When dredging hard cohesive soils such as clayey silt, mild clay and clay, traditional teeth such as chisel teeth can only penetrate to a shallow depth of the soil layer and bear more cutting resistance, which directly affects the dredging efficiency of the trailing suction hopper dredger.
In order to improve the excavation capacity of the draghead, especially for dredging the above mentioned soils, a plough-shaped tooth was designed and developed which can cut thicker soil layers with smaller resistance and therefore remarkably enhance the dredging efficiency.
This tooth is designed based on the working mechanism of the curved surface of the moldboard plow, and the mathematical model of horizontal straight generatrix plough body surface was established using tliree dimensional parameters. In order to design the accurate 3D model of the socket of the new tooth, reverse engineering techniques and the software Solidworks are used for 3D modeling. The finite element analysis is also carried out for optimizing the stresses and strains of the tooth. The excavation capability of the plough-shaped tooth manufactured by a quick forming technique and precision casting technique was improved through continuous laboratory tests and field tests.
The results of the laboratory test showed that when excavation of the same soil with the same cutting resistance of 80kg. the penetration depth of the traditional chisel tooth is about 3~4cm with an excavating width of 11.4 cm, the average penetration depth is only 3cm: however, the cutting depth of the new tooth is about 9~12cm with an excavating width of 13-14 cm, the average penetration depth is 11.2cm. In addition, under the same penetration depth and the same trailing speed, the average resistance of the traditional chisel tooth is 623kg and the average excavating width is 11.4cm.
However, the average resistance of the new plough-shaped tooth is 413kg and the average excavating width is 13 cm. The resistance of the new teeth is 34% lower than the traditional teeth and the excavating width is increased 14%. The field tests also showed that the concentration of the slurry dredged by the new teeth also increased compared with the traditional teeth under the same external conditions.
Dredging Today Staff, June 7, 2013