Compacted bentonite/sand mixture have been considered as possible sealing/backfilling material in the deep geological disposal of high-level radioactive nuclear waste. The swelling pressure of the compacted bentonite/sand mixture is of significance in the design of the geological repository, which requires good consistency between data obtained by laboratory and field measurement. In this work, a series of swelling pressure tests were performed on compacted MX80 bentonite/sand specimens prepared by methods commonly adopted in laboratory (As-compacted, Transferred) and those mimicking the real block manufacturing process (Trimmed, Inserted). Results shown that with identical dry density (especially when the dry density was larger than 1.70 Mg/m³), largest swelling pressure was obtained in specimens prepared by method Inserted, followed by method As-compacted, Transferred and Trimmed. The distinct difference between the swelling pressure could be largely attributed to the effects of residual post-compaction lateral stress. More interestingly, specimens prepared by methods Trimmed and Transferred followed a similar swelling pressure-dry density relationship. From this point of view, method Transferred without causing mass loss, change of bentonite content and possible technological voids effect was recommended in lieu of method Trimmed for specimen preparation in laboratory.

压实的膨润土/砂混合物已被认为是高放核废料深层地质处置中可能的密封/回填材料。压实的膨润土/砂混合物的膨胀压力在地质处置库的设计中具有重要意义，这要求实验室获得的数据与现场测量的数据具有良好的一致性。在这项工作中，对压实的 MX80 膨润土/砂试样进行了一系列膨胀压力测试，这些试样通过实验室常用的方法（压实、转移）和模拟真实砌块制造过程（修剪、插入）的方法制备。结果表明，在相同的干密度下（尤其是当干密度大于 1.70 Mg/m ³)，在通过插入方法制备的试样中获得最大的膨胀压力，其次是压缩、转移和修剪方法。膨胀压力之间的明显差异很大程度上归因于残余压实后侧应力的影响。更有趣的是，通过 Trimmed 和 Transferred 方法制备的试样遵循类似的溶胀压力-干密度关系。从这个角度来看，推荐在不引起质量损失、膨润土含量变化和可能的技术空隙效应的情况下转移方法来代替 Trimmed 方法在实验室进行试样制备。