Modelling volume changes of sand under thermal loads : a preliminary attempt

Abstract

Within the critical state framework, some thermo-mechanical models have been developed to simulate thermal volume changes of saturated soils. Most of the existing models are verified through the experimental results of silt and clay, and they cannot well capture the behaviour of sand under thermal loads. In this study, an elastoplastic model is newly proposed to predict thermally induced volume changes of saturated sand. The key component of the new model is the introduction of a state-dependent threshold temperature, TR, which can be determined experimentally. The TR is found to increase with an increase in the state parameter, which is defined as the difference between the current void ratio and the critical state void ratio. Depending on the state parameter, heating would induce overall contraction at temperatures below TR, but only cause overall expansion when the temperature is higher than TR. When the maximum temperature experienced by the soil specimen, Ty, is lower than TR, heating would induce not only elastic but also plastic strains. The plastic modulus becomes larger when the difference between Ty and TR is smaller. When Ty is larger than TR, sand response becomes essentially elastic. The new model is applied to simulate the behaviour of Toyoura sand under heating at different stresses and densities. It is shown that the measured and computed results are fairly consistent. The new model is able to capture well the state-dependent volume changes of sand under thermal loads.