The presence of moisture in hot mix asphalt (HMA) causes loss of strength and durability of the mix, which is referred to as moisture damage. This study deals with the development of experimental methods for measuring total suction in HMA, which can be defined as the free energy state of water in HMA mixes. The total suction is related to the ability of moisture to get into the mix under unsaturated conditions; it is also related to the ability of the mix to retain moisture. Soil suction has been studied extensively. However, suction in HMA as a porous material and its relationship to moisture damage have not been studied. The development of a procedure to measure the total suction in HMA mixes is the first objective of this research. The second objective is to relate suction measurements to physical and chemical properties of the mixtures. The objectives were achieved in two phases. In the first phase, the total suction was measured in HMA specimens with different types of aggregates (limestone and granite), and with different air void distributions and aggregate gradations. The results of this phase showed that the drying test using a 60 oC temperature-controlled room is the proper setup for measuring the total suction in HMA using thermocouple psychrometers. The characteristics of suction-moisture content curves were found to be related to the air void distribution in HMA. In the second phase, total suction was measured in sand asphalt specimens. These specimens had different combinations of aggregates and binders with different bond energies and exhibited different field performance in terms of resistance to moisture damage. The suction measurements in sand asphalt specimens were used to calculate the moisture diffusion coefficient. The results revealed that water diffused into sand asphalt specimens that are known to have poor resistance to moisture damage faster than those that are known to have good resistance to moisture damage

Doctor of Philosophy / Suction caissons have been used in the offshore industry in the last two decades as both temporary mooring anchorages and permanent foundation systems. Although there have been more than 500 suction caissons installed in various locations around the world,understanding of this concept is still limited. This thesis investigates the installation aspect of suction caissons, focusing on the installation in dense sand and layered soils, where sand is inter-bedded by silt and weakly cemented layers. The research was mainly experimental, at both normal gravity and elevated acceleration levels in a geotechnical centrifuge, with some numerical simulations to complement the experimental observations. This study firstly explored the suction caisson installation response in the laboratory at 1g. The influence and effect of different design parameters, which include caisson size and wall thickness, and operational parameters including pumping rate and the use of surcharge were investigated in dense silica sand. The sand heave inside the caisson formed during these installations was also recorded and compared between tests. The 1g study also investigated the possibility of installing suction caissons in layered sand-silt soil, where caissons were installed by both slow and rapid pumping. The heave formation in this case is also discussed. The mechanism of heave formation in dense sand and deformation of the silt layer was further investigated using a half-caisson model and the particle image velocimetry (PIV) technique. The installation response at prototype soil stress conditions was then investigated in a geotechnical centrifuge. The effects of caisson size, wall thickness, as well as surcharge were investigated in various types of sand, including silica sand, calcareous sand dredged from the North Rankin site in the North West Shelf (Australia), and mixed soil where silica sand was mixed with different contents of silica flour. Comparison with the 1g results was also made. The general trend for the suction pressure during installation in homogenous sand was identified. The installation in layered soil was also investigated in the centrifuge. The installation tests were performed in various sand-silt profiles, where the silt layers were on the surface and embedded within the sand. Comparison with the results in homogenous sand was made to explore the influence of the silt layer. Installations in calcareous sand with cemented layers were also conducted. The penetration mechanism through the cemented layer is discussed, and also compared with the penetration mechanism through the silt layer. Finite element modelling was performed to simulate key installation behaviour. In particular, it was applied to simulate the sand deformation observed in the PIV tests. The likely loosening range of the internal sand plug during suction installation in silica sand was estimated. By investigating the development of hydraulic gradient along the inner wall, the principle underlying the suction response for different combinations of selfweight and wall thickness was identified. FE modelling was also performed to explore the influence of the hydraulic blockage by the silt layer. This study found that the caissons could penetrate into all soils by suction installation. Among the key findings are the observations that the suction pressure increases with depth following a distinct pressure slope, corresponding to a critical hydraulic condition along the inner wall; and the installation was possible in both layered sand-silt and uncemented-cemented soils if sufficient pumping was available. While the caisson could penetrate the weakly cemented layers well with no notable adverse effects, problems were observed in the installation in layered sand-silt soil. These include piping failure in slow pumping rate installation at 1g, and the formation of extremely unstable soil heave during installation.

