An Impressive Engineering and Disaster-Response Effort

 

Imagine you wake one morning and find a huge sinkhole in the street passing in front of your house, measuring roughly 100 feet by 90 feet, and going down about 50 feet. The collapse has severed water, sewage and gas pipes, as well as cableways for electrical and telecommunications wires, leaving you in the dark with no way to flush. How long do you think it would take to fill the hole, open the street to traffic, and get your utilities working again? Several months might be an optimistic estimate for many.

Hakata Sinkhole, 8 November

In Fukuoka, Japan, the biggest city on the island of Kyushu in Western Japan, a sinkhole of this size occurred downtown on 8 November, last Tuesday. In an impressive feat, they have already filled the hole and restored the services. This morning they opened the street to traffic, and it looks better than it was before.

The street is completely repaired, 15 Nov

The sinkhole occurred about 3 blocks from Hakata Train Station, with the major cave in happening a little after 5 a.m. This section of Fukuoka is a business-district composed of high-rise buildings, some of which have underground parking. People nearby could hear the sound of water rushing while portions of the street and sidewalks collapsed. Buildings surrounding the sinkhole were evacuated, and the area suffered power and water outages. Underneath this section of street, the Nanakuma subway line is being extended. About an hour before the street collapsed, water started to leak into the new subway tunnel, forcing evacuation of the construction area underground. One elderly woman was injured during the evacuation while walking down the stairs.

As the collapse was happening, 8 Nov

Looking at the photos and video, you can see that the sinkhole goes right up to several buildings. The underground supports for the neighboring buildings are exposed. While I think it’s miraculous, none of the neighboring buildings suffered major damage.

Note the building pilings, 8 Nov

While the investigation to determine the cause of the sinkhole hadn’t been completed, the mayor decided to proceed with recovery work. A lot of people and businesses were being affected, and it would have had a major impact on the upcoming holiday period. They have experienced this problem before, it’s the third sinkhole to occur in the last 3 years during construction on this subway extension.

hkb118-jpp022705151

201611120008_000Just goes to show that government, properly focused and led, can get results.

Japan Times article

Asahi Shimbun article

Mainichi Shimbun article

NHK article

There are 40 comments.

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  1. Titus Techera Contributor
    Titus Techera
    @TitusTechera

    What an astounding achievement! If you have any more details or anecdotes, do share!

    • #1
  2. MJBubba Inactive
    MJBubba
    @MJBubba

    Wow, that is really impressive.  Thanks for this report.

    • #2
  3. RushBabe49 Thatcher
    RushBabe49
    @RushBabe49

    Wow!  I’d like to see a comment from @concretevol.

    • #3
  4. dnewlander Coolidge
    dnewlander
    @dnewlander

    This particular subway extension seems like a whole lot more trouble than it’s worth.

    I love the claim that they’re still trying to figure out what happened, despite this being the third sinkhole related to the subway extension, water pouring into the subway tunnel from above, and, oh, yeah, the subway extension being right underneath this sinkhole. Must be Fukushima, I’d say. smh

    • #4
  5. Arahant Member
    Arahant
    @Arahant

    dnewlander:This particular subway extension seems like a whole lot more trouble than it’s worth.

    I love the claim that they’re still trying to figure out what happened, despite this being the third sinkhole related to the subway extension, water pouring into the subway tunnel from above, and, oh, yeah, the subway extension being right underneath this sinkhole. Must be Fukushima, I’d say. smh

    Yeah, there does seem to be an issue here.

    • #5
  6. Ned Walton Inactive
    Ned Walton
    @NedWalton

    Filling up a hole with dirt and patching a few pipes and electrical conduits, big deal! Hop into the Wayback Machine with Mr Peabody to late 1941-1942 and see a real transformation and repair job!

    • #6
  7. Ryan M(cPherson) Member
    Ryan M(cPherson)
    @RyanM

    Wow!

    • #7
  8. Dustoff Inactive
    Dustoff
    @Dustoff

    In California we would still be determining liability and  the environmental impacts of reconstruction and which  Strom Water Quality Managment Practices (SWQMP) and permits are required in order to begin designing a reconstruction plan of action.

    • #8
  9. Arthur Beare Member
    Arthur Beare
    @ArthurBeare

    I, too, am surprised a mere mayor could get this done without some interference from higher ups & various regulations.

    Does anyone know of a roughly analogous event in this country in this decade?

    • #9
  10. Arahant Member
    Arahant
    @Arahant

    Arthur Beare: Does anyone know of a roughly analogous event in this country in this decade?

