Comparison of Pile-type and Gravity-type Coastal Levees in Terms of Resilience to Tsunami

抄録

In the Great East Japan Earthquake in 2011, many tide barriers and breakwaters collapsed due to the tsunami. On the other hand, one structure consisting of double sheet pile walls remained almost undamaged. This paper introduces a newly developed experimental apparatus called ‘Tsunami Simulator’, in which two types of tsunami, surge and reflux, can be simulated to investigate into the behavior of structures a part of which is embedded in the ground. It also summarizes the result of the adequately scaled model test on the behaviors of gravity-type and pile-type levees, when they are hit by surge-type tsunami. The test results showed that the pile-type levee remained resilient to tsunami while the gravity-type levee failed by sliding. This result demonstrates the effectiveness of the use of piles to improve the resilience of structures. On the other hand, the specification of piles should be adequately determined in design to assure the resilience of the system. It would be reasonable to allow some plastic deformation of piles, which cannot be adequately scaled in the model test, especially when a huge tsunami has to be considered.