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采用NaOH溶液模拟高放射性核废物处置库中可能产生的高碱性孔隙水,对初始干密度为1.70 g/cm3的高庙子(GMZ)膨润土试样进行渗透侵蚀试验,借助扫描电镜(SEM)和透射电镜(TEM)对侵蚀后试样的表观特性进行观察分析,对碱溶液侵蚀对膨润土试样膨胀性、渗透性、孔隙比和化学成分的影响规律进行解释,以研究碱性孔隙水侵蚀对膨润土性能影响的微观机理。结果表明,GMZ膨润土主要成分蒙脱石呈层片状结构,蒙脱石水化会在其表面形成羽翼状的胶体,会堵塞试样的孔隙;高碱性溶液的侵蚀会造成膨润土水化产生的羽翼状胶体溶解和膨润土结构的不可逆性破坏,并且破坏程度与碱溶液的浓度成正相关关系;经高碱性溶液侵蚀的膨润土试样,其表面有明显的溶蚀痕迹,说明碱溶液的入渗侵蚀会造成膨润土有效成分蒙脱石的溶解,试验结果与X射线衍射(XRD)测试结果吻合。因此,碱性孔隙水的入渗侵蚀会逐渐溶解膨润土中的蒙脱石,破坏了膨润土的结构,增大了膨润土的孔隙率,进而降低了膨润土的膨胀性,提高了膨润土的长期渗透性,最终造成膨润土的封闭和缓冲性能降低。
The NaOH solution was used to simulate the overbased pore water that may be generated in the high-level radionuclide waste repository. The penetration erosion test was carried out on the GMZ bentonite sample with the initial dry density of 1.70 g / cm3. Scanning electron microscopy (SEM) And transmission electron microscopy (TEM) were used to observe and analyze the apparent characteristics of eroded samples. The influences of alkali solution on the swelling, permeability, void ratio and chemical composition of bentonite samples were explained. MICROSCOPIC MECHANISM OF CORROSION ON THE PERFORMANCE OF BENTONITE. The results showed that montmorillonite, the main component of GMZ bentonite, was in a lamellar structure. Montmorillonite hydration formed wing-like colloids on its surface, which could block the pores of the sample. The erosion of overbased solution caused the hydration of bentonite And the irreversible destruction of bentonite structure. The degree of damage is positively correlated with the concentration of alkali solution. The bentonite sample eroded by overbased solution shows obvious corrosion marks on the surface, indicating that the infiltration of alkali solution Erosion can cause dissolution of montmorillonite, an active component of bentonite. The experimental results are in good agreement with the results of X-ray diffraction (XRD). Therefore, the infiltration and erosion of alkaline pore water gradually dissolves the montmorillonite in bentonite, destroys the structure of bentonite, increases the porosity of bentonite, reduces the expansibility of bentonite and increases the long-term permeability of bentonite, Eventually resulting in the closure of bentonite and cushioning properties.