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By G. Meschke

"This paper reports on computational and experimental research, performed at the Collaborative Research Center “Interaction Models for Mechanized Tunneling” at Ruhr-University Bochum, Germany. Research covers a broad spectrum of topics relevant for mechanized tunneling in soft soil conditions. This includes advances exploration methods and models for the characterization of the in-situ ground conditions, the interaction of the face support and the tail gap grouting with the porous soil, multi-scale models for the design of fiber reinforced segmental linings with enhanced robustness, computational methods for the numerical simulation of the tunnel advancement, the soil excavation and the material transport in the pressure chamber, logistics processes and risk analysis in urban tunneling.INTRODUCTIONMechanized Tunneling has proven itself as an economical and flexible construction method that continues to undergo a dynamic evolution process. Shield diameters continue to increase, and the application range of tunnel boring machines is being extended to an ever-increasing variety of geotechnical conditions. In order to maintain economic viability and to ensure an environmentally friendly construction process, realistic and reliable numerical models are required in order to make informed decisions during planning and construction. To provide a reliable numerical prognosis, it is necessary to accurately assess and understand the interactions between the components involved in mechanized tunneling with the surrounding site, the ground, and any pre-existing structures. Heterogeneous geological conditions and often only approximated ground parameters create, in contrast to other engineering projects, special demands. This necessitates new insights to new problems that can only be effectively solved through truly interdisciplinary research. To address these challenges, the German Research Foundation (DFG) has established the Collaborative Research Center “Interaction Models for Mechanized Tunneling” (SFB 837) at the Ruhr-University in Bochum in 2010. Collaborative Research Centers are interdisciplinary scientific research groups in which cooperative research is conducted under the umbrella of a central research theme. With a research budget of ca. 10 Million Euros for the second 4-year funding period, and a research team composed of 13 project leaders along with approximately 35 scientific assistants the SFB 837 is currently one of the largest research groups conducting fundamental research in tunneling related topics worldwide.RESEARCH TOPICSThe research topics of the SFB 837 encompass a number of relevant planning and construction related aspects in mechanized tunneling (Figure 1). These research themes are each supported by computational models and laboratory investigations and are all included in an SFB overarching Tunnel Information Model (TIM). Interaction groups integrate and combine the results of different submodels through prototypical cause-and-effect relationships, and through the analysis of the Wehrhahn metro line (WHL) project in Düsseldorf, which has been adopted as the reference project for the SFB 837."

Jan 1, 2016

By Jeffrey D. Smith, William G. Fahrenholtz, Jose M. Soto

Interactions between A356 aluminum (Al-Si alloy) and dense fused silica (FS) riser tubes used for low-pressure casting of aluminum alloys were evaluated using a sessile drop approach. The tubes have a short service life, but cost and thermal shock resistance make them an effective solution. The main problem encountered during use is the reaction of aluminum with silica to form alumina and silicon, which causes failure. Tests have been conducted on as-fired (uncoated) and modified (coated) tubes. Experiments were carried out in a horizontal furnace at 1225°C under argon to minimize the effect of the aluminum oxide on the interactions at the alloy-silica interface. Images of the drop were acquired and contact angle values were estimated for uncoated and coated samples, but no significant differences in the contact angles were observed. Scanning electron microscopy revealed the presence of cracks at the interface between the reaction zone and the unreacted silica. The presence of reaction products (silicon in the reacting alloy and aluminum in a reaction zone between the alloy and the unaffected silica) has been confirmed using energy dispersive spectroscopy. A two layer coating system was found to be effective in reducing penetration of the aluminum alloy.

Jan 1, 2004

By Y. Akin, M. Hancer, M. S. Celik, J. D. Miller

Flotation pulps with boron minerals such as colemanite and borax using primary amine collectors, e.g. dodecylamine, exhibit collector precipitation above a critical pH depending on the amine concentration. This was earlier attributed to the formation of a mine hydroborate. However, results from this current study indicate that the precipitate is dode-cylamine, rather than dodecylamine hydroborate. A systematic study involving solubility, zeta potential, microflotation, adsorption, and surface tension measurements is presented to elucidate the role of a mine precipitates in boron flotation systems.

