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

Abstract

Some laboratory tests showed 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.