Due to the problem of road collapses and underground cavities being found one after another in a residential area in Chofu City, Tokyo, the East Nippon Expressway, which is excavating tunnels underground, was on the 19th to prevent construction mistakes that caused the collapse. Announced measures to prevent recurrence.
In the residential area of Chofu City, Tokyo, there have been a series of depressions and cavities in the road since October last year due to a construction error in the tunnel excavation work of the "Tokyo Outer Ring Road" that is being carried out underground, and we ordered the work. The East Nippon Expressway Company held a meeting on the 19th and announced measures to prevent recurrence.
When moving a large machine called a shield machine that excavates a tunnel, the amount of earth and sand taken in is strictly controlled because the ground has loosened and cavities and depressions have been created due to construction mistakes such as taking too much earth and sand into the machine. doing.
In addition, additional boring surveys will be conducted as necessary, and additives suitable for the ground will be used to prevent them from loosening.
In addition, changes in the ground surface will be announced on a regular basis, and patrol monitoring of the section where excavation has been completed will be strengthened.
Professor Emeritus Atsushi Koizumi of Waseda University, who chairs the Committee of Experts, said, "This time there was a problem with the construction of the tunnel, so in the future, we will check what kind of ground it is while digging and how to deal with it. We need to carefully consider whether to do it. If we do so, we estimate that there will be no problem in the future. However, the risk is not zero. "
Regarding the resumption of construction on the East Nippon Expressway, ground repair in the area directly above the tunnel construction site is the highest priority, so it is not decided at this stage when to resume construction.