PREDICTIVE MODEL FOR SCOUR DEPTH OF COASTAL STRUCTURE FAILURES DUE TO TSUNAMIS

Ravindra Jayaratne, Adewale Abimola, Takahito Mikami, Shunya Matsuba, Miguel Esteban, Tomoya Shibayama

Abstract


Post-tsunami field surveys carried out after the 2011 Great Eastern Japan Earthquake Tsunami revealed that scour around the landward side of concrete sea dikes and seawalls was the most dominant failure mechanism. To better understand this phenomenon, detailed scour data were collected and soil samples from the surveyed locations in Miyagi and Fukushima Prefectures of Japan were comprehensively analysed. Mathematical modeling technique was employed with various combinations of input variables considered in order to determine the effective variables needed to predict the representative scour depth at the leeward of a concrete sea dike or seawall and possible design of these coastal structures against tsunami impact. Parameters such as impact overflowing pressure, height of structure measured at the landward side, inundation height, inundation velocity, angle of landward slope, Darcy’s coefficient of permeability and scour depth were found to be the effective parameters essential to generate proposed scour depth predictive model. The results indicate that the hydrodynamic parameters, soil properties and physical geometry of coastal structure play a crucial role in the scour process of such structures. In addition to that, numerical experiments were also performed in order to understand the characteristics of tsunami flow around a typical coastal dike, and to propose preliminary guidelines for structure resilience against future tsunamis.

Keywords


2011 Great Eastern Japan Earthquake Tsunami; mathematical modeling; impact overflowing pressure; representative scour depth; predictive model

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References


Breusers, H.N.C., and A.J. Raudkivi. 1991. Scouring: Hydraulic Structures Design Manual, Vol. 2 (IAHR Design Manual). CRC Press.

Jayaratne, R., T. Mikami, M. Esteban, and T. Shibayama. 2013. Investigation of coastal structure failures due to the 2011 Great Eastern Japan Earthquake Tsunami, Proceedings of 10th Coasts, Marine Structures and Breakwaters Conference, ICE, UK.

Kato, F., Y. Suwa, K. Watanabe, and S. Hatogai. 2012. Mechanisms of coastal dike failure induced by the Great East Japan earthquake tsunami, Proceeding of 33rd International Conference on Coastal Engineering, ASCE.

Matsutomi, H., K. Okamoto, and K. Harada. 2010. Inundation flow velocity of tsunami on land and its practical use, Proceedings of 32nd International Conference on Coastal Engineering, ASCE.

Melville, B.W., and S.E. Coleman. 2000. Bridge Scour, Water Resources Publications, USA.

Mikami, T., and T. Shibayama. 2013. Numerical analysis of tsunami flow around coastal dike, Proceedings of 7th International Conference on Asian and Pacific Coasts, 654-659.

Mizutani, S., and F. Imamura. 2001. Dynamic wave force of tsunami acting on a structure, Proceedings of ITS, Session 7, No. 28, 941-948.

Powrie, W. 2004. Soil Mechanics: Concepts and Applications, 2nd Edition, Spon Press, New York.

Smagorinsky, J. 1963. General circulation experiments with primitive equations, Monthly Weather Review, 91(3), 99-164.

Sumer, B.M., R.J.S. Whitehouse, and A. Torum. 2001. Scour around coastal structures: A summary of recent research, Coastal Engineering, Elsevier, 44, 153-190.

The 2011 Tohoku Earthquake Tsunami Joint Survey Group. 2012. Field survey of 2011 Tohoku earthquake tsunami by the nationwide tsunami survey, JSCE.

Yeh, H., and W. Li. 2008. Tsunami scour and sedimentation, Proceedings of 4th International Conference on Scour and Erosion, 95-106.

Zhao, M., L. Cheng, and Z. Zang. 2010. Experimental and numerical investigation of local scour around a submerged vertical circular cylinder in steady currents, Coastal Engineering, Elsevier, 57, 709-721.




DOI: https://doi.org/10.9753/icce.v34.structures.56