The dolphin dock construction method is a prompt and effective construction method for installing caissons for breakwaters (*), as well as underwater structures that include quay walls, seawalls, and intake of power plants by using a dolphin-type working ship. Since the equipment is settled in the mound at the seabed to be used in the dolphin dock construction method, the water area occupied for the work is small, which makes it superior with regard to safety and workability against waves generated at the time of manufacturing the caisson. Moreover, since high tranquility is ensured in the harbor, it can be used as a floating type working ship. This construction method has been adopted for more than 4,000 projects.
(*) Caisson: The concrete box composing breakwater. Patent: No. 595545

Since the dolphin-type working ship is settled on the seabed, it is possible to reduce the impacts of the sinking and floating movement, tilt, and shock caused by waves compared to when it is floating, thereby improving the operation rate.

The rocking movement is much less compared to when the ship is floating, which allows for a work environment equivalent to that of work on the ground.

As the ship is settled on the seabed, installation of a mooring anchor can be minimized, which makes it suitable for small water areas.

Because the large dolphin docks are equipped with auxiliary floats, it is also possible to control the tilt of the ship upon the launch of the caisson.

Thanks to the thin platform, it can also be launched in white water.

If the harbor is highly tranquil, it can be used as the floating type working ship.

The dolphin dock construction method was developed in the renovation work for Naoetsu Port in 1965. It was named the dolphin dock construction method because the ship floats and sinks like a dolphin. It was actively used in many projects as a construction method suitable for small water areas with high waves. In 1970, the method obtained patent No. 595545 as the Method for Building Concrete Structures in Water.