Volume 3, Issue 3 September 2018

On-site Interview

Construction of underground bicycle parking (Eco Cycle) inSumida ward, TokyoMs. Hongjuan HeIPA Secretariat
I visited the construction site of the underground bicycle parking system at the vicinity of the JR Kinshicho Station on
August 2, 2018. I met Messrs. Yohei Nakayama and Mizuho Yokoyama of GIKEN SEKO CO., LTD. there and interviewed
them. I sincerely appreciated that they shared a very valuable information with me.

Illustration 1 - Illustration 4 are the images of completion②①Construction Sequence③④

1. Installing piles to form
the cylindrical wall

2. Excavation of soil
from the cylinder

3. Installation of the Parking Machinery

4. Fixing the entrance booth22

Volume 3, Issue 3 September 2018

Profile of Mr. Yohei Nakayama, Assistant Manager of GIKEN SEKO CO., LTD.
Mr. Nakayama Joined GIKEN Group in April 1996 and have worked on the Press-in construction
projects including Hard Ground Press-in Method and Gyropress Method for 19 years. This is his
13th experience on the underground bicycle parking project and he is assigned as theoperational manager.
Qualifications: The certified First-class Civil Engineering works Execution managing engineer
and the Supervising Engineer in construction

Profile of Mr. Mizuho Yokoyama, Assistant Manager of GIKEN SEKO CO., LTD.
Mr. Yokoyama Joined GIKEN Group in April 1997 and has worked on the Press-in construction
projects including Hard Ground Press-in Method and Gyropress Method for 19 years. This is his
12th experience on the underground bicycle parking project and he is assigned as the ChiefOperator.
Qualifications: The certified Second-class Civil Engineering works Execution managing engineer
and the First-class Press-in technician

Q1. Please explain me about the background and overview of this project.
Mr. Nakayama: Many illegal parking bicycles have found in thevicinity of JR Kinshicho station. Those are not onlyinterfering pedestrians and emergency vehicles
traffic but also causing social problems by
impairing town’s landscape. This area is congested
with many commercial facilities and residential
houses around the station so that it is difficult tobuild parking facilities above ground. These aremain reasons why the underground mechanicalbicycle parking system (ECO Cycle) was adopted.
This underground bicycle parking system willaccommodate 456 bicycles in two units.
Construction period is scheduled in 8 months
between June 2018 and February 2019. We hope
this project will contribute to decrease thenumber of illegal parking bicycles substantiallyand a safe and comfortable walking space will be
secured upon completion.

20.6m

16.2m
Figure 1: Site plan

Q2. What are the features on this project?
Mr. Yokoyama: There are two remarkable features. Firstly, the construction is carried out in a tight space with 20.6 m by
16.2 m surrounded by commercial facilities, residentials and roads (Figure 1 and Photo 1). 640mm widthof Hat-shaped steel sheet piles in 18.2m long are installed in the project. The length of the steel sheet
piles is almost equivalent to the width of the construction site, therefore placement of construction
materials and equipment have to be properly arranged on the site with the progress of the project.
Secondly, the sheet pile installation is carried out in a circular shape by utilizing a special made press-inmachine. This special made press-in machine is the only one our company owns and the angles of theclamp and the chuck are adjusted along the arc of the circular installation, and the piling is carried out ina clockwise direction (Photo 2).

23Volume 3, Issue 3 September 2018

Clamp

Chuck

Photo 2 Silent Piler for Eco Cycle

Photo 1 A view of Construction

Q3. Looking at the soil boring log, the site does not seem a stiff ground.
Why is the augering system adopted?
Mr. Nakayama: There are two reasons. Firstly, the steel sheet piles in 18.2 m length
are used in the project. With the repeated up-and-down stroke
motions in the press-in operation, the longer sheet pile toe hastendency to be distorted during installation. Generally, there is thedifficulty to manage the pile toe in a right position by dealing with thelonger pile. The distortion of sheet piles is suppressed when thePressing-in operation is assisted with the simultaneous augering, sothat the position of the pile toe can be well controlled accurately(Photo 3). Secondly, we encountered underground obstacles which
are not reflected in the SPT N-value in the soil boring log. Those
obstacles have been left over in the ground due to the Great Kanto
Earthquake in 1923. To protect pile materials from being damaged
and to ensure accuracy in piling, the Press-in Method assisted withaugering was adopted.

Photo 3 Checking distortionand verticality

Q4. What kind of measures did you take to prevent groundwater seepage
from the interlocking of the steel sheet piles?
Mr. Nakayama: Expansive rubber water cut-off seal is securely mounted on theinterlocking joint of the sheet pile at the factory in advance (Photo 4).
To prevent water cut-off seal absorbing water like rain water prior toinstallation, the sheet piles are properly wrapped with waterproof
materials and transported to the site. The rubber water cut-off seal
expands by absorbing groundwater after the installation, then it
prevents groundwater seepage thereafter. This measure is a uniqueapplication steel sheet pile to interlockings developed by our groupcompany, GIKEN LTD.

