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A Mechanistic Model to Examine Mercury in Aquatic SystemsHarris, Reed 03 1900 (has links)
Elevated mercury levels have been observed in a wide variety of aquatic systems. A mass balance non-steady state model was developed to examine mercury cycling in lakes and reservoirs. Hg(ll), methylmercury, Hg° , dimethylmercury and solid phase HgS cycles were interconnected. Compartments included air, water, sediment, suspended solids, plankton, benthos, and two generic fish categories based on diet. Bioenergetics equations for individual fish were extended to consider mercury dynamics for entire fish populations. Biota represented large methylmercury fluxes in the water column and were found to be important methylmercury repositories. In a simulation of a generic well-mixed shield lake in Ontario, the fish population contained about 4 times as much methylmercury as water. Uptake of methylmercury by individual walleye and yellow perch was predicted to be dominated by the food pathway (eg. 99% of total uptake).
Based on simulations for the generic shield lake, the watershed has the potential to be an important source of methylmercury in some shield lakes (exceeding in-situ methylation in the generic simulation). Methylation in the water column and sediments were both simulated to be significant. Simulated net production of methylmercury in the generic shield lake was on the order of 0.05 to 0.15 ug methylmercury m⁻² year⁻¹ in the water column, with similar rates in sediments. Simulated rates of net methylation in polluted sytems were higher. Fractions of total dissolved Hg(II) or methylmercury available for methylation and demethylation in aerobic waters were thermodynamically predicted to be small (e.g. <1%). Dissolved organic carbon and sulphides (if present) were thermodynamically predicted to dominate Hg(II) and methylmercury complexation in freshwaters. Hg(II) burial and outflows represented about 85-90% of total mercury losses for the generic shield lake (2 year hydraulic retention time). Volatilization of Hg° , produced by demethylation and Hg(II) reduction, represented the remaining 10-15% of losses. Considerable system to system variability is expected for sources and sinks of total mercury and methylmercury in shield lakes. In simulations of two mercury contaminated environments, Lake St. Clair and Clay Lake, Ontario, sediment return of Hg(II) caused the lakes to be net sources of mercury to downstream areas. Sediment return of mercury could partially explain observed two-phase recoveries of fish methylmercury levels in some polluted systems. The time required for Hg(II) and methylmercury concentrations in various compartments to respond to changes in loads was simulated. There was a tendency towards relatively rapid internal cycling of Hg(II) and methylmercury, but slower overall system response times (eg. years to decades to respond to recover from flooding or pollution episodes). / Thesis / Master of Engineering (ME)
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Evaluation of compaction sensitivity of Saskatchewan asphalt mixesSalifu, Aziz 15 July 2010
Saskatchewan Ministry of Highway and Infrastructure (SMHI) currently use the Marshall compaction method for the preparation of hot-mix asphalt laboratory samples. Due to increases in commercial truck traffic on most provincial highways, there has been an observed increasing trend in the occurrence of permanent deformation within the hot-mix asphalt concrete (HMAC) layer. One of the most important material properties found to influence the resistance of HMAC to structural permanent deformation is volumetric air voids within the mix.<p>
End product air voids within a hot mix asphalt concrete pavement in the field is simulated by the method of compaction used during the laboratory design process. Based on findings of the Strategic Highway Research Program (SHRP), the gyratory compactor is believed to better simulate field compaction of asphalt mixes at the time of construction, as well as better predict mix consolidation over the field performance period. However, the SuperpaveTM sample preparation protocol specifies a fixed angle of gyratory compaction, which may not be the optimal parameters to evaluate Saskatchewan hot-mix asphalt concrete mixes during the laboratory mix design phase.<p>
The primary objective of this research was to investigate the relationship between laboratory characterization and field evaluation of Saskatchewan SPS-9A asphalt mixes across alternate laboratory compaction protocols. A second objective of this research was to quantify the effect of gyratory and Marshall compaction energy on the physical and mechanical properties of Saskatchewan SPS-9A asphalt mixes in the laboratory. The third objective of this research was to compare field ground penetrating radar dielectric permittivity profiles and rutting performance across Saskatchewan SPS-9A test sections.<p>
The hypothesis of this research is that gyratory laboratory compaction will provide improved sensitivity in the characterization of physical asphaltic mix properties. It is also hypothesized that varied volumetric properties of HMAC mixes influence the mechanistic triaxial frequency sweep material properties of both conventional Saskatchewan and SuperpaveTM dense graded HMAC mixes.<p>
The laboratory portion of this research included volumetric and mechanical properties of the seven Saskatchewan SPS-9A asphaltic mixes.
