Reconstruction after the major earthquake: Tsunami protection in Japan

Even three years after a major earthquake, the clean-up and reconstruction work is far from being completed in Japan. In addition to rebuilding destroyed buildings, the Japanese government is still struggling to improve the flood protection.

Consequently, in the Miyagi prefecture on the Japanese main island Honshu in Sendai Bay, the flood protection infrastructure was repaired and made serviceable again. There, Shimizu counted on MOBA for rebuilding the dyke systems and breakwaters. Two excavators were installed with the 3D excavation system Xsite® PRO to move and landscape a total of 52,000 cubic metres of earth within a specified construction period of just five months. A completely new dyke, taller than before, was built over a total length of 500 metres in order to ensure stronger and more effective protection against flooding.

"The difficult thing about this was having to build in a very steep embankment with an incline angle of 50 percent. With this system, however, that was no problem whatsoever", explains Osamu Kadowaki, echnical Head of Shimizu in Tohoku.

Machine and bucket positions known at all times First, the 3D model of the planned dyke, which had been previously created in the office, was transferred to the Xsite® PRO system. This model provided the task specification for the excavator operator, along with the respective incline angle and depth specifications. In order to correctly implement these specifications, each work step had to be precisely recorded and represented on the display. By means of sensors which were mounted on the boom, arm, bucket and chassis, the system was able to register the position of the bucket at all times. The machine position and orientation were determined by means of GNSS. Thanks to the representation on the display showing all values in the terrain model, the excavator operators could at any time recognise when the desired incline angle and depth had been attained and where further material still needed to be moved. In this manner, the dyke could be built precisely according to the model. And safety at the construction site rose as well because the excavator operators did not have to step out while performing their jobs in order to manually remeasure.

15 percent time-savings thanks to MOBA’s 3D system ""The time schedule was very tight, not a minute could be wasted. With the system, we were able to forego the manual staking of the terrain and other surveying tasks. That brought us a time-savings of about 15 percent"", relates Osamu Kadowaki. Not only time but also money was saved by the construction company: as it was unnecessary to deploy two surveyors usually required for conventional surveying.