THERMAL CONDUCTIVITY OF BENTONITE AND BENTONITE-SAND MIXTURE

In this study, the thermal conductivity was measured with changing the volume water content and the electric conductivity of grouting materials(bentonite and bentonite-sand mixture) for the geothermal heat pump system and the relation equations predicting the thermal conductivity were suggested.

The 5TE sensor(Decagon Devices, Inc.) was used to measure volume water content and electric conductivity of grouting materials and the QTM-500(Kyoto Electronics, Inc.) was used to measure thermal conductivity.

After grouting materials had been designed, 5TE sensor was equipped and left at 25°C(±1) condition for 1 days. After that, thermal conductivity and volume water content and electric conductivity were measured at 25°C(±1) condition for 10 days, the volume water content range of the bentonite was from 0.05 to 0.59 and the volume water content range of the bentonite-sand was from 0.11 to 0.31.

Consequently, thermal conductivity and electric conductivity decreased when volume water content decreased and also relation equations predicting thermal conductivity could suggest by analyzing correlation among them through multiple regression analysis.

This study is expected to assist in the construction of geothermal heat pump system and to use as input data for numerical analysis.