ADCP 이동관측을 통한 준설 부유토사 발생량 산정

Abstract

The loss of sediment into the water column caused by dredging operation which is essential data for the reliable environmental impact assessment largely depends on various site- and case-specific conditions such as current velocity, composition of bottom sediment, type and class of the dredger. Furthermore, the difference of the instrument and method for measuring the sediment plume may cause large difference in the loss rate even when the remaining conditions are similar.The loss caused by the operation of cutter suction dredgers, mechanical grab dredgers are evaluated by measuring the sediment flux along the cross-section of the dredging-induced plumes with a vessel-mounted acoustic Doppler current profiler (ADCP) which has been gradually and successfully applied for the study of sediment transport although a rigorous in-situ calibration is required to give reliable concentration profile.The rates of release per unit time and unit volume of dredging along the cross-section at 40m apart from the cutter suction dredgers range 0.3 to 3.14 kg/s and 2.36 to 13.5 kg/m3, respectively, those of the grab dredgers 0.13 to 6.85 kg/s and 2.65 to 188.87 kg/m3, respectively. The loss rate is rather dependent on the current velocity and the type of the bottom sediment than the capacity of the centrifugal pump and grab.It is recognized that grab dredging after crushing the sedimentary bedrock yields very high loss rate beyond 100 kg/m3, which seems to result from the lower production rate due to high water content among the rock fragments in the grab.