The scope of this research included an investigation of the Saskatchewan Specific Pavement Study-9A (SPS-9A) asphalt mixes constructed in Radisson Saskatchewan in 1996. Physical volumetric properties as well as mechanistic triaxial frequency sweep properties were characterized across all seven Radisson SPS-9A mixes. Rutting after ten years of performance in the field was quantified as well as in situ ground penetrating radar dielectric permittivities of the Radisson SPS-9A test sections.<p>
Based on the findings of the study, there was a significant reduction in VTM with an increase in Marshall compaction energy from 50 to 75 blows. Marshall stability was observed to be higher at 75 blow compared to 50 blows across the test sections.<p>
Similarly, with regards to gyratory sample preparation, there was an observed reduction in VTM with an increase in gyratory compaction energy. VTM of SuperpaveTM mixes were higher than VTM SMHI Marshall mixes. VTM of the SuperpaveTM mixes were above acceptable SMHI limits at all angles of gyration at Ndesign. SuperpaveTM gyratory compactor accurately predicted field air voids of the Radisson SPS-9A asphalt after ten years of traffic loading at 2.00° angle of gyration.<p>
In general, this research showed significant sensitivity of volumetric material properties across both Marshall and gyratory compaction energy.<p>
This research also demonstrated that there was an improvement in the triaxial mechanistic material properties of the Radisson SPS-9A HMAC mixes with an increase in gyratory compaction energy. Dynamic moduli across all test section mixes increased with an increase in gyratory compaction energy. Similarly, it was shown that Poissons ratio generally increased with an increase in compaction energy across all test sections. Phase angle also increased with an increase in gyratory compaction energy. Radial microstrain (RMS) displayed the most significant sensitivity to increased gyratory compaction energy.<p>
This research concluded that compaction energy in the laboratory can significantly influence the volumetric and mechanistic properties of hot-mix asphalt concrete mixes. As indicated by the field performance of the Radisson SPS-9A test sections, it is known that both volumetric and mechanistic properties can influence field performance. Mechanical material properties of HMAC may be improved by increasing compaction energy, as long as volumetric properties are adhered to. The use of rapid triaxial frequency sweep testing demonstrated the ability to characterize mechanistic material properties as a function of varied compaction energy.<p>
Based on the findings of this research, it is recommended that Saskatchewan asphalt mixes, both Marshall and SuperpaveTM types, be characterized using gyratory compaction with 2.00° angle of gyration and the SHRP specified number of gyrations. Further, the gyratory compacted samples provide the ability to characterize the mechanistic material constitutive properties of asphaltic mixes for mechanistic based road structural design purposes.<p>
Future research should evaluate the relationship of laboratory material properties to the field performance of various Saskatchewan asphalt mixes across various field state conditions.
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Evaluation of compaction sensitivity of Saskatchewan asphalt mixesSalifu, Aziz 15 July 2010 (has links)
Saskatchewan Ministry of Highway and Infrastructure (SMHI) currently use the Marshall compaction method for the preparation of hot-mix asphalt laboratory samples. Due to increases in commercial truck traffic on most provincial highways, there has been an observed increasing trend in the occurrence of permanent deformation within the hot-mix asphalt concrete (HMAC) layer. One of the most important material properties found to influence the resistance of HMAC to structural permanent deformation is volumetric air voids within the mix.<p>
End product air voids within a hot mix asphalt concrete pavement in the field is simulated by the method of compaction used during the laboratory design process. Based on findings of the Strategic Highway Research Program (SHRP), the gyratory compactor is believed to better simulate field compaction of asphalt mixes at the time of construction, as well as better predict mix consolidation over the field performance period. However, the SuperpaveTM sample preparation protocol specifies a fixed angle of gyratory compaction, which may not be the optimal parameters to evaluate Saskatchewan hot-mix asphalt concrete mixes during the laboratory mix design phase.<p>
The primary objective of this research was to investigate the relationship between laboratory characterization and field evaluation of Saskatchewan SPS-9A asphalt mixes across alternate laboratory compaction protocols. A second objective of this research was to quantify the effect of gyratory and Marshall compaction energy on the physical and mechanical properties of Saskatchewan SPS-9A asphalt mixes in the laboratory. The third objective of this research was to compare field ground penetrating radar dielectric permittivity profiles and rutting performance across Saskatchewan SPS-9A test sections.<p>
The hypothesis of this research is that gyratory laboratory compaction will provide improved sensitivity in the characterization of physical asphaltic mix properties. It is also hypothesized that varied volumetric properties of HMAC mixes influence the mechanistic triaxial frequency sweep material properties of both conventional Saskatchewan and SuperpaveTM dense graded HMAC mixes.<p>
The laboratory portion of this research included volumetric and mechanical properties of the seven Saskatchewan SPS-9A asphaltic mixes.
