No description available.

SammanfattningSyfteSyftet med föreliggande studie var att undersöka om olika förbehandlingar av metallens yta påverkar bindningsstyrkan mellan CoCr och porslin.Material och metodSexton metallbasar med totalt 64 porslinscylindrar tillverkades genom gjutning av CoCr och porslinsuppläggning (de olika skikten; bondingagent, opak och dentin). Metallbasarna delades slumpmässigt in i 4 grupper; SB 50 sandblästrade med 50 m Al2O3, SB 250 sandblästrade med 250 m Al2O3, OASB oxiderade med atmosfäriskt tryck och sandblästrade med 250 m Al2O3, samt kontrollgrupp OVSB oxiderade i vakuumtryck och sandblästrade med 250 m Al2O3, samtliga grupper blästrades med 3 bars tryck. Efter glansbränning termocyklades provkropparna i 5000 cykler, förvarades fuktigt i 36o C och testades enligt ISO/TS11405:2016. Resultaten analyserades med one-way ANOVA, Tukey´s test. Signifikansnivån sattes till  = 0,05. Brottytorna analyserades visuellt och fotograferades i mikroskop. ResultatMedelvärdet för samtliga grupper var likvärdiga men med stor skillnad i spridning inom grupperna. Brotten delades in i tre grupper, adhesiv-, kohesiv- och blandfraktur.Slutsats Med reservation för de begränsningar som finns inom föreliggande studie kan följande slutsatser dras:•De olika förbehandlingsmetoderna, oxidering med vakuum eller atmosfäriskt tryck följt av sandblästring eller enbart sandblästring med olika kornstorlekar, ger ingen specifik skillnad vad gäller bindningsstyrkan mellan metall och porslin.•Oxidering med vakuum har ingen negativ inverkan på bindningsstyrkan mellan metall och porslin. De-gasing av metallen kan utföras.•Sandblästring med 50 μm hade större spridning inom gruppen än de övriga tre grupperna. •Studiens nollhypotes kan bekräftas. / Abstract PurposeThe purpose of the present study was to investigate whether various pretreatments affect the bond strength between CoCr and porcelain.Material and method64 porcelain cylinders were manufactured (bonding agent, opaque, dentin) divided on sixteen metal bases. The metal bases were randomly divided into 4 groups; SB 50 sandblasted with 50 m Al2O3, SB 250 sandblasted with 250 m Al2O3, OASB oxidized with atmospheric pressure and then sandblasted with 250 m Al2O3 and control group OVSB oxidized in vacuum and then sandblasted with 250 m Al2O3. All groups were sandblasted with 3 bars pressure. After glazefiring, the specimens were thermocycled 5000 cycles, stored in moist at 36o C and tested according to ISO / TS11405: 2016. The results were analyzed with one-way ANOVA, Tukey's test with significance level  = 0.05. The fracture surfaces were analyzed visually and photographed in microscope.ResultsThe mean values in all groups were equivalent but with large difference in standard deviation within the groups. The fractures were divided into three groups, adhesive-, cohesive and mixed fractures.ConclusionWithin the limitations of the study, the following conclusions can be drawn: •The different pretreatment methods, vacuum or atmospheric pressure, oxidation with or without sandblasting do not affect the bond strength between metal and porcelain.•Oxidation with vacuum does not adversely affect the bonding strength between metal and porcelain. De-gasing of the metal can be performed.•Sandblasting with 50 μm had a greater deviation within the group than the other groups•The study's null-hypothesis can be confirmed

In Sweden, there exists a large number of dams. Many of them are founded on rock masses normally affected by the presence of sub-horizontal rock fractures, which makes sliding along rock joints under the dam foundation one of the most critical failure mechanism. Various attempts have been made to relate the peak shear strength of rock joints to measurable parameters. However, the uncertainty in the determination of the shear strength of rock joints is nonetheless still significant.The main aim of this thesis is to investigate, develop and apply analytical and numerical techniques for estimation of peak shear strength of natural and unfilled rock joints. In a first step, the peak shear strength of several natural and unfilled rock joint was calculated by using surface aperture measurements from high-resolution optical scanning and a modified version of the analytical criterion previously developed by Johansson and Stille in 2014. In a second step, PFC2D was utilised to perform numerical shear tests on two-dimensional profiles selected from high-resolution optical scanning on unweathered and perfectly mated tensile induced rock joints.The results from the analytical approach show that the calculated peak shear strengths of the analysed samples are in good agreement compared with the laboratory investigations. Conversely, the obtained results from the numerical approach show lower peak shear strengths in the analysed two-dimensional profiles compared with the conducted laboratory shear tests.The analytical approach together with the advanced techniques to measure surface roughness available today, may be a possible way forward towards a methodology to determine