Abstract
This study estimated the roughness factor of two type wave-dissipating blocks by wave overtopping experiments to calculate the amount of overtopping discharge based on EurOtop. The relationship between the roughness factor γf and surf similarity parameter ξm-1,0 was also examined. Experiments were conducted using a two-dimensional wave flume, and test blocks were GRASP and SEA-LOCK. The experimental conditions were set referring to Bruce et al. (2009). The input wave was random waves having JONSWAP spectrum of γ=3.3. The boundary of ξm-1,0 was set to 4.0, and γf was estimated by the least squares method. The relationship between the overtopping discharge q and the crest height RC was considered. Comparison of γf in cases with different layer thickness showed that the case of γf with large layer thickness was smaller than the γf with small layer thickness’ case. The results of Rock and Cube in the experiments by Bruce et al. indicated that the γf value of two-layers was smaller than that of single-layer, the present study was same tendency as existing results. By comparing γf in cases with different structure crest width GC, it was found the case of GC=150 mm was γf =0.36 of which value was about 8% smaller than the case of GC =104 mm. Consequently, it is considered that the γf value of wide structure crest became smaller than that of narrow crest. Under two-layer thickness condition, the roughness factors γf of SEA-LOCK were 15% smaller than the γf of GRASP. The installed volume porosity of GRASP is 63.5% and SEA-LOCK is 53%, GRASP is 10.5% larger than SEA-LOCK. In addition to the difference in block shape, it is thought that the difference in the installed volume porosity of the block also affected the overtopping discharge.
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References
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Acknowledgements
The authors would like to express appreciation to the former student of Kansai University, Mr. Shoya YASUTOMI for his efforts and contributions on hydraulic model experiments.
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Oguma, K., Matsushita, H., Hirayama, T., Kawamura, H., Yasuda, T., Mase, H. (2020). Roughness Factor of Two Type Wave-Dissipating Blocks Estimated by Overtopping Experiments. In: Trung Viet, N., Xiping, D., Thanh Tung, T. (eds) APAC 2019. APAC 2019. Springer, Singapore. https://doi.org/10.1007/978-981-15-0291-0_20
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DOI: https://doi.org/10.1007/978-981-15-0291-0_20
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