The scope of this research included an investigation of the Saskatchewan Specific Pavement Study-9A (SPS-9A) asphalt mixes constructed in Radisson Saskatchewan in 1996. Physical volumetric properties as well as mechanistic triaxial frequency sweep properties were characterized across all seven Radisson SPS-9A mixes. Rutting after ten years of performance in the field was quantified as well as in situ ground penetrating radar dielectric permittivities of the Radisson SPS-9A test sections.<p>
Based on the findings of the study, there was a significant reduction in VTM with an increase in Marshall compaction energy from 50 to 75 blows. Marshall stability was observed to be higher at 75 blow compared to 50 blows across the test sections.<p>
Similarly, with regards to gyratory sample preparation, there was an observed reduction in VTM with an increase in gyratory compaction energy. VTM of SuperpaveTM mixes were higher than VTM SMHI Marshall mixes. VTM of the SuperpaveTM mixes were above acceptable SMHI limits at all angles of gyration at Ndesign. SuperpaveTM gyratory compactor accurately predicted field air voids of the Radisson SPS-9A asphalt after ten years of traffic loading at 2.00° angle of gyration.<p>
In general, this research showed significant sensitivity of volumetric material properties across both Marshall and gyratory compaction energy.<p>
This research also demonstrated that there was an improvement in the triaxial mechanistic material properties of the Radisson SPS-9A HMAC mixes with an increase in gyratory compaction energy. Dynamic moduli across all test section mixes increased with an increase in gyratory compaction energy. Similarly, it was shown that Poissons ratio generally increased with an increase in compaction energy across all test sections. Phase angle also increased with an increase in gyratory compaction energy. Radial microstrain (RMS) displayed the most significant sensitivity to increased gyratory compaction energy.<p>
This research concluded that compaction energy in the laboratory can significantly influence the volumetric and mechanistic properties of hot-mix asphalt concrete mixes. As indicated by the field performance of the Radisson SPS-9A test sections, it is known that both volumetric and mechanistic properties can influence field performance. Mechanical material properties of HMAC may be improved by increasing compaction energy, as long as volumetric properties are adhered to. The use of rapid triaxial frequency sweep testing demonstrated the ability to characterize mechanistic material properties as a function of varied compaction energy.<p>
Based on the findings of this research, it is recommended that Saskatchewan asphalt mixes, both Marshall and SuperpaveTM types, be characterized using gyratory compaction with 2.00° angle of gyration and the SHRP specified number of gyrations. Further, the gyratory compacted samples provide the ability to characterize the mechanistic material constitutive properties of asphaltic mixes for mechanistic based road structural design purposes.<p>
Future research should evaluate the relationship of laboratory material properties to the field performance of various Saskatchewan asphalt mixes across various field state conditions.
