Four years have passed since the Great East Japan Earthquake, which killed thousands of people and damaged many properties. Japanese, as well as people around the world, vividly remember the deadly natural disaster, with some of the destroyed areas in the Tohoku region still unrestored.
While municipalities in Japan are working on projects to reduce disaster risks in preparation for possible huge earthquakes and tsunami, the “Implant Structure,” which Giken Ltd. promotes and practices, is garnering attention.
An Implant Structure is a resilient infrastructure in which preformed structural components, each of which is very sturdy, are pressed deep into the ground on site by various Silent Pilers. The structure is effectively integrated with the earth, and carries horizontal and vertical loads, using the “size of section” and “depth of penetration.” As a result, it is highly resistant to ground displacement caused by the motion of earthquakes, tsunami and other external forces, serving as a resilient disaster-prevention infrastructure.
An Implant Levee is one of applications. It has rigid backbones in the levee body filled by soil. Backbones are usually tubular pile walls or double sheet pile walls that are liquefaction-resistant. Even if the embankment collapses and subsidence is caused by liquefaction, the backbones withstand ground movement and double pile walls won’t allow soil to flow out. Thus the required height of levee can be maintained. When tsunami strike, they are resilient enough for both anaseism and backwash to remain standing. Consequently, the tops of Implant Levees can be used as emergency transportation routes and bases for pumping water out of submerged cities for prompt recovery.
Pile walls are constructed with the Press-in Method that utilizes reaction force derived from pre-installed piles to hydraulically push piles into the ground silently and vibration-free. As all necessary press-in machinery systematically works on the top of pile walls, it minimizes working space and eliminates the need for a temporary platform even on slopes, unlevel ground or above water.
The Press-in Method reduces the amount of work and enables rapid construction of tough and strong levees even in ground that consists of hard layers and concrete foundations. Its construction work always fulfills the Five Construction Principles, namely environmental protection, safety, speed, economy and aesthetics even under difficult site restrictions.
Implant Levees are increasingly being adopted for levees across Japan, especially for restoration work on coastal levees that were destroyed by the March 11, 2011 tsunami. They are also being used in reinforcement work of coastal levees in western Japan in preparation for possible huge earthquakes in the Nankai Trough, in the Pacific Ocean off the Tokai, Kinki and Shikoku regions.
The Implant Structure technology is also used for retaining walls to mitigate landslides and block falling landslide debris. For example, Implant Retaining Walls were built in restoration work in the wake of the large-scale sediment disaster on Izu-Oshima Island in October 2013. The walls are so-called training walls, which control the direction of landslides.
It is very clear that Implant Structures, which integrate structures with the earth, are highly resilient because there were many examples of similar structures surviving the Great East Japan Earthquake.
However, Giken will continue to refine the original technology. The company has developed a tsunami simulator, with which it can conduct tsunami experiments, and placed it in the Kochi head office. Giken will further expand facilities to conduct experiments, promote technological innovation on disaster prevention by using the toughness and tenaciousness of Implant Structures and spread Implant Structures as must-have technology with scientifically proven effectiveness.
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