Abstract In a deep geological nuclear waste repository gas can be generated by different processes. Understanding the gas transport mechanisms across the engineered and natural barriers in a repository is relevant for its security assessment, both in terms of mechanical stability and of radionuclide transport. The engineered barrier may be composed of compacted blocks of bentonite and the interfaces between these blocks might evolve into preferential fluid pathways, in particular for the gas generated around the waste canisters. Small-scale laboratory tests were performed in sound samples and in samples crossed by an interface to determine gas breakthrough pressure values after saturation and the effect on them of the interface. The FEBEX bentonite, a Spanish bentonite composed mainly of montmorillonite, was used in the tests. The gas breakthrough pressure of the saturated compacted samples increased with dry density and was higher than the swelling pressure of the bentonite. Gas breakthrough could take place either in an instantaneous or in a gradual way, the difference between both modes being the flow rate, much higher in the first case. The gas transport mechanism would be microscopic pathway dilation, with microfracturing in the case of the instantaneous episodes. A sealed interface along the bentonite did not seem to affect the breakthrough pressure or gas permeability values, since the behaviour patterns were similar in both kinds of samples, depending mostly on the bentonite dry density.

中文翻译：

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界面对用作放射性废物处理工程屏障的压实膨润土中气体突破压力的影响

摘要 在深地质核废料储存库中，气体可以通过不同的过程产生。了解跨越处置库中工程和天然屏障的气体传输机制与其安全评估相关，包括机械稳定性和放射性核素传输。工程屏障可由压实的膨润土块组成，这些块之间的界面可能演变成优先的流体通道，特别是对于废物罐周围产生的气体。在声音样本和界面交叉的样本中进行了小规模实验室测试，以确定饱和后的气体突破压力值以及界面对它们的影响。FEBEX 膨润土是一种主要由蒙脱石组成的西班牙膨润土，用于测试。饱和压实样品的气体突破压力随着干密度的增加而增加，并且高于膨润土的膨胀压力。气体突破可以以瞬时或渐进的方式发生，两种模式之间的差异是流速，在第一种情况下要高得多。气体传输机制将是微观通道扩张，在瞬时发作的情况下会出现微裂缝。沿着膨润土的密封界面似乎不会影响突破压力或气体渗透率值，因为两种样品的行为模式相似，主要取决于膨润土干密度。气体突破可以以瞬时或渐进的方式发生，两种模式之间的差异是流速，在第一种情况下要高得多。气体传输机制将是微观通道扩张，在瞬时发作的情况下会出现微裂缝。沿着膨润土的密封界面似乎不会影响突破压力或气体渗透率值，因为两种样品的行为模式相似，主要取决于膨润土干密度。气体突破可以以瞬时或渐进的方式发生，两种模式之间的差异是流速，在第一种情况下要高得多。气体传输机制将是微观通道扩张，在瞬时发作的情况下会出现微裂缝。沿着膨润土的密封界面似乎不会影响突破压力或气体渗透率值，因为两种样品的行为模式相似，主要取决于膨润土干密度。