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Mechanistic modeling of low salinity water injectionKazemi Nia Korrani, Aboulghasem 16 February 2015 (has links)
Petroleum and Geosystems Engineering / Low salinity waterflooding is an emerging enhanced oil recovery (EOR) technique in which the salinity of the injected water is substantially reduced to improve oil recovery over conventional higher salinity waterflooding. Although there are many low salinity experimental results reported in the literature, publications on modeling this process are rare. While there remains some debate about the mechanisms of low salinity waterflooding, the geochemical reactions that control the wetting of crude oil on the rock are likely to be central to a detailed description of the process. Since no comprehensive geochemical-based modeling has been applied in this area, we decided to couple a state-of-the-art geochemical package, IPhreeqc, developed by the United States Geological Survey (USGS) with UTCOMP, the compositional reservoir simulator developed at the Center for Petroleum and Geosystems Engineering in The University of Texas at Austin. A step-by-step algorithm is presented for integrating IPhreeqc with UTCOMP. Through this coupling, we are able to simulate homogeneous and heterogeneous (mineral dissolution/precipitation), irreversible, and ion-exchange reactions under non-isothermal, non-isobaric and both local-equilibrium and kinetic conditions. Consistent with the literature, there are significant effects of water-soluble hydrocarbon components (e.g., CO2, CH4, and acidic/basic components of the crude) on buffering the aqueous pH and more generally, on the crude oil, brine, and rock reactions. Thermodynamic constrains are used to explicitly include the effect of these water-soluble hydrocarbon components. Hence, this combines the geochemical power of IPhreeqc with the important aspects of hydrocarbon flow and compositional effects to produce a robust, flexible, and accurate integrated tool capable of including the reactions needed to mechanistically model low salinity waterflooding. The geochemical module of UTCOMP-IPhreeqc is further parallelized to enable large scale reservoir simulation applications. We hypothesize that the total ionic strength of the solution is the controlling factor of the wettability alteration due to low salinity waterflooding in sandstone reservoirs. Hence, a model based on the interpolating relative permeability and capillary pressure as a function of total ionic strength is implemented in the UTCOMP-IPhreeqc simulator. We then use our integrated simulator to match and interpret a low salinity experiment published by Kozaki (2012) (conducted on the Berea sandstone core) and the field trial done by BP at the Endicott field (sandstone reservoir). On the other hand, we believe that during the modified salinity waterflooding in carbonate reservoirs, calcite is dissolved and it liberates the adsorbed oil from the surface; hence, fresh surface with the wettability towards more water-wet is created. Therefore, we model wettability to be dynamically altered as a function of calcite dissolution in UTCOMP-IPhreeqc. We then apply our integrated simulator to model not only the oil recovery but also the entire produced ion histories of a recently published coreflood by Chandrasekhar and Mohanty (2013) on a carbonate core. We also couple IPhreeqc with UTCHEM, an in-house research chemical flooding reservoir simulator developed at The University of Texas at Austin, for a mechanistic integrated simulator to model alkaline/surfactant/polymer (ASP) floods. UTCHEM has a comprehensive three phase (water, oil, microemulsion) flash calculation package for the mixture of surfactant and soap as a function of salinity, temperature, and co-solvent concentration. Similar to UTCOMP-IPhreeqc, we parallelize the geochemical module of UTCHEM-IPhreeqc. Finally, we show how apply the integrated tool, UTCHEM-IPhreeqc, to match three different reaction-related chemical flooding processes: ASP flooding in an acidic active crude oil, ASP flooding in a non-acidic crude oil, and alkaline/co-solvent/polymer (ACP) flooding. / text
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Mechanistic investigation of catalytic organometallic reactions using ESI MSLuo, Jingwei 16 December 2014 (has links)
Electrospray ionization mass spectrometry (ESI-MS) has been applied to the real time study of air-sensitive homogenous organometallic catalytic reactions due to its soft ionization properties. Therefore, fragile molecules and complexes in these reactions were characterized. The kinetic studies of these reactions have also been done by following the relative abundance of different species including starting material(s), products, by-product(s) as well as intermediates. Based on the results, reaction pathways and mechanisms were proposed and numerical models were built to accurately mimic the reactions under specific condition.
In order to make the reactions detectable by ESI-MS, many charged ESI-MS friendly substrates were synthesized as tracking tags, including 1-allyl-1-(prop-2-yn-1-yl)piperidin-1-ium hexafluorophosphate(V), 1-allyl-1-(prop-2-yn-1-yl)pyrrolidin-1-ium hexafluorophosphate(V), (4-ethynylbenzyl)triphenylphosphonium hexafluorophosphate(V), hex-5-yn-1-yltriphenylphosphonium hexafluorophosphate(V) etc. The method for continuously monitoring water- and oxygen-sensitive reactions in real time named pressurized sample infusion (PSI) was developed, optimized and applied throughout all the projects in the thesis.
