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Kawasaki H.,Japan Dam Engineering Center | Kubo H.,Japan Anchor Association
ISRM International Symposium - 8th Asian Rock Mechanics Symposium, ARMS 2014 | Year: 2014

The anchoring method has spread quickly in Japan during the past 30 years, and many anchors have been installed in dams.θDam sites include a variety of anchored objects such as the dam-body, the rock foundation, the gate fixing part, and the slopes around the reservoir. These dam use anchors are all types of rock anchors, and, except the slope stability anchor, are used to reinforce structures. Generally, a dam anchor is large, and plays a very important role as a structural system supporting the safety of the dam. In this paper, we classified these as structure reinforcement anchors, and clarified their roles. Furthermore, we listed the design required performances and introduced the dam anchor design policy established by research conducted by the Japan Dam Engineering Center. Based on the required performance, we described the tensile load control range and the durability measures for anchor systems, and added the bond type anchor which makes an important contribution to the stability and durability of the structure. Finally, we proposed a technical judgment method used to calculate the number of anchors required when renewing existing anchors. Above all, the content of this paper includes various subjects concerning the design of rock anchors. © 2014 by Japanese Committee for Rock Mechanics.


Matsumoto N.,Japan Dam Engineering Center | Sasaki T.,Japan Dam Engineering Center | Sato N.,Japan Water Agency
International Journal on Hydropower and Dams | Year: 2012

The magnitude 9.0 Tohoku earthquake on 11 March 2011 caused catastrophic effects to eastern Japan including significant loss of life. About 400 dams were inspected immediately after the event. While most dams sustained no damage, one homogeneous earthfill dam for irrigation failed completely. Japan Society of Dam Engineers (JSDE) dispatched investigation teams and site-surveys were conducted at 14 facilities. Dam inspections started immediately after the earthquake. By 31 March 2011, about 400 dams had been inspected. Only about 10 per cent of these dams exhibited damage such as cracking, increased leakage, or uplift pressure. The preliminary ground motion investigation suggests that a very long duration of ground motion and a number of subsequent strong aftershocks generated greater effects on embankment dams than on concrete dams.


Kobori T.,Public Works Research Institute | Yamaguchi Y.,Japan Dam Engineering Center | Nakashima S.,Yamaguchi University | Shimizu N.,Yamaguchi University
ISRM International Symposium - 8th Asian Rock Mechanics Symposium, ARMS 2014 | Year: 2014

Exterior deformation is one of the most important items to measure when managing the safety of embankment dams. Exterior deformation is usually measured by a conventional surveying method using targets installed on the crest and the slopes of the embankment dams. It is difficult, however, to measure the deformation by such a method immediately after an earthquake or other emergency. A displacement monitoring system using GPS (Global Positioning System) was developed to continuously monitor the deformation of dams. The system can provide three-dimensional displacements at many points simultaneously with high accuracy at the millimeter level. The GPS measurement system has already been installed at many embankment dam sites in Japan to ensure their appropriate safety management in light of this system's excellent advantages. Ishibuchi Dam is a concrete-face rockfill dam; it is one of the oldest rockfill dams in Japan. After the large settlement caused by the Iwate-Miyagi Nairiku Earthquake of 2008, the above GPS displacement monitoring system was installed to continuously monitor the deformation behavior of Ishibuchi Dam. On March 11, 2011, the Great East Japan Earthquake struck near the northeast coast of Honshu Island. This paper describes the results of the deformation monitoring of Ishibuchi Dam before, during and after the Great East Japan Earthquake. © 2014 by Japanese Committee for Rock Mechanics.


Honda K.,Kokusai Kogyo Co. | Mushiake N.,Kokusai Kogyo Co. | Satoh W.,Kokusai Kogyo Co. | Satoh H.,Public Works Research Institute | And 4 more authors.
ISRM International Symposium - 8th Asian Rock Mechanics Symposium, ARMS 2014 | Year: 2014

The number of aging civil engineering structures is rapidly increasing in Japan. As for dams, it is estimated that in the year 2020, 58% of existing dams will be 50 years or more since completion. This situation increasingly requires not only efficient deformation monitoring systems for safety management of civil engineering structures but also safe and rapid methods in case of emergencies such as earthquakes. Remote sensing techniques, especially Synthetic Aperture Radar (SAR), can play an important role to conduct deformation monitoring of civil engineering structures such as dams and rock slopes. Differential Interferometric SAR (DInSAR) analysis using SAR satellite data can be suitable for deformation monitoring over wide areas. To examine the applicability of DInSAR analysis for deformation monitoring, a rockfill dam with a center core with a height of 66m is selected as a study area because deformation monitoring using GPS has been rigorously conducted since the completion of the dam in December 2006. The values of deformations calculated by DInSAR analysis are about 70 or 80% of those measured by GPS during the observation period of about four years. Although the DInSAR analysis results are expected to have some errors and are different from the GPS measurement results to some extent, DInSAR analysis is sufficient to monitor few-centimeter deformations. Additionally, the settlement and subsidence trends of the dam can be well reproduced utilizing time series changes by DInSAR analysis. This indicates potential for DInSAR analysis to be used for deformation monitoring of civil engineering structures and rock slopes. © 2014 by Japanese Committee for Rock Mechanics.


