低放射性廢棄物最終處置場在國際間採用多重障壁的設計理念，利用層層的處置設施隔絕放射性物質遠離生物圈。緩衝材料在多重障壁中扮演相當重要的角色，須具備低水力傳導度、適當的回脹壓力等。當處置場啟用後，未來可能受到地下水的入侵，緩衝材料可能受到影響改變原本預期的行為特性。 本研究主要分為兩部分，第一部分以MX-80膨潤土與K-V1膨潤土在不同乾密度下進行直接剪力試驗和單向度壓密試驗，模擬處置場初期荷重之影響。第二部分進行回脹壓力、水力傳導度試驗、飽和的應變/應力控制的直剪試驗與單向度壓密試驗，模擬處置場在飽和時之情況，最後使用有限元素軟體ABAQUS進行分析模擬。 研究結果顯示，(1)在回脹壓力上MX-80膨潤土較佳，因為MX-80膨潤土的蒙脫石含量高於K-V1膨潤土的關係；(2)MX-80膨潤土於高乾密度、高正向應力及飽和的直接剪力試驗中，比K-V1膨潤土有較佳的抗剪能力；(3)應力控制直剪顯示，施予剪應力越大，潛變發生的時間會加速；(4)單向度壓密試驗顯示，正向應力越大膨潤土的應變量也越大，潛變時間也會提前。 ;The low-level radioactive waste final disposal adopts the design concept of multiple barriers internationally, and uses layers of disposal facilities to isolate radioactive materials away from the biosphere. Buffer material play a very important role in multiple barriers system, and must have low hydraulic conductivity and appropriate swelling pressure. When the disposal site is enabled, the future may be subject to groundwater intrusion, buffer material may be affected by changes in the original expected behavior characteristic. This study is mainly two parts. The first part uses MX-80 bentonite and K-V1 bentonite at different dry density to conduct direct shear test and one dimensional compression test to simulate the effect of initial load at the disposal site. The second part conducts swelling pressure, hydraulic conductivity test, saturated strain/stress controlled direct shear test and one dimensional compression test to simulate the situation of the disposal site at saturation, and finally uses finite element software ABAQUS for analysis and simulation. The results of the study show that (1) MX-80 bentonite is better in terms of swelling pressure, because the montmorillonite content of MX-80 bentonite is higher than that of K-V1 bentonite. (2) MX-80 bentonite in the direct shear test has high dry density, high normal stress and saturation, it has better shear resistance than K-V1 bentonite. (3) Stress control direct shear shows that the greater the applied shear stress, the faster the occurrence of creep will be accelerated. (4) The one dimensional compression test shows that the greater the normal stress, the greater the strain of bentonite and the earlier the creep time.
