2011 Volume 67 Issue 1 Pages 133-144
In order to investigate the deformation and failure behaviors of ground with the interaction among tsunami, coastal structure and ground (seabed and rubble-mound over it), both of dram type-centrifuge model test and numerical simulation with the Smooth Particle Hydrodynamics (SPH) method were performed. In the model test, the tsunami fluid force with large momentum applied to a caisson-type breakwater was reproduced, and deformation behaviors of the ground were observed by PIV image analysis; subsequently, the pore water pressure in the ground could be measured. When we placed a highly permeable rubble mound over the seabed ground, the hydraulic gradient increased due to seepage flow from the tsunami, and this led to the occurrence of a local seepage failure. In the numerical analysis, we compared the resulting data with the experimental results related to dam break and the results obtained by finite difference calculation (using a numerical wave experimental channel called CADMAS-SURF which is widely used in coastal engineering field), and this confirmed the reproducibility of tsunami fluid behaviors. We could then calculate the tsunami flow field, including coastal structures, rubble mounds consisting of non-deformable porous materials, and the seabed ground. An overflow phenomenon and the pressures of the tsunami's wave distribution could be quantitatively reproduced. This clarified how the tsunami would act on coastal structures and showed how conditions likely to cause seepage failures in rubble mounds and the seabed ground with different hydraulic gradients and permeability could be identified.
