通过在膨润土中掺入不同量的 CaCO₃ 模拟高放射性核废料(high-level radioactive waste,HLW)处置库周围地 下水侵入屏障生成 CaCO₃ 后膨润土性状的变化。通过配置 4 组不同 CaCO₃掺入量的膨润土进行了有荷膨胀试验、压缩试验和直剪试验,运用太沙基一维固结理论计算了渗透系数,并采用扫描电子显微镜(scanning electron microscopy,SEM)对样本进行了微观分析。结果表明：最终膨胀率与竖向应力、CaCO₃含量有关,竖向应力越大, CaCO₃ 含量越高,最终膨胀率越小;压缩指数随 CaCO₃含量的增大而小幅下降;随着 CaCO₃ 含量的增多,膨润土-碳酸钙混合土渗透性变差;非饱和样的抗剪强 度随 CaCO₃含量变化存在一个峰值,黏聚力先增后减,饱和样则相反;电镜扫描图显示,CaCO₃ 的掺入填充了膨润土中的孔隙,使其结构更加 致密。

Different amounts of CaCO₃ are mixed in bentonite for the purpose of simulating the characteristic changes of bentonite mixed with CaCO₃ that precipitates from groundwater around high-level radioactive waste (HLW) repositories. In the process of the project, four groups of bentonite-CaCO₃ mixtures are prepared with different contents of CaCO₃. Then a series of experiments including swell-under-load, compression and direct shear tests are carried out. The permeability coefficient is calculated through Terzaghi consolidation theory. The microstructure changes are photographed by the scanning electron microscopy (SEM). Test results indicate that: (1) The final swelling strains are related to vertical stress and CaCO₃ content. While vertical stress and CaCO₃ content increase, the final swelling strains decrease. (2) The compression index deceases slightly as the content of CaCO₃ crystals increases. (3) The permeability turns worse with increasing CaCO₃ content. (4) With the content of CaCO₃ crystals changing, the shear strength of unsaturated samples will come to its peak value. Contrary to saturated samples, the cohesive of unsaturated samples increases firstly and then increases with the increasing CaCO₃ content. (5) The photographs show that the existence of CaCO₃ fills the pores which makes the structure denser.