A DETAILED MODEL STUDY OF DAMAGE TO A LARGE BREAKWATER AND MODEL VERIFICATION OF CONCEPTS FOR REPAIR AND UPGRADED STRENGTH

Omar J. Lillevang, Frederic Raichlen, Jack C. Cox, Daniel L. Behnke

Abstract


Ten years after it was completed, and intact as originally built, West Breakwater at Diablo Canyon on the central coast of California was severely damaged during a wave storm in January 1981. The paper describes uncommonly detailed site investigations that followed and the development of a large three-dimensional hydraulic model for discovering the specific mechanism that precipitated the damage, and then for verification of the effectiveness of concepts for rebuilding the breakwater to resist greater storm events than had been used for the original design. Unique procedures for modelling contorted terrain, for producing reflection-corrected irregular wave systems, for eliminating abnormal waves at the start and at the end of test runs are discussed. The tested final concept for reconstruction is described and surveyed results of closely packed Tribar armoring, as reconstructed in 1983-84, are illustrated. The authors conclude that investigations of problems involving wave attack on the termini of rubble mound breakwaters should always be undertaken with the aid of three-dimensional physical modelling unless owner and engineer are in a position knowingly to take large risks. Further, that physical modelling at suitably large scale is virtually mandated if the submerged terrain at a site is not regular.

Keywords


model study; breakwater damage; breakwater; model verification; breakwater repair

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