(Received 28 May 2015; accepted 13 November 2015)
Published Online: 08 March 2016
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This paper describes a new high-pressure, temperature-controlled isotropic cell used for evaluation of the thermal volume change mechanisms of saturated and unsaturated soils under isotropic stress states. Specifically, details of the experimental setup, instrumentation, thermo-mechanical calibration of the device, experimental procedures, and typical results are presented in this paper. The thermal isotropic cell includes suction control using the axis translation technique, saturation control/monitoring using a pore water pressure flow pump, cell pressure control using a high-pressure flow pump, and a stainless steel cell to permit application of isotropic net mean stresses up to 10 MPa. The cell fluid temperature is regulated by circulating heated water through a copper heating coil within the cell, and an internal circulating fan is used to promote homogenous temperature throughout the cell chamber. Non-contact proximity transducers are used to directly measure soil deformation in the radial and axial directions, permitting assessment of thermo-mechanical anisotropic strains during changes in mean effective stress or temperature while also avoiding the need to consider complex thermo-mechanical cell deformations. The high-pressure flow pump and thermal control system are designed to apply changes in net mean stress and temperature at slow rates to characterize the full soil compression and thermal volume change curves, respectively. Along with the thermo-mechanical calibration of the cell, the results from two tests on compacted silt specimen having different initial degrees of saturation are presented that show how the cell can be used to characterize changes in volume and degree of saturation during thermo-mechanical loading. Both normally consolidated soil specimens were contracted during heating, although the specimen with a lower degree of saturation showed slightly greater thermal volume change.
Coccia, Charles James Russell
Research Associate, Ph.D., Univ. of Colorado Boulder, Dept. of Civil, Environmental and Architectural Engineering, Boulder, CO
McCartney, John S.
Associate Professor, Ph.D., Univ. of California San Diego, Dept. of Structural Engineering, La Jolla, CA
Stock #: GTJ20150114