Eiji Yauchi

INFLOW OF ULVA SP. OF SPRING SEASON IN YATSU HIGATA

Yatsu Higata is one of the most significant remaining tidal flats in Japan. In recent years, Yatsu Higata has witnessed an extraordinary growth of Ulva sp. algae. This paper explores the possible origins of Ulva sp . in Tokyo Bay and describes field studies intended to explore the relationship between the Ulva sp. found in Yatsu Higata and in Tokyo Bay . As a result, the Ulva sp. flourishes in Yatsu Higata, due to the ready supply of nutrient runoff supplied by the Yatsu River. The movement of Ulva sp. from the flats to beyond may help reduce the pollutant load on Tokyo Bay while simultaneously helping to preserve the Yatsu Higata environment.

FIELD EXPERIMENT ON DEPOSITION CONFIGURATION OF EARTH-SAND DUMPED FROM HOPPER AND SPLIT BARGES

Hopper and split barges are frequently used in marine construction schemes for reclamation of offshore land for airports and caisson foundations. In order to realize a designed geometry accurately and effectively, the deposition configuration of earth and sand dumped by barges and the optimum interval of discharge sites of barges for a specified degree of uniformity in the mound surface must be predicted in advance.In the present study, a sailing arrangement system based on a prediction model was used in a construction project. It was confirmed by field engineers that the deposition configuration of earth and sand dumped by a hopper barge is different from that of earth and sand dumped by a split-type barge. The characteristics of the spatial deposition configurations resulting from dumping by each type of barge were investigated under the condition of a single discharge of earth and sand in field experiments

Comparison of deposition configurations dumped by tremie pipes and barges

The configurations of deposition mounds of earth and sand dumped on the sea floor from barges was studied by using physical model tests. The experimental results were compared using the stochastic simulation technique for the spatial geometry of rubble mounds discharged from barges (Matsumi;1992), which was developed by applying the Markov chain model to the distribution for the settling position of rubble. The application of the theoretical prediction method to mounds constructed by tremie pipes was validated by comparing the calculations with field measurements. Executability in the construction of mounds by using tremie pipes or barges was investigated on the some numerical calculations for the measurements.