The generation and migration of gas is an unavoidable process that should be considered in the safety evaluation of nuclear waste geological repositories. The first aim of this study is to determine whether the gas will affect the swelling and sealing properties of the bentonite-based barrier. The results show that the gas/water can significantly affect the pore pressure of the material, which can further affect the total pressure of the compacted bentonite/sand sample. There exists a mathematical relationship between the gas pressure, total pressure, and effective swelling pressure. Furthermore, the influence of the size effect on the swelling properties and gas breakthrough properties of compacted bentonite/sand mixture was also investigated. The change in the sample’s size has a limited impact on the swelling pressure of the sample, but delays the water saturation process. Concerning the gas breakthrough properties, the influence of the sample’s size is also not apparent. Finally, the results of laboratory experiments are compared with the results of in situ experiments. The results show that the laboratory experiments have a good reference value based upon the key indicators, such as swelling pressure, water/gas permeability, and gas breakthrough pressure. This means that the results obtained from the small-scale laboratory experiments are reliable and can be referenced for the in situ design of the nuclear waste geological repository.

气体的产生和迁移是不可避免的过程，应在核废料地质处置库的安全评估中予以考虑。这项研究的首要目的是确定气体是否会影响膨润土基屏障的膨胀和密封性能。结果表明，气体/水会显着影响材料的孔隙压力，从而进一步影响压实膨润土/砂样品的总压力。气体压力，总压力和有效膨胀压力之间存在数学关系。此外，还研究了尺寸效应对压实膨润土/砂混合物的溶胀性能和气体穿透性能的影响。样品尺寸的变化对样品的溶胀压力影响有限，但会延迟水饱和过程。关于气体穿透性能，样品尺寸的影响也不明显。最后，将实验室实验的结果与原位实验的结果进行比较。结果表明，基于溶胀压力，水/气渗透率和气体突破压力等关键指标，实验室实验具有很好的参考价值。这意味着从小规模实验室实验中获得的结果是可靠的，并可为核废料地质处置库的现场设计提供参考。结果表明，基于溶胀压力，水/气渗透率和气体突破压力等关键指标，实验室实验具有很好的参考价值。这意味着从小规模实验室实验中获得的结果是可靠的，并可为核废料地质处置库的现场设计提供参考。结果表明，基于溶胀压力，水/气渗透率和气体突破压力等关键指标，实验室实验具有很好的参考价值。这意味着从小规模实验室实验中获得的结果是可靠的，并可为核废料地质处置库的现场设计提供参考。