Permeability and strain-stress characteristics of phase-change clay under triaxial compression

The phase-change clay-included paraffin-based phase-change material (PPCM) provides a new way to solve the freeze-thaw problem during winter construction of clay-core walls in cold regions. However, the permeability and mechanical properties related to its service performance as a dam core wall need to be further studied. Accordingly, the permeability and mechanical properties of the phase-change clay under different stress and strain states are studied based on the triaxial permeability and compression tests. The results show that the stress-strain curves of the phase-change clay are strain hardening, and the dilatancy during loading is not obvious. The strength indices of the phase-change clay are close to those of the pure clay with the same initial dry density, but their stiffness indices are different. It is inferred that under the same initial dry density, the addition of non-polar PPCM significantly increases the brittleness of the soil but has small influences on the other mechanical indices. The hydraulic conductivity of the phase-change clay is always lower than that of the pure clay under the same conditions. This indicates that the hydrophobic PPCM can significantly improve the impermeability of soil. Moreover, the regression models established with the void ratio and deviatoric stress level as variables can well predict the hydraulic conductivities of the phase-change clay and the pure clay under different stress and strain states. These results may provide a basis for using the phase-change clay as a substitute of general clay for core-wall construction.