Thermoplastic modelling of soil–structure interface under different temperatures

Abstract

Heat exchange usually occurs between the energy geostructures and surrounding soil, where the soil–structure interface is subjected to non-isothermal loading conditions, with its stress–strain behavior affected by temperature. To address this issue, a two-surface thermoplastic model is developed by enriching an isothermal model with a cap yielding surface, a thermo-plastic hardening mechanism, and a fractional dilatancy rule, where detailed derivations of the loading index and plastic modulus are provided. Then, a numerical algorithm for implementing the developed non-isothermal model is provided. The model is validated by simulating a series of interface shear test results of soils subjected to different temperatures. It is found that the developed thermoplastic model can capture the stress-displacement behavior of soil–structure interface under different temperatures, and the strain response under heating and cooling cycles. The strain softening and normal dilatancy behavior of the interfaces can be reproduced. As the temperature increases, the predicted peak shear stress increases, which agrees well with the corresponding test results.