Search Documents

By M. M. C. Lima, L. C. S. Solimani, M. A. Quintela

Galvanized steel scrap is recycled to B OF converters where zinc escapes from the bath and is captured by the gas control system, appearing in BOF sludge. As BOF sludge contain high iron content, it could be recycled, but due to its zinc content, it is disposed in landfills. In this study techniques were evaluated for zinc layer removal from scrap by sulfuric acid leaching. The effects of coating weight, temperature, time and sulfuric acid concentration were evaluated for three different galvanized scrap. The results showed that the behavior of each galvanized scrap was different. Nevertheless zinc removal efficiency was more than 80% with low dissolved iron in the leached solution.

Jan 1, 2011

By G. R. Guillet

THE LATE Dr. D. F. Hewitt, Ontario's foremost authority on industrial minerals, was the first to point out the importance of urban minerals when he produced figures (Hewitt 1968) to prove that the Toronto-Hamilton area was Ontario's second largest mining camp in 1966 (Fig . 1). In that year, the value of mineral production within a 60-mile radius of downtown Toronto exceeded individually that of Steep Rock, Kirkland Lake, Timmins, Manitouwadge and Elliott Lake. Only the nickel and precious-metal production of Sudbury .surpassed in value that of Toronto's pits and quarries. Although that position was unchanged for some years during the early sixties, it was admittedly an unusual situation: gold was still pegged at an artificially low value; uranium was stagnant; and Texasgulf had not entered the scene. However, the point had dramatically been made. The combined value of production from hundreds of sand and gravel pits and dozens of limestone and shale quarries was of formidable proportions. The mining industry of the urban fringe could not be denied. Construction aggregates, cement, building stone and bricks were fueling an apparently insatiable appetite for urban expansion and redevelopment.

Jan 1, 1978

By S. S. Dimov, B. R. Hare

This paper describes two micro-beam analytical techniques(Dynamic SIMS and TOF-SIMS) which have become an intricate part of a comprehensive analytical approach for precious metal (PM) ore characterization and process mineralogy or deportment studies. The value of the D-SIMS technique is its capacity for accurate analysis in the sub ppm range along with the ability to produce high resolution elemental maps. The TOF-SIMS is significant for speciating and quantifying preg-robbed Au on the surface of carbonaceous material. In combination with traditional assays, the two techniques can provide invaluable information regarding the distribution of PMs within an ore along with providing insight into potential sources of PM loss in processing or where losses have occurred in process streams.

Jan 1, 2011

By M. Reda

Erosion corrosion is acceleration in the rate of corrosion attack in metal due to the relative motion of a corrosive fluid and a metal surface [1]. The increased turbulence caused by pitting on the internal surfaces of a tube can result in rapidly increasing erosion rates and eventually a leak [2]. Engineers and scientists in different disciplines have worked for many years on methods of complete protection from flow induced corrosion or partially reducing corrosion of this type, and they have proposed or applied different countermeasures [2]. The accident at the Surry-2 nuclear power plant (USA) and other similar incidents have once again disturbed the scientific-technical community. This has forced the plant operating personnel and the management to undertake wide-ranging measures in order to discover on time, assess, and monitor such cases. In these extreme cases, protective coating and even metallic bulk material coating (the substrate itself) may suffer considerably from mechanically induced damage [2]. At high velocities, the "leaching out" dissolution reaction of particular, for example, steel elements at the solid-liquid interface become the rate determining step. One practical example for the difference between erosion corrosion and flow induced corrosion is the famous steam eruption from a Japanese [3, 4] nuclear power plant cooling system at the pressurized water reactor (PWR), turbine and in the condenser-steam generator connecting pipe. The rupture occurred in the carbon steel pipe connecting the condenser and steam generator. The damage occurred in the easily eroded/corroded carbon steel at a vulnerable location downstream of an orifice plate, In general, when there is significant reduction in pipe thickness through erosion/corrosion, distinctive patterns are visible, but those patterns were not observed in this case, Thus one can speculate that another phenomenon is possibly controlling, Fluid flow within pipes reduces the pipe thickness leading to an eventual rupture, The thickness reduction mechanism is erosion/corrosion, One example is "cavitations corrosion", Erosion and corrosion occur at the same time, and it is difficult to determine which one is dominant, Therefore, the term, "erosion/corrosion," is used [5]. In the atomic energy field, the terms "Flow Accelerated Corrosion" and "Flow Induced Corrosion" are also used. It is the purpose here to show that during flow induced corrosion a different mechanism may possibly be operating and in some cases it can be different from the well known erosion corrosion. Another example is fretting failures in early Canadian nuclear steam generators which was thought to be due to excessive vibration caused by high.

