Tokyo, Japan
Tokyo, Japan

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Uemura K.,Tokyo City University | Sasaki T.,Kyokado Engineering Co. | Shimada S.,Kyokado Co. | Suemasa N.,Tokyo City University | Nagao K.,Sato Kogyo Co.
Proceedings of the International Offshore and Polar Engineering Conference | Year: 2015

Reasonable infusion materials are investigated using white carbon in this study. White Carbon, hereinafter written as WC, is aggregate silica micro-particles and the size of independent particle is several tens μm in diameter. Although the effect of the liquefaction countermeasure method using WC is to increase the density of sandy ground by injecting it, regular WC is relatively too large to be injected into the ground. Therefore, regular WC has to be grinded into much finer particles in order to grout them into sandy ground. In this study, a micro bubble generator was suggested to grind WC efficiently, utilizing the phenomenon of vortex breaking. In this paper, a series of grain size analysis of WC grinded by the micro bubble generator were conducted and infiltrating injection tests injecting the grinded WC were carried out in order to examine the feasibility of the WC injection method proposed. As a result, it was confirmed that the finer WC was able to permeate sandy ground. Copyright © 2015 by the International Society of Offshore and Polar Engineers (ISOPE).


Kitagawa S.,Sato Kogyo Co. | Kimura S.,Kanazawa Institute of Technology | Moriyama M.,Central Nippon Expressway Co. | Nabetani M.,Sato Kogyo Co. | Utagawa N.,Sato Kogyo 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

In recent years, reinforced concrete slab of a highway bridge is reported deteriorated by the salt damage. The deterioration due to salt damage, deterioration of the slab near the top surface is remarkable. The main inspection method is a visual inspection and hammering test, and obtaining quantitative results is difficult. This report, we have investigated for focusing on inpact acoustics method is one of the non-destructive inspect method to detect the deterioration of the RC slab from the top surface of asphalt concrete pavement. Result of studies, by using the impact acoustics method, it was confirmed that it may be considered a deterioration of RC slab inside. © 2015 Taylor & Francis Group, London.


Uno Y.,Sato Kogyo Co. | Kimura S.,Kanazawa Institute of Technology
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

In this paper, the authors propose a method to evaluate quantitatively the spalling risk of the lining concrete and the spalling risk variation model in a road tunnel, the method is based on probability theory. A concrete risk shall be evaluated by economic loss. The spalling phenomenon can convert them into each economic loss which the administrator and user of a tunnel receive. Furthermore, the prevention technology to spalling by using fiber sheet is proposed. This method is applied to seven tunnels including the site under construction as of March, 2014. As a result, the verification is presented certainly at these construction sites. © 2015 Taylor & Francis Group, London.


Akamatsu R.,Toin University of Yokohama | Utagawa N.,Sato Kogyo Co. | Sugimoto T.,Toin University of Yokohama | Katakura K.,Laboratory
IEEE International Ultrasonics Symposium, IUS | Year: 2013

We propose a new non-contact acoustic imaging method for nondestructive inspection using a high-power directional sound source and a S canning Laser Doppler Vibrometer (SLDV). In this method, vibration velocities on concrete surface, which is generated by an air borne sound, is measured with the SLDV. As a high-power directional sound source, an LRAD (Long Range Acoustic Device) is employed. Near a targeted concrete surface, very high sound pressure is required to excite the concrete wall. However, while the sound wave is emitted, the SLDV is vibrated by the sound wave. Thus, the vibration of the SLDV affects the signal-to-noise ratio. This paper describes about tone burst wave method for an improvement of the signal-to-noise ratio. Consequently, the signal to noise ratio of 12 dB was improved than using a chirp wave. © 2013 IEEE.


