A method called SRICOS-EFA is presented in this dissertation for scour prediction. The method is based on the calculation of two basic parameters: the maximum depth of scour and the initial rate of scour. The maximum depth of scour is based on an equation obtained from flume tests and the initial rate is based on an equation giving the initial shear stress obtained from numerical simulations. The initial scour rate is then read on the Erosion Function Apparatus (EFA) erosion function curve at the corresponding value of the calculated shear stress. A hyperbola is used to connect the initial scour rate to the maximum scour depth and describes the complete scour depth vs. time curve. The erodibility function curve can be measured in the EFA. As the results show, the SRICOS-EFA method can handle the multi-flood hydrograph and multilayer soil system. It can be used to solve the complex pier and contraction scour alone; it can also handle the superposition of complex pier scour and contraction scour. A simplified SRICOS-EFA method was developed based on the case histories for contraction scour. EFA tests were performed to investigate the influence of different pH values and different levels of salinity on the soil erodibility. An attempt was made to find the correlation between the critical shear stress, and the initial slope of the erodibility function on the one hand and some geotechnical parameters on the other. A solution for future hydrograph prediction was developed in this dissertation. The prediction consists of using a past hydrograph, preparing the frequency distribution plot for the daily stream flows, sampling the distribution randomly and preparing a future hydrograph, which has the same mean and standard deviation as the measured hydrograph. A frequency distribution plot of scour depths can be used to quote a scour depth with a corresponding probability of occurrence and risk level based on future hydrographs. In the verification process, 10 bridge case histories and 3 scour databases were used to check whether the method is good enough to provide sound results in real cases.

In recent years, extreme natural phenomena such as tsunamis or storm surges have affected populated coastal regions around many coastal regions around the world and with particular impact for countries bordering the Indian, Pacific and Atlantic Oceans. Such extreme events caused significant loss of life and extensive damage to coastal communities. Field surveys conducted from the 1992 Nicaragua Tsunami to the relatively recent 2011 Tohoku Japan Tsunami have recorded lots of evidence of scour around damaged buildings and bridge foundations. It is documented that scouring is one of the significant causes of coastal structural damages. In post-tsunami forensic engineering surveys of India and Thailand following the 2004 Great Sumatra Andaman tsunami, researchers were able to document local scour occurrences not only at buildings located close to shore, but also hundreds of meters inland. (Yeh and Li 2008, Nistor et al. 2012 and Li et al. 2012). The most damaging 2011 Tohoku Tsunami provided an outstanding opportunity to document (Chock et al., 2013) a variety of failure modes of infrastructure including coastal and onshore structures. This research program encompassed a comprehensive experimental and numerical investigation and analysis for the scour mechanism and vortex structures due to inland-propagating tsunami-like bores on a dry or flooded horizontal mobile bed, representing comprehensive tsunami-induced scour study. The primary objective of this thesis was to investigate the influence of different parameters on the bore propagation characteristics and how they affect the scouring process. To achieve this objective, a series of hydraulic bores consistent with the dam-break wave theory were generated. Extensive experiments were conducted to perform parametric analysis on both bore propagation and local scour (e.g., influence of structure size, bore height, bed initial condition, bed material size and second tsunami wave). The secondary objective involved development of a numerical model to simulate local scour and predict the threedimensional (3D) flow pattern around a structure induced by tsunami–like bore. The open source TelemacMascaret numerical model was used to determine flow characteristics adjacent to the structure and the associated bed evolution and resulting local scour. The 3D hydrodynamic Telemac model couples internally with the sediment transport module SISYPHE to solve bed evolution equations. The efficiency of the numerical model was assessed and compared quantitatively and qualitatively with the results of the physical experiments. The studies show a longer duration of a turbulent bore induced more scour depth compared to that generated by solitary or long waves. The short duration and very turbulent nature of the bores induced rapid scour. It was shown that the location of maximum scour depth and sediment deposition pattern downstream of the structure are well captured by the numerical model, however; magnitude of scour depth is underpredicted compared to that of the experimental work. It was found that the ASCE (2016) prescriptions on estimating scour underpredicts the maximum scour depth and thus, the use of the ASCE (2016) provisions, may lead to undesirable underestimations of maximum scour depth. The results of this study have contributed to the American Society of Civil Engineers (ASCE) 7 Chapter 6, which is the first standard written in mandatory language in the world, which specifically prescribes guidance for the design of tsunami resilient critical infrastructure using also a probabilistic framework for the determination of the extent of coastal inundation.

