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Mirjalili M.,Kyoto University | Kimoto S.,Kyoto University | Oka F.,Kyoto University | Hattori T.,Kinki Regional Development Bureau
Soils and Foundations

In this paper, the consolidation analysis of a large-scale embankment construction in Osaka City is presented, where a conventional levee with a height of about 8 m has been extended to a super levee with a total width of 215 m. The ground consists of alluvial sandy layers and soft clay deposits, which have been locally improved by several methods, including deep mixing beneath the conventional levee and the combination of sand drains and sand compaction piles under the extended back slope. A long-term consolidation analysis of this super levee construction is carried out using an elasto-viscoplastic constitutive model. The layered construction procedure is applied to properly simulate the construction sequence of the super levee. The effects of the structural degradation and the strain dependency of the shear modulus, as two aspects of destructuration in clay materials, are studied in terms of the consolidation behavior for the unimproved case. For the improved case, the analysis is implemented by including the ground-improved zones in the finite element simulation. The field observation data obtained during the preloading process, before the construction of the super levee, are employed to verify the assumptions and to calibrate the material properties of the improved layers. The effects of destructuration in the natural ground cases are observed as excess pore pressure build-up after construction and strain localization. The effects of ground improvement techniques are studied through a comparison of the deformation results and the excess pore water pressure responses with the natural ground cases. The numerical results show that it is important to carefully estimate the unequal long-term settlement for the construction of large-scale embankments. © 2012. The Japanese Geotechnical Society. Production and hosting by Elsevier B.V. All rights reserved. Source

Hinata H.,Japan National Institute for Land and Infrastructure Management | Fujii S.,University of Ryukyus | Furukawa K.,Japan National Institute for Land and Infrastructure Management | Kataoka T.,Japan National Institute for Land and Infrastructure Management | And 5 more authors.
Estuarine, Coastal and Shelf Science

Signals from the tsunami waves induced by the March 11, 2011 moment magnitude (Mw) 9.0 Tohoku-Oki earthquake and from subsequent resonances were detected as radial velocity variability by a high-frequency ocean surface radar (HF radar) installed on the eastern coast of the Kii Channel, at a range of about 1000 km from the epicenter along the eastern to southern coasts of Honshu Island. A time-distance diagram of band-passed (9-200 min) radial velocity along the beam reveals that the tsunami waves propagated from the continental shelf slope to the inner channel as progressive waves for the first three waves, and then natural oscillations were excited by the waves; and that the direction of the tsunami wave propagation and the axis of the natural oscillations differed from that of the radar beam. In addition, spectral analyses of the radial velocities and sea surface heights obtained in the channel and on the continental shelf slope suggest complex natural oscillation modes excited by the tsunami waves.The major advantage of the HF radars as tsunami detection is early warning as the tsunami is still far offshore. There is no doubt on this importance beside still technical and operational studies are needed. Our results adds a new role of the HF radars to measure the detailed surface current fields with high spatiotemporal resolution toward understanding detailed processes of resonant response to tsunami waves in coastal regions. © 2011 Elsevier Ltd. Source

Yamamoto H.,Kinki Regional Development Bureau | Moteki M.,PWRI | Shao H.,Chiba University | Ootuki K.,PWRI | And 5 more authors.
2010 IEEE/SICE International Symposium on System Integration: SI International 2010 - The 3rd Symposium on System Integration, SII 2010, Proceedings

Civil engineering work still involves many dangerous and grueling tasks, so improving work environments and ensuring safety are challenges facing this field. The development of construction machines are also essential to prepare for the aging problem of construction workers and shortage of young experienced workers in near future. This research project was conducted to overcome these problems by development of the basic technologies with three-dimensional information, and realize the autonomous operation of hydraulic excavators, which is, a typical general purpose construction machine. We have implemented a prototype of the autonomous hydraulic excavator, which performs the soil excavation and loading work under basic conditions. The achieved work speed and finished product precision were almost same as those of normal work by humans. ©2010 IEEE. Source

Takahashi T.,Fukada Geological Institute | Yamamoto T.,Kinki Regional Development Bureau
Exploration Geophysics

The internal structure of a river embankment must be delineated as part of investigations to evaluate its safety. Geophysical methods can be most effective means for that purpose, if they are used together with geotechnical methods such as the cone penetration test (CPT) and drilling. Since the dyke body and subsoil in general consist of material with a wide range of grain size, the properties and stratification of the soil must be accurately estimated to predict the mechanical stability and water infiltration in the river embankment. The strength and water content of the levee soil are also parameters required for such prediction. These parameters are usually estimated from CPT data, drilled core samples and laboratory tests. In this study we attempt to utilise geophysical data to estimate these parameters more effectively for very long river embankments. S-wave velocity and resistivity of the levee soils obtained with geophysical surveys are used to classify the soils. The classification is based on a physical soil model, called the unconsolidated sand model. Using this model, a soil profile along the river embankment is constructed from S-wave velocity and resistivity profiles. The soil profile thus obtained has been verified by geotechnical logs, which proves its usefulness for investigation of a river embankment. © 2010 ASEG/SEGJ/KSEG. Source

Matsuki H.,Kinki Regional Development Bureau
Journal of Disaster Research

Japan has suffered from natural disasters but sustained economic activity on not so commodious islands. This social resiliency is based on a time-honored risk management scheme that, like a tripod, consists of self-help, mutual help, and public help. This study analyzes the social infrastructure from Japan's disaster-fighting history. Japan's first political documents tell how the ancient Japanese people broke ground on floodplains to develop rice-paddy agriculture and underwent repeated water-related disasters after the Nara era (710-794). People had to deal with flooding and commence risk management to survive in flood-prone areas. During the Edo era (1603-1868), people expanded paddy agriculture to all arable land in the islands and tried to protect rice production from endless flood disasters in the same places. An effective flood-fighting scheme was then invented and expanded to nationwide. Its essence was coalition among people, a primary community and a local government. In Japan's modernization since 1868, traditional social rules have been enshrined into laws. The indigenous scheme for anti-flood measures has been translated into 3 major acts: the Disaster Management Basic Act, the Flood Fighting Act, and the River Act. These acts have been working and evolving, during qualitative transforming of Japanese society due to industrial restructuring, rapid urbanization, population fluidity, etc. Under such a legal infrastructure, the MLIT Himeji Office conducted a pilot program in an inundated community just after a downpour disaster in 2009 to improve local anti-flood measures. Output has indicated the importance of independency and interdependency of self-/mutual/public help. The "tripod" scheme provides recommendations for living with disaster not only in Japan but also in other countries in Asia. Source

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