Katakura K.,Meitoku Engineering Laboratory | Akamatsu R.,Toin University of Yokohama | Sugimoto T.,Toin University of Yokohama | Utagawa N.,Sato Kogyo Co.
Japanese Journal of Applied Physics | Year: 2014

We study a noncontact inspection method for large-scale structures such as tunnels and bridges. This method involves the use of a high-powered sound source and a scanning laser Doppler vibrometer (SLDV). In our previous study, we proposed a tone burst wave method to improve the signal-to-noise ratio (SNR) of the measured result. Using this method, a defect that was difficult to detect using our previous method was detected. In this study, we examined the detectable size and depth of the defect by using a model wall with circular defects. The distance between the sound source and the concrete test piece was 5m, and the output sound pressure was about 100 dB near the surface of the concrete test piece. As the transmitted wave, tone burst waves with different center frequencies from 500 to 7000 Hz were used. A conventional investigation by the hammer method was also simultaneously carried out for comparison and almost identical performance was confirmed. From the experimental result, we confirmed that the bending resonance frequency detected was proportional to the depth of the circular defect, and was in inverse proportion to the plane size (area) coincident to the analytical result for a circular plate. We also found that the vibration energy of the defect shows a strong dependency on its depth. Therefore, the possibility of defect depth estimation using the resonance frequency and the vibration energy ratio is expected. In the future, a practical investigation system that will replace the hammer method might be developed. © 2014 The Japan Society of Applied Physics.


Sugimoto T.,Toin University of Yokohama | Akamatsu R.,Toin University of Yokohama | Utagawa N.,Sato Kogyo Co. | Tsujino S.,Sato Kogyo Co.
IEEE International Ultrasonics Symposium, IUS | Year: 2011

We propose a new non-contact acoustic imaging method for nondestructive inspection using scanning laser Doppler vibrometer (SLDV) and long range acoustic device (LRAD). In this method, Surface vibration, which is generated by air borne sound, is measured using SLDV. This time, the styrofoam board (300 x 300 x 100 mm 3) was buried at 50 mm depth in the concrete are used as a substitute of a cavity in the concrete. As an experimental result, a styrofoam board is clearly imaged by the vibration velocity of the concrete surface. And also, we confirmed the response range of the frequency of a buried object. Clearer image is formed by the optimum frequency response range (OFR) method. © 2011 IEEE.


Akamatsu R.,Toin University of Yokohama | Sugimoto T.,Toin University of Yokohama | Utagawa N.,Sato Kogyo Co. | Katakura K.,Meitoku Engineering Laboratory
Japanese Journal of Applied Physics | Year: 2013

Maintenance for concrete structures such as buildings, bridges, and tunnels is necessary, because it is thought that a lot of them show deterioration. As a periodic inspection, a hammering test is the most popular method. However, it has several problems. One of the problems is that it is difficult to inspect the places where people cannot reach. Therefore, non contact inspection methods have been developed. As a noncontact inspection method, we propose a system consisting of a high-power directional sound source and a scanning laser doppler vibrometer (SLDV). In this method, an air-borne sound wave is used for the excitation of a concrete wall, and then the vibration velocities on the concrete wall are measured two-dimensionally by the SLDV. From the vibration velocity, defective parts can be detected. In this paper, we describe two types of experiment on the feasibility of our proposed method. In these experiments, concrete wall test pieces, which have artificial defects, are used. From the experimental results, we confirmed the effectiveness of our proposed method as a non contact inspection method for concrete structures. © 2013 The Japan Society of Applied Physics.


Sugimoto T.,Toin University of Yokohama | Uechi I.,Toin University of Yokohama | Sugimoto K.,Toin University of Yokohama | Utagawa N.,Sato Kogyo Co. | Katakura K.,Meitoku Enginnering Laboratory
Physics Procedia | Year: 2015

