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Yokohama, Japan

Kikuchi Y.,Port and Airport Research Institute | Nagatome T.,Toa Corporation | Mizutani T.-A.,Port and Airport Research Institute | Yoshino H.,Yachiyo Engineering Co.
Soils and Foundations | Year: 2011

Cement-treated clay with air foam, which is called Super Geo-Material (SGM), was developed to utilize dredged clay in an effective way. As SGM is mainly used at levels below the ground water table, water permeability and absorption properties of SGM will affect the durability of the material. In this research, the changes in SGM permeability and absorption as functions of the air foam fraction were investigated. First, permeability tests with triaxial apparatus and constant rate of consolidation tests were conducted on samples containing less than 10% of air foam by volume. From the results, air foam was found to be an impermeable medium in SGM. Secondly, a series of permeability tests and absorption tests were conducted for the SGM with different fractions of air foam while observing the specimen with a micro focus X-ray Computed Tomography (CT) scanner. The results showed that the permeability of SGM increased dramatically due to the appearance of interior water channels when the air foam fraction exceeded 30% by volume. The density distribution change and water absorbed zones of the specimens during absorption tests were estimated using the X-ray CT data. From these results, the air in the SGM was found to be progressively substituted with water from the surface to the inside of the specimen and the substituted zone expanded as it made its way to the specimen interior. The expansion velocity of the substituted zone was not affected by the coeffcient of permeability but by the fraction of the air in the specimen. Source


Hazarika H.,Akita Prefectural University | Yasuhara K.,Ibaraki University | Kikuchi Y.,Port and Airport Research Institute | Karmokar A.K.,Bridgestone | Mitarai Y.,Toa Corporation
Geotextiles and Geomembranes | Year: 2010

Scrapped tire-derived materials, such as tire chips and tire shreds, can be categorized as three dimensional geosynthetics. This paper introduces recent Japanese experience in geotechnical related applications of geosynthetics that focus mainly on tire chips and tire shreds. Three specific applications of tire chips and tire shreds are introduced here. They are: (1) tire shreds to improve drainage; (2) sand-mixed tire chips to mitigate earthquake damage; and (3) tire chips mixed with cement-treated clay to improve toughness and ductility. The developed techniques related to these applications, verification through model testing, as well as element testing and the field applications are presented. It was observed that tire shreds can maintain high permeability even under a high compressive load. When tire chips and/or sand-mixed tire chips are used as a compressible cushion, not only the dynamic load against a structure but also the dynamically induced permanent structural displacement could also be significantly reduced. On the other hand, mixing tire chips with cement-treated clay gives toughness to the geomaterial, and thus provides resistance against the development of cracks during deformation. In addition, an X-ray CT investigation of deformation behavior of such materials demonstrated the success of using cement-treated clay with tire chips as a sealing material to protect leakage of contaminated materials at a waste disposal site in Tokyo bay area. © 2009. Source


Kikuchi Y.,Port and Airport Research Institute | Nagatome T.,Toa Corporation
Geotechnical Special Publication | Year: 2010

Durability of cement treated clay with air foam, Super Geo-Material (hereafter referred to as "SGM"), was investigated in this paper. When SGM is used for the backfill of a quay wall or reclamation of a man-made island, this material will be used under water or under the water table. In this case, hydraulic conductivity and water absorption characteristics are important characteristics for the durability of this material. From a series of several permeability tests, air foam in SGM is an impermeable medium if the air volume ratio is less than 25%. However, when the air volume is higher, the air foam makes bleeding channels and the coefficient of permeability dramatically increases. From a series of absorption tests in the laboratory, the absorption properties of SGM under the wet sand condition were different from those under the water condition. The absorption velocity of SGM under the wet sand condition was more than 10 times slower than that under the water condition. And this conclusion was supported by a ten year investigation of a SGM used in the field. Source


Abe N.,Toa Corporation
Advances in Transportation Geotechnics II - Proceedings of the 2nd International Conference on Transportation Geotechnics, ICTG 2012 | Year: 2012

At 14:46 on March 11, 2011, an M9 earthquake struck the coast of the Tohoku region of eastern Japan. In this study, the damages to road pavement by the large seismic motion of the earthquake and the liquefaction of the subgrade were analyzed and classified by the morphology of the damage and causes. The pavement of roads in areas affected by the earthquake and/or that suffered liquefaction was surveyed by using Falling Weight Deflectometer (FWD). The survey showed that the pavement of roads designed for large traffic volumes of heavy vehicles was less affected by the earthquake and liquefaction than the thin pavement of roads designed for small traffic volumes and pedestrian paths. The paper also reports the damages to road pavement and public facilities caused by the huge tsunami that engulfed the coast one hour after the earthquake. Measures for mitigating damages to pavement during earthquakes and by liquefaction are also proposed. © 2012 Taylor & Francis Group. Source


Patent
Toa Corporation | Date: 2012-06-19

To provide a speaker apparatus that can detect miswiring to a speaker unit or trouble of a speaker unit itself. The speaker apparatus is configured to include: two or more speaker units

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