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A sinkhole swallows 5-lane road in Japan

A giant sinkhole appeared in the middle of a busy Japanese city road last November 08. Two separate holes steadily expanded as they sucked asphalt and soil. Not too long afterward, the sinkhole extended to a massive 27 meters wide by 30 meters long by 15 meters deep. This occurred near the city’s Hakata Station in the central business district of Fukuoka City. Fukuoka is the biggest city on the southernmost main Japanese island of Kyushu. Its railway station is a major intersection, including for the superfast bullet trains that criss-cross the country.

Work to extend a municipal subway line under the street caused this huge sinkhole. It was fortunate the cave-in didn’t harm any passerby or vehicles as it occurred very early in the morning. Dozens of workers at the site were able to flee in time. The road was blocked for traffic immediately. And just after 5 minutes, the cave-in started.

An evacuation order was issued for nearby buildings. At one point, about 800 households lost power, and water and gas supplies to many areas were cut since underground cables and pipes used for electricity, gas, water and telephone lines and others were all severed. The sinkhole also disrupted online banking systems.

At the time, a subway tunnel was being constructed in the bedrock directly under the area where the sinkhole appeared. The construction method involved digging ahead one meter at a time, and then reinforcing the wall with concrete. It seems that, for some reason, the bedrock cracked, and groundwater, soil and sand poured into the tunnel.

This apparently caused the sinkhole to open, which removed the under burden and left the structural surface with nothing to hold it up. Shortly after developing, the hole filled up with water and sewage from pipes that were severed when the earth gave way. (Floro Mercene)