Journal of the Japan Society of Engineering Geology
Online ISSN : 1884-0973
Print ISSN : 0286-7737
ISSN-L : 0286-7737
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Volume 53, Issue 4
Displaying 1-4 of 4 articles from this issue
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Original Article
  • Hydrogeological Structure and Groundwater Flow of Alluvium in the South Sarobetsu Moor
    Toshiaki SAKAI, Seiichiro IOKA, Toshifumi IGARASHI
    Article type: Original Article
    2012 Volume 53 Issue 4 Pages 172-182
    Published: August 10, 2012
    Released on J-STAGE: February 28, 2014
    DOIhttps://doi.org/10.5110/jjseg.53.172
    JOURNAL FREE ACCESS
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     The cross-sectional modeling of groundwater flow was carried out with the help of geological surveying, piezometer monitoring, and the chemical composition estimation of groundwater to investigate the groundwater flow system in the alluvial plain in Sarobetsu moor located in the northern part of Hokkaido. According to the previous studies, the geology of the alluvium is mud-rich. The Ho-la stratum (clay layer), which was deposited during the Hypsithermal age, had low permeability. The observation of the hydraulic head and chemical composition of the groundwater indicated that the Ho-la stratum inhibited vertical groundwater flow. In addition, the highest hydraulic head was measured at the basement rock in the eastern part of the moor and hydraulic heads were found to decrease in shallow areas and in the western part of the moor. The highest hydraulic head was guessed to have formed on account of tectonic movements. The distribution of the highest hydraulic head was estimated by analysis use with the groundwater flow model.
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  • Reducing Condition Surveys around the Underground Cavern by Measurements of pH and Self-potential
    Yoshiki INOHARA, Takahiro OYAMA, Kenji KUBOTA
    Article type: Original Article
    2012 Volume 53 Issue 4 Pages 183-190
    Published: August 10, 2012
    Released on J-STAGE: February 28, 2014
    DOIhttps://doi.org/10.5110/jjseg.53.183
    JOURNAL FREE ACCESS
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     Around the testing cavern of the subsurface disposal program of low level radioactive wastes in Rokkasho-mura, Aomori Prefecture of Japan, some surveys on the reducing environment assessment have been carried out in the Neogene sedimentary rocks. Through the hand drilling groundwater quality measurement and the self-potential measurement, the measurements of pH and self-potential are considered to be an effective method in the geochemical survey to evaluate the oxidation-reduction condition of the underground. The values of the pH and self-potential did not have a great variability, and had a stable profile in a few measurements. Thus, these items are important in the long-term monitoring of the underground environment. The classification of the reducing condition into some regions could induce a different aspect of the deep underground geochemical environment, and lead to the distribution of the reduction condition or damaged zone of the excavated rock mass.
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Report
  • Physical and Mechanical Properties of Beachrocks in Okinawa Island
    Takashi DANJO, Satoru KAWASAKI
    Article type: Report
    2012 Volume 53 Issue 4 Pages 191-200
    Published: August 10, 2012
    Released on J-STAGE: February 28, 2014
    DOIhttps://doi.org/10.5110/jjseg.53.191
    JOURNAL FREE ACCESS
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     There are very few reports about physical and mechanical properties of beachrocks in the world. To obtain the properties of beachrocks and to investigate their correlations between unconfined compression strength and other properties such as density, water content, etc., we performed a series of in-situ tests and laboratory tests for beachrocks in Okinawa Island. As a result, it was shown that the average values of unconfined compression strengths of the beachrock samples obtained from three testing sites were 11.14MPa, 19.91MPa and 42.23MPa, respectively. It was also understood that density and unconfined compression strength of the beachrocks increased along with the passage of time while water content decreased. Moreover, it was found that there was a relationship like qu = 0.00000654 t2+0.0101 t between unconfined compression strength, qu (MPa), and calibrated radiocarbon age, t(y Cal BP).
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