Bridge scour is the term which describes the erosion of soil surrounding a bridge foundation due to water. Bridge scour can cause the reduction of the load carrying capacity of bridge foundations, excessive foundation settlements, and damage to bridge abutments. Bridges with foundations that are unstable for calculated and/or observed scour conditions are termed scour critical bridges. Approximately 25,000 bridges in the United States are classified as scour critical and about 600 of them are in Texas. This designation comes in part from the use of over-conservative methods that predict excessive scour depths in erosion resistant materials. Other methods have been developed to eliminate this over-conservatism but are uneconomical because they require site-specific erosion testing. The major contribution of this dissertation is a new method to assess a bridge for scour and erosion classification charts which categorizes the erodibility of geomaterials according to conventional engineering properties. The new method is a three level Bridge Scour Assessment (BSA) procedure which is relatively simple and economical. It does not require site-specific erosion testing and eliminates the over-conservatism in current methods. The first level, BSA 1, uses charts that extrapolate the maximum scour depth recorded during the life of the bridge to obtain the scour depth corresponding to a specified future flood event. The second level, BSA 2, determines the maximum scour depth and is carried out if BSA 1 does not conclude with a specific plan of action for the bridge. The third level, BSA 3, determines the time dependent scour depth and is carried out if BSA 2 does not conclude with a specific plan of action. The scour vulnerability depends on the comparison between the predicted and allowable scour depths. The 11 case histories used to validate the new method showed good agreement between predicted values and field measurements. BSA 1 was then applied to 16 bridges. In this process, 6 out of 10 bridges classified as scour critical by current methods were found to be stable. These results show that the new method allows for more realistic evaluation of bridges for scour while not requiring site-specific erosion testing.

A series of relatively recent bridge failures due to pier scour, as reported in literature, has rekindled interest in furthering our understanding of the scour process and for developing improved ways of protecting bridges against scour. Moreover, increased attention is being given to the state of Canadas infrastructure, a major aspect of which is the transportation network. In part, there is concern about both the impact of a failure on the handling of traffic flow while the failure is being remedied and on the cost of replacing the failed system component. As such, attention is being given to the scour design of new bridges and to the inspection, maintenance and management of existing bridge structures. The two major countermeasure techniques employed for preventing or minimising local scour at bridge piers are increased scour resistance and flow alteration. In the former case, the objective is to combat the erosive action of the scour-inducing mechanisms using hard engineering materials or physical barriers such as rock riprap. In the latter case, the objective is to either inhibit the formation of the scour-inducing mechanisms or to cause the scour to be shifted away from the immediate vicinity of the pier. This research focuses on a particular application of the latter technique. <p> In this study, the use of collars for reducing the effects of local scour at a bridge pier is presented together with the time aspect of the scour development. The adoption of a collar is based on the concept that its existence will sufficiently inhibit and/or deflect the local scour mechanisms so as to reduce the local scour immediately adjacent to the pier. The overall objective of the research is to study the temporal development of the scour for a pier fitted with a collar and a pier without a collar. More specifically, the objectives are: i) to evaluate the effectiveness of a pier collar for mitigating the depth of scour that would otherwise occur at a bridge pier; and ii) to assess the occurrence of an equilibrium scour condition, if achieved, or of the implications of not achieving such a condition in respect of interpreting the results obtained from a physical hydraulic model study. <p>The study was conducted using a physical hydraulic model operated under clear-water conditions in cohesionless bed material. Tests were conducted using two different pier diameters so as to determine the effect of pier diameter on the temporal development of scour for a plain pier. Also investigated was the effect of collar size on the time development of scour and its efficacy at preventing scour at a bridge pier. The time development of the scour hole around the model pier with and without a collar installed was compared with similar studies on bridge piers. Several equations for the temporal development of scour depth and those for the prediction of the equilibrium scour depth were tested as part of this study. <p>The results of the model study indicated that the maximum depth of scour is highly dependent on the experimental duration. The depth of the scour hole increases as the duration of the increased flow that initiates the scour increases. The extent of scour observed at the pier also increases as the duration of the tests increases. It was found that the temporal development of the scour hole at the pier was dependent on whether or not the pier was fitted with a collar placed at the bed level. The pathway to an equilibrium scour depth is different depending on whether the pier is fitted with a collar or not. With a collar in place, the development of the scour hole is considerably delayed. A truly equilibrium scour condition is not readily attainable and was not achieved in the work reported herein. It was demonstrated that wrong conclusions may be reached if a test is stopped short of an equilibrium state. As regards the temporal development of scour depth and for the tests in which no collar was fitted to the pier, it was noted that the form of equation that fits the experimental data well was the one given by Franzetti et al. (1982). Furthermore, it is possible to reach a variety of conclusions about the efficacy of using collars as a pier scour countermeasure technique, depending on which definition of time to equilibrium scour is adopted.

