SEGJ Technical Conference

Estimation of thermal resistance of soil around underground power transmission line using geophysical surveys (6) - Relationship between physical properties and thermal resistance models for unconsolidated soil-

Abstract Design of underground power transmission lines requires simple and effective techniques for estimating soil thermal resistance which is one of the important factors to determine the capacity of power lines. We proposed the method for profiling soil thermal resistance based on the new model composed of sand particle, clay particle, pore water, and air. In this method, the unconsolidated sand model and the parallel circuit resistivity model are employed for modeling seismic velocity - porosity and resistivity - porosity relationships, respectively. The theoretical values based on the new thermal resistance model matched well the data for the artificial unconsolidated soil samples measured by laboratory tests. The proposed method was applied to a share velocity profile obtained by the surface wave survey and a resistivity profile by resistivity tomography for estimating its soil thermal resistance profile. As a result, we confirmed that the thermal resistance obtained by resistivity and share velocity profiles matched the values observed directly in a borehole along the survey line.