These techniques were applied to detailed studies of the intramolecular Pauson-Khand reaction (PKR) with Co2CO8 under different temperatures. The kinetic study results gave the entropy and enthalpy of the reaction and evidence suggested that the ligand dissociation step was the rate-determining step of the reaction.
Hydrogenation of alkynes with Wilkinson’s catalyst and Weller’s catalyst were also studied using PSI. The behaviour of starting materials and products were tracked, then various reactions were carried out by using different temperatures and concentrations. Furthermore, competition reaction and kinetic isotope effect study, mechanisms were proposed based on experimental results, numerical models were built, and rate constants for each step were estimated.
Different Si-H activation reactions were studied including hydrolysis of silanes, hydrosilation, dehydrocoupling of silanes, alcoholysis of silane and silane redistribution by using (3-(methylsilyl)propyl)triphenylphosphonium hexafluorophosphate(V). A variety of collaborative projects were also carried out including hydroacylation, fast-activating Pd catalyst precursor, catalyst analysis for Cu-mediated fluorination, CdSe - NiDHLA analysis, Ru catalyzed propargylic amination reaction, Zn catalyzed lactide polymerization, and Fe4S4 clusters. / Graduate / jingwei@uvic.ca
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Quantitative and kinetic studies of solid CACO3, Ca(OH)2 and CaO utilizing vibrational spectroscopyLegodi, Malebogo Andries 15 September 2010 (has links)
The decomposition of CaCO3 has been studied extensively for many decades. This reaction is the backbone of lime industry. The desired product of the decomposition of CaCO3 is CaO (lime), which is the integral part of many lime products. The decomposition is described by the following reaction: CaCO3 --> CaO + CO2 Limestone is a term that includes calcium carbonate with varying amounts of impurities, the most of which are silica and alumina. Therefore, the analysis of the decomposition of CaCO3 is the same as that of limestone, since CaCO3 is the major component of limestone. The main objectives of the studies revolved around acquiring qualitative, quantitative, kinetic and mechanistic information. The most frequently used methods of analysis have always been thermal methods (TG, DTG, DSC, etc). Due to many possible experimental conditions, reaction-influencing factors and the property of the product (lime), varying conclusions on mechanistic and kinetic properties of the decomposition of CaCO3 have been drawn. However, thermal methods are time consuming and use extremely small mass of samples. Other methods of analysis which gave excellent results (in agreement with thermal methods) were photoacoustic spectroscopy and loss-on-ignition. These methods are also prone to errors and could be umbiguous. In the present work, Fourier-Transform infrared spectroscopy was investigated for possible application to the quantitative study of this reaction. This was done on the mixtures of CaCO3 and Ca(OH) 2 containing 100, 85, 70, 50, 30, 15 and 0% of each component on the Brucker 113v spectrometer. A calibration curve of regression coefficient of 0.9950 was obtained. Following these good results, the FT-IR was then applied to the decomposition of natural limestone to obtain the kinetic information of the reaction. Four different industrial sample sizes of limestone were decomposed isothermally at 900, 950 and 1000°C. The results showed that the isothermal decomposition of limestone in air atmosphere can best be described by Contracting Volume or Ginstling-Brounshtein model. The kinetic parameter values fall within the range specified in the literature (as obtained using thermal methods). Furthermore, the quantitative FT-IR method was investigated for possible application to the determinations of the content of limestone used as an admixture to the cement blends. FT-IR quantitative analysis was performed on the cement blend samples containing gradually increasing amounts of limestone. Again, a good calibration curve with average regression coefficient of 0.9970 was obtained. A complementary study involving the weighing of the same samples before and after decomposition (for a set time at 1000°C) gave comparably good results (averaged regression coefficient of 0.9950). / Dissertation (MSc)--University of Pretoria, 2000. / Chemistry / unrestricted
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Synthesis and a Mechanistic Study of Nucleophilic Substitution in Halo-arene Chromiumtricarbonyl ComplexesSandilands, Linda 05 1900 (has links)