peak shear strength of large-scale natural rock joints in-situ. / Bergsprickors skjuvhållfasthet är en avgörande faktor för att kunna bestämma säkerheten mot gliding för dammar där sub-horisontella utbredda bergsprickor existerar. Samtidigt är parametern svår att bestämma då den påverkas av flera faktorer som sprickytans råhet, vittringsgrad, normalspänning, skala samt passning. Skjuvhållfasthet av bergsprickor kan bestämmas genom att använda empiriska och analytiska brottkriterier samt numeriska metoder. Problemet med de befintliga metodikerna är att de inte beaktar inverkan från sprickans passning. Detta innebär att hållfastheten riskerar att överskattas.Det övergripande syftet med denna licentiatuppsats är att studera, utveckla och tillämpa analytiska och numeriska metoder för uppskattning av skjuvhållfasthet för naturliga och ofyllda bergsprickor. I ett första steg beräknades skjuvhållfastheten för ett antal naturliga och ofyllda bergsprickor. Detta gjordes genom att mäta aperturen baserat på högupplöst skanning och en vidareutvecklad version av det analytiska kriteriet som föreslogs av Johansson och Stille 2014. I ett andra steg användes PFC2D för att genomföra numeriska skjuvtester på två-dimensionella sprickprofiler baserat på högupplöst skanning av perfekt passade och draginducerade bergsprickor.Resultaten från uppskattad skjuvhållfasthet med den analytiska metodiken visar på en bra överensstämmelse i jämförelse med de utförda skjuvförsöken. Resultaten från de utförda analyserna med PFC2D visar på en något lägre skjuvhållfasthet än vad som observeras i verkligheten.Den utvecklade analytiska metodiken, tillsammans med de avancerade tekniker som idag finns för att mäta sprickytornas råhet, bedöms kunna utgöra ett första steg mot att bättre kunna bestämma den storskaliga skjuvhållfastheten för bergsprickor i fält. / <p>QC 20190402</p>

Reservoir release patterns are determined by a number of purposes, the most fundamental of which is to manage water resources for human use. Managing our water resources means not only controlling the water in reservoirs but also determining the optimum release rate taking into account factors such as reservoir stability, power generation, water supply for domestic, industrial, and agricultural uses, and the river ecosystem. However, riverbank stability has generally not been considered as a factor, even though release rates may have a significant effect on downstream riverbank stability. Riverbank retreat not only impacts land properties but also damages structures along the river such as roads, bridges and even buildings. Thus, reservoir releases need to also take into account the downstream riverbank stability and erosion issues. The study presented here investigates the riverbank stability and erosion at five study sites representing straight as well as inside and outside channel meander bends located on the lower Roanoke River near Scotland Neck, North Carolina. Extensive laboratory and field experiments were performed to define the hydraulic and geotechnical properties of the riverbank soils at each site. Specifically, soil water characteristic curves were determined using six different techniques and the results compared to existing mathematical models. Hydraulic conductivity was estimated using both laboratory and in situ tests. Due to the wide range of experimentally obtained values, the values determined by each of the methods was used for transient seepage modeling and the modeling results compared to the actual ground water table measured in the field. The results indicate that although the hydraulic conductivities determined by in situ tests were much larger than those typically reported for the soils by lab tests, numerical predictions of the ground water table using the in situ values provided a good fit for the measured ground water table elevation. Shear strengths of unsaturated soils were determined using multistage suction controlled direct shear tests. The test method was validated, and saturated and unsaturated shear strength parameters determined. These parameters, which were determined on the basis of results from both laboratory and field measurements, and the associated boundary conditions, which took into account representative flow rates and patterns including peaking, drawdown and step-down scenarios, were then utilized for transient seepage analyses and slope stability analyses performed using SLIDE, a software package developed by Rocscience. The analyses confirmed that the riverbanks are stable for all flow conditions, although the presence of lower permeability soils in some areas may create excess pore water pressures, especially during drawdown and step-down events, that result in the slope becoming unstable in those locations. These findings indicate that overall, the current reservoir release patterns do not cause adverse impacts on the downstream riverbanks, although a gradual drawdown after a prolonged high flow event during the wet season would reduce unfavorable conditions that threaten riverbank stability. / Ph. D.

