Abstract Mixtures composed of 70% crushed Callovo-Oxfordian claystone and 30% MX80-bentonite are considered as materials, that could be used for backfilling a future radioactive waste repository in deep sedimentary rock formations. Their characterization is of interest, as the replacement of fractions of crushed claystone by bentonite enhances the chemo-hydro-mechanical performance of backfill. The materials are envisaged to be installed directly in the drifts and shafts by means of conventional compaction techniques. The hydro-mechanical behavior of materials containing expansive mineral phases, and especially their swelling behavior, is known to be significantly affected by the initial material properties and environmental and stress conditions. The present study aimed to assess the combined impact of variations in the material properties and environmental conditions, particularly the grain size distribution, dry density and saturating solution chemistry, on the swelling pressure of the mixtures, by conducting a comprehensive laboratory experimental program. The results revealed that the adjustment of the grain size distribution of employed bentonite enhanced the compaction behavior and, in turn, the swelling behavior of the mixtures. Generally, swelling pressures of mixtures were less affected by the employed saline and alkaline solutions than those of crushed claystone. The measured swelling pressures were exponentially related to the initial dry density of the expansive mineral phase, regardless of the grain size distribution. Based upon the finding that the expansive mineral phase being present in crushed claystone contributed to measured swelling pressures, a new approach was introduced to calculate the dry density of the expansive mineral phase in bentonites and their mixtures with non-expansive or less-expansive materials.

中文翻译：

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所选材料特性和环境条件对压实粘土岩/膨润土混合物膨胀压力的综合影响

摘要 由 70% 粉碎的 Callovo-Oxfordian 粘土岩和 30% MX80-膨润土组成的混合物被认为是一种材料，可用于回填未来深层沉积岩层中的放射性废物储存库。它们的表征很有趣，因为用膨润土代替碎粘土的部分增强了回填土的化学水力学性能。预计这些材料将通过传统的压实技术直接安装在巷道和竖井中。已知含有膨胀矿物相的材料的流体力学行为，尤其是它们的溶胀行为，受到初始材料特性以及环境和应力条件的显着影响。本研究旨在通过实施全面的实验室实验计划，评估材料特性和环境条件（特别是粒度分布、干密度和饱和溶液化学）变化对混合物溶胀压力的综合影响。结果表明，调整所用膨润土的粒度分布增强了压实行为，进而增强了混合物的膨胀行为。通常，混合物的溶胀压力受所采用的盐溶液和碱性溶液的影响比粉碎粘土岩的溶胀压力小。测得的膨胀压力与膨胀矿物相的初始干密度呈指数相关，而与粒度分布无关。