Failure Knowledge Database / 100 Selected Cases

Tachikawa City, the falling accident of the pile driver【16th March 1991、Tokyo, Tachikawa City, Akebono town】
Masahiko Kunisima・Koichiro Toyoda（note１）
In Akebono town , Tachikawa City, Tokyo, at the construction site of Tachikawa
JF building which was operated by a joint venture of Taisei Kensetsu and Goyo
Kensetsu, the large pile drive for the sheeting(weight: about 100ton, height: about30m) fell down to the east side with a roaring noise. A total of 7 buildings including
private houses and apartments were buried under the machine. Two citizens werekilled in the accident.
1. Event
On 16th, March, 1991, the accident occurred at just after 9:30a.m. In Akebono
town, Tachikawa city, Tokyo, at construction site of Tachikawa JF building which
was operated by a joint venture of Taisei Kensetsu and Goyo Kensetsu, the large
pile driver (weight: about 100ton, height: about 30m) fell down to the east side witha big noise. Some private houses and apartments were buried under the machine.
"Apartments were crushed completely, 2 buildings were partially destroyed, and theparts of 3 buildings were broken. In this accident, three people were killed. They
were university students. The workers in this site were not injured.（Fig.１）。

1

Failure Knowledge Database / 100 Selected Cases

Fig.１

The Situation of the accident（Source：“The construction accident”）
２．Course
The field was a densely housed area near JR Tachikawa Station. The construction
site of “Tachikawa JF building” (7-floor) was undertaken by the cooperationenterprise in Taisei Kensetsu and Goyo Kensetsu. The pile driving work wascarried out there. It was started in November, 1990, and the completion schedule
was for March, 1992. This accident was occurred in the construction work operated
by Seiko Kogyo (the headquarters: Osaka) whose specialty was foundation work.
Moreover, Marutoku Kigyo (the headquarters: Sendai) received the pile drivingfrom Seiko Kogyo.

Fig.2

The map of the siteNewspaper”）（Source：“Yomiuri2Failure Knowledge Database / 100 Selected Cases

On the day, the work was started at about 8:00a.m. On the day, they were digging
the holes with the pile driver in order to drive the piles for foundation work andreinforcement foot ground on the ground around the site. There were over 10 sheetsof steel (width: about 1.5m, length: about 6m, thickness: about 2cm) on the site. The
pile driver had moved on the sheets, but the ground was too muddy. Around thisarea, rocks underground had been removed and soil had been backfilled before thefoundation work.
After the same operation of the pile driver on the east side of steel sheets, it moved
back and the driver descended. Just after that, the head of the machine shank withthe steel sheets started to lean. The driver noticed this and tried to drive and movethe machine falling down and hoping one of the eastside steel sheets little up,
making a big noise.
The alarm buzzer of the crane truck informed about the danger from tipping
over just before the accident. When the buzzer rang, the safety equipment which
stopped the work automatically should have worked. But, on the day, the switch of
the safety equipment was cut, and it didn’t work. This pile driving method is called“the SMW method” ( Soil, Mixing, Wall) and the method is as follows as the piledriver empties the hole, the cement is poured from the tip, and in the cement before
the solidifications, the H steel was inserted. (Fig,3)It was heavy with 100 tons of the dead weight, since it had been equipped with 5 drillsof the 30m length for the excavation. Though they were fixed with three arms in theexcavation, it was not fixed because the work hadn’t start in the accident day.

The pile

driver was carried from the site, by dismantling it.
Until now, they struck and pushed them with the thing like a hammer from the upper
part, leaving the H steel.
However, in the thickly housed area, the SMW method would be adopted in, sincehardly any noise is made.

3

Failure Knowledge Database / 100 Selected Cases

Figure 3. The outline of the SMW method( Source : Seiko Kogyo home page )Figure4: The situation of the SMW method( Source : Marutoku Kigyou homepage )３．Cause(1) １ The elaborate geological survey beforehand must be carried out, as it can4

Failure Knowledge Database / 100 Selected Cases

prevent tipping over of construction heavy machine .
The pile driver was put on the ground which had reburied once. The back filling is a
general process for removing piping and bedsills of the building before, etc., whenbuildings a gent, etc. are constructed. Generally they don’t congeal the ground withcoagulating, etc. because the reburied ground may be drilled again in the process of theconstruction. It is not solidified.
However, the soil of the site was weak, “the Kanto- loam-layer”, and considerable
groundwater gushed on from the boring trace. Therefore, the loose ground seemed to beunable to resist the dead weight of the pile driver of 100 tons.

