Journal of the Japan Society of Engineering Geology
Online ISSN : 1884-0973
Print ISSN : 0286-7737
ISSN-L : 0286-7737
Volume 46, Issue 2
Displaying 1-4 of 4 articles from this issue
  • Takeshi YAMADA, Hisashi AOKI, Manabu TAKAHASHI, Yukinori MATSUKURA
    2005 Volume 46 Issue 2 Pages 72-78
    Published: June 10, 2005
    Released on J-STAGE: February 23, 2010
    JOURNAL FREE ACCESS
    To elucidate the effect of rock properties on rates of salt weathering, a laboratory experiment was carried out usingseven kinds of rock (two granites, two sandstones, welded tuff, tuff and porous rhyolite) and saturated salt solution ofNa2SO4. Some rock specimen had been gradually suffered salt fretting under the wetting and drying cycle condition. SinceP-wave velocity decreases due to salt fretting, the rate of weathering was obtained from the reduction rates of P-wavevelocity. On the other hand, several rock properties such as pore size distribution and rock strength were measured. Acomparison between the rate of salt weathering and rock properties suggests that salt weathering is more rapid in therocks with a larger proportion of micro-pores and/or lower tensile strength.
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  • Kenji DAITO, Shigeo SAEKI
    2005 Volume 46 Issue 2 Pages 79-88
    Published: June 10, 2005
    Released on J-STAGE: February 23, 2010
    JOURNAL FREE ACCESS
    The lowering groundwater level in the confined aquifers and a thick alluvial clay layer is thought as a cause of the large area subsidence. In this research, geo-environmental information such as altitude of B.M., groundwater level, and the thickness of the clay layer in Kanie region was arranged by using GIS.
    As a result, the change of the surface altitude in each year was made visible from altitude of B.M., and the place was clarified, where the influence of the subsidence was remarkable. The three-dimensional ground model was made from the geological cross sections and the boring logs of the subsidence observation wells. The stratum boundary depth and the thickness of the clay layer below each B.M. were presumed from the three-dimensional ground model. The calculated subsidence by one-dimensional consolidation analysis was corresponding to the measured subsidence.
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  • Yoshinori TANAKA, Chika KAZAMAKI
    2005 Volume 46 Issue 2 Pages 89-98
    Published: June 10, 2005
    Released on J-STAGE: February 23, 2010
    JOURNAL FREE ACCESS
    In the granitic areas of the Sanin district, Japan, an older style of iron manufacturing using iron sand, a process called Tatara, was widely used up until the Taisho era early in the 20th century. This study compares the distribution of the old iron sand quarries with the sites of slope failures associated with heavy rainfall in the Chugoku Mountains on the border between the Tottori and Shimane Prefectures. Field investigations and laboratory testing of rock samples shows that the weathering product of granite is characterized by extensive micro-cracking, which allows for easy mining of iron sand using simple tools. However, this character is also an important factor in slope failure. The change in slope stability with the development of the weathered layer is calculated using a slope model, and it is shown that higher slopes are susceptible to failure as weathering of the slope surface progresses. In contrast, lower slopes are resistant to failure even when weathering is advanced. Therefore, while deep wethering of granite facilitated the mining of iron sand, failure occurred on higher slopes with even very shallow weathering. The old iron-sand mining sites are considered to be related to slope failure by a joint dependence on weathering and the development of topography.
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  • Kazushi MORI, Eiichi ABE, Michihiko NAKAMURA
    2005 Volume 46 Issue 2 Pages 99-102
    Published: June 10, 2005
    Released on J-STAGE: February 23, 2010
    JOURNAL FREE ACCESS
    We assembled CCD camera system equipped with washer device and made inspections into clogged horizontal drain pipes drilled in landslide areas and obtained clear images at the maximum depth of 50.5 meters.
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