Jan 1, 2000

By Felicia F. Peng

In operation of column flotation of fine coal, the smaller bubbles are required to effectively recovery of fine hydrophobic particles. However, smaller size bubbles alone does not ensure an efficient flotation for fine particles. The sufficient available bubble surface area per unit column are essential for effective column flotation. The experiments are conducted in a lab-scale column using two different bubble size distributions and three different particle size distributions for flotation of Pittsburgh No.8 seam coal. The interaction between particle size, aeration rate, feed rate and wash water addition are examined in this investigation to establish the optimal operation conditions for flotation of fine coal. Despite of wide range of operation conditions used in this study, it is found that the experimental data fall in a single characteristic recovery-ash curve for a given bubble size distribution and particle size distribution. The major parameters affect the flotation performance points along -the characteristic recovery-ash curves are aeration rate/frother dosage, feed rate and wash water rate-.

Jan 1, 1994

By A V. Nguyen

Spherical calcium dioleate particles (~10 ¦m in diameter) were used as AFM (atomic force microscope) probes to measure interaction forces of the collector colloid with calcite and fluorite surfaces. The attractive AFM force between the calcium dioleate sphere and the fluorite surface is strong and has longer range than DLVO (Derjaguin-Landau-Verwey-Overbeek) prediction. The repulsive AFM force between the calcium dioleate sphere and the fluorite surface does not agree with the DLVO prediction. Consideration of non-DLVO forces, including the attractive hydrophobic force and the repulsive hydration force, was necessary to explain the experimental results. The non-DLVO interactions considered were justified by the different interfacial water structures at fluorite- and calcite-water interfaces as revealed by the numerical computation experiments using molecular dynamics simulation.

Jan 1, 2005

By Marcelo B. Mourao

Interactions of carbonaceous materials with liquid Fe-C melts have been investigated experimentally by determining the volatile yield due to rapid devolatilization (Flash Pyrolysis) and rates of dissolution at temperatures ranging from 1623 to 1873 K. The volatile yield increased with increasing the temperature. The comparison of results of different types of carbonaceous materials was possible by expressing the volatile yield in terms of Enhancement Factor, fE. The rates of dissolution of spectroscopic graphite and an industrial coke seemed to obey the correlation for natural convection under turbulent conditions. The experimental data for the graphite suggested that the rate of dissolution was controlled by the mass-transfer in the liquid boundary layer adjacent to the solid sample. The value for the empirical parameter correlating the dissolution coefficient and the operating variables was found to be 0.19 which was close to that reported in the literature. The comparison of the results obtained for the coke samples with those for the graphite revealed that the impurities and the porosity of the samples can effect the dissolution rates.

Jan 1, 1992

By R. Perez

The consumption of grinding media forms a significant part of the operating cost of a mineral processing plant. An estimated half billion pounds of steel in the USA and over one billion pounds in the world are consumed each year in wet grinding alone. However, there is some conjecture as to the interacting roles of abrasion and corrosion. In order to provide a more complete picture of the conjoint action of abrasion and corrosion, marked ball tests were conducted on different grinding ball compositions in a laboratory ball mill and the metal losses were measured on varying the conditions, i.e., pH, PO2, in wet grinding a Cu-Ni gabbroic rock and compared with taconite grinding. Ball wear rates ere discussed with respect to ball composition and microstructure and the varying conditions used in the grinding tests.

