Today, more than forty percent of the world’s population lives within 100 kilometers of a coastal area, and population densities are only increasing. In recent years, extreme conditions have resulted in several failures of coastal protection structures around the world. During these failure events, the incurred cost of damages and loss of life has been nearly immeasurable.
Rubble mound breakwaters have been used for millennia, and are critical even today for the protection of coastal areas. In the last several decades, the popularity of using concrete armour units in place of natural rock has risen greatly. However, the quantitative interaction between wave hydrodynamics and the armour layer is still not clearly understood. Due to highly complex, turbulent flow patterns that occur in the armour layer, direct assessment of forces acting on individual units has not been practical. This has prevented the coastal engineering field from applying a force-balance design approach that is commonplace in other civil engineering disciplines. Instead, a wealth of experimental testing and past case studies have resulted in a wide array of empirical formulae and design techniques. These approaches are often very idealized and do not account for all parameters that have been shown to affect armour unit stability.
The current study aims to quantify the forces and pressures acting on units within an armour layer, using an experimental approach. This was achieved by developing an instrumented Core-Loc armour unit. This armour unit was outfitted with 6 pressure sensors, and the ability to be mounted on a force transducer. This unit was then put through a performance analysis and calibration procedure, before being extensively tested in a breakwater setting. Wide ranges of wave conditions were utilized, with the unit at three different locations along the breakwater slope. This was done to isolate both the effect of various sea state parameters, and the effect of unit location along a breakwater slope versus generated forces and pressures. In addition to the experimental study, an accompanying numerical study was performed in OpenFOAM. This had the intent of both developing general modeling rules of thumb for rubble mound breakwaters, and for replicating the experimental results.
The results showed that using relatively low-tech, low-cost, and widely available instrumentation was capable of performing in a coastal engineering setting. The performance of the unit showed great promise for “smart-units” to usher in a new paradigm of experimental testing for rubble mound breakwaters. From the results of the performance analysis and calibration procedure, it was evident that the unit could record forces and pressures to a high degree of accuracy. From the breakwater testing program, notable relationships between unit location, surf similarity, and wave steepness emerged. It appeared that the largest hydrodynamic interaction with units occurs slightly below the SWL. As well, both decreased surf similarity, and increased wave steepness resulted in higher hydrodynamic interaction for all locations. General rules of thumb for modeling armour units, as well as wave conditions in a breakwater setting were developed for the numerical study in OpenFOAM. Additionally, the calibrated numerical model was capable of reproducing the experimental results with reasonable accuracy.
| Identifer | oai:union.ndltd.org:uottawa.ca/oai:ruor.uottawa.ca:10393/39058 |
| Date | 12 April 2019 |
| Creators | Eden, Derek |
| Contributors | Nistor, Ioan, Cornett, Andrew |
| Publisher | Université d'Ottawa / University of Ottawa |
| Source Sets | Université d’Ottawa |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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