rapid measurement of thermal resistivity of soil
Post on 28-Feb-2017
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Rapid Measurement of Thermal Resistivity of Soil V. V. M A S O N
ASSOCIATE MEMBER AIEE M O S H E K U R T Z
ASSOCIATE MEMBER AIEE
THE EFFECT OF the thermal resistivity of the soil on the temperature of a buried cable is well known. It is of more importance for the newer directly buried and pipe-type installations in which the temperature rise through the soil forms a larger percentage of the total temperature rise than is the case with the older concrete-duct types.
Laboratory methods of measuring the thermal resistivity of soils along a cable route are unsatisfactory because of the expense and the difficulty of obtaining an "undisturbed" sample. The well-known method of field determination using the steady-state temperature rise of a buried heated body is accurate but expensive and too slow for a survey of a proposed cable route. An inexpensive cast-aluminum sphere developed for this purpose reduced the construction cost but the labor involved in taking readings was still prohibitive.
However, a rapid "transient" method of measuring the thermal resistivity of the soil now is available. This is based upon the fact that the rate of temperature rise of a heated body, as well as the ultimate temperature rise, will depend upon the thermal resistivity of the material in which it is buried. This method. has been developed from an idea put forth originally by B. Stalhane and S. P y k i n m i . 1
The results obtained with this apparatus were compared with the results obtained by the steady-state buried-sphere