Open caissons are sunk into the ground by their own weight. A cutting edge of the caisson having a tapered inner face on loading – that is, raising of the steining – results in bearing failure by d...

Experimental evaluation of ultimate bearing capacity of the cutting edge of an open caisson

Numerical simulation of suction bucket foundation response located in liquefiable sand under earthquakes

Coastal protective structures, such as composite breakwaters, are generally vulnerable to earthquake. It was observed that breakwaters damage mainly due to failure of their foundations. However, th...

Countermeasures for breakwater foundation subjected to foreshocks and main shock of earthquake loading

Centrifuge modelling for stability evaluation of a breakwater foundation subjected to an earthquake and a tsunami

Experimental study on the seismic behavior of composite breakwaters located on liquefiable seabed

The Tohoku coastal area in Japan suffered massive damage in the Great Tohoku Earthquake, in which a prolonged major earthquake was followed by a large tsunami. The damage mechanisms of coastal structures during earthquake–tsunami events have not been fully explained. Thus, this study elucidates the damage mechanism of breakwaters by focusing on the interactions among earthquake–tsunami events, caisson structures, and soil composed of rubble mounds and seabed components. Centrifuge model tests, finite-element analyses, and smoothed particle hydrodynamics simulations with tsunami–soil–structure interactions were performed. The simulated breakwater was destabilized by not only wave pressure, but also long-acting tsunami seepage flow and overflow into the rubble mound and the seabed. These processes resulted in scour and fluidization/liquefaction, which decreased the bearing capacity. Moreover, the liquefaction resulting from earthquake motion caused caisson subsidence and excess pore water pressure i...

Instability of a Caisson-Type Breakwater Induced by an Earthquake–Tsunami Event

This paper discusses the experimental findings pertaining to a failure of composite breakwaters brought by the instability of a foundation mound due to the seepage flow induced by a huge tsunami. Centrifuge tsunami testing using a drum channel was applied to reproducing the reduction of the bearing capacity of a mound under seepage flow leading up to the failure of the mound. The results show the occurrence of boiling and fluidization as well as the spread of the instability zone in the mound at the vicinity of the caisson as a consequence of the seepage, yielding the significant displacement of the caisson. The effects of the resiliency structure, which is placing rubble on the back of a caisson, are also examined in the light of stability of a mound as well as a foundation bed under the seepage flow.

Instability of Breakwater Foundation under Tsunami Overflow and its Countermeasure

Instability on the sandy ground under breakwater due to earthquake and tsunami

Scouring due to tsunami causes a decrease in the bearing capacity of structures. Disaster of the breakwater with scour due to tsunami overflow was occurred at Hachinohe-port in East Japan Great Earthquake. The present study attempted to explicate the scouring mechanism due to overflow focusing on the tractive force and the pore water pressure in the sediment ground by using two-type geomaterials that is different permeability. As a result, scour was occurred with tractive force. The scour profile had same profile as proposed by Yeh et al. when sandy soil used. However, we found that the excess pore water pressure was generated in the ground due to jet flow, and liquefaction was occurred. Therefore, we need to recognize that the liquefaction-layer is generated due to overflow.

Tatsuya Matsuda

Papers

Instability of a Caisson-Type Breakwater Induced by an Earthquake–Tsunami Event

Instability of Breakwater Foundation under Tsunami Overflow and its Countermeasure

Instability on the sandy ground under breakwater due to earthquake and tsunami

Experimental speculation on scour due to jet flow focusing on the soil particle and the soil element scale level

Instability on dike with scour due to surface flow and seepage