渗流条件下含裂缝压实膨润土应力及渗透性能试验研究

发布时间：2018-08-12 18:31

【摘要】：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。
[Abstract]:Compacted bentonite is an ideal buffer / backfill material for radioactive waste disposal. However, it is easy to produce cracks in the process of dehydration and shrinkage. Whether the cracks can heal under the condition of immersion is an important issue in the safety evaluation of radioactive waste disposal. The permeation test was carried out on the sample of compacted bentonite containing longitudinal single crack. The change of stress and permeability of fractured compacted bentonite after water absorption and expansion was studied by taking permeability coefficient, normal stress and moisture content of gap surface as indexes. The effect of cracks on the properties of bentonite barrier layer was evaluated. The results show that the permeability coefficient of the sample decreases gradually with time, the normal stress of the gap surface increases with time, and the two parameters reach a stable level at 85 days. The permeability coefficient and internal stress of the whole compacted bentonite samples are 4.6410 ~ (-10) m / s and 2.5 MPA, respectively. It can be concluded that the soil is saturated and homogenized at this time. From the angle of permeability and stress, it is proved that the fracture has no significant effect on the permeability coefficient and stress parameter of compacted bentonite, and bentonite has good self-healing ability. The evaluation method of self-healing effect of bentonite crack is established, which provides a theoretical basis for the safety evaluation of bentonite as backfill material.
【作者单位】：西北核技术研究所;
【分类号】：TU443

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