Oedometer tests were conducted on Gaomiaozi (GMZ01) bentonite to understand the swelling behavior under different stress and volume state conditions. The range of boundary conditions examined in the tests include swell-reloading (SR), constant volume (CV), and flexible load ring-based boundary condition (FB) where applies increases in stress as a specified function of the volume increase. The results demonstrate that the measured swelling parameters of soil significantly depend on the applied boundary conditions during the liquid infiltration. The measured final swelling pressure by CV method is much less than that measured by SR method. The measured final swelling strain by FB method is much less than that measured by SR method. With increasing stiffness of the load ring, the finial swelling strain decreases while the final swelling pressure increases. Based on the results, a swell limit curve (SLC) was determined for this material, and this curve can be used to evaluate the final swelling state for the range of boundary conditions examined.
With the escalation of global energy crisis, nuclear energy development has seen an unprecedented surge in many countries. For example, France derives over 75% of its electricity from nuclear energy. China also plans to raise the ratio of nuclear energy to the total generating capacity from present 2% to around 5% until 2020. However, how to dispose the large amount of radioactive nuclear waste produced by the power plants in a safe way is a big challenge accompanying the rapid development of nuclear energy. According to the report of Wang (2008), the accumulated spent fuel in China will reach 1.03×104t with an annual output up to 1×103t by 2020. At present the widely accepted solution for high-level waste is deep geological disposal, that is, to bury the pretreated high-level waste in underground rock formations about 500~1000 meters below the surface. The host rock acts as a natural barrier and with the combination of multiple artificial barriers (waste packaging containers and buffer/backfilling material), it is possible to isolate the radioactive wastes from human environment for a long time.