低温で熱サイクルをうける含水岩石の熱膨張について

Abstract

Thermal expansions of several saturated rocks were measured under a cyclic temperature change between 110K and 300K at a slow rate. The following changes due to water saturation were observed in thermal expansion; suppression of thermal cracking, hysteresis in thermal expansion, and an increase within thermal expansion coefficient. These changes were explained by freezing of pore water within cracks and the difference in temperature between freezing and melting of pore water. When the ice forms in the crack pore of granitic rocks, it bonds the surfaces of each crack to impede crack extension. The residual strain and the temperature at which thermal cracking initiated, therefore, decreased in these rocks. The temperature difference between freezing and melting is probably caused by supercooled water and a capillary force acting on the pore water. The hysteresis therefore appeared in the thermal expansion of nongranitic rocks which showed no hysteresis in the dry condition. These rocks exhibited no residual strain in the wet condition as well as in the dry condition except for the tuff in which a large amount of residual strain was observed after the first cycle.