Effects of temperature and thermal cycles on the elastic shear modulus of saturated clay

Abstract

Thermomechanical behavior of soils has attracted great attention in recent years because of its great importance in some emerging geotechnical applications such as energy piles. So far, the thermoplasticity (e.g., the influence of temperature on the yield surface) has been well understood, but the thermoelasticity has not been purposely studied. In this study, a temperature-controlled oedometer equipped with bender elements was developed and then used to mainly investigate effects of temperature and thermal cycles on the elastic shear modulus (G0) of a saturated lateritic clay. In addition, one test was performed on kaolin clay to investigate the influence of thermal cycles on G0. Two types of thermomechanical paths were considered at different temperatures and stresses, including constant-temperature loading–unloading and constant-stress cyclic heating–cooling. Results from these tests consistently reveal that at a given stress, G0 is smaller at a higher temperature. This can be attributed to the reduction of interparticle force during the heating of saturated clay, according to the double layer theories. Furthermore, G0 of the lateritic clay increases by about 12% and 16% after four thermal cycles for overconsolidated and normally consolidated specimens, respectively. This can be due to soil densification and particle rearrangement during the heating–cooling cycles. These results are useful for improving the modeling of thermoelasticity and also for the analysis of thermally active structures such as energy piles.