Effect of technological voids on hydro-mechanical behavior of compacted bentonite

In the high-level radioactive waste geological disposal, the gaps between the waste canisters, buffer layer, and surrounding rock, will affect the hydro-mechanical behavior of bentonite blocks. In this paper, the gaps between the buffer layers were simulated by setting different technological void widths. The interaction between technological void width and the swelling pressure and hydraulic conductivity of compacted bentonite was investigated. Meanwhile, the effect of different boundary conditions on the hydration process of compacted bentonite simulated through stepwise pre-set technological void (SV) and completely pre-set technological void (CV) was studied. The results showed that, keeping the same dry density, the swelling pressure of compacted bentonite blocks with 33% technological voids remained unchanged compared to specimens without voids, while the hydraulic conductivity increased by 10%. Comparing the SV with CV specimens, the swelling pressure was similar, but the hydraulic conductivity of the latter increased by 6%. Microstructural test results indicated differences in overall homogeneity between compacted bentonite blocks with 33% technological voids and those without voids after complete hydration, and distinct differences were also observed between the void and block areas in specimens with voids. The SV method reduced the cumulative pore volume in the void area, resulting in a more uniform hydration process.