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Nishi-Tokyo-shi, Japan

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. Source

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. Source

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. Source

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. Source

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. Source

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