No / With increasing interest in hot melt extrusion for preparing polymer-drug systems, knowledge of the shear and extensional rheology of polymers is required for the formulation and process design. Shear and extensional rheology of three commercial grades of hydroxypropyl cellulose (HPC) was examined at 140, 145 and 150 degrees C using twin bore capillary rheometry at range of processing rates. The power law model fitted for shear flow behaviour up to shear strain rates of approximately 1000s(-1), above which measured shear viscosities deviated from the power law and surface instabilities were observed in the extrudate, particularly for higher molecular weight grades. Shear thinning index was found to be relatively independent of temperature and molecular weight, whilst the consistency index, indicative of zero shear viscosity increased exponentially with increase in molecular weight. Extensional viscosity of all grades studied was found to decrease with increasing temperature and increasing processing rate. Foaming of the extrudate occurred especially at low temperatures and with the high molecular weight grade. An understanding of the relationships between shear and extensional flows with temperature, processing rate and molecular weight is a useful tool for process design; optimisation and troubleshooting of Hot melt extrusion (HME) of pharmaceutical formulations.

The fully softened shear strength was defined by Skempton (1970) as the peak drained shear strength of a clay in a normally consolidated state. All the experience available on the applicability of the fully softened shear strength for slopes is based on back-analyses. Back-analyses of first-time failures in cuts in stiff-fissured clays and embankments constructed of fat clays have shown that, over a long period of time, the shear strength gets reduced from what is measured in the laboratory using undisturbed samples to the fully softened shear strength. These back-analyses require knowledge or assumption of pore pressures in the slope, which will have a significant influence on the shear strength obtained. Karl Terzaghi, in 1936, was the first person that qualitatively explained the behavior of cut slopes in stiff-fissured clays. According to Terzaghi (1936), a softening process is initiated by the water percolating into the fissures causing swelling and decreasing the overall shear strength of the clay mass. Investigations presented later by Skempton and his colleagues showed that the controlling shear strength for cuts in stiff-fissured clays was equal to the fully softened shear strength and recommended this shear strength to be used for design (Skempton 1970; Chandler and Skempton 1974; Chandler 1974; Skempton 1977). Skempton (1977) concluded that displacements caused by progressive failure decrease the shear strength of stiff clays toward the fully softened shear strength. At first, it was believed that only stiff-fissured clays were subjected to softening and that intact clays should be designed using the peak shear strength measured using undisturbed samples (Skempton and Brown 1961; Skempton 1964, 1970). Recent publications have showed that the likelihood of a clay experiencing softening is more dependent on the plasticity of the clay rather than the fissures (Bjerrum 1967; Chandler 1984a; Mesri and Abdel-Ghaffar 1993). Fat clays, when compared to lean clays, tend to be more brittle. This means that fat clays have a more pronounced decrease in shear strength after the peak shear strength is achieved and for this reason are more susceptible to progressive failure. First-time failures in stiff clays usually occur a long period of time after construction. For this reason, steady state seepage was used in the back-analyses of the case histories presented by Skempton and his colleagues. They found that a pore pressure ratio of 0.3 was applicable to first-time failures in cuts in stiff-fissured clays (James 1970; Vaughan and Walbancke 1973; Chandler 1974; Skempton 1977). Investigations presented by Professor Steve Wright and his colleagues of the University of Texas at Austin showed, based on back-analyses, that the fully softened shear strength is also the controlling shear strength of compacted embankments constructed of highly plastic clays (Green and Wright 1986; Kayyal and Wright 1991; Wright 2005; Wright et al. 2007). Steve Wright and his colleagues concluded that weathering, expressed in cycles of wetting and drying, was the main mechanism decreasing the shear strength of compacted clay embankments toward the fully softened shear strength. Failures in this type of projects were found to be shallow (less than 10 ft deep) and to occur numerous years after construction (USACE 1983; Stauffer and Wright 1984; Kayyal and Wright 1991; Wright et al. 2007). A pore pressure ratio ranging from 0.4 to 0.6 was found to be applicable for the case histories analyzed by Wright and his colleagues. Day and Axten (1989) recommended the use of the infinite slope method with seepage parallel to the slope face for slope stability analyses. This same recommendation was presented by Lade (2010). A seepage parallel to the slope face corresponds to a pore pressure ratio ranging from 0.4 to 0.5 for slopes with ratios of 2H:1V to 5H:1V. Failures on compacted clay embankments related to softening have been reported in Texas (Stauffer and Wright 1984; Kayyal and Wright 1991; Wright 2005; Wright et al. 2007), and Mississippi (USACE 1983). According to McCook (2012), softening of this type of structures also occur in Louisiana To perform slope stability analyses using fully softened shear strength parameter, the