a b s t r a c tThe thermal volume change of soils is typically interpreted using the stress history and changes in yield stress with temperature (thermal softening). However, the path followed to reach a given stress state may lead to different thermal volume changes. Alternative mechanisms of thermal volume change are explored using data from the literature and isotropic, drained heating tests on compacted silt. No relationship between thermal volume change and degree of saturation was observed. However, a clear relationship with the secondary compression prior to heating was observed, indicating that thermally accelerated creep may provide better thermal volume change predictions than thermal softening.

This study involves an investigation into issues that may be encountered when using the backfill in mechanically stabilized earth (MSE) walls as a heat sink for spurious heat generated by nearby industrial facilities or buildings. The deformation behavior of thermally active MSE walls is evaluated using a simplified analytical model adapted to consider the effects of temperature, confining stress and unsaturated soil conditions on the stiffness of geosynthetic reinforcing elements. The major conclusions that can be drawn from the model results are that it is important to select a geosynthetic that has a high glass-transition temperature, and that confining effects of unsaturated backfill may lead to a reduction in the thermal deformations of the geosynthetic.

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a b s t r a c tThis study presents the development of an alternative constitutive model for predicting the thermal volume change of saturated and unsaturated soils using the concept of thermally-accelerated secondary compression. The model requires observation of the secondary compression response prior to drained heating to estimate the coefficient of secondary compression. The model was found to successfully capture the trends in thermal volume change arising from accelerated secondary compression resulting from prior mechanical loading for unsaturated, compacted Bonny silt. The model was also used successfully to represent data from the literature for normally consolidated and heavily overconsolidated soils prepared with different loading paths.

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