Effects of thermal cycles on soil behaviour: theoretical and experimental studies

Abstract

Fundamental understanding and proper modelling of soil behaviour under thermal cycles are increasingly important and essential for the analysis and design of many emerging infrastructures, such as geothermal structures and embankment-atmosphere interactions under a changing climate. Previous studies mainly focus on monotonic thermal loading of thermo-mechanical behaviour of soils. Based on a unified, state-dependent theoretical framework in the form of compliance matrix, a new constitutive model is developed to simulate the cyclic thermo-mechanical behaviour of saturated and unsaturated soils. This new bounding surface model is formulated in terms of Bishop’s stress and suction. Apart from the loading and bounding surfaces, a memory surface is incorporated in the model to simulate cyclic thermal behaviour of soils. To verify the new model, computed results are compared with measured data from cyclic heating-cooling tests on saturated and unsaturated soils at various suctions. Based on this new model, two engineering applications are analysed including cyclic thermally loaded floating energy pile foundations and a deep excavation in the unsaturated ground. Consistent results are obtained between computed and measured data.