Japanese contractor Kajima and heavy equipment maker Komatsu announced that they jointly developed the world’s first hybrid tunneling machine taking advantages of the Tunnel Boring Machine method and New Austrian Tunneling method. The machine has been successfully excavating at a construction site in Itoigawa City, Niigata Prefecture. The TBM mode is used for excavation normally, and when the machine hit a bad ground, it is switched to the NATM mode. The contractor started excavation in the TBM mode in January, and reached about 1.3 km of the total 4 km tunnel. As the bad ground is expected to appear later, the companies aim to complete excavation in April 2021 by making full use of the both modes.

The hybrid tunnel excavator “NATBM” combines the TBM, which features high-speed excavation, and the NATM, which can flexibly respond to the complicated geological formations of Japan. It works in the TBM mode in the hard ground. When reaching a bad ground, the machine is retracted to secure the excavation space in the front, and the cutter head is opened to switch to NATM mode. The mode can be changed from TBM to NATM in 1.5 days. (2020/05/28)