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压实膨润土是放射性废物处置库的理想缓冲/回填材料,但它在失水收缩过程中易产生裂缝,该裂缝在浸水条件下能否愈合是放射性废物处置安全评价中的重要课题。其研究对含纵向单裂缝的压实膨润土样品开展渗透试验,以渗透系数、隙面法向应力及含水率为指标,研究含裂缝压实膨润土吸水膨胀后应力及渗透性能的变化,从而评价裂缝对膨润土屏障层性能的影响。研究结果表明,样品渗透系数随时间逐渐递减,隙面法向应力随时间逐渐递增,且在85 d时两参数达到稳定水平,分别为4.6410~(-10)m/s和2.5 MPa,与完整压实膨润土样品的渗透系数及内部应力处于相同水平,可以认为,此时土体实现了饱和及均一化。该研究从渗透性和应力角度证实了裂缝对压实膨润土渗透系数及应力参数未产生显著影响,膨润土具有较好的自愈合能力。研究建立了膨润土裂缝自愈合效果评价方法,为膨润土作为回填材料的安全性评价提供理论依据。
Compacted bentonite is an ideal buffering / backfilling material for radioactive waste disposal. However, it is easy to crack during water loss and shrinkage. Whether the fracture can heal under immersion is an important issue in the safety evaluation of radioactive waste disposal. In this study, the penetration tests were carried out on compacted bentonite samples with longitudinal single cracks, and the permeability and fracture surface normal stress and water cut were taken as indexes to study the changes of stress and permeability after water-swelling of crack-compacted bentonites so as to evaluate the fracture Effect on Bentonite Barrier Properties. The results show that the permeability coefficient decreases gradually with time, and the normal stress in the gap surface gradually increases with time. At 85 days, the two parameters reach a stable level of 4.6410 ~ (-10) m / s and 2.5 MPa respectively, Compacted bentonite samples of the permeability coefficient and internal stress at the same level, it can be considered, at this time the soil to achieve saturation and homogenization. From the perspective of permeability and stress, the study confirms that the fractures have no significant effect on the permeability coefficient and stress parameters of compacted bentonite, and bentonite has better self-healing ability. The method to evaluate the effect of self-healing of bentonite crack was established, which provided a theoretical basis for the safety evaluation of bentonite as backfill material.