Shipbuilding facilities in Kesennuma port were completely destroyed in the Great East Japan Earthquake on 11 March 2011, and Penta-Ocean Construction was tasked with creating a new successor shipyard in the same port.
The project started in May 2015, with the merger of the four family-owned shipbuilders, Yoshida Shipyard, Kidoura Shipyard, Kosaba Shipyard, and Sawada Shipyard, whose facilities were damaged by the quake and tsunami.
The merger resulted in the creation of Mirai Ships, which builds and repairs fishing vessels. Shortly afterwards, Penta-Ocean was chosen to construct the shipyard facilities, at a total cost of JPY10.5 billion (USD85.76 million), which was partially subsidised by funds raised by the Nippon Foundation.
It was a challenging assignment due to the the construction site being on soft ground. Kesennuma sits on the coast of Sanriku in Miyagi prefecture and, bordering the Pacific Ocean, the port is heavily dependent on commercial fishing.
First, it was decided to construct a shiplift based on the Syncrolift system invented by Raymond Pearlson, because the design is less susceptible to tsunami damage.
On the platform, a vertically moving and a horizontally moving truck were installed in two stages. The vessel is then moved along the rails to be installed in the working position.
The shiplift system necessitated the construction of a pier that involved driving piles into the bay.
Penta-Ocean said that the company’s proprietary technology, AR Navi Geomoni II, which manages pile driving through video, was used to guide the pile driving.
This system uses a camera to photograph the site and creates a 3D design that uses augmented reality (AR) to guide the crane operator.
In this construction, the accuracy of the pile placement was confirmed by the crane operator, who checked the installation location while monitoring the image on the camera attached to the vehicle.
“This improved the efficiency. We planned to install four to five lines of piles per day, but with the technology, we do up to eight lines a day,” said Penta-Ocean.
Penta-Ocean’s head of construction, Yuichiro Tsuruta, said, “The construction site was on soft ground, and there was concern about the disturbance of the peripheral ground. Therefore, an impact loading test was performed on representative foundation piles, and a bearing capacity management formula was established based on the characteristics of the construction site, and the bearing capacity of each pile was managed.
“In addition, since the reconstruction work had caused congestion around the site, it was necessary to make sufficient adjustments. If there was a delay in the soil improvement of the structures that the company constructed in advance, it could affect the work process, so we held monthly process adjustment meetings with related organisations to take countermeasures.”
The works were completed in June 2019.