THERMAL AND FREEZING STRAINS ON A FACE OF WET SANDSTONE SAMPLES UNDER A SUBZERO TEMPERATURE CYCLE

摘要

Some laboratory tests shoved rather strange hysteresis loops in strain-temperature space, where the strains were measured with a strain gauge on the surface of a wet cubic rock sample under a subzero temperature cycle. This report gives introductory remarks and the first result on a new project launched by the present authors. The project is intended to make clear the major mechanisms responsible for the unexpected hysteresis loops in the strain-temperature diagram, in which an abrupt increase in strains appeared at a halfway point of the cooling process at higher cooling rates. The hysteresis loops suggest that various thermal and mechanical (or physical) phenomena take place within the rock sample; some possible candidates of causes behind the phenomena are discussed and a hypothesis associated with them is proposed. Furthermore, to separate an unexpected part of the hysteresis loop from its "regular" part, thermal strains on the surface of a spherical sample under a temperature cycle are calculated within the framework of linear thermoelasticity. The equivalence between strains on the surface of a cubic sample and that of a spherical one is discussed.