Thermo-mechanical coupled behaviour of a silty clay under K₀ consolidation

A series of temperature-controlled laboratory tests is reported in this paper to study the thermo-mechanical behaviour of a saturated silty clay under K₀ consolidation. Thermo-plastic responses of thermal strains and thermal pore pressures are found both under heating and cooling with strong dependency on overconsolidation ratio (OCR) and K₀. The tests show heating-induced thermal contractions of normally consolidated specimens and cooling-induced thermal dilations of overconsolidated specimens, implying both thermo-plastic contraction and expansion. Under K₀ conditions, both the thermal volumetric and shear strains and their coupling with each other are observed in the tests, which strongly depend on the OCR and the anisotropy of stress and fabric. These test observations are interpreted by a multi-mechanism-based theory of thermo-plasticity associated with adsorbed bound water and residual elastic volumetric and shear strains. The effects of OCR and stress-and-fabric anisotropy on the thermal consolidation under anisotropic stresses are comprehensively accounted for by way of the state-dependent thermo-elasto-plastic coupled relations considering the thermally induced shear dilation, the residual elastic strains and the fabric anisotropy. Accordingly, simplified analytical formulations of the thermal volumetric and shear strains are derived and validated by the test data.