Japanese Geotechnical Journal
Online ISSN : 1880-6341
ISSN-L : 1880-6341
Volume 13, Issue 1
Displaying 1-8 of 8 articles from this issue
  • - A verification and improvement of evaluation method -
    Goro ITOH, Yu KIKUCHI, Yutaka BENNO, Makoto ISHIMARU
    2018 Volume 13 Issue 1 Pages 1-11
    Published: March 31, 2018
    Released on J-STAGE: March 31, 2018
    JOURNAL FREE ACCESS
    This study verified a slip safety factor evaluation method, as developed subsequent to equivalent linear analysis, for the existing rock slope subject to earthquake ground motion records of the 2011 Tohoku earthquake off the Pacific coast of Japan. Results demonstrated that, although a large deformation was not confirmed via slope measurements taken after the earthquake, the minimum slip safety factor was determined to be lower than 1.0. Therefore, it was found that a certain margin is included in the slip safety factor evaluation method. However, for the purpose of developing a more practical seismic stability evaluation method, the slip safety factor was calculated based on seismic response analysis in the time domain while taking into account the stress redistribution. The analysis revealed the results to be consistent with the existing rock slope.
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  • Katsuo SASAHARA, Naoki IWATA, Naotaka KIKKAWA, Nobutaka HIRAOKA, Kazuy ...
    2018 Volume 13 Issue 1 Pages 13-25
    Published: March 31, 2018
    Released on J-STAGE: March 31, 2018
    JOURNAL FREE ACCESS
    Monitoring of displacement on full-scale model slope under multi-step excavation was implemented and the monitored data was analyzed to establish time-prediction procedure of an onset of slope failure due to excavation. The velocity of displacement showed not only increase but also decrease before failure. The relationship between the velocity of displacement and the acceleration of displacement showed different linear correlation between in positive acceleration region and in negative acceleration region. Time prediction was implemented based on the monitored displacement data. Several methods based on the relation between the velocity and the acceleration of the displacement proposed by Fukuzono were adopted for the prediction. Prediction based on non-linear regression analysis for the relationship between the velocity and the acceleration showed best result. The method only used displacement data for the region of positive acceleration and the relationship between the velocity and the acceleration wasn’t influenced so much by the disturbance of the data. This fact suggested picking up of displacement data for positive acceleration was necessary for stable result of time prediction by Fukuzono formula.
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  • Takafumi KITAOKA, Yoshihisa SHINJI, Thirapong PIPATPONGSA, Hiroyasu OH ...
    2018 Volume 13 Issue 1 Pages 27-40
    Published: March 31, 2018
    Released on J-STAGE: March 31, 2018
    JOURNAL FREE ACCESS
    This study describes an assessment of the saltwater intrusion due to the change in groundwater flow caused by an increase in the piezometric head in Bangkok Metropolitan Area and decrease in the piezometric head in the suburban areas bordering Bangkok. Firstly, the data of the piezometric head using arc-GIS confirms the change in groundwater flow. In addition, there are reports of saltwater intrusion in the area. Furthermore, the groundwater vulnerability due to saltwater intrusion in the region is estimated using the GALDIT method. As a result, the high vulnerability areas can be located by the salt water intrusion due to the change in the groundwater flow.
