Keywords:irradiation aging, Na-bentonite, montmorillonite, mechanical strength, swelling property
Bentonite was often used as the back filling materials in high-level radioactive waste geological disposal. In order to study the effect of gamma irradiation on the mechanical strength and swelling properties, some experiments was taken on the natural of bentonite sodium Na-bentonite, from Gaomiaozi(GMZ), Inner Mongolia. The bentonite samples were performed at different cumulative doses of electron irradiation aging at room temperature firstly. Then by D8 Advance X- ray diffraction, the mineral composition of bentonite was detected and analyzed. And then triaxial shear test and swelling test were conducted to study the evolution law of the mechanical strength and deformation characteristics before and after irradiation. Results showed that mineral components changed after γ-rays irradiation in bentonite. The microstructure of montmorillonite changed and transformed to the stable silicate and aluminosilicate minerals. After irradiation, with the increase of the irradiation dosage under the same confining pressure, the shear strength of bentonite increased, and the peak shear strength of bentonite had gradually increased, due to the change in the mineral composition. With the increase of confining pressure, the strength increase trend gradually slow, and the effect of irradiation dose on the strength turned to be weaken, which indicates that the confining pressure inhibited the strength growth Bentonite. Due to the decrease of montmorillonite content after different irradiation effects, the expansion force of bentonite was also weakened in logarithmic law. The free expansion and loaded expansion strain decreased in different ratios. The expansion deformation ratio decreased slowly till it reached to a constant.