Hydraulic Conductivity and X-Ray Diffraction Tests of Unsaturated Bentonites with a Multi-Ring and Their Predictions by Pores Distributions

Following instantaneous profiling method, a multi-ring was applied in the wetting apparatus to ascertain water diffusivities of three bentonites (MX-80, Kunigel-V1, and Kunibon). Hydraulic conductivities of unsaturated bentonites were calculated though water diffusivities and soil water retention curves (SWRC) with Darcy equation. Basal spacings were achieved by sending slices from the multi-ring to X-ray diffraction (XRD) tests. A dual pores system was proposed: 1) micro pore (inter-layer pores); and 2) macro pore (inter-particle pores and inter-aggregate pores). By discussing flow mechanisms of waters in bentonite, it was supposed that: moveable waters flow through macro pore. Porosity and tortuosity of saturated macro pore were used instead of porosity and tortuosity of saturated total pore in traditional Kozeny-Carmen (KC) equation, which was designated as modified KC equation. A new relative permeability was raised for predicting hydraulic conductivities of unsaturated bentonites. Macroporosity and macrovolumetric water content were obtained from estimated basal spacing during saturation. Comprehensive comparisons between experimental database and predictions were conducted. Results revealed that the modified KC equation can predict both saturated and unsaturated hydraulic conductivities well