(2) Even while the construction heavy machine is not driven, it must be kept in thestable condition by supporting it with the arms etc.
Though the pile driver was fixed with three arms in the excavation, but it was not fixed
because the work hadn’t started in the accident day. For that reason, the weight of thepile driver leaned to the other side because of losing balance, and it came to tipping over.

(3)The safety equipment didn’t work.
The alarm buzzer of the crane truck informed about the danger from tipping overjust before the accident. When the buzzer rang, the safety equipment which stopped
the work automatically should have worked. But, on the day, the safety equipment
was not put into motion because the switch of the safety equipment was switchedoff.
４．Immediate Action
The site was near the JR Tachikawa station. The JR TACHIKAWA station was
the center oh the town and has heavy traffic. Tens of fire trucks and ambulances
rushed there, and the rescue operation by the helicopter was carried out.

Therescue team searched for the bottom of the collapsed house using the fiberscope.
They tried to extend the clearance by hydraulic jacks, etc. for the rescue, but therescue operation was difficult because of the fallen arms.
５．Countermeasure
As a safety countermeasure in the case of the construction using heavy machine in
the place with the soft ground, the tipping over prevention, and the ground made to
be reliable by injection of coagulating agent, etc.; are necessary before theconstruction is carried out.

After they should put materials such as the outrigger

outside in the circumference of heavy machine, it is a considerable countermeasure
to prevent falling.

5Failure Knowledge Database / 100 Selected Cases

６．Generalization
The direct cause of the accident is based on the fact that they did not take the safety
countermeasure of congealing the ground, in spite of carrying out the work over theweak ground and even though the pile driver wasn’t fixed with the arms. For thatreason, the loose ground seemed to be unable to resist the dead of pile driver of 100
weight tons , and the weight of the pile driver leaned to the other side because oflosing balance, it came to tipping over.
In the meantime, the indirect background of the accident was the followings: that
tower building construction in the residential section was increasing and that
construction work itself was enlarging in scale. This accident had occurred because theleveling of ground work was not sufficient in order to introduce the large machine into
the place like the residential section without sufficient space.
The accident which originates from the slipshod safety management in the place nearresidential area arises becomes a factor which produces the society distrust for thewhole construction industry, and it also has a big social effect. It is necessary to do thesafety management in the handling of heavy machines thoroughly in order to preventthe recurrence.

７．Knowledge
１ The elaborate geological survey beforehand must be carried out, as it can prevent
tipping over of heavy construction machines .
２ In the case of using the heavy machine over the weak ground which has thepossibility of tipping over, the coagulating agent must be injected, etc. to make theground firm.
３ Even while the construction heavy machine is not driven, it must be kept in thestable condition by supporting it with the arms etc.
４ The condition of the safety equipment can always be operated .
That is to say, the accident always happens in the point of variation. It happened
during construction in the case of the construction.
building decays naturally.

It is seldom that the finished

However, they should know that the oblong pile driveritself is unstable. It is insufficient to only use suspension and outrigger.

８．BackgroundAt that time, tower building constructions were increasing in Tokyo because of6Failure Knowledge Database / 100 Selected Cases

the economic growth. Especially in Tokyo, the construction of high buildings wasincreasing in residential towns. According to it, the case in which the industrial
accident involved nearby inhabitants and passers-by increased. There are manycases which made a collapse, because the leveling of ground work is not sufficient,in order to introduce the large machine into the place without the even space.
Again, according to the enlargement of the construction work, over-heavy objects
were held by the high machine for construction, for example, pile drivers and cranetrucks. It makes the machine to lose balance easily.

Especially it is said that it isextremely dangerous to work on the soft ground.
９．On the Side
This accident happened only 2 days after the big disaster “the bridge girder falling
accident in a new transportation system construction site, Hiroshima”. That accident
became a social problem because many people were injured in the accident (2 dead, 8injury). Many residents around the site had felt the anxiety about the construction
before the accidentbecause that the pile driver (height: 30m)

was used in the thickly

housed area before the accident because it was right after the accident in Hiroshima.

＜Information Source＞“The construction accident”(2000）
Nihon Keizai Simbun（16th March, 1991 the evening edition, 17th March 1991 themorning edition, 18th March 1991 the morning edition）

Asahi Simbun（16th March, 1991 the evening edition, 17th March the morning edition,
18th March the morning edition,

20th March 1991 the morning edition）

Mainichi Simbun（16th March 1991 the evening edition, 17th March 1991 eveningedition）

Yomiuri Shimbun（16th March 1991the evening edition、17th March 1991 the morningedition）

Seiko Kogyo homepage

http://www.seikou-knet.co.jp/

Marutoku Kigyou homepage（note

http://marutokukigyou.co.jp/１）

Department of Civil engineering, School of engineering, University of Tokyo7