Evolution of Preconsolidation Pressure of Kaolinite Clay with Heating-Cooling Cycles

This study aims to assess the evolution of preconsolidation pressure of a kaolinite clay with heating-cooling cycles. For this purpose, a thermally modified oedometer was utilized to investigate the change in preconsolidation of a kaolinite clay over one full heating-cooling cycle. Seven consolidation specimens with an initial preconsolidation pressure of 100 kPa were prepared. Each specimen represents one point on the considered thermal path of 20 degrees C-50 degrees C-20 degrees C, with four specimens on the heating path and three on the heating-cooling path. The consolidation cell was set up and surrounded by an internal copper coil. This internal coil is connected to a temperature control unit to regulate the temperature of the fluid inside the consolidation cell. Specimens are first subjected to their considered thermal path under a vertical stress of 5 kPa. Expansive axial strains were recorded over the thermal cycle, agreeing with the expected thermal behavior of highly overconsolidated soils. After the strains and the temperature stabilized, isothermal consolidation tests were performed, and preconsolidation pressures on the heating and heating-cooling thermal paths were estimated using Casagrande's method. The results suggest that the preconsolidation pressure decreased as the temperature increased. However, the results suggest a hysteresis between the yield stress and temperature, when the heating-cooling cycle is considered. A sensitivity analysis using a correlation of yield surface with temperature was also performed. The results showed that as the initial "undisturbed" preconsolidation pressure increases, the absolute change of yield stress with temperature becomes more significant.