    Nope. The Loop Flood might be a good example, but 1992.

    • #10
  11. Tedley Member
    Tedley
    @Tedley

    dnewlander:This particular subway extension seems like a whole lot more trouble than it’s worth.

    That’s what first came to my mind when this happened.

    dnewlander:

    I love the claim that they’re still trying to figure out what happened, despite this being the third sinkhole related to the subway extension, water pouring into the subway tunnel from above, and, oh, yeah, the subway extension being right underneath this sinkhole.

    Agreed, but in this case they’re looking for the engineering assessment, with all the technical details.  They build tunnels all the time.  They’ve developed methods, systems and technologies to prevent incidents like this.  They wouldn’t have decided to construct this tunnel unless they were confident they could do it without impacting anyone above it.  From what’s been reported, the earlier sinkholes had different causes.  They want to determine if this one had a similar cause.

    • #11
  12. Tedley Member
    Tedley
    @Tedley

    Ned Walton:Filling up a hole with dirt and patching a few pipes and electrical conduits, big deal! Hop into the Wayback Machine with Mr Peabody to late 1941-1942 and see a real transformation and repair job!

    That may be true, but we live in a different day and age.  Just like in the U.S., construction projects don’t just begin, construction teams are used to conducting a lot of planning and assessments before beginning any project.  The area affected is in the middle of a metropolis, so it’s complicated by the number of organizations involved and their respective requirements.  I’m sure that they did damage assessments of the surrounding buildings, but at this pace, I don’t think they could have been 100% thorough.  That they proceeded with repairs on this schedule shows some courage and a willingness to accept risk.

    It’s apparent that they pulled together a public-private team which effectively collected and shared information about the damage, determined the best way forward, coordinated repair efforts, collected the assets necessary to make the repairs (probably pulling things away from other projects) and finished the repairs almost on schedule (rain on Monday impacted the laying of asphalt and painting of the lines on the street, pushing the completion back a half day).  My emergency management background tells me that they handled this incident well.

    I look forward to comments and impressions from Ricochet civil engineers.

    • #12
  13. Giaccomo Member
    Giaccomo
    @Giaccomo

    Fantastic example of city administration t its best.  Were that sinkhole to have occurred in NYC, Washington, D.C., or indeed any other American city with a Democrat administration, months would be consumed on tenders, bids, environmental impact studies, identifying racial set-asides, and seeking a balance in awarding contracts to one’s political friends and donors.  Then, of course, labor unions would have their say, the EPA would weigh in on the need to protect some ecologically important creature (maybe the vermis vorax cityhallensus?), etc.

    • #13
  14. Bruce W Hendricksen Inactive
    Bruce W Hendricksen
    @BruceHendricksen

    This reminds of a story I read a few years ago about a bridge washout in Kauai. The picture below isn’t great, but you get the idea.  Just a tiny bridge. Local businesses were cut off from tourist dollars, so it was significant to the people living there. The State of Hawaii estimated it would take 2 years to finish the repair. The locals just fixed it themselves.  http://www.cnn.com/2009/US/04/09/hawaii.volunteers.repair/index.html?iref=topnews

    art-kauai-crane

    • #14
  15. Curt North Inactive
    Curt North
    @CurtNorth

    We had a similar but much smaller thing happen in my small northern Michigan town last year.  It was a 16″ sewer line collapse, followed by a sink hole developing.  We had the line repaired and the road patched up in a few days, the biggest hurdle was getting the local council to meet and authorize the spending, then waiting for the pipe to arrive.  It looks bad but it really is a simple matter of filling the hole and patching the pipes.

    I’m not taking anything away from our Japanese friends however, the sinkhole in the article is admittedly huge, and the repair was done quickly.  By the way, it really is shocking the buildings nearby didn’t suffer any lasting damage.  Or did they….?

    • #15
  16. Concretevol Thatcher
    Concretevol
    @Concretevol

    Wow very cool report!  I think one thing that demonstrates is the superiority of local government action vs the federal government.  The city can get things done more efficiently and more than likely had a protocol in place with local contractors after the previous sinkholes you mentioned.

    As you can see from the picture showing the neighboring building’s exposed foundation it was built on Cassions (drilled shafts) that transfer the load all the way to bedrock so there shouldn’t be any significant damage to the structure itself just because the shafts were exposed.

    The two concrete pumps pouring down into the water is pretty cool.  Probably pouring flowable fill to fill any voids in the bottom of the hole and to give them a surface to work/pump water from.

