Journal of the Japan Society of Engineering Geology
Online ISSN : 1884-0973
Print ISSN : 0286-7737
ISSN-L : 0286-7737
Volume 58, Issue 3
Displaying 1-3 of 3 articles from this issue
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  • Takeshi KUWANO, Tomoharu IWASAKI, Takashi HARA, Masanori TOZAWA
    2017 Volume 58 Issue 3 Pages 166-177
    Published: August 10, 2017
    Released on J-STAGE: November 08, 2017
    JOURNAL FREE ACCESS

    Bhutan is located between China and India along the Himalayan Mountains and almost entirely mountainous country with nearly 95 percent of the country being above 600 meters altitude. Roads are major means of travel and transportation in Bhutan, and development of an efficient and safe road network is essential for Bhutan's social and economic development.

    However, large parts of the country consist of steep slopes and cliffs, and there are few roads with sufficient road slope disaster countermeasures in place. Consequently, slope failures and landslides frequently occur and isolate areas from the capital or other areas of the country, disrupting travel and the transport of agricultural crops.

    Therefore the authors have implemented a slope disaster inspection on roads in the National Road 1 and 4 as an activity of the development of a road slope management master plan. To prepare the inspection sheet in Bhutan where there are few engineers who have experience on slope disaster inspection, the authors have discussed the factors and their contributions that affect on each disaster and decided the item in the list on the slope disaster inspection sheet in Bhutan using multivariate statistical analysis, namely quantification theory.

    Through the multivariate statistical analysis in this study, the following was observed: “collapsed factors on topography”,“topsoil and detached rock on surface” and “dip on profile” have greatly affected the hazard on rock slope failure; “dip slope of bedding plane on geology” and “dip on profile” have greatly affected the hazard on debris slope failure; and “surface anomalies on topography” have greatly affected the hazard on landslide in Bhutan. Based on the analysis, new evaluation sheets are proposed for the slope inspection on roads for each slope disaster, which are suitable to the conditions of geology and topography in Bhutan.

    The analysis and discussion in this study help the Bhutanese Government understand which feature and condition they should pay attention to identify accurately the hazard on slope disasters in Bhutan.

    The Bhutanese Government has to keep fighting slope disasters like the Japanese Government does. Data accumulation of the evaluation sheets is important for the continuous inspection to improve the accuracy of hazard evaluation on each slope disaster.

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  • Takashi MIZUNO, Teruki IWATSUKI, Tatsuji MATSUZAKI
    2017 Volume 58 Issue 3 Pages 178-187
    Published: August 10, 2017
    Released on J-STAGE: November 08, 2017
    JOURNAL FREE ACCESS

    This paper describes a methodology for calculating equivalent NaCl concentration of matrix pore water in the Tertiary sedimentary rocks based on the result of resistivity logging in deep boreholes at the Horonobe area, Hokkaido, Japan. Archie's law is used to calculate the equivalent NaCl concentration of matrix pore water. Consistency between the equivalent NaCl concentration calculated by Archie's law and the analytical data of pore water extracted from drilled core was statistically verified by t-test. As the result of the t-test, significant similarity between calculated NaCl concentration and analytical data was observed in nine out of eleven boreholes. In these boreholes, a good correlation was confirmed for both. It suggests that the equivalent NaCl concentration can be calculated based on the resistivity logging result. The significant difference found in two of the boreholes are considered to be due to contamination of pore water caused by penetration of drilling fluid into the rock matrix.

    Based on these, attention points for estimating the equivalent NaCl concentration of matrix pore water from the resistivity logging result are summarized, and the procedure for applying at the field investigation is presented.

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  • Hideki INAGAKI
    2017 Volume 58 Issue 3 Pages 188-196
    Published: August 10, 2017
    Released on J-STAGE: November 08, 2017
    JOURNAL FREE ACCESS

    The slope sediment related disaster caused by the Kumamoto earthquake in April 2016, there were six types of natural slope failure and artificial slope failure. The slope failures occur within 10 km on both sides of the active strike slip fault, especially large slope failures occurred in vicinity of the active fault. The slope failure value pattern of separate length from the active strike slip fault is found to be located between the active reverse fault and active normal fault in almost the same magnitude.

    The expansion of the slope failures due to the earthquake and the new slope failures in the rainfall catchment topography are caused by the torrential rain in couple of months after the earthquake. And about half of the slope failures caused debris flow.

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