Jan 1, 1984

By Allen J. Sobczak, Peter J. Peters

The five tunnel contracts of Milwaukee Northeast Side Relief Sewer System are about 80 percent complete. The tunnels are all excavated for 1.9 meter (6'-0") finish diameter sewers in a variable rock, mixed face, and glacial soil environment. Different contracts were let under two primary types of specifications, performance and prescriptive, which treated aspects of construction, such as primary ground support and groundwater control, differently. Interfacing of design and construction through field personnel allowed the needs of all parties to be met and resulted in savings in time and money to the Milwaukee Metropolitan Sewerage District (MMSD). Interfacing, cooperation and risk sharing allowed resolution of problems such as line and grade variations and potential differing site conditions. It also allowed the parties to pursue constructive changes to construction activities. Thus on one contract prescribed use of compressed air was eliminated, but migration of fines into the tunnels was stopped with filter fabric. Use of an expensive primary support system was dropped, but concern about deterioration of lagging was alleviated by use of special materials.

Jan 1, 1983

By Q. G. Reynolds

The presence of dust and fume suspended in the freeboard region is a common feature of the operation of direct current (DC) plasma smelting furnaces. This occurs primarily as a result of the use of fine feed materials together with the open-arc, open-bath operation of such smelters, and is exacerbated by the high velocities and turbulent mixing of the gas in the vicinity of the arc jet. Dust and fume losses into the furnace off-gas system can be significant in some cases and may have economic, operational, and environmental impacts on the process. A computational modelling study is presented in which the concentration of dust material was considered as a continuous field subject to a governing partial differential equation. Settling behaviour was calculated as a function of particle size, local gas/plasma temperature, and other physical properties. Development of the coupling between the concentration field and a magneto-hydrodynamic description of the arc is shown, and the resulting models were used to compute various aspects of the behaviour of the concentration field in the arc region for a variety of furnace conditions. Time-averaged as well as transient models of the arc were used to generate the results presented. Qualitative case studies produced several practical suggestions for furnace operation, including increased dust capture by the bath when feed ports are located closer to the electrode, and the possible effects of feed segregation in the furnace freeboard based on dust particle size and density.

Jan 1, 2014

By Q. G. Reynolds

The presence of dust and fume suspended in the freeboard region is a common feature of the operation of direct current (DC) plasma smelting furnaces. This occurs primarily as a result of the use of fine feed materials together with the open-arc, open-bath operation of such smelters, and is exacerbated by the high velocities and turbulent mixing of the gas in the vicinity of the arc jet. Dust and fume losses into the furnace off-gas system can be significant in some cases and may have economic, operational, and environmental impacts on the process. A computational modelling study is presented in which the concentration of dust material was considered as a continuous field subject to a governing partial differential equation. Settling behaviour was calculated as a function of particle size, local gas/plasma temperature, and other physical properties. Development of the coupling between the concentration field and a magnetohydrodynamic description of the arc is shown, and the resulting models were used to compute various aspects of the behaviour of the concentration field in the arc region for a variety of furnace conditions. Time-averaged as well as transient models of the arc were used to generate the results presented. Qualitative case studies produced several practical suggestions for furnace operation, including increased dust capture by the bath when feed ports are located closer to the electrode, and the possible effects of feed segregation in the furnace freeboard based on dust particle size and density.

Jan 1, 2015

By Das S. C

A detailed study was undertaken on the effect of Fe+3 in combination with LIX64N during copper electrowinning from sulphate electrolytes. The results show that the presence of Fe+3 not only affects the current efficiency during copper electrowinning but also affects the cathode quality. The effect is enhanced by electrolysis parameters like temperature, circulation rate, current density, etc. No significant effect was found from the presence of Fe+2. The presence of Fe+3 along with LIX64N causes a synergistic effect and results in a drastic fall in current efficiency. Moreover, cathode quality is also affected. A pyramidal structure is favoured in the presence of Fe+3 but the presence of LIX64N along with Fe+3 promotes a ridge structure. Addition of thiourea not only causes modification of cathode deposits, but also a rise in current Efficiency.