    • #16
  17. Old Bathos Moderator
    Old Bathos
    @OldBathos

    I’ve seen this movie. The only reasonable explanation for numerous sinkholes is that despite warnings from an eccentric brilliant scientist some fool has disturbed the underground resting place of Ghidora and so now Mothra, Rodan and Godzilla must be roused to defeat it. Hope Tokyo office workers are wearing their running shoes to work these next few days.

    • #17
  18. Majestyk Contributor
    Majestyk
    @Majestyk

    Yeah, they couldn’t just dump dirt into the hole, they would have to fill it up with low strength concrete or (as Concretevol said) flowable fill in order to ensure that they could get compaction as they brought the collapse back up to subgrade.

    We’d have to see the geotechnical report in order to draw any definitive conclusions about why the collapse occurred, but it could be that the soils are poor or cohesionless and subject to caving.  When you’re tunneling underneath this stuff, there’s also a lot of vibration which could cause settling in certain kinds of material.

    I would have thought, given that there are all of those drilled piers that an extensive geotechnical study would be available and that this kind of thing could be avoided… the contractor should be keeping pretty careful track of how much material they’re tunneling out and if that amount exceeded the volume of the tunnel by any significant amount (over and above swelling) you know you have a problem.

    • #18
  19. Richard Harvester Member
    Richard Harvester
    @RichardHarvester

    Arthur Beare:le than it’s worth.

    I love the claim that they’re still trying to figure out what happened, despite this being the third sinkhole related to the subway extension, water pouring into the subway tunnel from above, and, oh, yeah, the subway extension being right underneath this sinkhole. Must be Fukushim

    Vermont recovery from Irene?

    • #19
  20. RyanFalcone Member
    RyanFalcone
    @RyanFalcone

    Not to be a wet blanket but this may very well be a perfect example of government stupidity. Everything about this story points to executive incompetence and impending tragedy. We have sinkholes like this in Pennsylvania quite often. The absolute worst thing you could possibly do is just quickly fill the hole and move on with business as usual. That appears to be what these idiots have done multiple times with the problem predictably coming back worse than before each time. Sinkholes require a time consuming and very difficult fix. This is really worrisome!

    • #20
  21. Tedley Member
    Tedley
    @Tedley

    Curt North: I’m not taking anything away from our Japanese friends however, the sinkhole in the article is admittedly huge, and the repair was done quickly. By the way, it really is shocking the buildings nearby didn’t suffer any lasting damage. Or did they….?

    There was an immediate engineering assessment done of 42 buildings closest to the sinkhole.  There was no damage noted during the assessment.  However, the exposed cassions (thanks for the right word, @concretevol!) were cause for concern amongst the engineers.  This was one of reasons why the city proceeded with filling the hole as quickly as they did, to help prevent the exposed cassions from deforming.

    • #21
  22. Tedley Member
    Tedley
    @Tedley

    Concretevol: The two concrete pumps pouring down into the water is pretty cool. Probably pouring flowable fill to fill any voids in the bottom of the hole and to give them a surface to work/pump water from.

    That’s exactly what they did.  Since the breach led all the way to the subway tunnel, they needed to give it a big concrete bandaid.

    • #22
  23. Arthur Beare Member
    Arthur Beare
    @ArthurBeare

    I think one major factor in the limited damage is that the surrounding buildings were probably built to survive earthquakes, a threat the Japanese take very seriously.

    • #23
  24. Tedley Member
    Tedley
    @Tedley

    Majestyk:We’d have to see the geotechnical report in order to draw any definitive conclusions about why the collapse occurred, but it could be that the soils are poor or cohesionless and subject to caving. When you’re tunneling underneath this stuff, there’s also a lot of vibration which could cause settling in certain kinds of material.

    I would have thought, given that there are all of those drilled piers that an extensive geotechnical study would be available and that this kind of thing could be avoided… the contractor should be keeping pretty careful track of how much material they’re tunneling out and if that amount exceeded the volume of the tunnel by any significant amount (over and above swelling) you know you have a problem.

    Your expertise is showing.  That technical report is what the news commentators wanted to see.  Based on previous studies that have been done of that area, (I’m not up on the terminology in English or Japanese, but Google translate says) the type of ground in that area is “backward wetland.”  This is defined as “a humid lowland plain, consisting of viscous soil, peat and humus soil.  It’s highly susceptible to liquifaction.”  One report said that while the subway tunnel is in bedrock, there’s a thick layer of sand above it.  They don’t know how it ended up breaking into the tunnel.  Your hypothesis regarding vibrations may be correct, although it probably cannot be confirmed now.