Jan 1, 2010

By N. Gharib, F. Hassani, P. Nekoovaght

"Novel rock breakage techniques are becoming more viable and attractive to industry. Microwave energy, as a thermal energy capable of inducing micro cracks through differential heating (therefore expansion) is a technology gaining considerable attention in mineral processing and ore comminution applications. Recently, the use of microwave radiation has been evaluated as a possible avenue for terrestrial and extra-terrestrial drilling applications as well as full face tunneling or rock breaking machines. As part of an overall research on use of microwave in rock breaking systems, the influence of microwave energy on the mechanical properties of common hard rock types as basalt has been investigated. The results revealed that microwave energy irradiation imposes micro and macro cracks to the surface of the rock being irradiated. In explosive free tunneling applications using TBM, jointed and cracked surface of rock eases the cutting process and increases penetration rate. The experimental setups have been simulated with the help of a multi-physics numerical modeling and the results have been compared with practical experiment. The wave propagation of microwave has been simulated and the distances where the power intensity is higher are identified. Experimental and simulation results underlined the potential impact of the use of microwave energy in underground or surface excavation applications such as mining and tunneling. This will also contribute economically when mine-to-mill operation is fully considered to improve the efficiency of rock crusher stages. INTRODUCTIONDuring hard rock breakage (i.e., separation of a piece of a rock from its parent deposit) in mining and civil applications, the performance of mechanical equipment such as tunnel boring machines (TBMs) is limited by high levels of bit wear and maintenance. Preweakening natural rock prior to breaking it by machine is one approach to lower bit wear and maintenance costs. Some preweakening methods apply heat directly or indirectly. For example, flame torch-assisted TBMs (Lauriello et al., 1974; Resource Technology, 1984) have been deemed economical in terms of equipment, but their feasibility is limited by high fuel consumption. Microwave energy could offer several advantages over the flame torch method: it does not produce emissions or increase fuel consumption (electricity source is available on the machine), and is easy to control (quick power on and off)."

Jan 1, 2015

By Chris Dougherty

"This presentation will provide a demonstration of the methodology used in designing a modern shaft and hoisting plant utilizing a review of the challenges faced and solutions delivered for the Elk Creek Superalloy Materials Project (Niobium/Scandium). The development of the design required the review of complex hydrogeological conditions, mine production requirements, demanding capital expenditure (CAPEX) limitations and tight schedules. Through an extensive review of various alternatives to satisfy these constraints, the Nordmin Group (including Nordmin Engineering Ltd.) (Nordmin) was able to define a concept and design that addressed risks to the project, met production requirements, cost and schedule constraints and improved constructability. INTRODUCTION The Elk Creek Project, owned by NioCorp Developments Ltd. (NioCorp) presently, will become Nebraska’s first underground metals mine, built to access the Elk Creek Niobium/Scandium deposit. The development of the design for this facility required the review of challenging hydrogeological conditions, mine production requirements, demanding CAPEX limitations and tight schedules. Through an extensive review of various alternatives to satisfy these constraints, the Nordmin Group was able to define a concept and design that addressed risks to the project, met production requirements, cost and schedule constraints and improved constructability. This paper will review the challenges faced, and solutions arrived at in a demonstration of a methodology used in designing a modern shaft and hoisting plant. THE CHALLENGES Nordmin became involved in the project in 2015, invited by the Feasibility Study Consultant to provide input on estimating and layouts for the new operation. Many of the fundamental decisions regarding mining methodology, water handling and production strategy had been made, and the scope of Nordmin’s involvement was very limited in this first engagement. Following submission of that study in late 2017/early 2018, Nordmin had opportunity to discuss the overall effort, and its many assumptions and challenges, with NioCorp’s project team. The dialogue quickly identified several significant opportunities to improve the project construction schedule and costs along with the mine production profile and operational approach while reducing project risk."