Hammering test is widely used to inspect the defects in concrete structures. However, this method has a major difficulty in inspect at high-places, such as a tunnel ceiling or a bridge girder. Moreover, its detection accuracy is dependent on a tester's experience. Therefore, we study about the non-contact acoustic inspection method of the concrete structure using the air borne sound wave and a laser Doppler vibrometer. In this method, the concrete surface is excited by air-borne sound wave emitted with a long range acoustic device (LRAD), and the vibration velocity on the concrete surface is measured by a laser Doppler vibrometer. A defect part is detected by the same flexural resonance as the hammer method. It is already shown clearly that detection of a defect can be performed from a long distance of 5 m or more using a concrete test object. Moreover, it is shown that a real concrete structure can also be applied. However, when the conventional LRAD was used as a sound source, there were problems, such as restrictions of a measurement angle and the surrounding noise. In order to solve these problems, basic examination which used the strong ultrasonic wave sound source was carried out. In the experiment, the concrete test object which includes an imitation defect from 5-m distance was used. From the experimental result, when the ultrasonic sound source was used, restrictions of a measurement angle become less severe and it was shown that circumference noise also falls dramatically. © 2015 The Authors.


Nguyen D.L.,Ho Chi Minh City University of Transport | Nguyen D.L.,Nagaoka University of Technology | Ohtsuka S.,Nagaoka University of Technology | Hoshina T.,Sato Kogyo Ltd. Company | Isobe K.,Hokkaido University
Soils and Foundations | Year: 2016

Currently, many formulas are used to calculate the ultimate bearing capacity. However, these formulas have disadvantages when being applied in practice since they can only be applied for calculating simple footing shapes and uniform grounds. Most formulas do not take into account the size effect of the footing on the ultimate bearing capacity, except for the formula by the Architectural Institute of Japan. The advantage of using the finite element method (FEM) is its applicability to non-uniform grounds, for example, multi-layered and improved grounds, and to complicated footing shapes under three-dimensional conditions. FEM greatly improves the accuracy in estimating the ultimate bearing capacity. The objective of this study is to propose a rigid plastic constitutive equation using the non-linear shear strength property against the confining pressure. The constitutive equation was built based on experiments for the non-linear shear strength property against the confining pressure reported by Tatsuoka and other researchers. The results from tests on Toyoura sand and various other kinds of sand indicated that, although the internal friction angle differs among sandy soils, the normalized internal friction angle decreases with an increase in the normalized first stress invariant for various sands despite dispersion in the data. This property always holds irrespective of the reference value of the confining pressure in the normalization of the internal friction angle. The applicability of the proposed rigid plastic equation was proved by comparing it to the ultimate bearing capacity formula by the Architectural Institute of Japan, which is an experimental formula that takes into account the size effect of the footing. The results of rigid plastic finite element method (RPFEM) with the proposed constitutive equation were found to be similar to those obtained with the Architectural Institute of Japan's formula. It is clear that RPFEM, with the use of the non-linear shear strength against the confining pressure, provides good estimations of the ultimate bearing capacity of the footing by taking account of the size effect of the footing. © 2016 Japanese Geotechnical Society.


Nagao K.,Sato Kogyo Co. | Suemasa N.,Tokyo City University | Jinguuji M.,Japan National Institute of Advanced Industrial Science and Technology | Nakazawa H.,Chiyoda Corporation
Proceedings of the International Offshore and Polar Engineering Conference | Year: 2015

As a countermeasure of liquefaction, the microbubble water injection method has been proposed by our research group, and the feasibility study of the method is tackled at present. As one of the attempts, a field test of the microbubbles injection was held in Urayasu city which is one of the most severe damaged cities due to liquefaction in 2011 off the Pacific coast of Tohoku Earthquake. At that time, as a large number of housing lot suffered liquefaction damage, any countermeasure against liquefaction at such place is required. As performance requirements for the countermeasure at housing lots, inexpensiveness and construction even in a narrow space are needed. As a relatively simple construction method, the application of the microbubble water injection method is expected, which is carried out by injecting water containing micro-air bubbles (MB water) into ground. This method is not only simple and cost-effective but also friendly to environment. A half-year full-scale test for confirmation of workability and durability was carried out on silty sand ground enclosed by grid-shaped diaphragm walls in Urayasu. As a result, the sufficient performance of the method was confirmed and the possibility of re-improvement by re-injecting MB water into the ground was also examined. Copyright © 2015 by the International Society of Offshore and Polar Engineers (ISOPE).

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