TY - JOUR
T1 - Failure mechanisms and local scour at coastal structures induced by Tsunami
AU - Jayaratne, Mantripathi Prabath Ravindra
AU - Premaratne, Buddhika
AU - Adewale, Abimbola
AU - Mikami, Takahito
AU - Matsuba, Shunya
AU - Shibayama, Tomoya
AU - Esteban, Miguel
AU - Nistor, Ioan
N1 - Funding Information:
The authors would like to acknowledge the financial contribution of the Strategic Research Foundation Grant-aided Project for Private Universities (No: S1311028) from Japanese Ministry of Education, Culture, Sport, Science and Technology. The authors also wish to thank the Great Britain Sasakawa Foundation (GBSF) and the University of East London (UEL) for granting funds to carry out field surveys and modeling between 2011 and 2013.
PY - 2016/12/1
Y1 - 2016/12/1
N2 - On 11 March 2011, an exceptionally large tsunami event was triggered by a massive earthquake offshore, the northeast coast of Japan, which affected coastal infrastructure such as seawalls, coastal dikes and breakwaters in the Tohoku region. Such infrastructure was built to protect against the Level 1 tsunamis that previously hit the region, but not for events as significant as the 2011 Tohoku tsunami, which was categorized as a Level 2 tsunami [Shibayama, T., Esteban, M., Nistor, I., Takagi, H., Thao, N. D., Matsumaru, R., Mikami, T., Aranguiz, R., Jayaratne, R. & Ohira, K. [2013] "Classification of tsunami and evacuation areas," Nat. Hazards 67(2), 365-386]. The failure mechanisms of concrete-armored dikes, breakwaters and seawalls due to Level 2 tsunamis are still not fully understood by researchers and engineers. This paper investigates the failure modes and mechanisms of damaged coastal structures in Miyagi and Fukushima Prefectures, following the authors' post-disaster field surveys carried out between 2011 and 2013. Six significant failure mechanisms were identified for the coastal dikes and seawalls affected by this tsunami: (1) Leeward toe scour failure, (2) Crown armor failure, (3) Leeward slope armor failure, (4) Seaward toe scour and slope armor failure, (5) Overturning failure, and (6) Parapet wall failure, in which leeward toe scour being recognized as the major failure mechanism in most surveyed locations. The authors also propose a simple practical mathematical model for predicting the scour depth at the leeward toe of the coastal dikes, by considering the effects of the tsunami hydrodynamics, the soil properties and the type of structure. The key advantage of this model is that it depends entirely on quantities that are measurable in the field. Furthermore this model was further refined by conducting a series of hydraulic model experiments aimed to understand the governing factors of the leeward toe scour failure. Finally, based on the results obtained, key recommendations are given for the design of resilient coastal defense structures that can survive a level 2 tsunami event.
AB - On 11 March 2011, an exceptionally large tsunami event was triggered by a massive earthquake offshore, the northeast coast of Japan, which affected coastal infrastructure such as seawalls, coastal dikes and breakwaters in the Tohoku region. Such infrastructure was built to protect against the Level 1 tsunamis that previously hit the region, but not for events as significant as the 2011 Tohoku tsunami, which was categorized as a Level 2 tsunami [Shibayama, T., Esteban, M., Nistor, I., Takagi, H., Thao, N. D., Matsumaru, R., Mikami, T., Aranguiz, R., Jayaratne, R. & Ohira, K. [2013] "Classification of tsunami and evacuation areas," Nat. Hazards 67(2), 365-386]. The failure mechanisms of concrete-armored dikes, breakwaters and seawalls due to Level 2 tsunamis are still not fully understood by researchers and engineers. This paper investigates the failure modes and mechanisms of damaged coastal structures in Miyagi and Fukushima Prefectures, following the authors' post-disaster field surveys carried out between 2011 and 2013. Six significant failure mechanisms were identified for the coastal dikes and seawalls affected by this tsunami: (1) Leeward toe scour failure, (2) Crown armor failure, (3) Leeward slope armor failure, (4) Seaward toe scour and slope armor failure, (5) Overturning failure, and (6) Parapet wall failure, in which leeward toe scour being recognized as the major failure mechanism in most surveyed locations. The authors also propose a simple practical mathematical model for predicting the scour depth at the leeward toe of the coastal dikes, by considering the effects of the tsunami hydrodynamics, the soil properties and the type of structure. The key advantage of this model is that it depends entirely on quantities that are measurable in the field. Furthermore this model was further refined by conducting a series of hydraulic model experiments aimed to understand the governing factors of the leeward toe scour failure. Finally, based on the results obtained, key recommendations are given for the design of resilient coastal defense structures that can survive a level 2 tsunami event.
KW - 2011 Tohoku tsunami
KW - coastal structures
KW - failure modes and mechanisms
KW - mathematical model
KW - post-disaster field surveys
KW - scour failure
KW - scour laboratory experiments
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U2 - 10.1142/S0578563416400179
DO - 10.1142/S0578563416400179
M3 - Review article
AN - SCOPUS:85004008297
VL - 58
JO - Coastal Engineering in Japan
JF - Coastal Engineering in Japan
SN - 0578-5634
IS - 4
M1 - 1640017
ER -