It has been nine years since the accident in which the ceiling board collapsed in the Sasago tunnel on the Chuo Expressway in Yamanashi prefecture, killing nine people.
Inspections conducted nationwide after the accident revealed that about 70,000 of the bridges managed by the local government need repair, but even now, about 70% of the bridges are not finished, and recently they have been newly damaged. Is being found one after another.
In response to this situation, the Ministry of Land, Infrastructure, Transport and Tourism estimated that it would take more than 20 years to complete the bridge repairs that are currently required.
Following the Sasako tunnel accident that occurred nine years ago in 2012, the Ministry of Land, Infrastructure, Transport and Tourism obliged local governments to inspect bridges and tunnels nationwide, and for bridges managed by local governments, this year at the end of March. At that time, it was determined that repairs were required at approximately 68,000 locations.
However, about 46,000 bridges, which is about 70% of the total, have not been repaired.
In addition, the government requires inspection once every five years, but the bridge, which was not required to be repaired in the first inspection, was found to be damaged due to the progress of aging for the second time and needs to be repaired. There are many cases where it is done.
Based on the results so far, the Ministry of Land, Infrastructure, Transport and Tourism estimates that about 5,000 bridges are likely to need new repairs every year, and it will take 20 years to complete the current bridge repairs. I understand that it will take more than that.
Professor Ichiro Iwaki of the Faculty of Engineering, Nihon University, who is familiar with infrastructure maintenance, said, "By inspecting all infrastructure on a regular basis, the actual situation has become clear for the first time as to how much aging will progress. It is important to take "preventive maintenance" efforts to get out of the "whac-a-mole" state and prevent aging. "
A series of bridges that "need repairs" due to aging
How is the state of "whac-a-mole" created?
While the inspection once every five years, which is obligatory for local governments, is entering the second round, the background is that there are a number of cases where bridges that had no problems at the beginning are said to "need to be repaired".
After the accident at the Sasako tunnel, the national government obliged local governments to inspect it once every five years, and it was completed by March 2019, and is now in the second round.
The 70-meter-long "Azumabashi" in Nakanojo Town, Gunma Prefecture, was inspected for the second time in 2020, and it was found that the wooden parts of the bridge girder were corroded in multiple places and had holes. ..
Road closures continue, saying that the worst of the four stages is "urgent action is needed".
Six years ago, in the first inspection conducted in 2015, no corrosion was confirmed, and it was judged that "repair is not necessary", which is the second best of the four stages.
As for the reason, the town suspects that it has deteriorated and the antiseptic treatment has become ineffective and has corroded rapidly.
According to the inspections so far, the town needs to repair 41 bridges including Azuma Bridge, but in general, there is a budget problem that it costs around 10 million yen to repair the bridge. Construction has not started on 34 bridges.
Yotaro Seki, construction manager of Nakanojo Town, said, "It is a big burden to increase the number of bridges that need repairs while the budget is tight. We will prioritize the abolition of bridges and the consolidation of two bridges. I think it is necessary. "
Expert “Residents also participate in preventive conservation efforts”
What should I do to prevent the deterioration from progressing?
Professor Ichiro Iwaki of Nihon University College of Engineering, who is familiar with infrastructure maintenance, points out that even people with specialized skills can carry out "preventive maintenance" efforts.
According to Professor Iwaki, "water" is a major factor in the deterioration of bridges.
For example, if mud or fallen leaves clog the drainage ditch of a bridge due to a typhoon or heavy rain, water will not flow and a puddle will form on the bridge.
As a result, water enters from the cracked part, which accelerates the deterioration of concrete.
To prevent this,
▽ after heavy rain, remove the mud and fallen leaves that have accumulated near the bridge to make it easier for water to flow into the drainage ditch, and
▽ paint the peeled part of the railing of the bridge. Even so, it is effective.
Professor Iwaki said, "In many cases," preventive maintenance "initiatives can be done without specialized skills, and one of the methods is to have local government officials respond or have local residents cooperate. Some local governments have already practiced it, and I hope that such examples will spread. "
Infrastructure "damage map" published on the net
In response to the current situation where repairs to aging infrastructure are slow, the Ministry of Land, Infrastructure, Transport and Tourism has begun efforts to publish the status of infrastructure that needs repairs on an Internet map in August.
The "National Road Structure Information Map", the so-called "Damage Map", is an inspection once every five years required by the government, and of the four stages,
it is the most aging and "urgent measures are required". Those
marked as "need early measures"
are shown in red, and those
marked as "need early measures" are
shown in
yellow
.
When you click on a point, the year of inspection and whether measures have already been taken are also displayed.
In Tokyo, the climb of "Katsushika Ohashi" on National Highway 298 in Katsushika Ward was "urgently needed".
According to the office of the country that manages it, after taking emergency measures, measures such as monitoring with a camera for abnormalities have been completed, and repairs will be started promptly.
In addition, several pedestrian bridges near Shimotakaido Station on National Highway No. 20 "Koshu Kaido" are in a situation where "early measures are required" such as water leaks in some of the bridges, but repairs have not been completed. Hmm.
According to the Ministry of Land, Infrastructure, Transport and Tourism, even if "emergency measures" or "early measures" are required on the map, they are taking emergency measures and will not pose an immediate danger.
Professor Iwaki of Nihon University, who is familiar with infrastructure maintenance, said, "It is important for people to be aware of whether there are bridges that have not been repaired in the area where they live. If you notice any abnormalities such as making a noise, please report it to the local government immediately. "