Jan 1, 2019

By S. Esfahani, M. Barati, Y. Kauwachi

"Heat recovery from slag has gained attention due to its high potential in lowering energy intensity of metal extraction processes. A direct method to recover the thermal energy of slag is to use countercurrent air flow that extracts the heat from falling droplets. Often, the solidified slag is aimed to be used as a substitute for Portland cement, thus high cooling rates are required to form an amorphous slag with sufficiently strong hydaulicity. Rapid cooling however involves using large gas flow rates that in turn lower the thermal efficiency of the process. This article presents a mathematical model that was developed to determine the optimum conditions in the heat recovery process and to investigate the effect of the air flow and granule diameter on the cooling rate of the droplets as well as the thermal efficiency of the heat recovery system. INTRODUCTIONMetallurgical slags are the largest by-product of high temperature materials refining and extraction processes. The total amount of metallurgical slag produced in the year 2008 has been estimated at up to 422 million tonnes containing up to 222 TWh/y (Barati and Esfahani, 2011) of thermal energy. Over the past four decades attempts have been made to recover this substantial amount of energy as heat, electricity, or fuel, while none of the proposed method has been commercialized yet.During slow cooling the slag tends to crystallize the constituents (CaO, SiO2, Al2O3, etc.) into a hard, heavy solid. In the past, over 90% (Bengt, 1983) of the molten waste was discharged onto heaps and allowed to cool slowly, then crushed and used in road construction or land filling or as coarse aggregate for concrete. However, later it was found if cooled rapidly, the slag can be used as a substitute for Portland cement. As a result, processes such as wet granulation were created in which molten slag is fragmented with water, forming amorphous (glassy) phases. Despite its effectiveness in producing a suitable material, heat would not be recovered through this process. Thus, dry granulation was introduced in 1930’s and was developed further in 1970 – 1980’s."

Jan 1, 2012

By M. Mai Manga, M. Renaud, A. Faucher, C. Bazin

ABSTRACT Grinding circuits are operated in the presence of disturbances resulting from ore changes and equipment malfunctions, such as hydrocyclone overloading, worn or partly plugged apexes, surging, and internal liner detachment that may cause a loss of classification performance. Metal recovery losses in downstream leaching or flotation circuits justify the development of methods for rapid detection of hydrocyclone malfunction. Two methods are presented in this paper. The first method uses measurements from sensors available in a grinding circuit and the second uses vibration sensors installed on the individual hydrocyclones of a nest.

Jan 1, 2011

By J. F. Liu, L. Chen, C. P. Wang

"Calcite-cemented joints abound in the rock masses of Beishan area, which is the most potential area for the high-level radioactive waste (HLW) disposal of China. The mechanical properties of Beishan granite containing a calcite-cemented joint with a dip angle of 82° was investigated under uniaxial compression and the acoustic emission (AE) characteristics were also studied in this paper. Compared to intact granite, the calcite-cemented joint caused a decrease more than 50% in uniaxial compressive strength and a decrease more than 90% in shear strength. The Young’s modulus was also decreased, while the circumferential deformation of jointed granite was sharply increased. The AE monitoring system successfully recorded the process of micro-crack development and the results indicated that the risk of rock-burst could be reduced due to the appearance of calcite-cemented joint.INTRODUCTIONThe properties of jointed rocks differ considerably from that of intact rock. Due to the difficulties in specimen preparation, analogue experiments with artificially prefabricated fractures are often used to study the mechanical behavior of jointed rock (Chen et al. 2012; Kulatilake et al. 2001; Singh et al. 2001). However, natural joints are not quite similar to the artificial fractures and it is necessary to investigate the mechanical behavior of jointed rocks. Xie et al. 2011 studied the mechanical properties of marbles with natural joints by uniaxial compression tests and found that the uniaxial compressive strength of jointed rock is greatly decreased. With the unaxial compression tests, Jacobsson 2005, 2007 tested the intact and jointed granites, which were taken from the potential site for high-level radioactive waste (HLW) disposal of Sweden. However, no significant difference in strength or modulus was found. The above research results are inconsistent and it indicates the complexity of the mechanical properties of natural joints."

