DEVELOPMENT OF TFIE METHOD FOR MAINTENANCE OF WATER ROUTE FRONT OF DISCHARGE GATE LINES ON ARIAKE SEA COAST

为维持填海造地排放口前的航道，有效的方法是利用闪水清除淤积的淤泥，或利用渔船的螺杆进行冲刷。为此，本文通过对泥沙淤积机理的实地调查，为建立航道养护体系提供了基本依据，并在此基础上进行了试验研究，分析了细粒沉积物的侵蚀与沉积行为、泥沙随自重固结的临界侵蚀速率变化以及有明湾底部螺旋船的侵蚀速率特征。在佐贺县纳诺拉潮地，在闸门不放水的情况下，测得水路区泥沙沉积速率约为5cm/d。用Ariake粘土与海水在环形旋转通道中进行试验，研究了自重固结发生后72hr粘土的含水量、黏聚力和临界侵蚀速率的变化。此外，还揭示了泥区含水率的垂直分布规律。在本试验中，随着时间的推移，固结的进展明显表现为距离底部10cm处含水率的变化；开始时为900%，6小时后为540%，72小时后为300%。螺杆旋转引起的流动特性符合喷流理论，揭示了螺杆对底部的作用。流轴速度随距螺杆-1次幂的远近而衰减，底部流量按高斯分布增大。实验结果新颖，对水路养护系统的发展具有重要意义。

Concerning to maintain the water route in front of discharge gate setting at land reclamation, the effective methods are said to remove the mud deposit by flash water, and/or erode by the screw of the fishing boat. Thus, to obtain the basic aspects for developing the water route maintenance system, the field survey for the mechanism of the mud accumulation was carried out, then the experiments were attempted to analyze following items, 1) the erosional and depositional behaviors of fine sediments, 2) the change of critical erosion rate of mud according to dead weight consolidation and 3) the characteristics of the erosional rate by a screw of boatIn the bottom area of Ariake bay, Nanaura tidal land in Saga prefecture, the deposition rate of mud at water route region was measured as about 5cm/day, when the water was not discharged from the gate.The experiment using Ariake clay with sea water in the annular rotating channel elucidated the change of water contents, the cohesion and the critical erosional rate of the clay during 72hr after the dead weight consolidation occurring. In addition, the vertical distribution of water contents ratio was also revealed in mud area. In this experiment, the progress of consolidation by passing time was obviously shown as the change of water content ratio at 10cm depth from the bottom level; 900% at the beginning time subsequently turning to 540% and 300% after 6hr and 72hr, respectively.The flow characteristics caused by rotating of a screw were accountable with the Jet theory, and revealed its action against the bottom. As the axis velocity of flow was decayed with distance from screw -1 powers, the flow rate on the bottom was widen according to Gaussian distribution.The results obtained in this experiment were new and believed to contribute to develop the water route maintenance system.