The Tachiaigawa River’s Rainwater Discharge Pipe Project aims to reduce damage from flooding in the vicinity while at the same time improving the quality of the water that flows directly into the Katsushima Canal through the existing sewerage by constructing two 775 m long, 5 m inner diameter sewage pipelines underneath the Tachiaigawa river in Shinagawa Ward, Tokyo.

It is inevitable to face various restrictions and difficulties when planning large-scale infrastructure projects in Tokyo, one of the most densely populated cities in the world. This project was strictly restricted in its tunnel alignment along the route both horizontally and vertically due to the narrow width of the river coupled with the existence of the underground structures of the sewerage facilities. Thus, to cope with these restrictions, the H&V Shield Tunneling Method (Horizontal to Vertical) was adopted, which is capable of simultaneously constructing two adjacent tunnels in a spiraling manner by two inter-connected TBMs.

The H&V Shield Tunneling Method has three types of spiral excavation modes, Type-A, Type-B, and Type-C. This project adopted Type-B, in which two tunnels shift their relative positions from horizontally parallel to vertically parallel while one tunnel serves as the rotational axis for the adjacent tunnel to rotate spirally. After the spiral, two interconnected TMBs were stacked vertically and continued the excavation underneath the river until the arrival shaft.