Simulation of thermal drains using a new constitutive model for thermal volume change of normally consolidated clays

Abstract

This paper focuses on the thermo-hydro-mechanical behavior of clay surrounding a thermal drain. A new constitutive model for prediction of thermal volume change of clays is presented that incorporates an improvement to existing models by capturing the effect of initial effective stress on the thermal volume change of normally consolidated clay observed in element-scale tests. A numerical framework with the proposed constitutive model was used to simulate the coupled effects of heat transfer, fluid flow and volume change in clay surrounding a thermal drain. The simulated results were validated using experimental data from a large-scale laboratory experiment on a thermal drain under different thermal and surcharge loads. The results indicate that the required surcharge can be reduced when using a thermal drain in lieu of a conventional vertical drain and a significant increase in the rate of consolidation is observed when using a thermal drain. The proposed constitutive model allows better prediction of thermal volume changes of normally consolidated clays as a function of depth which is important to understand the efficient application of in-situ heating for ground improvement.