Yang Gaosheng, Bai Bing, Chen Wenxuan, Mao Haitao, Liu Zhonghua, Lan Xiaoling
College of Urban and Rural Construction, Shanxi Agricultural University, Jinzhong 030801, China.
School of Civil Engineering, Beijing Jiaotong University, Beijing 100044, China.
Materials (Basel). 2024 Aug 26;17(17):4211. doi: 10.3390/ma17174211.
The joints of buffer material composite blocks as potential weak parts in the engineering barrier system of a high-level radioactive waste (HLW) repository must be studied in depth. Therefore, a laboratory experiment device suitable for unsaturated composite bentonite samples was developed. The evolution of temperature and volumetric water content at different locations of Gaomiaozi (GMZ) composite bentonite samples with time before and after simulated water inflow was measured by the experiment device. According to the experimental results, the thermal conductivity and hydraulic conductivity of the joint location after healing of the composite bentonite samples were obtained. The experimental results show that the change in the internal temperature of the composite bentonite samples is mainly affected by the temperature boundary and that the change in the internal water has little effect on it. In a short period of time, the loading of hydraulic boundary conditions only makes the volumetric water content of the soil near the hydraulic boundary increase significantly but has little effect on other locations. And, affected by the temperature boundary, the volumetric water content of the soil near the temperature boundary gradually decreases with time. The process of hydration swelling of the composite bentonite sample is accompanied by the adjustment of stress. The composite bentonite samples are continuously squeezed to the joint area after hydration swelling, the whole composite samples are generally homogenized, and the joints between the composite bentonite samples tend to heal. The thermal conductivity and permeability of the joint location after healing can meet the requirements of the engineering barrier of the HLW repository.
缓冲材料复合块体的接缝作为高放废物（HLW）处置库工程屏障系统中的潜在薄弱部位，必须进行深入研究。因此，研制了一种适用于非饱和复合膨润土样品的室内实验装置。利用该实验装置测量了高庙子（GMZ）复合膨润土样品在模拟进水前后不同位置的温度和体积含水量随时间的变化情况。根据实验结果，得到了复合膨润土样品愈合后接缝位置的导热系数和水力传导率。实验结果表明，复合膨润土样品内部温度的变化主要受温度边界的影响，内部水分的变化对其影响较小。在短时间内，水力边界条件的加载仅使水力边界附近土体的体积含水量显著增加，而对其他位置影响较小。并且，受温度边界的影响，温度边界附近土体的体积含水量随时间逐渐降低。复合膨润土样品的水化膨胀过程伴随着应力调整。复合膨润土样品水化膨胀后不断向接缝区域挤压，整个复合样品总体趋于均匀化，复合膨润土样品之间的接缝趋于愈合。愈合后接缝位置的导热系数和渗透率能够满足高放废物处置库工程屏障的要求。