A series of relatively recent bridge failures due to pier scour, as reported in literature, has rekindled interest in furthering our understanding of the scour process and for developing improved ways of protecting bridges against scour. Moreover, increased attention is being given to the state of Canadas infrastructure, a major aspect of which is the transportation network. In part, there is concern about both the impact of a failure on the handling of traffic flow while the failure is being remedied and on the cost of replacing the failed system component. As such, attention is being given to the scour design of new bridges and to the inspection, maintenance and management of existing bridge structures. The two major countermeasure techniques employed for preventing or minimising local scour at bridge piers are increased scour resistance and flow alteration. In the former case, the objective is to combat the erosive action of the scour-inducing mechanisms using hard engineering materials or physical barriers such as rock riprap. In the latter case, the objective is to either inhibit the formation of the scour-inducing mechanisms or to cause the scour to be shifted away from the immediate vicinity of the pier. This research focuses on a particular application of the latter technique. <p> In this study, the use of collars for reducing the effects of local scour at a bridge pier is presented together with the time aspect of the scour development. The adoption of a collar is based on the concept that its existence will sufficiently inhibit and/or deflect the local scour mechanisms so as to reduce the local scour immediately adjacent to the pier. The overall objective of the research is to study the temporal development of the scour for a pier fitted with a collar and a pier without a collar. More specifically, the objectives are: i) to evaluate the effectiveness of a pier collar for mitigating the depth of scour that would otherwise occur at a bridge pier; and ii) to assess the occurrence of an equilibrium scour condition, if achieved, or of the implications of not achieving such a condition in respect of interpreting the results obtained from a physical hydraulic model study. <p>The study was conducted using a physical hydraulic model operated under clear-water conditions in cohesionless bed material. Tests were conducted using two different pier diameters so as to determine the effect of pier diameter on the temporal development of scour for a plain pier. Also investigated was the effect of collar size on the time development of scour and its efficacy at preventing scour at a bridge pier. The time development of the scour hole around the model pier with and without a collar installed was compared with similar studies on bridge piers. Several equations for the temporal development of scour depth and those for the prediction of the equilibrium scour depth were tested as part of this study. <p>The results of the model study indicated that the maximum depth of scour is highly dependent on the experimental duration. The depth of the scour hole increases as the duration of the increased flow that initiates the scour increases. The extent of scour observed at the pier also increases as the duration of the tests increases. It was found that the temporal development of the scour hole at the pier was dependent on whether or not the pier was fitted with a collar placed at the bed level. The pathway to an equilibrium scour depth is different depending on whether the pier is fitted with a collar or not. With a collar in place, the development of the scour hole is considerably delayed. A truly equilibrium scour condition is not readily attainable and was not achieved in the work reported herein. It was demonstrated that wrong conclusions may be reached if a test is stopped short of an equilibrium state. As regards the temporal development of scour depth and for the tests in which no collar was fitted to the pier, it was noted that the form of equation that fits the experimental data well was the one given by Franzetti et al. (1982). Furthermore, it is possible to reach a variety of conclusions about the efficacy of using collars as a pier scour countermeasure technique, depending on which definition of time to equilibrium scour is adopted.

