膨润土膨胀力长期衰减特性的数值分析

Numerical simulation of bentonite swelling attenuation processes in long time scale

利用Phreeqc软件对膨润土缓冲层在多场耦合作用下10 000 a内的孔隙溶液浓度、晶层离子交换量及蒙脱石含量变化进行数值模拟,并结合分形理论,计算得到膨润土垫层的膨胀力在长时间尺度下的衰减变化过程。研究结果表明:膨胀力衰减幅度由膨润土垫层与围岩接触的外边界至内部逐步降低;海水环境中膨胀力衰减较地下淡水环境更为显著;膨润土的膨胀力经一段时间衰减后趋于稳定且10 000 a后仍存在较高膨胀力,证明膨润土能长久地有效确保核废料处置库的安全性。

By using software Phreeqc,the pore solution concentration change,crystal layer ions exchange capacity and the variation in content of the montmorillonite were simulated under the effect of multi-field coupling during 10 000 a.Bentonite swelling force attenuation processes in long time scale were obtained based on fractal theory.The results show that the swelling force becomes stable with time increasing and the attenuation decreases along the bentonite buffer from the boundary contacted with external rock mass to interior.The attenuation of the swelling force in seawater is more significant than that in the groundwater,and the expansion force of bentonite tends to be stable after a period of attenuation and still obtains a relative high value after 10 000 a.Thus,bentonite is certainly a secure material in nuclear waste disposal repository environment.