<p> Arenechromiumtricarbonyl complexes have been known for many years and numerous studies of the chemistry of these molecules have been reported. The presence of the chromiumtricarbonyl unit changes the reactivity of the complexed arena, in most cases due to its strong inductive electron withdrawing effect. The resulting lowered electron density in the aromatic ring allows reactions to be carried out which would otherwise be extremely difficult if not impossible, notably nucleophilic substitution. When methoxide ion was reacted with optically pure methyl o-fluorobenzoatechromiumtricarconyl, racemization of approximately 50% was observed in the product. A brief study confirmed SN2 kinetics, but further investigation was warranted. Having eliminated the possibility of decomplexationrecornplexation, two other mechanisms were postulated -a partial decomplexation allowing the arene to roll over, or attack by methoxide at another ring position. In an effort to determine which mechanism was operating, the synthesis of a number of appropriately substituted halo-arenechromiumtricarbonyl complexes was attempted. The successful synthesis of methyl 2-chloro-5-methylbenzoatechromiumtricarbonyl wns achieved, albeit with some difficulty in in low yield, but the corresponding 2-chloro-3-methyl complex could not be made. In the case of the corresponding 2-fluoro compounds, the arenes themselves could not be made by a variety of synthetic routes, 80 synthesis of
the complexes could not be attempted. The results of the reaction of methoxide ion with methyl 2-chloro-5-methylbenzoatechromiumtricarbonyl indicate that the reaction proceeds via the roll-over mechanism, although a definite conclusion cant be drawn at this time. A potentially useful synthesis of bis-(chromiumtricarbonyl)-benzo-phenones has also been developed. </p> / Thesis / Master of Science (MSc)
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Implementation Of A Mechanistic- Empirical Pavement Design Method For Uruguayan RoadwaysScavone LaSalle, Martin 27 June 2019 (has links)
Mechanistic-Empirical (M-E) methods are the cornerstone of current pavement engineering practice because of their enhanced predicting capabilities. Such predicting power demands richer input data, computational power, and calibration of the empirical components against distress measurements in the field.
In an effort to spearhead the transition to M-E design in Uruguay, the aim of this Project is twofold: (1) develop an open-source, MEPDG-based, simplified M-E tool for Uruguayan flexible pavements [Product-One], and (2) compile a library of Uruguayan input data for design [Product-Two].
A functional, Matlab-based beta version of Product-One with default calibration parameters and a first collection of Uruguayan input data are presented herein. The Product-One beta is capable of designing hot-mix asphalt (HMA) structures over granular bases on top of the subgrade. Product-Two features climate information from the INIA weather station network, traffic distribution patterns for select Uruguayan highways, standard-based (Level-3) HMA properties, and Level-3 and Level-2 unbound materials' parameters. Product-One's outcomes were against other available M-E software, as a means to test the code's performance: Product-One reported a distress growth similar to CR-ME (MEPDG-based) on default calibration parameters but different to MeDiNa (calibrated core).
In conclusion, Product-One managed to perform like another MEPDG-based software under the same design inputs and constraints, accomplishing one of this Thesis' objectives. However, Product-Two could not be created to the initially-desired extent. Nevertheless, the author remains confident that significant leaps forward can be made with little extra effort and further research on M-E design can be encouraged from this project. / Master of Science / The design of pavement structures historically relied on methodologies developed after experimental results, the so-called “empirical methods”. Advances in technology over the recent years allowed for more complex but more reliable methods – the mechanistic-empirical (M-E) methods – to finally be adopted by practitioners both in the US and abroad. In an effort to encourage the transition to M-E design in Uruguay, this project aimed at developing an open-source M-E design tool for Uruguayan flexible pavements based on the American MEPDG design methodology [Product-One], and assembling a library of Uruguayan data necessary for design with such an M-E method [Product-Two]. In this project, a beta version of the Product-One design tool for the design of asphalt-surfaced pavements and a collection of climate, traffic distribution, and materials’ properties data from Uruguayan sources for design is presented (load information was not available for this project); this Thesis is the log of the data collection effort as well as the guide to using and understanding all the components of Product-One. In addition, Product-One has been tested by comparing its pavement design results for a given Uruguayan highway against other M-E design software tools: MeDiNa and CR-ME. Product-One’s outcomes resembled the results given by CR-ME (also MEPDG-based) but differed with those from MeDiNa (crafted specifically for design of Brazilian roads). In conclusion, Product-One managed to perform like another MEPDG-based design tool under the same inputs and constraints, accomplishing one of this Thesis’ objectives. However, some of the Uruguayan information sought for could not be retrieved and so added to Product-Two. Anyway, the author remains confident that both Products can be significantly improved with little extra effort and that this project may encourage further research on M-E design.
