Surface fractal dimension of bentonite and its application to determination of swelling properties

Bentonite with a low hydraulic conductivity is often used as engineered barriers to prevent groundwater contamination by leachate from the nuclear waste. When bentonite is immersed into the water solution, swelling deformation and swelling pressure will occur to create a tight contact with confining rock. The swelling deformation and swelling pressure are proportional to the amount of water volume absorbed by bentonite. The water volume absorbed by bentonite is related to its surface fractality. The correlation of the normalized water volume by bentonite volume (Vw/Vm) to vertical overburden pressure (p) is obtained as Vw/Vm=KpDs−3, which presents a method to determine the surface fractal dimension of bentonite using the swelling tests. The surface fractal dimensions (Ds) of Wyoming bentonite and Tsukinuno bentonite are 2.64, 2.65, respectively obtained from the swelling tests. The surface fractal dimension of bentonite can be used to estimate the maximum swelling strain and swelling pressure in the disposal system of nuclear waste.