type of soils, type of projects, and depths where this shear strength is applicable, and the pore pressures and factor of safety to be used in design should be determined. As stated above, the fully softened shear strength has been found to be the controlling shear strength of cuts in stiff clays and compacted embankments constructed of highly plastic clays. Steady state seepage conditions should be used to design cuts in stiff clays, and a pore pressure ratio ranging from 0.4 to 0.6 or a phreatic surface at the surface of the slope should be used to design compacted embankments made of fat clays. In cuts in stiff clays, both shallow and deep failures related to fully softened shear strength have been observed. For this type of project, the recommended methodology for design is to assign a curved fully softened failure envelope to the whole slope, search for the critical failure surface, and obtain the factor of safety. This approach will provide the correct factor of safety but the critical surface obtained might not be what is expected to occur in situ. Pore pressures corresponding to steady state seepage should be used for design. It should be emphasized that the recommendation to use fully softened shear strength in first-time failures in stiff clays is based on the back-analyses of case histories. Research is required to better understand progressive failure and its influence on the shear strength mobilized in situ. In compacted embankments constructed of fat clays, only shallow failures related to fully softened shear strength have been observed. For this type of projects, the recommended methodology for design is to assign a curved fully softened failure envelope to the whole embankment, search for the critical failure surface, and obtain the factor of safety. If for any reason deep failures are to be considered in designing compacted embankments constructed of fat clays, based on the fact that failures in this type of projects are usually shallow, the first 10 ft below the surface of the slope should be assumed to have a shear strength equal to the fully softened shear strength. Pore pressures should be calculated based on a water table coincident with the slope face. The fully softened shear strength should not be used in the foundation soil. If any softening occurred in the foundation soil, this should be reflected in the shear strength measured using undisturbed samples. Softening of the foundation soil is not expected to occur after the embankment is constructed. The consequences of shallow and a deep failures are usually not the same. For this reason, is reasonable that the same factor of safety should not be required for both cases. A shallow failure may be considered by some agencies solely as a maintenance issue. The factor of safety should be based on the uncertainties in the parameters being used for design and the consequences of failure of the structure (Duncan and Wright 2005). The parameters that have more impact on the factor of safety obtained for slope stability are shear strength and pore pressures. The fully softened shear strength is the lowest shear strength expected to be mobilized in first-time slides. This shear strength, coupled with a conservative assumption of pore pressure gives a low uncertainty in the parameters that have the most influence in the factor of safety. For shallow failures, the consequences of failure are very low. For this reason, if the fully softened shear strength is used, coupled with a water table corresponding to the worst case scenario possible, a factor of safety as low as 1.25 can be used. For deep failures, the consequences of failure will vary depending on the structure. The pore pressure for this type of analyses should be based on the worst seepage condition expected throughout the life of the project. In this case, for structures with low to mid consequences of failure, a factor of safety of 1.35 can be used. For structures with a high consequence of failure, a factor of safety of 1.50 can be used. These factors of safety are based on the recommendations presented by Duncan and Wright (2005) for factors of safety based on uncertainties in the parameters and consequences of failures. The fully softened shear strength should be measured using normally consolidated remolded specimens as recommended by Skempton (1977). Soil samples should be hydrated for two days using distilled or site-specific water. The soil sample should then be washed or pushed through a No. 40 (425 µm) sieve. To achieve the desired water content, the soil sample cab be air-dried or more water should be added. Water contents equal to or higher than the liquid limit should be used to prepare test specimens for fully softened shear strength measurements. The direct shear device is recommended for fully softened shear strength measurements. The Bromhead ring shear device does not provide accurate values of fully softened shear strength. The triaxial device requires more time and effort to measure the fully softened shear strength and provides about the same fully softened shear strength as the direct shear device. The fully softened shear strength failure envelope can be estimated using the correlation presented in Figure 6.59 for the parameters required for Equation 4.1. This correlation is only intended to be used in preliminary design or if better information is not available. Laboratory determination of fully softened shear strength is always recommended for final designs. If this is not possible, the confidence limits presented in Figure 6.59 should be used to determine the fully softened shear strength parameters. / Ph. D.

