Water retention behavior and double porosity model study of GMZ bentonite considering temperature effects

Abstract

The current study investigates the influence of temperature on the water retention capacity of Gaomiaozi (GMZ) bentonite by conducting free swelling tests at different temperatures. The experimental results reveal that the equilibration time, as well as the water retention capacity, decreases significantly with temperature. A constitutive model for predicting the water retention characteristics was derived and the temperature effects were taken into account. More consistent with previous studies, the model divides the pore space into microstructural pore space (always saturated) and macrostructural pore space (presence of capillary water), with the macroscale quantifying temperature effects on water retention capacity by incorporating the suction variation and the microscale considering the introduction of a temperature-dependent microstructural deformation coefficient. The efficiency of the model was also verified using experimental data. For the GMZ bentonite with the initial dry density of 1.70 g/cm3, the threshold value for the transition from adsorbed water to capillary water is greater than 22 MPa. The microstructural deformation coefficient shows a linearly increasing relationship with temperature. The presented model allows an effective application to the hydraulic characteristics of bentonite artificial barriers for the long-term operation of nuclear waste repositories.