyor of a unique design has gone into commercial operation at the Soma power plant facilities of the Turkish state electricity organization, Türkiye El¬ektrik Kurumu (TEK). The conveyor re¬places truck transport to ensure economical use of the lignite deposits. Computer-aided design (CAD) added more precision, qual¬ity, and flexibility of engineering in design activities. It also helped quick realization of the project that was executed in cooperation with the German company Krupp Industri¬etechnik and the Turkish firm Gama Endüstri AS. Unique features The conveyor includes several major features rarely combined in a single flight: Overland long distance conveyor. • Horizontal curves. -Steep vertical concave and convex curves to match the difficult terrain. Down-hill conveying. Frequency converter drives with vari¬ able belt speed. Generating operation mode to backfeed the energy to the network. Layout The 8.5 km (5 mile) long conveyor takes the -200 mm (-8 in.) lignite from the primary crushing plant located near the mine to the central, final crushing plant located in the stockyard area near the power station. The drive and belt tensioning assemblies are situated near the tail end of the flight. The high voltage switchgear is housed in a room in the primary crushing plant build¬ing upstream from the conveyor flight. The frequency converters are installed in the low voltage switchgear room located below the control room within the primary crushing plant building. Conveyor design The conveyor includes two 4 km (13,120 ft) radius horizontal curves, one left-hand and the other right-hand. The minimum radii

Jan 1, 1989

By E. J. Meets, C. F. Meyer

Bord and pillar mining at shallow depth (400 m approx. maximum) is widely used in South African coal mines. One of the problems encountered in extracting coal in this manner is the ventilation of advancing bord and pillar headings. The traditional ventilation methods of force, exhaust and overlap (force/exhaust) are reasonably effective but tend to be both cost and labour intensive. Ducting often restricts the available free area of roadways thus impeding the transport of coal and other materials inbye the coal production section. Due to the above facts, ductless fans are currently being used to minimize the amount of ducting required in advancing sections. Two different types of fans are used, namely, vortex fans and the so-called `jet' fans. Vortex fans were developed from the fan blade design used for vertical take-off aircraft. The fans have the capability of delivering air over distances of about 30 m in the underground situation without any ducting attached to it. Jet fans are standard axial flow fans fitted with outlet reduction pieces which increase the velocity pressure at the discharge to such an extent that the air delivery distance is improved to almost match that of vortex fans. The paper describes some applications of both these fan types in advancing bord and pillar sections.

Jan 1, 1993

By William Gleason

"The city of Denver, CO has experienced extreme growth in the past decade, with the population of the city topping more than 700,000 people in 2018. The current storm water drainage system was put in place in the early 1900s and has not been able to keep up with the growth of the city.When it rains north and east of the city, the runoff goes toward the South Platte River. With the dense population and sometimes severe thunderstorms in the summer, the city has experienced significant flooding that not only endangers lives of residents, but some of the storms have caused millions of dollars of property damage.The Platte to Park Hill Project is a $298-million nearterm, four-phase solution to the flooding that includes the Globeville landing outfall; an open drainage project in the Cole neighborhood in north Denver; an area for temporary water detention and another temporary water detention in Park Hill.The largest and most complex phase of the project is the Globeville landing outfall — a $70-million box culvert project that includes a pair of 157-m (515-ft) long, 243-cm (96-in.) diameter storm water tunnels that pass beneath a busy rail yard with 17 tracks for the Union Pacific Railroad (UPRR) and two Regional Transportation District (RTD) commuter rail tracks. The tunnels, which were installed parallel to a pair of existing 243-cm (96-in.) tunnels, were designed by Brierley & Associates as a client of Merrick & Company for the City & County of Denver, and Bradshaw Construction constructed the one-pass tunnels.From the start, it was evident that the tunneling portion of the project would be the most challenging because of the rail yards.“It’s a little bit more complicated because the railroads have such tight restrictions for settlement,” said Rebecca Brock, Brierley’s project manager. “We had a lot of meetings with Union Pacific and RTD to figure out what are prescribed versus tolerable settlements.”“The portion extending beyond the UPRR under the RTD rails was challenging, as RTD is new to tunnel installations under its tracks,” said Lester Bradshaw, president of Bradshaw Construction. “The RTD tracks employed a unique foundation of continuous concrete with integral raised concrete ties on rubber bushings. Minimizing settlement to these tracks was a critical requirement.”"

Jan 9, 2018

By Jerry M. Whiting, Neil J. Duncan

"Does Canada need a mining industry? Isn't it a chronically depressed collection of businesses that pollute the air and water and tear up the countryside? Wouldn't it be better if Canada's investors devoted their attention to high-technology endeavours, tourism, and other relatively pleasant tasks?Probably the answer to whether Canada needs a mining industry in the 21st century is to look at the real mining industry that is in operation today. The facts indicate that mining is a very important contributor to Canada. It has certainly encountered some challenging times during periods of recession, and it face s severe and continuing problems of cost and competition in world markets. However, uneconomic mines have been closed, others suspended, and productivity has risen dramatically with employment at 77 000, down from 101 000 in 1981. The country's metal and non-metal mines, metallurgical plants and semi-fabricated metals industries employed an estimated 378000 workers in 1986, and paid wages than any other sector of the Canadian economy. This effort resulted in the production of 60 different metals, non-metals and structural minerals valued at $13.5 billion.The trade aspects of the mining industry are of paramount importance. If there is a reason for this situation to change during the next century. it eludes the authors. Canada has the well-developed expertise to discover, evaluate, develop, operate and profit from existing and new businesses based in an enormous area endowed with a nearly unbelievable variety of mineral resources. Many countries throughout the world must rely on producers like Canada, if they are to maintain and/or improve their standard of living."

Jan 1, 1988