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Haraguchi T.,Osaka City University | Goto K.,Tohoku University | Sato M.,Arc Geo Support Co. | Yoshinaga Y.,CTI Engineering Co. | And 2 more authors.
Marine Geology | Year: 2013

The 11 March 2011 MW 9.0 Tohoku megathrust earthquake off the Pacific coast of Japan was a salient event in the history of Japan. The resultant huge tsunami (the 2011 Tohoku-oki tsunami) inundated a vast coastal area of northeastern Japan, causing widespread devastation. Twenty days after the tsunami, we analyzed the impact of the tsunami on the sea bottom of the Kesennuma inner bay using side-scan sonar to explore the damage and bathymetric change in the harbor. Herein we present the first direct evidence that the sea bottom sediments of around 10-15m were largely reworked by the tsunami to thickness of a few meters, and that large dunes were formed by the tsunami. Considering that the sea wave influence is as weak as it is inside the inner bay, the potential exists that even meter-thick paleo-tsunami deposits are preserved in shallow sea bottoms with large bedforms. This finding will be a stepping-stone to future geological studies of tsunami effects in shallow sea regions. © 2012 Elsevier B.V.

Oshikawa H.,Saga University | Mito Y.,CTI Engineering Co. | Komatsu T.,Kyushu University
Journal of Disaster Research | Year: 2015

The new Cascade concept of flood control is demonstrated in laboratory experiments in which upstream dams in a series of dams constructed along a river overflow from emergency spillways while the final downstream dam is required only to use its normal spillway and never do its emergency spillway. Multiple small dry dams lacking a slide gate in a normal spillway should be constructed in a series rather than as a single large dam to prevent flood disasters and to preserve the natural environment. Dry dams for flood control have recently been reviewed, planned, and built at sites in Japan. In this paper, we compare the Cascade method to conventional flood control in laboratory experiments conducted based on the condition that dams all have the same reservoir capacity. Results have shown that the Cascade method using multiple dry dams was considerably more effective than conventional flood control. Furthermore, the additional flood control effect of a dry dam equipped with closable and openable gate in its regular spillway was experimentally confirmed although there is no such kind of the gate on an ordinary dry dam. This new dry dam should be constructed in the river’s upper reaches away from the existing downstream storage dam needing still more its capacity for water utilization, thus ensuring the amount of water available by closing the regular spillway after the dry dam is filled to capacity. The flood control capacity of dams including the new dry dam is stronger than that of an ordinary storage dam thanks to the dry dam’s storage function. © 2015, Fuji Technology Press. All rights reserved.

Oshikawa H.,Kyushu University | Mito Y.,CTI Engineering Co. | Komatsu T.,Kyushu University
Journal of Disaster Research | Year: 2013

The new concept for flood control called 'Cascade' method which permits dams to overflow around an upstream region with a sequence of dams constructed in a river is proposed. Multiple small scale dry dams should be constructed in series instead of a large scale dam in order to prevent flood disaster and preserve the natural environment. Recently a flood control dam with a bottom outlet hole as its regular spillway, known as 'dry dam', has been reviewed, planned and built in some sites in Japan. Under a condition of a common reservoir capacity, the Cascade type flood control permitting upstream dams to overflow except for the most downstream dam in a river is compared with a conventional one not to overflow each dam in a numerical simulation. As a result, it is made clear that the Cascade method using multiple dry dams is much more effective than the conventional one. In this connection, the Cascade type flood control method permitting upstream dams to overflow from emergency spillways except for the most downstream dam can be applied to normal storage dams with slide gates operated conventionally. Therefore, it could become an effective adaptation method for the global warming problem since it is performed by only changing how to operate slide gates in existing storage dams constructed in series. In addition, we also propose a new type of dry dam that has a closable and openable gate for its regular spillway primarily to retain the water for the water utilization. The new type of dry dam, which should be constructed in the upper reach away from the existing downstream storage dam needing still more its capacity for water utilization, ensures the amount of water available for the use by closing the regular spillway after the new dry dam is at full capacity, and the flood control capacity of the dams including the new dry dam is stronger than that of the normal dams owing to the storage function with the new dry dam. The new dry dams may improve the water utilization, the flood control, and environmentfriendliness under the current condition in Thailand damaged by the severe flood in 2011.

Akutagawa S.,Kobe University | Kusui A.,Kobe University | Nomura M.,CTI Engineering Co.
Rock Mechanics in Civil and Environmental Engineering - Proceedings of the European Rock Mechanics Symposium, EUROCK 2010 | Year: 2010

Several application examples are shown in which Light Emitting Deformation Sensors are used for deformation monitoring of infrastructures (slopes, tunnels, etc) and other purposes. Unlike conventional method of data acquisition, the use of this new device enables real-time data processing and visualization onsite, so that the state of deformation for a rock structure in concern is grasped with no delay in time and is shown visually to anyone nearby. Rationally designed use of this sensor could minimize risks not only during construction of infrastructures but also during their service time. © 2010 Taylor & Francis Group.

