In-Situ Thermal Conductivity Exploration Using Penetrometer.

概要

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The measurement of ground thermal property is important for the design of under ground heat facilities or the estimation of thermal impact to the geo-environment. The data from core samples obtained by drilling are commonly used for this purpose. However, for the thermal conductivity, the in-situ measurement is suitable because the property correlates well with geo-environmental properties such as water content or porosity of soil. On the other hand, the measurement of ground thermal property at each depth is also important, because the geological structure in Japan is complex and ground water level is shallow. As for the in-situ measurement of thermal conductivity, the needle-probe method is used commonly for the geothermal manifestation field or the mud at sea floor, but this method aims at the shallow depth measurement of very soft soil. In this study, we are interested in the penetrometer that is commonly used for the measurement of N value of soil. The instrument penetrates about 30m in the common soil. We applied this method to the measurement of thermal conductivity. The measurement probe consists of hollow rods, cable heater and optical fiber thermo-meter. In a field study, we used this thermal conductivity measurement method and we also measured the N value and the resistivity at the same time. The trends of measured conductivity, N values and resistivity along depth are consistent with each other.
日本地熱学会の論文