The basic construction method for cutter suction dredgers is the transverse dredging method. The transverse dredging method includes steel pile positioning and anchor cable positioning. In the steel pile positioning method, two steel piles are alternately inserted into the riverbed to serve as pivot points. The left and right swing cables (dragon beard cables) at the front of the cutter head are alternately tightened and loosened, causing the vessel to swing back and forth for dredging. When the cutter head swings to the right (left) edge of the dredging trench, the left (right) steel pile is lowered and the right (left) steel pile is raised. Simultaneously, the right (left) cable is loosened and the left (right) cable is tightened, causing the cutter head to swing back to the left (right). At this point, the vessel moves forward a certain distance, called the forward movement distance. With this positioning method, because the vessel has two pivot points during dredging, the dredging trajectories of the cutter head overlap and leave gaps.
To overcome the shortcomings of the above method, the main and auxiliary pile method (also known as the single-pile forward movement method) can be used. In this method, one steel pile serves as the main pile, always aligned with the center line of the dredging trench, acting as the pivot point for transverse dredging, while the other steel pile serves as the auxiliary pile for forward movement and pile replacement. Because there is only one dredging pivot point, the dredging trajectories of the cutter head are parallel to each other. As long as the forward movement distance of the steel pile is kept appropriate, over-excavation and under-excavation can be avoided. To accurately control the pile replacement position, a pair of sight markers must be added on both sides of the dredging trench center line.
Below is a discussion of the economic adaptability of cutter suction dredgers:
1. The production capacity of the dredger at different locations.
2. The investment cost of purchasing the dredger and the return on investment (meaning: accumulation of future profits).
3. The failure rate during operation.
4. The maintenance performed and the costs incurred during the service life.
5. The convenience of operation.
