Mechanisms for Damage and Failure from the Great East Japan Tsunami - Tohoku, Japan Earthquake and Tsunami of 2011 - page 50

3.3 Tsunami Uplift Forces
When tsunami waves completely or partially submerge a structure, or when they pass
underneath a structure resulting in entrapment of the waves on the underside of the
structure (i.e., bridge decks, piers), the structure experience uplift forces due to the
hydrostatic buoyancy including effects of excessive pore pressure and hydrodynamic
forces. The hydrodynamic forces result from the vertical difference in the dynamic
pressure forces over the surface of the structure, and the Bernoulli (aerodynamic)
effect as water flows around the structure (Figure 27). The uplift forces reduce the
structure's total effective dead weight, which may affect the structure's resistance to
overturning and sliding (Figure 28). Excessive tsunami-induced uplift forces can lift a
structure from its foundation, especially when the structure does not have sufficient
anchorage. Figures 29 - 35 show examples of structures subjected to tsunami uplift
forces.
Figure 27. Hydrostatic uplift forces
Figure 28. Hydraulic uplift and overtopping