Wednesday, November 30, 2016


We’ve touched on Fukuoka and its attention grabbing sinkhole at several points this November, from when it first manifested by eating up a busy intersection, to Japan’s remarkable rush repair job. We knew the cause of the collapse was ascertained to be the underground construction work of a new subway line in Fukuoka, something that continues apace even as the sinkhole was fixed and order restored. It would seem however that the story of this inconvenience hasn’t come to an end. Sometimes you just can’t keep a persistent geological depression down, in a manner of speaking.

TIME has it that the ornery Fukuoka sinkhole isn’t through yet, when observers noted that the newly replaced roadway over the original pit has begun to sink into the ground. This was noticed over the weekend of November 26-27, and the depth of the new surface collapse was around 7cm or 2.7 inches from street level. Initial elation to the city’s reconstruction effort that was hailed online as a shining example of reputed Japanese engineering efficiency came to an abrupt pause, most especially when out of concern for the new (but still incremental) sinking, traffic at that intersection was diverted. 

Fukuoka residents didn’t have to wonder at this for very long however, as Mayor Soichiro Takashima went on the city’s Facebook page to explain away the fears of a resurgent sinkhole in the same place. Apparently the local government and engineering crews were well aware that the ground would sink from street level again, but only by the range listed above, for the simple reason that the amounts of sand and cement that were poured into the depression during the road repair would begin to settle and compact after starting to bear the weight of traffic upon the roadway on top.

From their engineers’ own estimates, there’s a possibility that the repaired street would go down a few centimeters more, at least until the material underneath has been packed to solid hardness by the burden above. The explanation was accompanied by, as is proper from the Japanese, a statement of profuse apologies to the people of Fukuoka, this time for neglecting to inform them that the settling would happen.

It is possible for filled-in sinkholes to erupt again in the future. An example is one that opened up in Florida inside a man’s bedroom while he slept, plunging him to his death. After similar repair efforts the hole opened up again. This is a fear that now passes the minds of the Fukuoka residents whenever they see that intersection, but hopes lie in the completed repair job holding the burden, and that soon the subway construction will also end.

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