关键词: 膨润土, 裂缝, 渗透系数, 应力, 愈合

Abstract: Compacted bentonite is widely applied in many countries as a suitable barrier material for the geological disposal of radioactive waste. However, cracks occur in compacted bentonite during shrinkage process. Whether the crack coalesces with other crack or not is a basic issue of the safe geological disposal of radioactive waste. In order to evaluate the influence of cracks on the performance of bentonite barrier, penetration test is carried out on compacted bentonite with a single longitudinal crack. The permeability coefficient, normal stress and water content are measured to indicate the impacts of cracks on the permeability and mechanical property of samples. The results show that the permeability coefficient decrease and the normal stress increases with time elapsing, and both of them finally reach a stable level after 85 days. At that time, the values of permeability coefficient and normal stress are about 4.64 m/s and 2.5 MPa respectively, which are the same level with that of integral bentonite. It means that the bentonite is saturated and homogeneous. It also can be concluded that the cracks have no obvious influence on the permeability coefficient and stress of bentonite. The compacted bentonite has a better self-healing ability. Not only the basic knowledge for bentonite as backfill material is acquired, but also a novel evaluation method is established in this study.

Key words: bentonite, crack, permeability coefficient, stress, coalescence