Abstract: The GMZ01 bentonite was mixed with 1 mol/L NaOH solution and sealed tightly. After different preset time of placement, the swelling deformation tests of specimens were produced in distilled water to research the variation of swelling characteristics influenced by the alkaline pore water during long time, and the swelling property was found to decrease with the reaction time. Mineral composition analysis of the specimens reveals a decrease in the montmorillonite content with reaction duration while an increase in the feldspar content, and suggests that during the longtime exposure to NaOH solution, the montmorillonite dissolute gradually to precipitate the non-swelling minerals, leading to the swelling attenuation. The swelling fractal model was employed to analyze the swelling test results, the montmorillonite void ratio of specimens during different reaction time can be expressed by a unique em-pe fractal relationship using an effective stress incorporating with osmotic suction of pore water. It suggests the swelling deformation of specimens corroded by NaOH solution are mainly dependent on the montmorillonite content with few variation in the other properties of montmorillonite.

Key words: bentonite, alkaline pore water, swelling characteristics, mineral composition, fractal