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Data-Based Mechanistic approach to modelling of daily rainfall-flow relationship : a case of the Upper Vaal water management areaOchieng, G.M., Otieno, F.A.O. January 2008 (has links)
Published Article / Although deterministic models still dominate hydrological modelling, there is a notable paradigm shift in catchment response modelling. An approach to represent the daily rainfall-flow (R-F) relationship using Data-Based Mechanistic (DBM) modelling is presented. DBM modelling is an inductive empirical transfer function (TF) approach relating input to output. The study used secondary data from the Department of Water Affairs and Forestry for the Upper Vaal water management area at station C1H007. The R-F model identification and optimisation was implemented in the CAPTAIN Toolbox in MATLAB. The best estimated R-F model was a 2nd order TF with an input lag of one day and R 2T= 56%. In mechanistic interpretation, three parallel flow pathways were discerned; the fast flow, slow flow and the loss component each constituting 49.8%, 24% and 26.2% of the modelled flow respectively. The study demonstrates that the approach adopted herein produces reasonably satisfactory results with a minimum of the readily available catchment data.
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Characterization of reclaimed asphalt concrete pavement for Saskatoon road construction2013 June 1900 (has links)
The City of Saskatoon (COS) manages diverse road infrastructure assets. Given the present day challenges of structurally upgrading in-service road infrastructure assets in diverse field state conditions, there is a need to incorporate new innovative materials, changing field state conditions, and mechanistic design methods in sustainable road rehabilitation decision making. The COS is faced with challenges including rising material and labour costs, budget shortfalls, depleting virgin aggregate sources in close proximity to the COS, and an increase in stockpiled asphalt and concrete rubble materials due to transportation infrastructure renewal.
As a result of the COS impact crushing program, a need to determine the design and performance properties of using recycled reclaimed asphalt concrete (RAP) rubble materials in urban pavement structures was established. RAP materials had never been used as a structural base layer in COS pavement structures because no material characterization had been conducted and there was no performance information with regards to their structural behaviour and field performance available. Other jurisdictions documented benefits of using recycled RAP in road structure include: reduced demand on depleting aggregate sources; reduced energy consumption; diversion of stockpiled RAP materials from landfills; and reduced overall handling and disposal costs. Given the amount of crushed RAP material available to the COS, it was determined there are potential benefits to implementing the use of recycled crushed RAP rubble in pavement structures, leading to the implementation of the “Green Street” Infrastructure Program.
The findings of this research indicate that RAP materials have improved mechanistic properties compared to conventional granular materials; therefore, RAP materials can be used as a base layer in a road structure. This research indicates that cement stabilization and cement with a slow setting (SS-1) emulsion stabilization improved the moisture susceptibility of well graded (GW) and open graded base course (OGBC) RAP materials. These findings demonstrated that RAP materials stabilized with cement and/or SS-1 emulsion can be used as a base layer in a pavement structure.
This research also found that the standard Proctor compaction method is not applicable for RAP materials to quantify moisture-density behaviour under compaction, due to the bound-nature of RAP aggregates, which are composed of asphalt and aggregate. California bearing ratio (CBR) values of Proctor-compacted RAP specimens did not accurately reflect field performance observations.
As part of the COS “Green Street” Infrastructure Program, two test sections using crushed GW RAP rubble materials as a base layer were constructed as part of this research and include Marquis Drive (eastbound lanes from Thatcher Avenue to Idylwyld Drive) and 8th Street East (westbound lanes from Boychuk Drive west 0.540 kilometers). Test sections were constructed by the City of Saskatoon with conventional construction equipment and showed structural improvement in structural performance and visual distresses. Using RAP materials as a base layer was economically feasible because the RAP material cost less than conventional virgin aggregate base materials.
This research demonstrates that processed and crushed RAP rubble materials are technically feasible to be used as a structural base layer in a recycled pavement structural system for urban road rehabilitation systems, and provide economic benefits over conventional granular base materials.
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