No / Transient liquid phase (TLP) brazing of Mg–AZ31 alloy and Ti–6Al–4V alloy was performed using double Ni and Cu sandwich foils. Two configurations were tested; first, Mg–AZ31/Cu–Ni/Ti–6Al–4V and second, Mg–AZ31/Ni–Cu/Ti–6Al–4V. The effect of set-up configuration of the foils on microstructural developments, mechanical properties and mechanism of joint formation was examined. The results showed that different reaction layers formed inside the joint region depending on the configuration chosen. The formation of e phase (Mg), r (CuMg2), d (Mg2Ni) and Mg3AlNi2 was observed in both configurations. Maximum shear strength obtained was 57 MPa for Mg–AZ31/Ni–Cu/Ti–6Al–4V configuration and in both configurations, the increase in bonding time resulted in a decrease in joint strength to 13 MPa. The mechanism of joint formation includes three stages; solid state diffusion, dissolution and widening of the joint, and isothermal solidification. / The authors would like to acknowledge The German Jordanian University (GJU), and NSERC Canada for the financial support for this research.

Sammanfattning Syfte Studiens syfte var att utvärdera bindningsstyrkan mellan protesbas och protestand beroende påframställningsteknik, med 3D-printning eller fräsning, och efter åldring. Material och metod Totalt framställdes 40 provkroppar varav 20 tillverkades genom 3D-printning (P) med SprintRay EU(SprintRay GmbH, Iserlohn, Tyskland) och 20 genom fräsning (F) med Ivotion (Ivoclar Vivadent AG,Schaan, Liechtenstein). Hälften av de frästa (TF) och 3D-printade provkropparna (TP), det vill säga10 av varje, utsattes för 5 000 termocykler i temperaturerna 5 och 55 °C (T) och förvarades idestillerat vatten i 48 timmar vid en temperatur på 37° C. Bindningsstyrkan mättes genom ettskjuvkrafttest enligt standardiserade metoder. Envägs-ANOVA och Tukey’s test användes för statistisk utvärdering av resultaten därsignifikansnivån sattes till α=0,05. En frakturanalys utfördes för att bedöma frakturtyper. Resultat Resultaten visade att P hade en signifikant högre bindningsstyrka än F (p&lt;0,001). Skillnaden kvarstod även efter åldring. Det var ingen signifikant skillnad (p=0,626) i bindningsstyrkan mellan F och TF. TP uppvisade signifikant lägre bindningsstyrka jämfört med P (p=0,007). Alla F fick en adhesiv och kohesiv blandfraktur. P fick nio kohesiva och en adhesiv fraktur. TF fick sex adhesiva och fyra blandfrakturer. TP fick sju kohesiva och tre blandfrakturer. Slutsats 3D-printade material har en högre bindningsstyrka mellan protesbas och protestand jämfört med frästa. Åldring har en större negativ inverkan på bindningsstyrkan mellan protesbas och protestand om materialen är 3D-printade jämfört med om de är frästa. / Abstract Objective The aim of the study was to evaluate the bond strength between denture base and denture toothdepending on the manufacturing technique, fabricated through either 3D-printing or milling, and afterageing. Material and methods 40 specimens were produced, 20 were produced through 3D-printing (P) using SprintRay EU(SprintRay GmbH, Iserlohn, Genmany) and 20 through milling (F) using Ivotion (Ivoclar VivadentAG, Schaan, Liechtenstein). Half of the milled (TF) and printed specimens (TP), i.e., 10 of eachgroup, underwent 5 000 cycles of thermocycling and were stored in distilled water for 48 hours at acontrolled temperature of 37° C. Bond strength was evaluated using a shear bond strength test. One-way ANOVA and Tukey’s test were employed to assess the results with a significance level atα=0.05. Fracture analysis was conducted to evaluate the fracture type. Results The result showed that P had significantly higher bond strength compared to F (p &lt;0.001). The difference remained after the ageing process. The comparison between F and TF yielded non-significant results (p=0.626). P had significantly higher bond strength than TP (p=0.007). All F had mixed fractures of adhesive and cohesive. P had nine cohesive and one adhesive fracture. TF had six adhesive fractures and the remaining were mixed fractures. TP had seven cohesive fractures and three mixed fractures. Conclusion 3D-printed materials have higher bond strength between the denture base and denture tooth compared to milled materials. Ageing has a greater negative impact on the bond strength between the denture base and denture tooth of printed materials compared to milled materials.

