Impact of Soil Ambient Temperature on the Accuracy of Measured Thermal Resistivity

Abstract

Comprehensive knowledge of soil thermal resistivity is important for the design and installation of buried pipeline and cables, as build up of heat within the vicinity of the buried pipeline could cause it to crack and rust, or the cable becomes overheated and melts. Hence, the aim of this research work is to examine the effect of soil ambient temperature on the measured thermal resistivity values. To achieve this, six thermal resistivity measurements were carried out at the same point, at a depth of 0.5 m, within the space of 3 hours intervals between each measurement, for 15 hours. The ambient soil temperature was noted each time the thermal resistivity of the soil was determined by making use of heating element and a digital thermometer as the probe to monitor temperature increase with time. The range of the determined thermal resistivity is between 0.200030345 oCm/W to 0.404745201 oCm/W, with a significant difference of 0.204714856 oCm/W, that is comparable to the difference between thermal resistivity of sand and water. The results from the plotted graph of temperature against thermal resistivity with positive slope, gave a good indication that the thermal resistivity of the soil increase with increase in ambient soil temperature. The  implications of this research work therefore is that the thermal resistivity values measured in the early hours, will be different from thermal resistivity values measured at noon, equally different from thermal resistivity value measured after sunset. Therefore the need for standardization becomes very paramount among the international scientific community for the purpose of harmonization. The notable difference between thermal resistivity measured in situ and thermal resistivity measured in the laboratory could be attributed to soil ambient temperature difference.