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 55, Issue 1
Displaying 1-3 of 3 articles from this issue
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Original Article
  • Quantitative Evaluation of Rock Blocks Stability by Hammering Test
    Tomokazu ISHIHARA, Takehiro OHTA, Akihiro KAMOHARA, Hidehumi YOKOYAMA, ...
    Article type: Original Article
    2014 Volume 55 Issue 1 Pages 2-16
    Published: April 10, 2014
    Released on J-STAGE: June 11, 2014
    DOIhttps://doi.org/10.5110/jjseg.55.2
    JOURNAL FREE ACCESS
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     To evaluate stability of rock blocks on slope, professional engineers now carry out the qualitative investigations, such as topography reading, field study. Therefore, quantitative evaluation technique which field engineers can execute is needed. Hammering test is one of qualitative evaluating methods about the stability of rock blocks on slope. We investigated quantitative evaluating method of rock blocks stability using hammering test by experiments and field measurements. The results of experiments and the field measurements show that we can evaluate rock blocks stability by the amplitude and frequency of the sound pressure spectrum obtained from hammering test. As the bonded zone area between rock block and bedrock become small, the maximum amplitude of the sound pressure spectrum become large and the dominant frequency of the spectrum become lower. The frequencies of the sound pressure spectrum peaks distributed under 0.5kHz harmonize with the maximum peak of velocity spectrum measured by vibration measurement. These results are recognized in both of the experiments and the field measurements. If the spectrum amplitude and the dominant frequency of the sound pressure spectrum from the rock blocks are normalized by those of the bedrocks, we can evaluate the rock blocks stability regardless of rock type variation. Based on the above-mentioned results, we proposed an evaluation procedure of the rock blocks stability on slopes.
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  • Experimental Study using Artificial Fractures for Application of Ground Penetrating Radar to Survey Groundwater Flow in a Fractured Rock Mass
    Kazuhiko MASUMOTO, Keisuke KURIHARA
    Article type: Original Article
    2014 Volume 55 Issue 1 Pages 17-27
    Published: April 10, 2014
    Released on J-STAGE: June 11, 2014
    DOIhttps://doi.org/10.5110/jjseg.55.17
    JOURNAL FREE ACCESS
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     To survey the groundwater flow in fractures in a rock mass is important not only for groundwater management in geological disposal of radioactive waste and rock cavern for oil/LPG storage using water sealing system, but also for planning of effective measures for seepage of a dam or mountain tunnel. Especially, flow path along the excavation damaged zone around the tunnel should be evaluated from the view of safety assessment of geological disposal.
     The reflection method of GPR (ground penetrating radar) is a unique technique to survey the flow path in fractures around the tunnel, indirectly, and with no disturbance of groundwater condition. In order to estimate the possibility of application of GPR to survey the water condition in the fractures, an experimental study was conducted using the artificial fractures, which consisted of the wooden cement-boards between a concrete block. The results showed that the reflection wave form from the artificial fractures was changed and the intense of amplitude increased according to change of water content or saline concentration in the fractures. From the results, it was concluded that the flow paths and transport channels along the fractures could be evaluated two-dimensionally using the survey of GPR.
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Report
  • Estimation of S-wave Velocity Structure of OHNO Basin Based on Microtremor Observation
    Keisuke KOJIMA
    Article type: Report
    2014 Volume 55 Issue 1 Pages 28-37
    Published: April 10, 2014
    Released on J-STAGE: June 11, 2014
    DOIhttps://doi.org/10.5110/jjseg.55.28
    JOURNAL FREE ACCESS
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     The microtremor array observations and the 3-components single site observations were conducted to clarify the S-wave velocity structure of the Ohno basin in Fukui Prefecture. The Rayleigh wave phase velocities at each array site were calculated by the spatial autocorrelation method. The phase velocities at each site were inverted to a 1D S-wave profile using a genetic inversion. The subsurface structures down to the Neogene were back analyzed based on the H/V spectra. The 3D S-wave velocity structure around the Ohno Basin was interpolated by using Kriging techniques. The validity of the estimated structure from the microtremor observation was confirmed by comparing with the density structure and with the existing boring logging data. The estimated S-wave velocity structure indicated that the newly developed urban area of Ohno city was located on the low velocity zone.
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