含水率对非饱和黏土渗透与弥散特性及核素迁移的影响研究

基于拟建某低中放废物处置单元的包气带地质环境，研究了该区黏土材料在非饱和条件下的渗透系数K（）和弥散系数D（）随黏土体积含水率的变化特征。研究显示，在非饱和状态下，当体积含水率 25%时，黏土实际处于不透水状态；当 15%时，的微小变化，即可导致黏土非饱和渗透系数K（）发生数量级的改变。实验表明，非饱和黏土弥散系数随着体积含水率的降低而减小，当体积含水率=38%时，实测弥散系数为4.12 m2 a-1；当=6%时，弥散系数为0.04m2 a-1，仅为前者的1%左右。核素迁移模拟结果显示，当体积含水率 25%时，钚在黏土屏障中不发生显著迁移；当 30%时，核素迁移作用明显增强。

INFLUENCE OF WATER CONTENT ON PERMEABILITY AND DISPERSION CHARACTERISTICS OF UNSATURATED CLAY AND RADIONUCLIDE MIGRATION

In view of the aeration zone of a future low and intermediate radioactive waste repository, variations on unsaturated permeability coefficient K() and dispersion coefficient D() of a clay with its volumetric water content were studied. The results indicate that the unsaturated clay is actually impermeable when 25%, and small change in will change the orders of magnitude of K() when 15%. The experiments show that dispersion coefficient of unsaturated clay tends to reduce with the decrease of . As =38%,the measured dispersion coefficient is 4.12m2a-1, and as =6%,the dispersion coefficient is 0.04m2a-1,which only about 1% of the former. The migration simulations show that as 25%,plutonium migrates very slowly in the clay barrier, whereas its migration rate will be enhanced obviously when 30%.