Sand and soil dredged during port improvement work has been returned to dredged trenches as backfill since 2011. Considering the coastal environment,construction work has employed the double pipe tremie process with a suspended turbidity barrier and monitoring of water cloudiness. To gauge the spread of turbidity,an on-site experiment was performed in which soil and sand were loaded into the water with no barrier,in 2012. In light of these findings and the circumstances of construction,it was thought that the suspended turbidity barrier could be replaced with a freestanding type. This would be an effective method as it would prevent the rise of sand and soil lifted up by work barges,render the task of setting up and removing the barrier unnecessary,and enable extension of the construction period.