    • #24
  25. Tedley Member
    Tedley
    @Tedley

    Old Bathos:I’ve seen this movie. The only reasonable explanation for numerous sinkholes is that despite warnings from an eccentric brilliant scientist some fool has disturbed the underground resting place of Ghidora and so now Mothra, Rodan and Godzilla must be roused to defeat it. Hope Tokyo office workers are wearing their running shoes to work these next few days.

    That’s o.k., so long as they leave Yokohama alone…. ;-)

    • #25
  26. Tedley Member
    Tedley
    @Tedley

    Arthur Beare:I think one major factor in the limited damage is that the surrounding buildings were probably built to survive earthquakes, a threat the Japanese take very seriously.

    Sounds right to me.  One of the articles I read quoted the engineers as saying that they wanted to make sure the cassions wouldn’t deform, since that would likely reduce their ability to withstand earthquakes.

    • #26
  27. Tedley Member
    Tedley
    @Tedley

    RyanFalcone:Not to be a wet blanket but this may very well be a perfect example of government stupidity. Everything about this story points to executive incompetence and impending tragedy. We have sinkholes like this in Pennsylvania quite often. The absolute worst thing you could possibly do is just quickly fill the hole and move on with business as usual. That appears to be what these idiots have done multiple times with the problem predictably coming back worse than before each time. Sinkholes require a time consuming and very difficult fix. This is really worrisome!

    Cannot discount gov’t or contractor stupidity, since there may have been malfeasance along the way.  Initially, the officials wanted to determine the technical reasons why this sinkhole happened.  However, this particular incident was complicated by the need to avoid weakening the cassions of the buildings surrounding the sinkhole.  This appears to have become the major factor in the decision to fill the hole quickly.

    One report I saw said that Japan gets thousands of sinkholes a year.  I wasn’t aware that they get this many, but they’re familiar with them and what’s necessary to prevent them at construction sites.  Why this one happened (industrial accident?  unique nature of that spot?  malfeasance?) will probably never be known.

    • #27
  28. Majestyk Contributor
    Majestyk
    @Majestyk

    Tedley:Your expertise is showing. That technical report is what the news commentators wanted to see. Based on previous studies that have been done of that area, (I’m not up on the terminology in English or Japanese, but Google translate says) the type of ground in that area is “backward wetland.” This is defined as “a humid lowland plain, consisting of viscous soil, peat and humus soil. It’s highly susceptible to liquifaction.” One report said that while the subway tunnel is in bedrock, there’s a thick layer of sand above it. They don’t know how it ended up breaking into the tunnel. Your hypothesis regarding vibrations may be correct, although it probably cannot be confirmed now.

    Not terribly surprising.  From the perspective of geomorphology, what you’re describing here is an area with underlying consolidated bedrock that pushed up either old seafloor or lakebed – the sand layer with silty soils on top of it, most likely due to millennia of sedimentation.

    Highly organic, cohesionless soils are subject to liquefaction (in addition to sandy soils.)

    It’s lucky nobody was killed.

    • #28
  29. Trinity Waters Inactive
    Trinity Waters
    @TrinityWaters

    I spent a week in Fukuoka and it is in a beautiful locale.  My experience in Japan convinced me that they are very focused workers and stoic.  You don’t see five sidewalk supervisors barely watching one guy dig.

    • #29
  30. Trinity Waters Inactive
    Trinity Waters
    @TrinityWaters

    Majestyk:

    Tedley:Your expertise is showing. That technical report is what the news commentators wanted to see. Based on previous studies that have been done of that area, (I’m not up on the terminology in English or Japanese, but Google translate says) the type of ground in that area is “backward wetland.” This is defined as “a humid lowland plain, consisting of viscous soil, peat and humus soil. It’s highly susceptible to liquifaction.” One report said that while the subway tunnel is in bedrock, there’s a thick layer of sand above it. They don’t know how it ended up breaking into the tunnel. Your hypothesis regarding vibrations may be correct, although it probably cannot be confirmed now.

    Not terribly surprising. From the perspective of geomorphology, what you’re describing here is an area with underlying consolidated bedrock that pushed up either old seafloor or lakebed – the sand layer with silty soils on top of it, most likely due to millennia of sedimentation.

    Highly organic, cohesionless soils are subject to liquefaction (in addition to sandy soils.)

    It’s lucky nobody was killed.

    Was this area one of the many in Japan that was rebuilt on reclaimed land that used to be underwater?

    • #30
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