Mechanisms for Damage and Failure from the Great East Japan Tsunami - Tohoku, Japan Earthquake and Tsunami of 2011 - page 49

(d) Produce impact loads such as hydrodynamic drag forces, impulsive forces,
debris acting as projectiles that either strike the structure or cause debris
damming resulting in damage
(e) Produce excessive buoyant forces that uplift and move the structure from its
foundation
(f) Produce excessive lateral loading that result in the structure's overturning

The examples shown in Figures 23 - 26 all exhibit various combinations of these
loads. In Figure 26, for example, the wall sections at Kojirahama experienced
overturning due to lateral loading. However, the landside scour that occurred during
overtopping and the added buoyancy in the units from the airspace of a built-in tunnel
on their landside face exacerbated damages caused by overturning.

Figure 23. Noda Tsunami Seawall (old
wall) —Backside erosion/concrete
armor units tossed over wall; wall
sections broken off

Figure 24. Noda Tsunami Seawall (new
wall) — Backside erosion with loss of
precast concrete panels; one upper
section of wall sheared off

Figure 25. Omoto Port breakwater —
3.5m high x 56m long section of wall
sheared off

Figure 26. Kojirahama tsunami wall —
Five wall sections overturned due to
landside scouring resulting in 74m-
breach