Pipeline Installation Project with URUP Method

The “Nanbu mainline”, a core city gas pipeline, is being constructed to improve supply stability in the Mikawa area of Aichi Prefecture. As a project engineer, I have been involved in the excavation of the part of the Takahama construction area since the end of January 2020.

One of the major features of this project is the use of the URUP method, which employs an Earth Pressure Balance Shield Machine. Unlike conventional shield tunneling which involves digging a vertical shaft and launching and arriving underground, the URUP method defies the conventional wisdom by launching from and arriving at the ground level. Without the excavation of the vertical shaft, the construction period is significantly shorter, and there are less construction-generated soil, vibration, and noise.

On the other hand, as the overburden becomes small near the launching and arrival points, the tunnel uplift due to groundwater remained a concern at the launching of this project.
As of October 2021, excavation progresses smoothly and about 1,300m of the approximately 2,500m along the tunnel has been completed.

Cautious in planning, bold in execution

I have been with the company for 20 years now. I was first assigned to the Shield Engineering Department, but after that, I have always been at shield tunneling sites and was in charge of totals of more than 10 km of tunneling. This project is my seventh one.

At the site in Kitami, Hokkaido, I was responsible for not only the construction but also segment design, finding joy in materializing what I had designed and being able to respond immediately to small troubles. The site-specific design I learned then is useful when considering cost reductions.

In shield tunneling, both the shield machine and the segments to be assembled after excavation are arranged in advance, so I keep in mind that “80% is in the preparation.” It means that I should identify unexpected things and all possible risks and mull both physical and non-physical types of preparations in advance to prevent a standstill in construction.

Power of imagination

Visual confirmation of the ground is conducted in the mountain tunneling method, while in the shield tunneling method, excavation can be continued to the end without visually checking the ground. In addition, the excavated muddy soil contains water and additives, making it difficult to accurately determine the true state of the ground. Thus, the ground property needs to be presumed based on the analytical data obtained through the excavation.

This "imagination from data," I suppose, gives a glimpse into the essence of shield tunneling which I find very interesting. For this job, proper handling of data and full use of imagination are crucial. As was the case with me, I hope that novices will freely share their opinions based on data, working as a team for high-quality performance.

As a Leader in Shield Construction

I have worked with numerous seniors in shield construction work, including the members who invented the URUP method, and the main members of this project, all of whom are not constrained by conventions.
The "we’ll do it because there is a chance" spirit is there, even with extremely difficult projects. They are brilliant at considering options with figures and exchanging solid opinions based on experiences at the work site. They are all people with a high level of human qualities.
In the near future, I would like to stand on their side as one of the leaders. Making full use of my imagination, I aim to manage the progress of the current project and complete it with no accidents.