Some Practical Aspects on the Seismic Behavior of Rubble-Mound Breakwaters

Rubble-mound breakwaters are port structures of major importance. Their seismic behavior has so far attracted limited attention due to the fact that in case of failure, one can simply add more material to restore the structure to its previous shape. However, more thorough investigation is required in cases where settlement of a breakwater would produce unacceptable damage to port installations in its lee, or have other detrimental effects. The present study, funded by the General Secretariat for Research and Technology, Greece, aims at investigating the seismic response of a rubble-mound breakwater. To this effect experiments were carried out, supported by mathematical modeling. Two physical models were used: one on solid bed and another sitting on a layer of sand. Acceleration and pressure sensors were fitted in the models. The latter were placed in a container fixed onto the shaking table of the Engineering Seismology Laboratory of the National Technical University, Greece. Both models were tested to horizontal shaking of increasing intensity. In total 38 tests were carried out on both models. It was found that the most prominent mode of failure was due to the settling of the structure into the loose foundation soil, which produced the characteristic swelling of the sea-bed close to the mound toes.