Tomotsuka Takayama

Factors of Caisson Sliding Failures Affected by Damage of Armor Concrete Blocks

Recently, caisson sliding failures affected by large waves have occurred. The damage of the breakwaters in Susami port due to Typhoon 0423 is a typical sliding failure and the caissons were tilted down in the rear of rubble mound. The damage at Fushiki-Toyama port on February 2008 is also another typical sliding failure and concrete blocks were settled down. The present paper describes the factors of their caisson sliding failures affected by damage of armor concrete blocks. It concludes that the caisson sliding failure at Susami port was caused by insufficient weight of the caisson. Even if heavier concrete blocks are placed as armors, the caisson would be slid. The numerical simulation suggests that the caisson sliding failure at Fushiki-Toyama port was caused by the combination of three factors of large wave height, long wave period and duration time.

ADCP Application for Long Term Monitoring of Coastal Water Quality

The water quality (turbidity, chlorophyll) was compared with ADCP echo data in the long-term observation in order to examine the applicability of ADCP for long term monitoring water quality. The echo has remarkable influence by sea surface reflection and air bubbles back scattering. It is important to remove these noise to get good estimation of turbidity from echo data.

CHARACTERISTICS OF WAVES OBSERVED AT TANABE BAY FOR 5 YEARS

We have observed waves, tide, winds and temperatures at the tower named Tanabe-Nakajima Storm Surge Observation Tower standing at the mouth of Tanabe-Bay in Wakayama Prefecture. After removing many kind of noise in the original data by a special filter, significant wave heights and periods are calculated from Dec. 1994 to Aug. 1999. Comparing between wind and wave conditions, characteristics of seasonal and yearly variations are analyzed. In winter season, wind waves are dominant and there is an upper criterion of wave height restricted from wave slope. In summer season, swell become predominant. Yearly maximum wave heights are generated by typhoons so that the yearly variation is bigger than mean seasonal one.