THERMAL STRAINS ON ROCK SAMPLE SURFACE UNDER A SUBZERO TEMPERATURE CYCLE

摘要

Preliminary laboratory tests showed a somewhat strange hysteresis loop in a strain-temperature space, where the strains were measured with strain gauge on the surface of a wet cubic rock sample under a subzero temperature cycle. This report gives an introductory remark on a new research project of the authors that is intended to make clear some major mechanisms of the unexpected hysteresis loop in the strain-temperature diagram, in which an abrupt increase in strains appeared at a halfway point of cooling process at higher cooling rates. This hysteresis loop suggests that various thermal and mechanical (or physical) phenomena took place within the rock sample; some possible candidates of the phenomena are discussed. Furthermore, in order 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 obtained within the framework of linear thermoelasticity, followed by some consideration of equivalence in surface strains between the cubic and spherical samples for future complicated analyses.