Jan 1, 2015

By L. Chunpongtong

One of the challenges of mine planning is to determine the most cost-effective replacement time for aging equipment. The lifespan of equipment, such as haul trucks and shovels, deployed in mining operations varies due to the nature of the material and ground conditions in which it operates. For engineering economists dealing with aging equipment, the options become an economic trade-off between higher maintenance cost versus the cost of new equipment. The discount rate plays a significant role in this decision; the higher the rate, the longer the economically optimal lifespan. Therefore, the ultimate question is: ?How can the relationship between the discount rate and the economically optimal lifespan be expressed mathematically??

Aug 1, 2013

By G. V. Theja, V. B. Maji

Large infrastructure projects like tunnel excavations, underground constructions face innumerable risks. For successful completion of these projects, it is essential that we foresee and understand risks that could occur during different phases of the project. One of the risks affecting underground excavation projects is the inaccurate performance prediction of TBMs. As this could severely affect the project, resulting in lower advance rates and could also result in changing the excavation machine or method, due to difficulties in excavation, thereby increasing the overall cost of tunnelling. This makes performance prediction of the TBMs as one of the crucial aspects in tunnelling, as a precise estimation of its performance is required for planning and estimation of time and cost of the tunnelling projects. This performance prediction of TBM is a challenging geotechnical problem that is intricate and complex in nature, this is possibly due to the fact that TBM performance prediction involves understanding the rock fragmentation process in wide range from micro-scale (i.e. the interaction of surface of rock material and cutter tip) to macro-scale (including the interaction of rock mass and TBM). Thus in order for the performance prediction model to be efficient, parameters of both TBM specifications and ground conditions have to be considered. Various models have been proposed by researchers since the early phases of TBM application, these studies resulted in the development and improvement of numerous penetration prediction models. Most of these models consider the geotechnical parameters that are input to the model to be consistent along the TBM drive and neglect the uncertainties in parameters that occur. And so to improve the predictive capability of these models and to incorporate the above uncertainties, the penetration rate is modeled as a stochastic variable depending on the geotechnical and TBM parameters, its statistical distribution is determined and is used to characterize the penetration rate instead.

Jan 1, 2015

By A. R. MacLean

This mine is situated at Point Aconi, Cape Breton , Nova Scotia, and is a replacement for the 100-year-old Princess Collie ry. It is a slope mine which is the continuation of a s trip mine operation. There are fives lopes from the surface driven with Dosco Dintheaders - this marks the first time these machines were used in North America. There are four room -and-pillar sections, each equipped with a Lee Norse HH106 continuous miner, a "Top Dog" roof bolter and two Wagner diesel Teletrams. There are also two Eimco 913 diesel LHD's , which are used for clean-up in the mines. This paper describes the mining operations of this 800,000-tpy mine which, in less than a year and a half , has been developed to the stage where four sections are producing coal at the desired rate.

