Estimation of the Depth of Frozen Soil

Abstract

The electrical resistance of soil changes abruptly upon freezing. (This journal, second series, 15, (1937), 321). The phenomenon can be applied to the estimation of the depth of frozen soil without turning up the ground. The writers attemptto make the estimation on a trip survey. Two fat iron rods are struck into frozen ground at the distance of 20cm and the electrical resistance between the rods are measured with an ohmmeter, commonly used for the construction and repair of radio-sets. When the point of the rod reaches the unfrozen part of the soil the electrical resistance changes rather abruptly and the depth of the freeze can be estimated on a curve of the resistance against the depth (see Fig. A No.1-C No.9 in the text). At the same time the ground is turned up to ascertain the result of the estimation. The abrupt change of the response of the rod to the hand, when the rod is struck into the ground with a heavy hammer, assists the estimation. The distribution of the depth of the freeze near Hunatu Observatory, at the northern foot of Mt. Huzi, is observed in this way.