Bosai Solution ID : JBP00005

Implant™ Confined Ground Seismic Damper
Liquefaction Prevention by Enclosure of Base GroundHazard
Earthquake

Solution Purpose
Prevention & Mitigation Recovery

Solution ThemeInfrastructure Technology Building Technology

Technology Subject
River & Basin Coast Road Railways Port Essential Utilities Urban Emergency Base & Back-up Facility＜ Downloaded from www.bosai-jp.org ＞

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Advantages
Aseismic Ground Enclosure is one of the most effective countermeasures against liquefaction. Ordinary
seismic base isolation technique mainly applies to superstructures, not to infrastructures. And it costsquite long duration and huge amount of expenses in construction. On contrary, technique of GIKEN isjust to enclose structures by pressing-in sheet piles from ground level. Required working space andremoval of existing facilities can be minimized. So, Aseismic Ground Enclosure is best suited toliquefaction prevention measure for the existing structures both above ground and underground.

Solution Illustrated

In Aseismic Ground Enclosure, sheet pile walls have 5 major functions to protect structures fromearthquakes.
1. Prevention of Sliding Failure: Sheet pile walls around a structure block occurrence of sliding failurecaused by shaking and liquefaction.
2. Prevention of Ground Deformation: Sheet pile walls block ground deformation inside the enclosure.
3. Prevention of Sideways Soil Movement: Sheet pile walls block sideways movement of liquefied soil
and keep it inside the enclosure.
4. Prevention of Excessive Pore Pressure: Sheet pile walls block pore pressure transmitting outwards
and also inwards from surrounded ground.
5. Prevention of Uneven Load: Sheet pile walls receive load of structures and guide it to verticaldirection inside the enclosed area.

Background
Liquefaction caused by Earthquake
When severe shaking associated with earthquakes occurs in the ground with underlying waterloggedlayers, once firm ground temporarily turns into a fluidlike mass because of increased pore pressure andreduced effective stress between solid particles. This phenomenon is called liquefaction.
Damages caused by Liquefaction
Liquefaction and related phenomena have been responsible for tremendous amounts of damage inhistorical earthquakes around the world. Liquefied ground can no longer support the weight ofbuildings, so these tend to sink. The overlying ground can also sink, spread and crack. Water fountains＜ Downloaded from www.bosai-jp.org ＞

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and sand boils can burst upwards through any cracks. Underground pipes and tanks float and break.
Power poles fall and break cables. And the port has been built on artificial islands collapses.
A Solution discovered at Disaster Sites
Through a great number of researches at disaster sites, we discovered an effective solution. In a disasterarea, there was one undamaged house surrounded by many severely damaged ones. The house standson the ground that was enclosed by steel sheet piles. They should have been extracted after completionbut left without apparent reason. It showed us the empirical proof of the effect of Aseismic Ground
Enclosure.

Exposition of the Solution
Implant Structure (Principle)
Implant Structure consists of an "allowablestructural member" that is combined withstructural and foundation elements. Everystructural member is pressed-in and securely
supported by the Earth. Therefore, it is highly
resistant to ground displacement caused by themotion of earthquakes, tsunami, and otherexternal forces, serving as a “resilient” disasterprevention infrastructure.

Aseismic Ground Enclosure (Application)
All advantages of Implant Structure are applied to Aseismic Ground Enclosure. It is a kind of seismicbase isolation but doesn’t require isolation units between foundations and superstructures. Being
enclosed by sheet piles, the ground on structures starts behaving as energy-absorbing soil block.
Liquefaction is a phenomenon occurred as the result of that energy of seismic movement was absorbed.
The critical effect of liquefaction is uneven settlement and sideways movement of liquefied soil
afterwards. As they are confined to inside of the enclosure, the ground can maintain support ofstructures in the most similar condition to the original state before earthquakes.
Implant Method (Construction)
Pile walls are constructed by Press-in Method that utilises
reaction force derived from pre-installed piles to hydraulically
push into the ground silently and vibration-free. As all necessarypress-in machinery systematically works on the top of pile walls,
it minimises working space and eliminates a need for temporary
platform even on slope, unlevelled ground or above water. Thus
the Implant Structure can be constructed whilst fully satisfying
the Five Construction Principles, which include consideration ofenvironmental protection, safety, speed, economy andaesthetics in the form of a balanced equilateral pentagon.

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Achievements of Examples
Wide Application to Various Structures
Aseismic Ground Enclosure can basically apply to any buildings and infrastructures that contact theground. From achievements of GIKEN, this technology has already applied to embankment of railways
and roads, bridge foundations, underground installation like water tank, grit chambers, petroleum tanks,
houses and buildings, and quay walls. Embankment of Shinkansen bullet train was also reinforced bythis technology. An application to petroleum tanks is particularly called Implant Ring Method after
shape of enclosure and adopted to many tanks. Double sheet pile wall of Implant Levee is alsofunctioning as Aseismic Ground Enclosure.

Evidence by the Great East Japan Earthquake of March 11, 2011
The effectiveness of Aseismic Ground Enclosure was proved by the earthquake. Engineers ofGIKEN visited disaster sites and confirmed that the applied structures were safe and maintaining theoriginal state without damage, whereas unapplied structures were damaged by settlement, crack,floating and breakage.
Proactive Measures against the greatest Nankai Megathrust Earthquakes
Since the the Great East Japan Earthquake, Japanese government has been strongly promoting
proactive measures against the forth-coming earthquakes in parallel with disaster restoration works.
Implant Levee consisting of Aseismic Ground Enclosure has been adopted to protect lives and cities
from the threat of earthquake tsunami.

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Corporate Profile
GIKEN LTD.
16F Ariake Central Tower, 3-7-18 Ariake, Koto-ku, Tokyo 135-0063, Japan Tel. : E-mail : international@giken.com
 Website : https://www.giken.com/en/＜ Downloaded from www.bosai-jp.org ＞

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