Honda K.,Kokusai Kogyo Co. | Nakanishi T.,Kokusai Kogyo Co. | Haraguchi M.,Kokusai Kogyo Co. | Mushiake N.,Kokusai Kogyo Co. | And 4 more authors.
International Geoscience and Remote Sensing Symposium (IGARSS) | Year: 2012

To promote efficiency of safety management of filldams, this study examines the applicability of DInSAR that is used to measure exterior deformation of filldams using ALOS PALSAR data. The results of Single pair DInSAR measurement are equivalent approximately to 85% of GPS measurement results that are referred to as true data. At the same time, the results of Time series DInSAR measurements are equivalent approximately to 80% of the GPS measurement results. Like the GPS measurements, the Time series analysis results also reveal a trend that includes a major displacement of a crest line. Consequently, this study indicates that it is possible to monitor exterior deformation of filldams by DInSAR techniques using ALOS PALSAR data. © 2012 IEEE.


Yoshida H.,Japan Dam Engineering Center | Nakamura A.,Japan Dam Engineering Center | Matsumoto N.,Japan Dam Engineering Center | Kasai T.,Tohoku Regional Bureau
Dams and Reservoirs under Changing Challenges - Proceedings of the International Symposium on Dams and Reservoirs under Changing Challenges - 79 Annual Meeting of ICOLD, Swiss Committee on Dams | Year: 2011

The Ishibuchi Dam is a dumped rock CFRD with height of 53 m, completed in 1953. During the Iwate-Miyagi Nairiku Earthquake in 2008, a seismograph installed on the crest of the Ishibuchi Dam, which was located 9.4 km from the epicenter, recorded maximum acceleration of 14.61 m/s 2 horizontally and 20.70 m/s 2 vertically. However, the concrete facing was largely unaffected, the water storage function of the dam was completely maintained, and the damage to the dam body and the appurtenant structures remained within a repairable range. This paper presents the damage to the Ishibuchi Dam by the Iwate-Miyagi Nairiku Earthquake in 2008. The paper also introduces the results of performing a dynamic deformation analysis of the rockfill dam, and analyzing contributing factors which could maintain the seismic stability of the dam under such strong motion. © 2011 Taylor & Francis Group.


Matsumoto N.,Japan Dam Engineering Center
International Journal on Hydropower and Dams | Year: 2012

The article describes the development of construction capabilities compaction of materials, seismic aspects, and spillway capacity. The basis of Japan's present technology for earth core rockfill dams was established by the Miboro dam, completed in 1961 ,and also Makio dam. The core material was prepared by stockpile mixing of clay and weathered granite, which was extremely coarse grained material compared with previously used core materials. It was roller compacted to a thickness of 20 cm, with a 20 t sheepsfoot roller. The core of the Makio dam was also coarse, with 60 per cent of the material having a particle size more than 4.75 mm. Shortly after World War II, Sannokai dam was built, partly manually and partly using small-scale machinery for about 30 per cent of the total fill volume. Then, from 1950, embankment materials began to be placed using machinery.


Fujisawa T.,Japan Dam Engineering Center | Sasaki T.,Japan Dam Engineering Center
International Journal on Hydropower and Dams | Year: 2012

The trapezoidal CSG dam differs from conventional concrete gravity dams and embankment dams in that its body is trapezoidal in shape, and it is constructed of cemented sand and gravel (CSG). CSG, which can be produced easily by mixing cement and water with materials obtained near to a dam site, without gradation or washing, does not have the same strength as concrete. Rationalization efforts in dam engineering generally relate to three aspects: design, materials, and construction. A trapezoidal CSG dam is made with CSG being used for the main part of dam body, and with protective concrete being placed on its surface to increase durability. A gallery, structural concrete and a seepage control system made of concrete are placed underneath on the upstream side. The CSG on the bottom surface of the dam body is rich-mix material, to ensure durability.


Ohmachi T.,Japan Dam Engineering Center | Tahara T.,Tokyo Institute of Technology
Dams and Reservoirs under Changing Challenges - Proceedings of the International Symposium on Dams and Reservoirs under Changing Challenges - 79 Annual Meeting of ICOLD, Swiss Committee on Dams | Year: 2011

The effect of the Iwate-Miyagi Nairiku earthquake in 2008 (Mj 7.2), Japan on the Aratozawa dam which is a 74.4 m high rockfill dam with a central clay core is studied with a main focus on the change in the vibration period, shear wave velocity, shear modulus, and pore-water pressure. During the main shock, the acceleration exceeded 10 m/s 2 at the gallery, inducing large shear strains in excess of 10 -3 and a sudden build-up of the excess pore water pressure in the core. Due to the large strains, the shear wave velocity and shear modulus showed a significant decrease from their initial values and the vibration period was elongated. The full recovery of the wave velocity was found to take at least one year, while the dissipation of the excess pore water pressure seemed faster than the recovery of the wave velocity. © 2011 Taylor & Francis Group.


Matsumoto N.,Japan Dam Engineering Center | Sasaki T.,Japan Dam Engineering Center | Shimamoto K.,Japan Dam Engineering Center | Sugiura Y.,CREARIA | Zhao H.Q.,CREARIA
Dams and Reservoirs under Changing Challenges - Proceedings of the International Symposium on Dams and Reservoirs under Changing Challenges - 79 Annual Meeting of ICOLD, Swiss Committee on Dams | Year: 2011

Newmark procedure is one of the methods to predict earthquake-induced deformations of embankment dams. It assumes that the sliding mass is rigid and the mass begins to move when the safety factor of the sliding mass becomes less than 1.0 and cease to move when the velocity of the sliding mass becomes equal to the rest of the embankment. Most of the Newmark procedures are based on the equilibrium equation of one-dimensional horizontal motion ignoring the vertical component. According to recent strong motion monitoring, large vertical accelerations were recorded. Hence the inertia force of vertical component is introduced in the paper. By using sinusoidal and recorded earthquake acceleration records, the earthquake-induced deformations were computed and the effects of vertical motion on permanent deformation of embankment dams are described. © 2011 Taylor & Francis Group.

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