Nomura M.,CTI Engineering Co. | Naotsuka K.,CTI Engineering Co.
Life-Cycle of Structural Systems: Design, Assessment, Maintenance and Management - Proceedings of the 4th International Symposium on Life-Cycle Civil Engineering, IALCCE 2014 | Year: 2015

This essay introduces a surveying method for creating documents for maintenance policy making or basic documentation, whereby the shape of the lining surface of a deep shaft, especially those without scaffolding, is determined, properly extracting cracks, wall separation, leaks, free lime, and deformation. The shaft’s lining wall surface, which is one of the most important facilities, was surveyed using newly-developed digital video cameras. Because of their particular attributes, being a vertically long structure, inspection of the wall surface of shafts is extremely difficult through visual inspection at proximity unless there is some scaffolding; this has been a significant issue for executing inspections. The "damage/deterioration detection system for concrete structures" is originally an inspection system for highway tunnels that does not require the tunnel to be closed. However, by applying this system using newly-introduced digital video cameras, survey results that equal or outperform the previous proximity visual inspection method can be obtained without the need for scaffolding. The essay will describe the details of the system through two case studies, where site surveys were actually carried out in deep shafts. © 2015 Taylor & Francis Group, London.

Kido E.M.,CTI Engineering Co.
Engineering for Progress, Nature and People | Year: 2014

Travel by railways is now more popular than it was several years ago. Along with the "station renaissance", many new stations have been built and many historical stations have been refurbished and developed. Stations have become more user-friendly, satisfying many needs and various additional functions. This paper examines factors, which have an influence that railway stations in Europe and Japan have become more designated for people than, like before, for trains. The conclusion is that both in Europe and Japan many factors of station design are essential for people and make travel by rail more convenient.

Yoshikawa M.,Tokyo University of Agriculture and Technology | Hoshino Y.,Tokyo University of Agriculture and Technology | Iwata N.,Tokyo University of Agriculture and Technology | Iwata N.,CTI Engineering Co.
Journal of Vegetation Science | Year: 2013

Questions: A natural gravel-bed river is an important habitat for xerophytic plant species that prefer dry and periodically disturbed environments. However, human-impacted gravel bars covered with fine sandy sediments are often rapidly occupied by hygrophytic and mesophytic species, including weedy species, after a flush event. What is the mechanism by which these plant seeds are carried on gravel bars through a flush event? Can the seed traits of floating capability (buoyancy or settleability) and settling velocity in water explain seed accumulation in sandy sediments? Location: The Tama River, central Japan. Methods: Seed buoyancy/settleability and settling velocity in water were examined for 70 herbaceous species growing on newly deposited sediments of a river gravel bar. Settling velocities of sand particles of different sizes were estimated using theoretical formulas to compare with those of plant seeds. In addition, actual seed content of 36 samples of fresh sandy sediments were examined using a germination test to confirm coincident sedimentation of seeds and sand particles. Results: Of the 70 species examined, only nine had apparently buoyant seeds and the remaining 61 species had non-buoyant seeds. We found that 53 (86.9%) of the 61 species having non-buoyant seeds had settling velocities comparable to those of very fine sand and fine sand particles, ranging from 0.062 to 0.25 mm in diameter. Furthermore, fresh sandy sediments deposited by a flush event contained many non-buoyant seeds of common species of above-ground vegetation. Both the germinated seedling number and species richness in the sediment samples showed positive correlation with the percentage weight of very fine sand and fine sand. Conclusions: Seeds of most of the species that appeared after a flush event were considered carried by submerged dispersal through flowing water than through floating dispersal, because of their settleability. Many plant seeds could deposit together with fine sandy sediments as water velocity declined, since they had correspondent settling velocities. The main reason for rapid colonization by hygrophytic and mesophytic species was the settleability and settling velocity of the seeds. © 2012 International Association for Vegetation Science.

Kido E.M.,CTI Engineering Co.
Large Structures and Infrastructures for Environmentally Constrained and Urbanised Areas | Year: 2010

The paper describes structural art and aesthetics of distinguished large railways stations that has been built or are still under development as a part of the re-urbanization of large cities and as a highlights of "Station Renaissance" trend. Three mega-stations - Berlin Hauptbahnhof, St Pancras and Tokyo station are examples of aesthetic stations that have qualities of structural art.

Akamatsu Y.,Yamaguchi University | Ikeda S.,CTI Engineering Co.
Journal of Hydro-Environment Research | Year: 2015

A surface and subsurface water coupled ecological model is presented to describe material cycling in a mangrove area, to which an ecosystem model is applied in order to account for chemical and biological reactions as well as physical processes. In this model, the nutrient transport from the groundwater to the river is estimated by the combined use of field measurements and numerical simulation of subsurface flow. The water movement and temporal variations in nutrient concentration obtained from the numerical simulation show a good agreement with the field observations, indicating that this model is valid for simulating material cycling in a mangrove area. The numerical simulation reveals that the supply of dissolved nutrients from the mangrove to the coastal area during spring tides is about 1.6 to 5.5 times larger than that during neap tides. © 2015 International Association of Hydro-environment Engineering and Research, Asia Pacific Division.

Kido E.M.,CTI Engineering Co.
Assessment, Upgrading and Refurbishment of Infrastructures | Year: 2013

Since 1980s, railway architecture has been experiencing "station renaissance". Along with this trend, many large historical stations have been refurbished, upgraded and developed. Modern extensions need to fit to historical settings and to add additional values of modernity and attractiveness to railway stations. This paper examines such stations on the example of Europe and Japan and concludes that these transport facilities with their re-born buildings improving travel by rail, are new-generation station and often urban landmarks.

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