BUTSURI-TANSA(Geophysical Exploration)
Online ISSN : 1881-4824
Print ISSN : 0912-7984
ISSN-L : 0912-7984
Original Papers
Interpretation of the integrated geophysical survey using the interpretation template based on the rock physics model: Estimation of clay content and porosity for unsaturated soils.
Chisato Konishi
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2017 Volume 70 Pages 56-68

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Abstract

Integrated geophysical survey result has been used for the simple soil type classification of the river levee. As for an another application, an interpretation method using the interpretation template based on the rock physics model is developed to estimate two dimensional profile of useful geotechnical parameters. In this method, clay content and porosity are estimated from the S-wave velocity and resistivity by using the interpretation templates. The clay content and porosity are employed to infer the soil type and the looseness of the soil, respectively. In this study, a velocity model based on the granular media and a parallel circuit resistivity model are adopted for unsaturated soils. The rock physics models used in this study are hybrid model developed by both theoretical and empirical approaches for a practical method. Clay content and porosity are not estimated by an inversion; instead these are estimated by using the interpretation templates that are created by the forward modeling beforehand. The latter approach is easy to be applied and has a benefit to evaluate the sensitivity of the parameter estimation. Several input parameters required for the rock physics model are assumed from the laboratory measurements of artificial soil samples. For a case study, clay content and porosity have been estimated from the integrated geophysical survey at a river levee. There are six excavated locations in the survey interval; thus we can compare the estimation and actual soil type and condition at those locations. As a result, I confirmed that silty soil exists at the location which the estimated clay content is high, while gravel exists where the clay content is low. In addition, predicted porosity is high at the location which the levee body consists of loose soil. These results indicate that the soil type and the looseness can be evaluated from the surface by the integrated geophysical survey.

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© 2017 The Society of Exploration Geophysicists of Japan
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