FIELD INVESTIGATIONS ON WAVE-DISSIPATING CONCRETE BLOCKS COVERING VERTICAL WALL BREAKWATER

摘要

The failures experienced in Japan by wave-dissipating concrete blocks (WDCB) covering vertical wall breakwaters are investigated, and the deformation characteristics such as failure features and factors are examined. Typical examples for failures are illustrated, and two main types for failures are suggested: (a) scattering of WDCB due to shortage of their weight, (b) settlement of WDCB following deformation of the toe area. These types are analyzed and then the latter is discussed with some preliminary experiments. The results suggested that both stability of WDCB and applicability of the Hudson formula depend on the location and their cross-sectional shape, and that a weakening of sand bed due to wave action, especially wave-induced liquefaction, is an important factor of settlement deformation as well as scouring. From these results and additional field surveys, finally, two parameters are suggested which can explain the effect of stability of WDCB and toe area on both scattering and settlement behavior, and a classification of resultant failure characteristics and a conceptualized diagram of failure behavior of WDCB are presented.