Résumé : Cette étude examine l'impact de la taille et de la gradation de particules sur les corrélations théoriques et empiriques existantes les plus connues entre la résistance au cisaillement et le comportement dilatatant des matériaux granulaires en condition de déformation plane et en compression triaxiale drainée. À cette fin, 276 tests de cisaillements symétriques directs et 35 tests de compressions triaxiales drainées ont été menés sur des échantillons composés de billes de basalte (particules rondes), et de sables constitués de particules angulaires (sable de Péribonka et sable d'Eastmain) sur une échelle de 63 µm à 2000 µm afin d'évaluer leur résistance au cisaillement et leur comportement de dilatance sur une vaste échelle de pressions normales et de densités relatives initiales. Premièrement, la fiabilité et l'applicabilité des limites de mesure à l’aide de tests physiques de cisaillements symétriques directs dans l'interprétation de la résistance au cisaillement frictionnel en déformation plane des matériaux granulaires ont été discutées et confirmées par l'usage du code informatique DEM, SiGran. L'accent a été particulièrement mis sur la validation du modèle DEM au moyen de comparaison des résultats des simulations DEM avec leurs équivalents physiques à une échelle macro. Les résultats virtuels DSA sont abordés du point de vue de la coaxialité entre les principales tensions et les principales directions des paliers de pression ainsi que de la déviation de la direction d'extension nulle à partir de la direction horizontale. Les résultats numériques fournissent également des données quantitatives sur les différentes formes d'énergie consommées durant le cisaillement confirmées par d'autres résultats physiques et numériques publiés. Sur la base des postulats précédents, un examen minutieux des résultats des essais de cisaillements directs et de données issues de la littérature a été accompli afin d'évaluer la fiabilité des formules empiriques bien connues de Bolton et Collins et al. avec leurs constantes couramment employées en condition de déformation plane. L'étude montre qu'une application des relations empiriques de force-dilatation de cisaillement avec les constantes proposées par Bolton (1986) et Collins et al. (1992) aux sables ayant une distribution de taille de particules différente peut conduire à surestimer leurs valeurs en terme de force de cisaillement. Dans cette étude, les coefficients des équations de Bolton et Collins et al. ont donc été ajustée afin de prendre en compte les caractéristiques des particules, en particulier le diamètre médian, D50. De manière analogue, les effets microstructuraux imposés par la géométrie interne des particules (par exemple la taille, la forme et la gradation des particules) sur la relation tension-dilatation très connue, celle de Rowe (1962), et son ajustement empirique en condition triaxiale drainée ont été examinés dans cette étude. Une comparaison des prédictions des formules proposées avec les données de force de cisaillement issues de la littérature fournit de nombreuses preuves en faveur des contraintes mises en place au sein des relations existantes de force-dilatation de cisaillement en condition de déformation plane et triaxiale. Ces comparaisons prouvent également que la prise en compte de la taille des grains conduit à des résultats plus tangibles que lorsque la taille de la particule n'est pas considérée. Les formules de force-dilatation ajustées peuvent se révéler avantageuses pour évaluer indépendamment la cohérence des forces de cisaillement déterminées expérimentalement et pour introduire des lois d’écoulement plus précises dans les analyses géotechniques analytiques et numériques. / Abstract : The present study examines more closely the potential impact of particle size and gradation on the most famous existing theoretical and empirical correlations between the shear strength and the dilation behavior of granular materials in plane strain and drained triaxial compression conditions. For this purpose, 276 symmetrical direct shear and 35 drained triaxial compression tests have been carried out on samples made