When we will evaluate an influence on the turbidity due to the harbor construction, it is very important to investigate the behavior of the fine sediment. Earth filling soil contains the fine sand which settling velocity is very low and floats for a long time. Therefore especially the dumped soil by hopper barge can be thought to cause large-scale water pollution around the surface of the water.
In the previous study, the property of settling soil and the flowing characteristics of the muddy water lump after the bottom collision usually have been considered. But, the occurrence mechanism of turbidity to diffuse around the surface of the water just after the injection is hardly being studied. When harbor construction is performed, the turbidity, which usually causes a problem, might be occurred by not only the turbidity from the bottom layer, but also turbidity around the water surface floating for a long time.
Therefore in this research, the turbidity to diffuse around the surface of the water just after the injection is investigated experimentally. Form the experimental results, it is found that the falling fine sediments might be lifted to the water surface due to the bubble way of the air contained in the injection soil.