Jan 1, 1992

By M. Baumann

Introduction Gold Quarry is one of the largest gold deposits in Nevada, located along the Carlin Trend, approximately seven miles north of Carlin, NV. Owned and operated by Newmont Mining Corporation, as of December 31, 2005, Gold Quarry had produced over 13 million ounces of gold. Multiple simulations were constructed for gold and metallurgical variables using the Stepwise Conditional Transformation method. Analyses of these simulations have been used for a variety of purposes, including an assessment of uncertainty with various ore types. This assessment provides insight for improved modeling and reconciliation. Geological Framework Gold Quarry is a large, low-grade disseminated gold deposit hosted in Silurian-Devonian aged sediments at the Chukar/Alunite-Good Hope fault intersection. Gold bearing hydrothermal fluids appear to have migrated upwards along the Chukar/Alunite and Deep Sulfide Feeder faults and then moved outward along favorable stratigraphic horizons and structural intersections.

Jan 1, 2007

By B. M. Thethwayo

Graphite blocks are currently used in the concentrate - slag zone in primary PGM smelters, and can possibly be extended to the matte zone. This project evaluates the interaction between synthetic matte and graphite blocks on a laboratory scale. Static crucible tests were performed where graphite crucibles (prepared from standard and high-grade graphite) were filled with synthetic matte (27.7 per cent S ? 46.1 per cent Fe ? 17.0 per cent Ni ? 9.2 per cent Cu) and heated to 1550°C for different time periods (1?5 days). Matte penetration was evaluated using a SEM, while graphite dissolution was evaluated by measuring the carbon content of the matte with a LECO carbon analyser. Matte penetrated into standard grade graphite up to approximately 2 mm, while matte infiltration into the high grade graphite was limited to the immediate hot face. The saturation solubility of graphite in the synthetic matte at 1550°C was 0.43 per cent. Copper, iron, nickel, and sulphur were detected in an accretion that formed in the water-cooled part of the furnace. This accretion consists of mainly Cu-S and Cu-Fe-S based phases.

Jan 1, 2012

By Y. M. Jiang, D. W. Park, S. M. Lee

A vast majority of longwall operations in the US use shield-type hydraulic supports to provide ground control along the longwall face. The three-dimensional, finite-element technique combined with a progressive failure approach was utilized to simulate interaction between shields and surrounding strata and determine various loading conditions. In addition, a separate finite-element model of the shield structure was made to study responses of each longwall shield to the different loading conditions. Shield responses under various loading conditions and the shield characteristics, such as shield stiffness, the ability of resisting horizontal forces, and the effect of shield height, were studied based on the results from finite-element analyses. The results can provide the basis of effective shield design and be used for evaluation of the shield performance. It is suggested that a technique incorporating the finite-element method be developed to evaluate real-time shield performance for the purpose of effective ground control.

Jan 1, 1993

By D. W. Park

A vast majority of longwall operations in the United States use shield-type hydraulic supports to provide ground control along the longwall face. The three-dimensional finite-element technique combined with a progressive failure approach was utilized to simulate interaction between shields and surrounding strata and determine various loading conditions. In addition, a separate finite element model of the shield structure was made to study responses of each long wall shield to the different loading conditions. Shield responses under various loading conditions and the shield characteristics, such as shield stiffness, the ability of resisting horizontal forces, and the effect of shield height, were studied based on the results from finite-element analyses. The results can provide the basis of effective shield design and be used for evaluation of the shield performance. It is suggested to develop a technique incorporating the finite-element method to evaluate the real-time shield performance for the purpose of effective ground control.

Jan 1, 1992

By B. T. Lu, J. L. Luo, T. Yu, C. W. Chen

In this paper, the synergism in erosion-corrosion process occurring in oil sand wastewater transportation caused by the interaction of mechanical and electrochemical factors was experimentally investigated. The erosion-corrosion tests were conducted with A1045 steel in synthetic slurries comprising tap water and silica sand. The material loss due to corrosion-enhanced erosion was assessed with the chemo-mechanical model developed by the authors recently. The results indicate that the material loss produced by corrosion-enhanced erosion at the open circuit potential can be formulated as a linear function of logarithm of corrosion current density. The wastage caused by the erosion-enhanced corrosion was analyzed based on the concept of non-equilibrium thermodynamics. The material loss induced by the erosion-enhanced corrosion is approximately a linear function of overall erosion rate measured in synthetic slurries, indicating that erosion-enhanced corrosion could be reduced by adopting surface strengthening techniques to improve the resistance to the plastic deformation in surface layer.

