STIRRING-UP OF SOFT SEA BED MATERIAL DUE TO ACTIONS OF WAVES AND CURRENTS IN OSAKA BAY

Stirring-up of soft sea bed material in Osaka Bay were investigated through field observations and hydraulic experiments. Field observations were carried out at the point of 14m-deep and 15km apart from Kansai International Airport. The bed material size at the filed is 0.01mm in mean diameter. Echo Intensity data of ADCP were used to detect the stirring-up of bottom material induced by wave and current. The threshold value of current velocity for stirring-up has been estimated to be about 20-cm/s. The different properties of stirring-up between fine sand and silt were has experimentally been checked in wave oscillatory flow in t e wave channel. In less than 10cm/s flow condition, the fine sand was stirried-up easily with ripple formation. The silt needs fas er current for stirring-up because it could not move individually.