高放废物处置库中COx黏土岩回填材料压缩特性研究

COMPRESSION BEHAVIORS OF CRUSHED COx ARGILLITE USED AS BACKFILLING MATERIAL IN HLW REPOSITORY

高放废物处置库中回填材料需要预先压缩到一定密实度,其压缩特性对处置库的设计和安全性有重要影响。目前,粉碎后的Callovo-Oxfodian(COx)黏土岩(法国)被考虑为可选的回填材料之一。通过开展一维压缩试验,研究2种不同粉碎工艺下获得的粗/细COx土样的压缩特性,结果表明:压缩曲线受粒度成分的影响非常明显,为获得同等压实度,细粒土所需的压实功能较粗粒土高,除此之外,细粒土的压缩指数也高于粗粒土,表现出较强的压缩性;随着土样压实密度的增加,粗/细土样的压缩曲线逐渐靠拢,粒度成分对压实功能影响逐渐减弱;土样卸荷时回弹指数随干密度的增加而增加,受粒度成分的影响不明显;高压实(ρd=2.0g/cm3)粗粒土样在7MPa的轴向应力下饱和时,体积发生明显的塌陷现象,饱和后土样的压缩指数小于饱和前,而回弹指数则较饱和前高。

In high-level radioactive waste（HLW） repository, backfilling material should be pre-compacted. The compression characteristics are very important for the design and security of HLW repository. The Callovo- Oxfodian（COx） argillite（France） is now proposed, after being crushed and compacted, as an alternative backfilling material in the geological HLW repository. In this investigation, the compression behavior of COx argillite with two different grain size distributions（GSDs）, which were obtained by two different crush procedures, was studied by running 1D compression tests with several loading-unloading cycles. It is found that the compression curves are significantly influenced by the GSD of the soils. To obtain the same degree of compaction, the axial stress applied to finer soil is much higher than that of coarser soil. In addition, the compression index at initial water content of the finer soil is bigger than that of coarser soil. During the compression, both the compression curves of the finer and coarser soils tend to be close to each other with increasing dry density. It is shown that the effect of GSD on the compression behavior is weakened after the soil is highly compacted. The swelling index at initial water content increases with the dry density and seems to be independent of the GSD. During saturation, the highly compacted coarser soil sample（ρal= 2.0 g/cm^3） shows evident collapse behavior under 7 MPa axial stress. The compression index decreases and the swelling index increases after the saturation.