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  • Takaaki ARIKI
    2018 Volume 13 Issue 1 Pages 41-59
    Published: March 31, 2018
    Released on J-STAGE: March 31, 2018
    JOURNAL FREE ACCESS
    The ground reinforcing pile used in this experiment composed of the soil column and the nodular thin steel pile which had significant different elastic modulus and yielding strain. In this paper, the vertical bearing properties and composite effects were considered by the axial force of the static axial compressive load test results of single ground reinforcing pile. The composite effects of the ground reinforcing pile could be considered by the axial stiffness ratio and the deformation of the composed materials. And the load which sheared with soil cement column and nodular thin steel pipe depended on the axial stiffness, then the yield of the ground reinforcing pile was defined by the yield strain of the thin steel pipe. In the composition with the soil cement column and the thin steel pipe, the axial stiffness ratio over 1 was not profitable because the compressive capacity of the column was over to the compressive capacity of the thin steel pipe. On the other hand, when the ratio fell below 0.1, the compressive capacity of the thin steel pipe became equal to the compressive capacity of the ground reinforcing pile because the value of the compressive capacity of the column approached 0. The column reinforced with the nodular thin steel pipe having the sufficient punching capacity supported the axial force, the ground reinforcing pile was possible to efficiently obtain the vertical bearing capacity of the ground in the depth direction. Furthermore, when the compressive strength of the column was especially small, the compressive capacity of the ground reinforcing pile was improved compared with that of the column alone. The ratio of the limited value of the test result to the value calculated by the allowable stress design method was greater than the safety factor.
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  • Shunzo KAWAJIRI, Takayuki KAWAGUCHI, Hijiri HASHIMOTO, Yuki TANAKA, Da ...
    2018 Volume 13 Issue 1 Pages 61-74
    Published: March 31, 2018
    Released on J-STAGE: March 31, 2018
    JOURNAL FREE ACCESS
    In this paper, we investigate the relationship between S wave velocity distribution and dry density immediately after completion of two test embankments constructed by changing degree of compaction. In addition, we compare the change of S-wave velocity distribution before and after the rainfall, and examined the applicability of surface wave exploration to the change of the properties inside the embankment. As a result, the distribution of the dry density and the S wave velocity distribution obtained from the surface wave survey were well matched. In low embankment, the saturation increased due to rainwater infiltration, and the S-wave velocity remarkably decreased after rainfall. From these results, it is possible to estimate the property change in the embankment by the S-wave velocity distribution obtained from the surface wave survey, and it was confirmed that the surface wave exploration can be applied as the primary screen for the property evaluation of the embankment.
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  • Yoshimitsu YAMADA, Takashi TSUCHIDA, Nyan Myint Kyaw, Tatsuru AOYAMA, ...
    2018 Volume 13 Issue 1 Pages 85-99
    Published: March 31, 2018
    Released on J-STAGE: March 31, 2018
    JOURNAL FREE ACCESS
    In this papers, soil laboratory test results are shown which are obtained from samples taken with a sampling method prescribed in JGS (Japanese Geotechnical Society) Standard, at Thilawa Area along Yangon River. Physical and mechanical properties of Thilawa soft clay are identified and compared with ones of soft clay in Japan and also with existing research results in other countries. As a result, it is identified that the quality of sampler affects the result of unconfined compression test of Thilawa soft clay, friction angle of Thilawa soft clay under effective stress are smaller than ones of soft clay in Japan, and also coefficient of consolidation is smaller with 1/6 to 1/3 times of soft clays in Japan.
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  • Yuji TAKESHITA, Nobutaka KATAYAMA, Ryotaro TSUKUNI, Shinya NIGO
    2018 Volume 13 Issue 1 Pages 101-110
    Published: March 31, 2018
    Released on J-STAGE: March 31, 2018
    JOURNAL FREE ACCESS
    It is important to measure the seepage flow behavior in the river levee caused by heavy rainfall and flood for estimating the safety factor of the river levee related to seepage. In this paper, the long term continuous field observations of soil water content and water level have been carried out in the back slope of the leaking river levee. Soil water contents at the different depths with in the soil profile were measured by using several intrusive soil moisture probes. Observed soil water contents with time were used to estimate the movement of two dimensional soil water content profiles of the back slope of the river levee. Changes in pore water pressure at the local scale in the river levee and the permeable base layer were measured by using several driven piezometers to confirm the existence of seepage flow line or water level. Through the observed variations in soil water contents and pore water pressure, the specific features of the seepage behavior in the leaking river levee are investigated.
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