Jan 1, 1978

By Rolf Andreas Lauten, Yanhong Wang, Yongjun Peng

"In mineral flotation, bentonite as a kind of clay mineral imposes deleterious effects on the flotation of valuable minerals, possibly through its ability to increase the pulp viscosity. A higher viscosity lowers the amount of froth and affects the bubble-particle collision frequency. A previous study found that adding gypsum to a bentonite-ore mixture lowered the viscosity, possibly by inhibiting the formation of interconnected network structures. In this study, sulfate as an anion with different types of cations, Na+, K+, Mg2+ and Ca2+ were used to reduce bentonite viscosity and to improve flotation performance. It was found that at the same concentration, MgSO4 was the most effective salt in reducing bentonite suspension viscosity, while CaSO4 was not as effective likely due to the lower solubility of CaSO4. Na2SO4 and K2SO4 reduced bentonite suspension viscosity at high concentration. Flotation kinetics of ore blended with bentonite was increased with increasing the electrolytes concentration, which generally correlated with the reduction of bentonite viscosity. Meanwhile, significant discrepancies were found between flotation results and rheological measurements in the presence of monovalent ions. It is indicated that the morphology of bentonite aggregates in electrolytes solution is likely to influence the hydrodynamics in the froth zone.INTRODUCTIONClay is present in many ore bodies as a gangue mineral. Presence of clay presents several challenges in the processing of valuable minerals. They are soft compared to valuable minerals, which means that during grinding of the ore, clay particles are likely to obtain a smaller particle size than the valuable mineral. Often clay particles may be within the colloidal size domain (<20 µm). The smaller size increases the probability of entrainment in the concentrate. Another challenge is their anisotropic charge distribution, where depending upon the pH, edges (E) and faces (F) carry charges of opposite sign. This facilitates formation of aggregation structures that may impede percolation of bubbles through a froth, but also increase the viscosity more than expected from the mere change in volume fraction. In addition to lowering the froth mobility, a high slurry viscosity will have implications for the gas dispersion in the flotation column as it affects the dispersion of the suspended particles, and it modifies the bubble-particle collision rate and attachment efficiency (Bakker, Meyer, & Deglon, 2009; Shabalala, Harris, Leal Filho, & Deglon, 2011). A pragmatic approach to this problem is to blend high clay ore with ore of lower clay content, reducing the overall clay concentration. Alternatively, one may lower the solids content of the flotation slurry to counteract the viscosity-building properties of clay. While feasible, this approach has the disadvantage of increasing required flotation volume, and it also affects the properties of the froth. Thus, there are currently limited options in lowering the impact of clays and their tendencies to increase viscosity in flotation slurries."

Jan 1, 2016

By D. Furrer, M. Dallaire

The arrival of Image analysis in the last 20 years has changed the world of quantitative metallography. Many standard measurement techniques which were previously manual can now be done with fully automated systems. This reduces subjectivity and operator fatigue and therefore enhances the quality of the statistical results. In many laboratories, Titanium Alloy microstructures continue to be evaluated by traditional methods, where quality of results is subject to operator fatigue and level of experience. Advances in Camera technology have tremendously improved image acquisition. One can often see clearly at 500x what can not be observed at 1000x, allowing for a larger area to be analyzed, without the inconveniences associated with very high magnification objectives. Powerful and versatile Image analysis software combined with a high precision motorized stage gives access to a multitude of applications, which were extremely challenging or impossible until now. Image Analysis tools such as Multilayer Grab, which reconstructs an uneven image into one plane of focus (ex. Observation at high magnification of texture resulting from etching) and Mosaic which builds an image from a number of fields of view (ex. Reconstruction of very large grains at low magnifications) expand even further the power and flexibility of IA systems. This presentation will describe how automated methods are applied to the point count method and grain size measurement. We will show how cameras and software work together to permit quantitative measurements of primary alpha and prior beta microstructures, as well as lamellar alpha plate thickness in titanium alloys.Automated and semi automated quantitative measurements of various Titanium microstrures have been assessed, using the Clemex Vision PE. Examples of the methods and steps used are presented.

Jan 1, 2006

By Xiu-Xiang Tao

This study investigated bio-liquefaction of lignite and its model compounds of thymol, bezioc acid and quinoline by a fungus, Hypocrea lixii AH. It analyzed, during bio-liquefaction, enzyme activity of oxidase, LiP, Lac, MnP and polyphenol oxidase, and degradation products by UV-Vis, FTIR, 13C NMR and GC-MS. The results showed that the bio-liquefaction percentage (by mass) of lignite was up to 44.86 %. The bio-liquefaction products of lignite were mainly aniline, amide, ether, carboxylic acid ketone and ester. The aromatic ring number was 1-3 with an aromatic carbon ratio of 0.328, which indicated rings opening, bonds breaking and oxidation reaction. By considering with the enzyme activity analysis results, it showed that LiP and Lac catalyzed reactions to open aromatic cycles and to break bonds; esterase to break ester bond; and peroxidase in oxidation reaction.

