Bosai Solution ID : JBP00122

Implant™ Lock Levee
Shift to "Anti-collapsed Levee

HazardEarthquake Tsunami Cyclone Storm Surge Flood

Solution Purpose
Prevention & Mitigation Recovery

Solution Theme
Infrastructure Technology

Technology Subject
River & Basin Coast

Advantages
Large-scale flood damage occurs every year in various places due to global climate change. The biggest
factor behind the serious damage is the collapse of an embankment. A typical river levee is a "soilembankment" that only fills the soil, and it contains scientific factors that cannot withstand the increaseof water in the river and overflow. The "Implant™ Lock Levee" is designed to strengthen a resilient levee＜ Downloaded from www.bosai-jp.org ＞

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by constructing double rows of continuous walls with Implant Structure and a partition within this "soilembankment."

Solution Illustrated

The Implant Lock Levee remains functional as a levee even if the embankment is eroded due to flood
overtopping or seeping. In addition, in the event of an earthquake, the ground surrounded by double
steel sheet pile walls with partition walls can be restrained by so called “confined ground seismicdamper” in order to restrain the flow of liquefied ground and ground subsidence. The main feature ofthis embankment is its structure which aims not only to overflow and seep but also to prevent frombreaking down in the event of a major earthquake.

Background

Most of the river levees are built of soil, which is being raised and widened after flood damage.
When planning and designing, there are numerous factors to consider, such as the complex distributionof soil quality and strength, the potential for differential settlement, the need for long-term maintenance,
and the close relationship with the livelihoods and natural environment of the watershed, which plays acrucial role in the landscape. Therefore, comprehensive disaster countermeasures, including
earthquake and tsunami countermeasures are desired, with a focus on realizing resilient performance＜ Downloaded from www.bosai-jp.org ＞

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against overtopping water.

Exposition of the Solution

Sourse: "Japanese Geotechnical Journal"Vol.12，No.1，109-122,P.117,Figure 13

The seismic performance of embankments reinforced by this method has been verified for coastal
embankments and river embankments.
Even in the situation where the side of the levee body collapses due to an earthquake accompanied byliquefaction, it has been clarified that double steel sheet pile walls and tie rod materials restrain thedeformation of the core part and that the top height is maintained by the steel sheet pile walls placed in
the supporting ground.
This earthquake-resistant mechanism is reproduced by a FEM (finite element method) that can considerliquefaction and build an earthquake-resistant design method for level 2 earthquake ground motion
The following points are demonstrated as features of this method.
・During flooding, the steel sheet pile wall is properly embedded to control boiling, and even if overflow
occurs, the crest height can be maintained and the amount of overflow can be limited.
・In an earthquake, the deformation of the core part is suppressed by the restraint effect of double steel
sheet piles joined by tie rod materials, and it is possible to reduce the liquefaction damage.
・Even for complex disasters in which tsunami strikes immediately after an earthquake, the amount ofovertopping water by the tsunami can be limited because the crest height during the earthquake ismaintained by placing the lower end of the steel sheet pile on a strong ground.

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Achievements of Examples

Kochi coastal levee improvement construction at the Nino section (Kochi City, Kochi Prefecture)/ Kochi
River National Road Office of Shikoku Regional Development Bureau, Ministry of Land, Infrastructure
and Transport

Implant Lock Levee has been adopted in some sections of the Kochi coastal embankment improvement
work.
Orikasa, Yamadamachi, Shimohei-gun, Iwate Prefecture＜ Downloaded from www.bosai-jp.org ＞

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At the time of the Great East Japan Earthquake, a similar structure was adopted as a temporary
cofferdam structure for the construction of a tide gate near the river mouth of the Iwakasa River in Iwate
Prefecture. While the surrounding river embankments and the residential area were destroyed, double
steel sheet pile walls and the floodgates built inside the cofferdam were almost free from the tsunami
damage, demonstrating their high earthquake resistance and tsunami resistance.

Other References

Corporate Profile
GIKEN SEKO CO., LTD.
75-1

Minato Urayasu-shi Chiba 279-0024 Japan Tel. : +81-47-318-9111
 E-mail : murashima@giken.com
 Website : https://www.gikenseko.co.jp/for-english/＜ Downloaded from www.bosai-jp.org ＞

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