缓冲材料热-水-力耦合模型试验研究

高放废物深地质处置采用多重屏障设计体系,缓冲材料是位于废物罐和围岩之间的一道重要的人工屏障。在放射性衰变热、地下水入侵和围岩应力等作用下,缓冲材料经历复杂的热-水-力耦合过程,评价其长期性能对高放废物地质处置库的稳定运行至关重要。缓冲材料模型试验是研究膨润土在多场耦合环境下性能变化的重要途径。中型实验台架是大型实验台架(China-Mock-up)的重要补充,用来模拟与大型实验台架边界相同的环境下,即热量和水分别从缓冲材料的不同侧向另一侧传递和渗透的条件下膨润土的行为特征。通过实时监测缓冲材料在长期加热和加水条件下的温度、相对湿度、力学等特征参数,揭示了在热-水-力耦合条件下缓冲材料的性能变化规律,同时对台架进行了拆解,对拆解样品的含水量、干密度和微观结构等进行了分析测试,研究结果可为高放废物处置库缓冲材料的工程设计提供参数支持。

Study on Thermo-hydro-mechanical Coupling Behaviors of Buffer Material

The concept model of high-level radioactive waste (HLW) repositories in deep geological media is based on a multi-barrier system. Buffer material is considered as an important artificial engineered barrier between the canister and the surrounding rock. Coupled thermo-hydro-mechanical (THM) phenomenon will occur in the buffer material under conditions of the heat generated by the radioactive decay and of the underground water and geo-stress supplied by the surrounding rock, et al. Therefore, it is considered of fundamental important for the evaluation of long-term behavior that the processes taking place in the near filed for the safety operation of the HLW repository. Following the need for understanding the coupled THM behaviors of bentonite, mock-up test is considered as one of the most effective approach. An experiment at middle scale is proposed as a complementary step for the China-Mock-up test. The middle one is carried out to obtain the bentonite parameters and to identify the processes by simulating the conditions of the China-Mock-up test. The aims intended are to know and understand the long-term behavior of the bentonite submitted to thermal and hydraulic gradients at the opposite direction. The characteristic of the bentonite related to swelling pressure, relative humidity and temperature are presented and interpreted. Meanwhile, the water content, dry density, chemical composition and micro-structure of samples are analyzed and compared after dismantling. The results can provide design parameter and theoretical basis for HLW repository.