Aug 1, 2013

By A. Aftabi

To evaluate geochemical aspects of sheared zones, 35 samples of granitoid rocks from an area of shearing >5 km2at Derehamzeh, Iran were studied geochemically. Relatively unaltered samples within the shear-zone area average 38 ppm Cu, 1.45 ppm Mo, 4.6 ppb Au, 0.21 ppm Ag, <1ppm Re, 46 ppm Zn, 28.5 ppm Pb, and 0.34% S. Bleached, hydrothermally-altered samples areanomalous in Cu (>896 ppm), Au(>59.5 ppb), Ag(>24.4 ppm), Re(>1.28 ppm), Zn (>164 ppm), Pb(>218 ppm), and S(>0.9%). Some samples from bleached sheared zones that are highly anomalous in Cu (5000 ppm), Mo(23 ppm), Ag(74 ppm), and Au(200 ppb) are characterized by a typical sericitic alteration assemblage consisting of sericite, pyrite, chalcopyrite, and granular quartz. The main anomalous zone extends over about 0.4 km2in the southern part of the area. The strong Cu-Mo-Au-Ag association in the sericitic shear zones suggests a possible relationship to porphyry cop-per mineralization, similar to that found in northern Chile. Further studies on drill-core samples in the southern sericitized shear zones are required to determine if more extensive porphyry-type sul?de mineralization is present.

Jan 1, 1997

By A. J. Hargraves

"It is difficult to quantify comparatively the gassiness of a property. The most common index to gassiness, cubic feet of gas per ton of coal mined, is very arbitrary and does not take into account the geological setting nor the mining operation. The gassiness of a virgin coal in situ can be assessed, but no method is precise and the most accurate methods involve prolonged field and laboratory experiments. In general, gassiness increases with depth. Whereas 'gas' normally implies methane, other gases such as nitrogen, carbon dioxide, etc. may be present in seam gas also. The inflammability of methane is a problem, particularly the explosibility of a methane-air mixture; also oxygen dilution is involved in high gas concentrations and some gases are poisonous even in low concentrations. Cross measuring into a virgin seam is usually not as troublesome as development in the seam, where narrow openings may require strong ventilation to dilute gases exuding from the face and sides. Total extraction presents problems of gas from the working seam, or from adjacent seams, particularly at the return side, or of gas-laden air from the goaf streaming out or sometimes surging out intermittently, again on the return side. In pillar extraction or longwall retreating special roadways may be required to allow the side-to-side and end-to-end flushing of the goaf which is somewhat inherent in longwall advancing. Layering may occur, particularly where ventilation conditions are not brisk. Outbursts of gas from adjoining seams may be induced by sudden rupture of roof or floor in caving workings. Outbursts of coal and gas from the working seam may occur, mostly in development work, under special environmental circumstances. Gas problems may be reduced or eliminated by predrainage of gas ....:. rarely successful from the working seam - usually undertaken from adjoining seams prior to escape of gas released by caving. The ideal solution - general predrainage of gas to the surface from measures prior to mining - has yet to be accomplished. • In the planning of gassy mines it is possible to make an assessment of gas contained in the seams and to estimate what proportion will be released into the mine air, but emission of gas into mine workings is never steady and at present there is no better planning criterion than experience at the mine next door!"