Thesis (M.S.)--University of Wisconsin--Madison, 1981. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 77-82).

abstract: Fluctuating flow releases on regulated rivers destabilize downstream riverbanks, causing unintended, unnatural, and uncontrolled geomorphologic changes. These flow releases, usually a result of upstream hydroelectric dam operations, create manmade tidal effects that cause significant environmental damage; harm fish, vegetation, mammal, and avian habitats; and destroy riverbank camping and boating areas. This work focuses on rivers regulated by hydroelectric dams and have banks formed by sediment processes. For these systems, bank failures can be reduced, but not eliminated, by modifying flow release schedules. Unfortunately, comprehensive mitigation can only be accomplished with expensive rebuilding floods which release trapped sediment back into the river. The contribution of this research is to optimize weekly hydroelectric dam releases to minimize the cost of annually mitigating downstream bank failures. Physical process modeling of dynamic seepage effects is achieved through a new analytical unsaturated porewater response model that allows arbitrary periodic stage loading by Fourier series. This model is incorporated into a derived bank failure risk model that utilizes stochastic parameters identified through a meta-analysis of more than 150 documented slope failures. The risk model is then expanded to the river reach level by a Monte Carlos simulation and nonlinear regression of measured attenuation effects. Finally, the comprehensive risk model is subjected to a simulated annealing (SA) optimization scheme that accounts for physical, environmental, mechanical, operations, and flow constraints. The complete risk model is used to optimize the weekly flow release schedule of the Glen Canyon Dam, which regulates flow in the Colorado River within the Grand Canyon. A solution was obtained that reduces downstream failure risk, allows annual rebuilding floods, and predicts a hydroelectric revenue increase of more than 2%. / Dissertation/Thesis / Ph.D. Civil and Environmental Engineering 2010

No description available.

Three-dimensional two-phase unsteady CFD simulations were run on three and four-blade inducers for the purpose of analyzing differences in cavitation stability at design and off-design flow rates. At design flow rates, there were very small differences between the breakdown curves for the three and four-bladed inducers. However, at lower cavitation numbers, the three-bladed inducer exhibited up to three times the rotor forces than the four-bladed inducer. When moving to off-design flow rates, both inducers experienced multiple modes of cavitation instabilities including rotating cavitation, alternate-blade cavitation, and cavitation surge. The four-bladed inducer began experiencing the formation of these modes of instability beginning at a cavitation number of $sigma = 0.047$ whereas the three-bladed inducer began at a cavitation number of $sigma = 0.091$. Additionally, the three-bladed inducer showed rotor forces up to ten times higher than the four-bladed inducer at similar cavitation numbers.Three-dimensional single-phase steady CFD simulations were run on four-blade inducer geometries with $7^{circ}$, $9^{circ}$, $11^{circ}$ and $14^{circ}$ inlet tip blade angles with a stability control device (SCD) installed. The simulations were ran at multiple flow coefficients. Results show interesting flow effects from the SCD. For example, at lower flow coefficients, the incidence angle actually decreases at greater than 70\% span. This is due to a region of accelerated axial flow coming from the recirculation of the SCD which occurs near the shroud. Results also show strong correlations between efficiency and head rise to the local mass flow gain experienced due to the recirculating flow through the SCD. A best fit curve was generated to predict mass flow gain based on the inducer's inlet tip blade angle and flow coefficient. Based on this research, the ability to predict mass flow gain and consequently efficiency and head rise for similarly designed inducers with varying inlet blade angles has been demonstrated.

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第22491号 / 農博第2395号 / 新制||農||1076(附属図書館) / 学位論文||R2||N5271(農学部図書室) / 京都大学大学院農学研究科地域環境科学専攻 / (主査)教授 村上 章, 教授 藤原 正幸, 教授 白岩 立彦 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

In an effort to understand the behavior of the laminar separation bubbles on NACA 0012 and Liebeck LA2573a airfoils at different Reynolds numbers and angles of attack, the boundary layers on the solid airfoils were investigated by measuring the mean and fluctuating components of the velocity profiles over the upper surfaces of the airfoils. Surface pressure measurements were carried out to complete the mapping of the laminar separation bubble and to calculate the lift generated by the airfoils. The experiments were carried out at Reynolds numbers of 150,000 and 250,000. The locations of separation, transition and reattachment were determined as functions of angle of attack and Reynolds number for the two airfoils. The drag was estimated from wake pressure measurements and was based on the momentum deficit generated by the airfoil. The size and location of the laminar separation bubble did not show significant changes with Reynolds number and angle of attack for values of the angle of attack between 0 and 6 d grees. The baseline results of the size and location of the laminar separation bubble on the LA2573a airfoil were used to design a suction distribution. This suction distribution was designed based on Thwaites’ criterion of separation. The effects of applying suction on the size and location of the laminar separation bubble were investigated. The results showed that the suction distribution designed in this work was effective in controlling the size of the laminar separation bubble, maintaining an un-separated laminar boundary layer to the transition point, and controlling the location of transition. The effects of different suction rates and distributions on the drag were investigated. Drag reductions of 14-24% were achieved. A figure of merit was defined as drag reductions divided by the equivalent suction drag to assess the worthiness of the utilizing suction on low Reynolds number flows. The values of the figure of merit were around 4.0 which proved that the penalty of using suction was significantly less than the gain obtained in reducing the drag.

No description available.

No description available.