up of basalt beads (rounded particles), and sands consisting of angular particles (Péribonka sand and Eastmain sand) in the range of 63 µm to 2000 µm to evaluate their shear resistance and dilation behavior over a wide range of normal pressures and initial relative densities. First, the reliability and applicability of boundary measurements in physical symmetrical direct shear tests to interpret the plane strain frictional shearing resistance of granular material have been discussed and confirmed using DEM computer code SiGran. Particular emphasis is placed on the validation of the DEM model by comparing the results of DEM simulations with their physical counterparts at the macro-scale. The virtual DSA results are discussed in terms of the coaxiality between the principal stresses and the principal strains increments directions as well as the deviation of the zero extension direction from the horizontal direction. The numerical results also provide quantitative data on different forms of energy consumed during shearing confirming other published physical and numerical results found in the literature. Following the assumptions above, a close scrutiny of symmetrical direct shear test results and strength and dilation data from the literature have been done to evaluate the reliability of well-known empirical Bolton’s and Collins et al.’s formulations with their commonly used constants in plane strain condition. The study shows that an application of empirical shear strength-dilation relationships with the constants proposed by Bolton (1986) and Collins et al. (1992) to sands with different particle-size distribution may strongly over-predict their shear strength values. In this study, the coefficients of Bolton’s and Collins et al.’s equations have been, therefore, adjusted to account for particle characteristics, in particular for D50. Similarly, the microstructural effects imposed by internal particle geometry (e.g. particle-size, particle shape, and particle gradation) on most popular stress-dilatancy relationship of Rowe (1962), and its empirical adjustment in drained triaxial condition have been investigated in this study. A comparison of the predictions by the proposed formulas with shear strength data from the literature provides evidences in support of the implemented constraints into existing shear strength-dilation relations in plane strain and drained triaxial conditions. These comparisons also proves that accounting for the grain size yields more authentic results than when particle size is not considered. The adjusted strength-dilation formulas may be beneficial for independently assessing the consistency of the experimentally-determined shear strengths, and introducing more refined flow rules into analytical and numerical geotechnical analyses.

Master of Science / Department of Biological and Agricultural Engineering / Donghai Wang / Algae proteins have similar amino acid compositions as conventional plant proteins, and are comparatively richer in the essential amino acids. Algae protein has the potential to be used in the development of a wide variety of products, including foods, animal feeds, bioplastics, and adhesives. The utilization of algae protein for value-added products would increase the economic feasibility of algae biodiesel. This research evaluated the adhesion, rheological, morphological, and thermal properties of adhesives made from algae protein extracted from Cladophora sp. and modified with either sodium hydroxide (pH 9, 10, 11) or sodium dodecyl sulfate (SDS, 0.5, 1, and 3%). Both alkali-modified and SDS-modified algae protein adhesives displayed improved dry shear strength compared to unmodified algae protein. However, only 3% SDS-modified algae protein significantly improved the water resistance as shown in wet and soak shear strength tests. Thermal analysis using differential scanning calorimetry showed that SDS modification caused complete denaturation of the algae protein. SDS modification also increased the viscosity of the adhesive and created rougher particle surface texture. These data suggest that SDS modification can effectively increase shear strength and water resistance of algae protein adhesives caused by protein denaturation and protein structure change.