A new cavity near the site of the collapse in a residential area in Chofu, Tokyo November 5, 18:55
Last month, it was revealed that a new cavity had been found near the site where a road caved in a residential area of Chofu City, Tokyo. The East Japan Expressway, which is building a tunnel of roads deep underground at the site, held a press conference and explained the situation of the cavity and additional investigations.
In a residential area of Chofu City, Tokyo, last month, a road caved in, and when the East Japan Expressway, which is building a tunnel for the “Tokyo Outer Ring Road”, was investigating the cause, it became clear on April 4 that a new cavity had been found 40 meters north of the site of the collapse.
The cavity spread below 5 meters deep from the ground surface and was about 4 meters wide, 30 meters long, and 3 meters high.
The East Japan Expressway discussed this with the Countermeasure Committee on May 5, and after the completion of the meeting, the person in charge and experts held a press conference to explain the state of the cavity after not understanding the relationship with the tunnel construction.
As a result, there is a hard ground between the ground surface and the cavity, and it is not a state that immediately changes the ground surface, and there was groundwater about one meter deep in the cavity.
Professor Jun Koizumi of Waseda University, who is the chairman of the committee to consider the measures, said, “Since the location of the cavity is close to the river, it is possible that groundwater from the river flowed in, which may have caused the cavity to form. It is necessary to examine the flow of groundwater to determine whether the cause of the cavity is due to the original ground or the influence of the construction work.”
Mr Koizumi also pointed out to the East Japan Expressway that a detailed investigation should be conducted this time, as the site of last month’s collapse was quickly buried and a detailed investigation could not be conducted.
On this, the East Japan Expressway said, “Considering the anxiety of the residents, it is not possible to leave the cavity as it is in order to conduct an investigation.”
The East Japan Expressway measures the direction and speed of groundwater flow in a few days before the back-to-back work is ready to be completed, and confirms its relationship with the river.
In addition, we will increase the number of boring surveys conducted in the surrounding area from eight to ten, and respond individually to requests for surveys from residents.
Kenji Kato, Director of the Kanto Branch Construction Division of the East Japan Expressway, said, “We have been promoting our business with the safety and security of our lives as our top priority, but now that we are in a state of anxiety, we would like to work to dispel the concerns of the residents.”
The East Japan Expressway will hold a briefing session for residents in the surrounding area from 6th.
Residents “Clarify whether there is a causal relationship with tunnel construction”
In response to the discovery of a new cavity in a residential area in Chofu City, Tokyo, there have been calls from nearby residents for anxiety and to clarify whether there is a causal relationship with the tunnel construction.
Haruyo Kikuchi, who lives near the newly found cavity, said, “I was surprised. I’ve lived my life because I like it when it’s a good place, but I feel like I’ve been made into a place where I can’t continue to live.”
The causal relationship with the tunnel construction is not known, but according to Mr. Kikuchi, cracks in the fence have been confirmed at home and in surrounding houses since construction began.
After the 6th, Mr. Kikuchi made a document summary of the situation such as the collapse and the cavity for the residents’ briefing held by the government and the East Japan Expressway, etc., and visited neighboring houses on the 5th to call for participation.
The woman who received the document said that her home is right next to the cavity and right above the tunnel, “I was afraid to hear that there was a cavity, and my legs trembled. I’m worried that it’s under my home, and when I go to bed, I can’t sleep just by making a few noises.”
On top of that, “there is also a place for children to play, so it’s not a problem to be able to say, ‘I’m glad that no one lost their lives or wasn’t injured.'” We don’t know what’s going on underground, so we want the government and businesses to do more research and disclose the data.”