Journal of Japan Society of Dam Engineers
Online ISSN : 1880-8220
Print ISSN : 0917-3145
ISSN-L : 0917-3145
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Volume 15, Issue 1
Displaying 1-5 of 5 articles from this issue
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  • A Simplified Method to Determine a Required Depth of Destratification against Algal Bloom
    Noriko UEDA, Nobuo YOSHIDA, Shigeki YOKOYAMA, Hisashi SAWADA
    Article type: Others
    Subject area: Others
    2005 Volume 15 Issue 1 Pages 5-13
    Published: 2005
    Released on J-STAGE: January 11, 2008
    DOIhttps://doi.org/10.11315/jsde.15.5
    JOURNAL FREE ACCESS
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    Destratification system, or artificial circulation, is one of major countermeasures to control algal bloom in eutrophied dam reservoirs. Effects of destratification largely depend on the depth of the surface mixed layer formed by the circulation. The depth of the mixed layer corresponds to that where the destratification system is installed, so that a formulation is needed to optimize the depth of installation and operation of the system. Our idea is based on the model introduced by Lorenzen (1975), but chlorophyll-a is used in this paper to estimate algal biomass. By using a diagram showing the relation between the depth of mixed layer and the chlorophyll-a concentration that is possible to be produced in the dam reservoir, a required depth of circulation is easily estimated to prevent algal bloom. We applied the formulation to several dam reservoirs and confirmed its effectiveness.
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  • Study on Dynamic Characteristics of Artificial Abutment Method for Dams
    Daisuke HIRAYAMA, Hideaki KAWASAKI, Hidetaka YOSHIOKA
    2005 Volume 15 Issue 1 Pages 14-27
    Published: 2005
    Released on J-STAGE: January 11, 2008
    DOIhttps://doi.org/10.11315/jsde.15.14
    JOURNAL FREE ACCESS
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    To minimize the excavation area in dam abutment, concrete abutment method was developed in Japan, getting popular in many dams. Concrete abutment method can prepare sound foundation for concrete dam abutment by replacing weak rock to concrete mass, and it should be designed to satisfy the equivalent safe level to a concrete dam. In this paper, a design concept and dynamic characteristics of concrete abutment method are studied based on stress analyses using FEM.
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  • A Study on Efficiency of Selective Withdrawal and Its Influence to Water Quality
    Tetsuo HOTTA, Hikaru SHOJI, Yoshihiro YAMASHITA, Feiyong CHEN, Hideo I ...
    Article type: Others
    Subject area: Others
    2005 Volume 15 Issue 1 Pages 28-36
    Published: 2005
    Released on J-STAGE: January 11, 2008
    DOIhttps://doi.org/10.11315/jsde.15.28
    JOURNAL FREE ACCESS
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    It's known from previous studies that intake dimensions, such as thickness and width, structural conditions such as projection of piers, and external conditions such as distance from dams are important factors, which affect efficiency of selective withdrawal. The importance of these factors is realized, but the methodologies to evaluate these factors are not established. So even though these factors affect the water quality of dam reservoirs, they are rarely considered in environmental impact analysis. In this paper we will show the information about the efficiency of selective withdrawal, based on field data obtained.
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  • Development and Practical Use of High Speed Conveyance System for Concrete of Dam
    Mitsuo TAKEDA, Tetsukazu KIDA, Hajime NISHIKAWA, Katsuteru KUDO
    2005 Volume 15 Issue 1 Pages 37-51
    Published: 2005
    Released on J-STAGE: January 11, 2008
    DOIhttps://doi.org/10.11315/jsde.15.37
    JOURNAL FREE ACCESS
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    For the development of surface-shaped dam construction systems, several combinations including new technologies, of concrete conveyance equipment have been developed. Among them the belt conveyor system for the transportation of large quantities of concrete for large-scale dams is being used successfully. However, there were some problems related with the slope limit of the belt conveyor and the top part switching equipment. In order to solve these problems and attempting to have a high-speed execution system, a tower type belt conveyor is proposed in this research. This system was actually used in the transportation and placing of concrete of a fill dam to test its capability and functionality. Moreover, a comparison with other construction systems was done for different scale of dams, which proves that the proposed system is more economic than others. It was also clarified the range where the proposed construction system can be used.
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  • Downstream Sliding Plane with Minimum Safety Factor for Rockfill Dams with a Central Earth Core
    Yoshikazu YAMAGUCHI, Makoto NAKAMURA
    Article type: Others
    Subject area: Others
    2005 Volume 15 Issue 1 Pages 52-66
    Published: 2005
    Released on J-STAGE: January 11, 2008
    DOIhttps://doi.org/10.11315/jsde.15.52
    JOURNAL FREE ACCESS
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    In Japan, the stability of a rockfill dam is generally evaluated using the circular sliding method. In this paper, we make stability analyses for a rockfill dam with a central earth core, which is designed by the present design standard, using circular sliding method, compound sliding plane method and sliding-wedge method. Based on the analytical results, we discuss the downstream sliding plane with the safety factor for rockfill dams with a central earth core.
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