This thesis is a contribution to the existing knowledge of the nature of the scour hole around bridge piers. The analysis is based on the fictitious, long contraction concept developed by Dr. Emmett M. Laursen. This concept and its equation has been used herein to determine the size of rip-rap particles which will reduce the local scour at bridge piers. Evaluation of the parameters involved in it is required for sizing the rocks in a prototype. Values such as approach velocity, water depth, average diameter of the rip-rap particles in the scour, and geometry of the pier are among the values to be known. Both a graphic and an analytical procedure are proposed as a means to find the size of particles to be used as protection. The discussion and conclusions derived from this investigation will be of great help to civil engineers working in the field of river engineering.

Baihetan Dam is sited on the lower reaches of the Jinsha River in the southwest of China between the boarders of Sichuan and Yunnan province. The dam is scheduled to be taken into operation in the year of 2020 with an installed generation capacity of 14 GW which will put Baihetan Dam on the map as the third largest hydropower station in the world considering installed power output. In comparison, the world’s biggest dam Three Gorges has an installed generation capacity of 22,5 GW. To ensure a sufficient safety evaluation in terms of erosion (scour) formation at the bottom of the plunge pool, pressure simulations in the plunge pool floor in an experimental model at the Department of Hydraulic Engineering in Tsinghua University, Beijing, China has been performed. Data from two experiments with two different outflow configurations has been obtained and analyzed together with three earlier performed experiments on the same experimental model. The results from outflow configuration one had an incomplete data set and could not be compared to the other experiments. The results retrieved from the other experiments however showed the importance of a spillway design with nappe splitters and nappe blocks implemented and the value of a sufficient water cushion in the plunge pool. All four outflow configurations with nappe splitters or nappe blocks implemented held a hydrodynamic pressure below the recommended maximum pressure value of 15 cm water head (experimental model scale) stated by the East Asian Investigation and Design Institute, whilst the one configuration with no nappe splitters or nappe blocks exceeded the value. The design of outflow configuration two is four nappe splitters implemented in two spillways and two nappe blocks in two spillways. In this thesis, this configuration has proven to be the most suitable one in terms of maximum pressure minimization and pressure distribution at the plunge pool floor.

No description available.

Bridge scour is the loss of soil by erosion due to water flowing around bridge supports. Scour has been the number one cause of bridge collapse in the United States with an average rate of 22 bridges collapsing each year. This dissertation addresses three topics related to bridge scour. First, three sets of databases are used to quantify the statistical parameters associated with the scatter between the predicted and measured scour depth as well as the probability that a deterministically predicted scour depth will be exceeded. The analysis results from these databases will also be used to provide the bias factors in the scour depth predictions in practice. In the second part of the dissertation, these statistical parameters are used to develop a reliability-based Load and Resistance Factor Design (LRFD) for shallow and deep foundations subjected to scour. The goal is to provide a design procedure for the bridge foundations, where the reliability of the foundation is the same with or without scour. For shallow foundations, the key of the design issue is the location of the foundation depth and the probability that the scour depth will exceed the foundation depth. Therefore, for shallow foundations, the proposed LRFD calibration is based on the probability of exceedance of the predicted scour depth. However for deep foundations, the key of the design issue is the resistance factor associated with the axial capacity of a pile. Hence, the proposed LRFD calibration for deep foundations is based on a reliability analysis using First-Order Reliability Method (FORM). The dissertation is broadened in the third part by analyzing he risk associated with bridge scour, where the risk is defined as the probability of failure times the value of the consequences. In the third part, the risk associated with bridge scour is compared to risks associated with other engineering structures as well. Target values of acceptable risk are recommended as part of the conclusions. The outcome of the research will modify the current “AASHTO LRFD Bridge Design Specifications” developed by the American Association of State Highway and Transportation Officials (AASHTO) and help the practitioners design foundations of bridges over rivers for a uniform probability of failure in the case of scour. The risk of bridge scour is also quantified in the dissertation, and compared with common societal risks and civil engineering risks. It will help engineers understand the risk level associated with bridge scour.

The main objective of this study was to describe the overflow of freshwater onto the sea ice surface in the Mackenzie Delta and to investigate the hydraulic behaviour of the upwelling and strudel events. This study was performed from the analysis of data collected during field investigations, from satellite images and from experimental laboratory studies. A forecasting method using the water level in the Mackenzie River was formulated to predict the overflow initiation about five days before its occurrence. The physical modelling of a strudel flow through a circular hole established a relation between the overflow depth and the discharge coefficient. Velocity measurements of the free-surface vortex using an Acoustic Doppler Velocimeter found that velocities at the vortexs core were influenced by its vorticity. Finally, predictions of maximum strudel scour, which are of great importance for the determination of burial depth of pipelines, were predicted from published impinging jet experiments. / Water Resources Engineering

Thesis (Ph. D.)--Lehigh University, 2004. / Includes vita. In two parts. Includes bibliographical references (leaves 145-153).

Thesis (Ph. D.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2005. / Yoganathan, Ajit, Committee Member ; Sturm, Terry, Committee Member ; Webster, Donald, Committee Member ; Roberts, Philip, Committee Member ; Sotiropoulos, Fotis, Committee Chair ; Fritz, Hermann, Committee Member. Includes bibliographical references.

Thesis (Ph.D.)--University of Western Australia, 2007.

Thesis (M. En.)--Miami University, Institute of Environmental Sciences, 2006. / Title from first page of PDF document. Includes bibliographical references (p. 32-35).

Thesis (M.S.)--University of Missouri-Columbia, 2005. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (January 11, 2007) Includes bibliographical references.