Failure Mechanisms and Local Scour at Coastal Structures Induced by Tsunami

Mantripathi Prabath Ravindra Jayaratne, Buddhika Premaratne, Abimbola Adewale, Takahito Mikami, Shunya Matsuba, Tomoya Shibayama, Miguel Esteban, Ioan Nistor

    Research output: Contribution to journalArticle

    12 Citations (Scopus)

    Abstract

    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.

    Original languageEnglish
    JournalCoastal Engineering Journal
    DOIs
    Publication statusAccepted/In press - 2016

    Fingerprint

    Tsunami
    Scour
    Tsunamis
    Failure Mechanism
    Levees
    Retaining walls
    Armor
    Breakwaters
    Slope
    Infrastructure
    Hydraulic models
    Evacuation
    Failure Mode
    Disaster
    Hits
    Earthquake
    Japan
    Hazard
    Hydraulics
    Disasters

    Keywords

    • 2011 Tohoku tsunami
    • coastal structures
    • failure modes and mechanisms
    • mathematical model
    • post-disaster field surveys
    • scour failure
    • scour laboratory experiments

    ASJC Scopus subject areas

    • Civil and Structural Engineering
    • Modelling and Simulation
    • Ocean Engineering

    Cite this

    Jayaratne, M. P. R., Premaratne, B., Adewale, A., Mikami, T., Matsuba, S., Shibayama, T., ... Nistor, I. (Accepted/In press). Failure Mechanisms and Local Scour at Coastal Structures Induced by Tsunami. Coastal Engineering Journal. https://doi.org/10.1142/S0578563416400179

    Failure Mechanisms and Local Scour at Coastal Structures Induced by Tsunami. / Jayaratne, Mantripathi Prabath Ravindra; Premaratne, Buddhika; Adewale, Abimbola; Mikami, Takahito; Matsuba, Shunya; Shibayama, Tomoya; Esteban, Miguel; Nistor, Ioan.

    In: Coastal Engineering Journal, 2016.

    Research output: Contribution to journalArticle

    Jayaratne, Mantripathi Prabath Ravindra ; Premaratne, Buddhika ; Adewale, Abimbola ; Mikami, Takahito ; Matsuba, Shunya ; Shibayama, Tomoya ; Esteban, Miguel ; Nistor, Ioan. / Failure Mechanisms and Local Scour at Coastal Structures Induced by Tsunami. In: Coastal Engineering Journal. 2016.
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