Photo 4 rubber water
cut-off seal

Q5. What was the most difficult problem in this project? How did you solve it?
Mr. Yokoyama: The most difficult thing was to control the curved sheet piles alignment. Forty-four (44) sheet piles are24

Volume 3, Issue 3 September 2018

installed as a unit of bicycle parking system. All of the 44 sheet piles are installed with different angles
due to a circular shape. Further, the actual products are not accurately uniformed with 640 mm width
as the catalogue data because of the product dimensional error. To make a circular enclosed coffer dam
with 44 sheet piles, it is necessary to decide the placement of each sheet pile one by one for a resultant
radius of the circle. In other words, angle and position of each 44 sheet pile are determined by themeasured width, then the radius and circumference of a circle shall be determined accurately. At thesite, a pile laser and a steel wire with a length of the radius are set up on the control platform located at
the center of the circle, and the laser is radiated on the point measured by the steel wire. The forward
angle and location of each sheet pile are determined with this way, and the press-in operation is carriedout, putting emphasis on the construction accuracy (Photos 5 & 6). Placement of materials andequipment are also decided from the planning stage, while a construction plan is made, including how
the piles used should be stuck up.

Control platform

Photo 5 Control platform

Photo 6 Checking sheet pile position
with the Piler laser

Q6. What was the most difficult and challenging site for you through your career?
Mr. Yokoyama: One-third of the Miyako-city in Iwate prefecture experienced serious disaster, due to the gigantic
tsunamis occurred by the Great East Japan Earthquake in 2011. I was assigned to the site in Miyako-city
in 2013 and took charge of a foundation construction of the disaster restoration work to build the 165
m wide flood control gate at the mouth of a river. The existing bedrock was found in shallower depth
than expected during construction, and piles with a prescribed length had to be penetrated in to thebedrock. This seriously affected the progress of the construction duration. I was an under the extreme
pressure to penetrate piles into stiff rock with very tight construction schedule. The issue has beenstudied and the prime contractor finally confirmed that “As long as enough bearing capacity is ensured,
it is not necessary to embed the piles into ground with planned length.” As the conclusion, we ceased
piling by ensuring an appropriate embedded length after the piles reached the bedrock. We havelearned that the making a right decision in a timely manner is very essential as well as the improvementof construction understandings and skills for a disaster restoration work in particular.
Mr. Nakayama: I worked on the underground bicycle parking system like this project in front of the JR Chiba station in2008. It was my first experience to conduct duties on site management. Since our company was theprime contractor for the project, I was in a position to assist the construction management. I could getto learn how to manage construction site little by little through valuable advices from experienced
seniors parallel to daily work. There was the restaurant belowground next to the construction site. The
restaurant owner filed complaints with respect to noise and vibration during the construction. I
negotiated with him as the site administrative manager and took some measures including adjustmentof construction time schedule to minimize the effect to restaurant’s business. I strongly felt, as the site
administrative manager that it was very important to have a good site management programme tocarry out a safe and smooth construction together with a good technical skill required in construction.

Q7. What is your view on how the young engineers and technicians should be trained?
Mr. Yokoyama: I feel some gap between young engineers and my generation now a days. However, I think it isimportant to train people for their needs, in a way goes with the times. We always tell them that themost important thing on site is safety, and we should carry out a risk prediction activity every day prior
to the start of the daily work. We instruct them to predict risks in advance and carry out construction
activities safely. It is important to train them in the technical parts, but the first priority is always safety.
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Q8. What is your view on the future of the press-in technology?
Mr. Nakayama: As Japan heads for an aging society, the number of workers is gradually decreasing. I think the complete
automation of the construction machinery could solve the problem of manpower shortage. In particular,
the construction of ECO Cycle in which a high construction accuracy is required has high potential to beautomated. To obtain accuracy required for coffer dams built in a circular shape, construction accuracy
with high precision of positioning is required. I think automated operation of machinery will surely behelpful.
Mr. Yokoyama: Japan is a country with lots of natural disasters such as earthquakes and tsunamis. Very dangerous insites after a disaster, since it is unknown when the secondary disaster will take place. Safe construction
is considered possible, with remotely-controlled operations in a place away from the disaster area. I amhoping that if remote-control operation becomes possible, we can secure safety of the operators in thepositive applications of press-in technology in disaster restoration works.

Photo 9 Mr. Yokoyama is operating
the Piler.

Photo 8 Mr. Nakayama is checkingalignment with laser.

★ Editorial notes：
Prior to the interview, we had paid attention to the function and convenience of the underground mechanical bicycle
parking system from the users’ point of view. But we found out through the interview that a high accurate planning andexecution were required on actual construction sites.
We would like to thank the two persons we interviewed and other staff members for their cooperation.

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