Thermo-mechanical Calibration of a Temperature-Controlled Oedometer

In the emerging field of energy geotechnics, many applications involve changes of temperature above and below ambient temperature. This has led to the development of laboratory apparatus to enable the study of soil behavior under various temperature ranges and under well-controlled conditions. To understand the effect of temperature on soil behavior, it is necessary to separate the thermal behavior of the apparatus itself and of the instrumentation used to measure loads and displacements from the soil behavior, i.e., a careful calibration of the equipment is required. The thermal calibration of an oedometer with temperature control in the range of 5°C–70°C is discussed here in detail. As the innovative design of the new oedometer enables isotropic heating of the soil specimen and thermal isolation of the instrumentation, the calibration focuses on the thermally induced deformations of the apparatus and the differential radial thermally induced deformation of the soil and of the stainless steel confining ring. Although the developed methodology has limitations when used to predict the results of one-dimensional tests, as do previously proposed methodologies, it represents improvements on previous schemes, as it allows for Poisson’s ratio effects to be taken into account. An example of how the proposed calibration can be used in practice and how the confining ring correction compares with previous schemes is presented.