Jan 1, 2004

By R. H. Crist

Reactive components of algal cell walls include uronic and alginic acids: In addition, many marine species have half ester sulfate groups which function as fixed anions. Associated metals vary with the media, eg., Ca and Mg in fresh water (FV) and Na, Ca, Mg in seawater. . These metals readily exchange with aqueous phase protons or metal cations. A plot of the total amount of metal cations displaced by protons vs .. pH shows one inflection at pH 4 for FV algae and' in addition a second inflection at pH 2, 3 for marine algae. The first inflection is interpreted as. Indicating the cations associated with carboxyl groups ,and the ,second with half ester ?Sulfate groups. The exchange capacities of various aigal ,species vary widely. When FV algae is placed in a Pb2+ solution,- the amount of Pb2"' deposited on the algae is. Equivalent to the. Total Ca2?, Mg2, and H+ displaced? thereby confirming the ion exchange mechanism. Ion exchange equilibrium constants are reported for the displacement of ca2+ from Vaucheria. With Mg2+, sr2+, Cd2+, Pb2+_ and Na+ as well as the reverse reactions. Cd2+ can .be removed partially from algae by precipitating it as CdS or Cd(OH) 2 Pb2+ and Cu2+ are also partially removed as the hydroxides. Rates of reaction for various alkali hydroxides decrease with increasing .unhydrated cation radius. It is concluded that theory is useful in predicting viable applications for algae in pollution abatement.

Jan 1, 1991

By N. Z. Fotoyi

Keywords: MgO-MgR2O3 refractory, SO2-containing gases, chemical attack The reaction mechanisms occurring when MgO-MgR2O3 refractories are exposed to SO2-containing gas atmospheres were examined. The study examined the characteristic structures of magnesite-chrome, chrome-magnesite and magnesite refractories exposed to SO2-O2 gas mixture at temperatures of 700°C to 1350°C. The phase characterization was conducted with scanning electron microscopy (SEM) and powder X-ray diffractometry (XRD). The results show that the physical characteristics of the refractory matrix along the grain boundaries are important refractory features during chemical attack from SO2-containing gas. Upon heating in SO2-containing gas, the changes in phase-chemical compositions and accompanying grain growth causes loosening of the structure and the pore volume promotes gas diffusion. The chemical reactions that occur form stable sulfate compounds identified as MgSO4, CaSO4 and CaMg3(SO4)4, and lead to disintegration of various phase structures and consequently erosion of the refractory. In conclusion, the reaction mechanisms in MgO-MgR2O3 refractories exposed to SO2-containing gases progress through a combination of structural disintegration and chemical attack.

Jan 1, 2011

By Igor Plaksin

Interaction of sulfide minerals and native metals with reagents in flotation is largely determined by particle-surface changes resulting from action of the medium and dissolved gases. A number of early studies were devoted to the selective action of various gases on minerals.1 Mc- Lachlan2 paid attention to oxygen as the most active gas affecting flotation properties of sulfide minerals.

Jan 3, 1959

By Larry G. Stolarczyk

This report deals with the creation of an efficient method to determine if command, control, communication and monitoring (3cm) equipment in coal, metal and non-metal mines is susceptible to Radio Frequency Interference (RFI) from the Medium Frequency (MF) radio communications system. A qualitative and quantitative RFT test plan was developed for in-mine and laboratory evaluation of the equipment. The laboratory testing was accomplished using the TEM Test Chamber. Detailed information on the Test Plan and the TEM Test Chamber is included. During in-mine testing of the MF System some underground equipment malfunctioned when the transmitter's radiating antenna was in close proximity. Electromagnetic Compatibility (EMC) testing was done on three levels; Component (circuit or box), subsystems and system. Nine tables are included which show the results of testing various equipment for RFI.

Jan 5, 1986