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Master of Science / Department of Civil Engineering / Stacey Tucker-Kulesza / The erosion rate, or erodibility, of soil depends on many soil characteristics including: plasticity, water content, grain size, percent clay, compaction, and shear strength. Many of these characteristics also influence soil in situ bulk electrical resistivity (ER) measurements. The objective of this study was to characterize soil erosion potential by correlating the in situ ER of soil with erodibility measured in the Kansas State University Erosion Function Apparatus (KSU-EFA). ER surveys were conducted at eleven bridge sites. Soil samples were also collected at each site with a drill rig from the surface to three meters using thin-walled Shelby tubes. Five samples were collected at each site, tested in the KSU-EFA, and classified according to the Unified Soil Classification System. Analysis showed that the rapid in situ data obtained from an ER survey can be used to categorize the level of erodibility. As such, ER surveys may be used to characterize the soils at future bridge sites or prioritize existing bridges for additional testing to measure the scour potential. Moreover, ER surveys may be used to determine which existing bridges should be closed or closely monitored for scour potential during a flood event. Analytical models to predict critical shear stress using ER and other soil parameters were constructed.

Maximum equilibrium scour depths, equilibrium scour volumes, and induced equilibrium movements at isolated obstacles on river beds were investigated in clear-water scour. The research was achieved by a systematic flume study based on the results of dimensional analysis of local scour. The main tested obstacles for local scour were cubes. Local scour at a circular cylinder of aspect ratio 1 and a sphere were also examined for comparison with scour at cubes. Each obstacle was placed on a flat movable bed and oriented normal to the incident flow. Non-cohesive uniform medium sand and very fine gravel were used as movable beds. The tested flow conditions were controlled to give many combinations of the relevant dimensionless parameters for local scour: the flow Froude Number, relative obstacle size, and relative roughness of bed material. Water surface profiles and longitudinal velocity profiles along the plane of symmetry, as well as the horizontal velocities near the bed around isolated obstacles on a fixed bed were examined in several runs. For a slightly submerged cube, the path of maximum velocity downstream of the cube moves from the water surface into the lower part of the flow. At a greater distance downstream, the path of maximum velocity tends to move upward toward the water surface. An increase of flow Froude Number leads to a hydraulic jump behind the cube. The relative longitudinal velocity near the bed is increased in this region. The decrease of relative water depth or the increase of flow Froude Number can lead to increased average relative horizontal velocity (V/u) near a cube. The cube has the highest average V/u value, as compared to flow near a circular cylinder and a sphere. The local scour processes and equilibrium scour patterns at isolated cubes on movable beds were also examined. There is not a unique equilibrium scour pattern for clear-water scour at a cube on a movable bed. Equations were developed to predict the maximum equilibrium scour depth and scour volume and the critical condition for incipient motion of bed material at a cube in clear-water scour. As the water becomes relatively deep, the shape effect of the circular cylinder and the sphere become negligible. The major equilibrium movement of a cube on a movable bed due to scour involves longitudinal displacement, vertical settlement, and longitudinal inclination. Equations were developed to predict the equilibrium movement and the critical condition for incipient upstream movement of a cube in clear-water scour. / Graduation date: 1991

A new state-of-the-art CFD solver capable of simulating a broad range of complex engineering flows at real-life Reynolds numbers is developed. The method solves the three-dimensional incompressible unsteady Reynolds-averaged Navier-Stokes (URANS) equations closed with statistical turbulence models. Three such models are incorporated in the solver: the standard k - e model with wall functions, the Spalart-Allmaras model and the detached-eddy simulation (DES) model. The numerical solver employs domain decomposition with structured Chimera overset grids to handle complex, multi-connected geometries. The governing equations are discretized with second order accuracy schemes both in space and time. The capabilities and versatility of the numerical method are demonstrated by applying it to simulate two widely different flow problems: a) flow past a geometrical complex array of multiple bridge piers mounted both on a natural river reach and on a flat bed experimental flume; and b) flow in mechanical, bileaflet, prosthetic heart valve with the leaflets fixed in the fully-open position. Overset grid systems with several millions of grid nodes are used and grid-refinement and other numerical dependency studies are carried out to explore the sensitivity of the computed solutions to various numerical parameters. For all simulated cases, large-scale unsteadiness appears naturally as a result of excited mean-flow instabilities and the computed mean flowfields are shown to be in good quantitative agreement with experimental measurements. By analyzing the instantaneous flowfields numerous novel insights into the physics of both flow cases are obtained and discussed extensively. The results of this thesis demonstrate the potential of the new method as a powerful simulation tool for a broad range of cross-disciplinary engineering flow problems and underscore the need for physics-based numerical modeling by integrating CFD with laboratory experimentation.