膨润土颗粒混合物的堆积性质与水-力特性研究进展

膨润土颗粒混合物是高放废物深地质处置库中的一种缓冲/回填材料,掌握其堆积性质与水-力特性是开展处置库安全性能评估的关键基础。本文全面回顾和总结了近年来国内外学者对膨润土颗粒混合物的堆积性质、持水特性、结构特征、渗透特性、胀缩特性及本构模型等方面的研究进展与取得的成果,展望了几个值得进一步研究的问题。结果表明,颗粒混合物的堆积性质与粒径级配密切相关;湿化过程中,颗粒混合物由初始松散结构逐渐转变为胶结融合结构,孔隙结构逐渐趋于均一化,并伴随着颗粒破碎和错动,进而影响其水-力特性。考虑到处置库实际运营环境的复杂性,颗粒混合物的原位填充技术以及多场(热-水-力-化)耦合条件下颗粒混合物的水-力特性是今后值得深入研究的方向。

A REVIEW ON PACKING AND HYDRO-MECHANICAL BEHAVIOUR OF BENTONITE PELLET MIXTURES

Bentonite pellet mixtures are considered as an alternative buffer/backfilling materials for high-level radioactive waste(HLW)repository. The packing and hydro-mechanical behaviour of bentonite pellet mixtures are of great significance for the safety evaluation of the HLW repository. In this paper, previous researches on the packing and hydro-mechanical behaviour of bentonite pellet mixtures are systematically reviewed and summarized. They include the packing dry density and homogeneity, water retention, structural change, hydraulic behaviour, swelling and compression behaviour as well as constitutive model. Meanwhile, several research subjects worthing further investigation are pointed out. Results in the literature indicate that the packing behaviour are highly dependent on the gradation. Upon wetting, the initial loose-structured pellet mixture can gradually transfer to cemented state and finally present a homogeneous appearance at saturation, accompanied with pellet breakage and movement, which can in turn affect the hydro-mechnical behaviour. Considering the complexity of the operation conditions in a HLW repository, further investigations on the emplacement technique and the hydro-mechanical behaviour under coupled thermo-hydro-chemo-mechanical conditions should be carried out.