Study on Sedimentation and Overspills from Dredging Operation using Numerical Model

• Main Author: Sharini, Noor Azima
• Format: Final Year Project
• Language: English
• Published: Universiti Teknologi Petronas 2011
• Subjects: TA Engineering (General). Civil engineering (General)
• Online Access: http://utpedia.utp.edu.my/8728/1/2011%20-%20Study%20Sedimentation%20and%20Overspills%20from%20Dredging%20Operation%20using%20Numerical%20Model.pdf; http://utpedia.utp.edu.my/8728/

Trailing Suction Hopper Dredger (TSHD) is commonly used to dredge soft bed material. Problem .arises when the fme sediment which has low settling ability is often released along the overflow of TSHD as suspended sediment. This contributes to high turbidity which could continue over a time span. The objective of this study is to measure the overspill's volume from hopper and to establish relations between inflow discharge (Qi), hopper area (AI=50 m x 15m, Az=25 m x 15m and A3=12.5 m x 15 m), settling velocity of sediment (i) v,=0.0004 m/s (ii) v,=0.0001 m/s (iii) v,=0.000027 m/s, sediment concentration (i) Ci=IO kglm3 (ii) Ci=S kg/m3 (iii) Ci=3 kg/m3 (iv) C1=1 kg/m3 , and overspills (OV0 ). The scope of study will cover modelling of sedimentation of fine sediment in Trailing Suction Hopper Dredger (TSHD) using MIKE 21 Hydrodynamic (HD) and Mud Transport (MT) software. The constant overspills is acquired through line discharge function and from there the trapping efficiency is calculated. All values are plotted in Graph Trapping Efficiency versus A/Qi. The result shows a function of trapping efficiency D A/Qi, where the trapping efficiency will increase if inflow is decreased (inversely proportional) and efficiency will increase if hopper area is increase (directly proportional). The inflow concentration does not affect the trapping efficiency. However, low inflow concentration and low inflow discharge will lengthen the dredging loading time which is uneconomical and unproductive. The study provides good estimates on trapping efficiency for a hopper. The higher the trapping efficiency the lesser the overspills and there will be less negative impact towards the environment