Effects of temperature compensation on electrical resistivity during subsurface characterization

Electrical resistivity has been used to estimate the spatial variability of subsurface soil. The objective of this study is to evaluate the effects of temperature on electrical resistivity to create more accurate subsurface characterization using a temperature-compensated resistivity probe (TRP). The TRP consists of a two-electrode electrical resistivity module and temperature sensors, which are used to monitor temperature changes and the compensation of electrical resistivity that occurs due to temperature changes. Temperature transfer probes with diameters of 5 and 10 mm are developed to measure temperature changes during the penetration of probes into sandy soils. The temperature sensors are attached 15 mm behind the probe tips to minimize electrical interference with the electrical resistance measurement component of the TRP. Laboratory application tests are conducted in an acrylic cell containing uniform Jumunjin sand, and field application tests are conducted in loose silty clay and sand in the Kimpo area near Seoul. The test results show that the temperature changes continuously during probe penetration in both the laboratory and field tests, and electrical resistivity is over- or under-estimated when temperature compensation is not considered. This study demonstrates that temperature changes should be accounted to improve the accuracy of electrical resistivity measurement and the quality of subsurface characterization.