Journal of the Japan Society of Engineering Geology

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Since seventy percent of countries are mountain ranges in Japan, and there is also much rain, the present condition is that landslides have occurred in many domestic areas. In such a slope disaster, when carrying out design construction of the preventive measures, it is necessary to grasp the geological structure of an object area. Generally, it is mainly investigated by the drilling survey which is able to check a stratum certainly. However, if it is going to hold the geological condition of the whole foundation which a landslide has produced, many drilling surveys are required, and it takes much cost and time. From the former, exploration tools, such as elastic wave exploration and resistivity tomography, are applied. However, development of more compact and simple investigation system is made into pressing need.
In this research, in order to measure the low resistivity layer in near a landslide side, a compact measurement machine is developed, and its precision for measurement was checked at the actual site by comparison with drilling surveys. This machine is improved from electromagnetic method with separate coil to electromagnetic method with coaxial coil based on central induction method. Moreover, the applicability of the method in real ground was examined.

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The 2011 off the pacific coast of Tohoku earthquake caused widespread liquefaction. We mainly investigated, liquefaction concentrated. Geomorphologicall setting of mainly liquefaction traced fairway of the tideland, Inagekaigan, Chiba Prefecture. Geotechnical condition is sandy soil deposits, N-value less than 5. Especially, creek of the tideland is sandy soil and groundwater gather easily. Other type Liquefaction is generated on the boundary in reclaimed lands. These liquefaction generated the 1987 Chiba-ken Toho-Oki Earthquake.

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