Jan 1, 1973

By J. L. Feng, F. Zhang, S. K. Hu

"Cracking is one of the most serious damages in tunnel linings, which is often observed by in-situ inspection to tunnel engineering. It is difficult to better characterise for the deformations from continua to discontinua by the traditional continuum mechanics due to emerging of crack initiation, crack propagation, and coalescence, at several scales. In this paper, the process of failure that was from micro damage to macro crack in concrete tunnel linings under experimental load conditions, was quantitatively simulated by the combined finite-discrete element method (FDEM). Comparison of the simulating results with that obtained by the full-scale test of concrete lining under different loading conditions in the literature was respectively good agreed and shows that such FDEM technique is appropriate to model the continuousdiscontinuous problems. The present study indicates that the FDEM technique could be benefit to quantitatively evaluate the stability and damage level of tunnel lining system. INTRODUCTIONMost damage to tunnel linings is caused during the construction phase, which can emerge in a form of single macro cracks or even large-scale spalling. The cause of such damage is mostly the occurrence of, either impermissibly large contact stresses resulting from high thrust loads combined with production and installation tolerances in the segments resulting in a geometrical lack of fit (Maidl et al., 2012; Transportation Research Board, Basic Research and Emerging Technologies Related to Concrete Committee, 2006), or unallowable tensile/shear stresses appearing in the tunnel linings under complicated loading conditions (Ansell, 2010). Such a macro failure phenomenon may also be regarded to as a result of growth, coalescence, initiation of microcracks in tunnel linings due to the complicated loading action, and even potentially lead to an instability or collapse of the local or entire tunnel system. Much work has been devoted to investigate for the characters of micro and macro cracks, the influence factors of damage patterns, the settlement of a tunnel, the width, length and density of lining cracks, especially from classifiedly and qualitatively (Wang, 2010; Huang et al., 2013). However, the safety evaluation of tunnel is definitely required to not only inspect in situ, but further also quantify computing and analyzing for tunnel lining systems, so as to provide a global viewpoint of process of the tunnel deformation, which aims to help for subsequent decisions, e.g. controlling traffic flow or immediately repairing task. Additionally, the design of lining thickness and its structural analysis that is mostly determined by previous experience and similar construction examples is also needed to be improved."

Jan 1, 2015

By Nathaniel S. Scott

Caland Ore Company Limited, a subsidiary of Inland Steel Company of Chicago, Illinois, leased an iron ore deposit from Steep Rock Iron Mines Limited on January 1, 1953.. This deposit lay underneath a lake and was covered with 161,000,000 cubic yards of Jake bottom material, mainly silt. Removal of this material was done on a contract dredging basis. This contract was divided into a plant phase and an operating phase. The plant phase consisted of supplying two cutter-type suction dredges, each with two booster pumps in the discharge lines. All six pumps were centrifugal, had 36" discharges and were powered by 10,000 horsepower electric motors. Peak demand was 59,157 kilowatts. One hundred and forty miles of steel tower line were built to bring power to the site. The balance of the plant consisted of tugs, 12 miles of discharge line, varying from 36" diameter to 42" diameter and attendant land-based equipment. A number of interesting dams were constructed

Jan 1, 1961

By T. T. Wang, T. H. Huang, Y. C. Chiu

Quantitatively analyzing deformation of a tunnel with lining anomalies for structural safety evaluation is essential for sustainable tunnel engineering. However, a complete theory and associated methodology accounted for displacement of a built tunnel is absent. This manuscript introduces a novel characteristic matrix method proposed by the authors which is an integrated procedure that analyzes displacement of rock tunnels in operation. First, establish a numerical model expressing a specific state of the tunnel in interest. Derive the characteristic displacement modes by a unit disturbances and check their independency. Once the characteristic displacement modes are proved to be orthogonal (independent), they are ready for use. Given a tunnel displacement, modal decomposition returns the magnitude of each characteristic displacement modes that together consist the given displacement. By realizing the definite value of horizontal and vertical translation, rotation, uniform compression/expansion, elliptic deformation, triangular deformation…etc. for a tunnel displacement, one can distinguish tunnel displacement and deformation types from their modal composition. A circular tunnel with elastic structure and surrounded by elastic rock mass is chosen to demonstrate the outcome of characteristic modes and how they work. The influences of tunnel shape, elastic modulus ratio between rock mass and tunnel structure, and numbers of monitoring points on a tunnel profile were also discussed. Identifying possible tunnel deformation causes is attainable if further connections between mode combination and force increments were built.

Jan 1, 2015