Impact of initial effective stress on the thermo-mechanical behavior of normally consolidated clay

This study aims to investigate the impact of initial mean effective stress on the thermo-mechanical behavior of saturated normally consolidated kaolinite clay. Specifically, a series of isotropic thermal triaxial tests in a cell equipped with image analysis for volume change tracking was performed to understand the impact of the initial mean effective stress on the drained thermal volume change response as well as the undrained shear strength before and after drained heating. Anisotropically consolidated clay specimens were recompressed isotropically to four different initial mean effective stresses corresponding to normally consolidated conditions before drained heating and undrained shearing. While contractive volumetric strains were observed during drained heating of all normally consolidated specimens, the thermal radial strains were greater than thermal axial strains due to the application of isotropic stresses after anisotropic consolidation from a slurry. The magnitude of thermal volumetric strain increased with increasing initial mean effective stress, which is a departure from expected trends from established constitutive models. A corresponding increase in undrained shear strength with both temperature and initial mean effective stress was observed. The results indicate the need for considering the impact of initial mean effective stress in geotechnical applications involving normally consolidated clay under non-isothermal conditions. •Thermal volume change increases with mean effective stress prior to heating.•Undrained shear strength increases with both drained heating and initial effective stress as expected.•Experimental data may guide new constitutive relationships for normally consolidated soils.•Image analysis permits tracking of thermal deformations in axial and radial directions.•Sedimented normally consolidated clays heated in isotropic conditions show greater radial strain.