黏土岩水力耦合特性试验研究

Experimental study on the hydro-mechanical behavior of a clayey rock

对于高放废物地质处置工程,地质屏障系统是放射性有害物质进入环境的最后一道屏障,也是一条重要防线。黏土岩由于其低渗透性、渗透损伤自修复以及较强的吸附能力等特性,被认为是一种合理的高放废物处置地质屏障。结合比利时正开展的黏土岩高放废物地质处置相关研究课题,通过一系列室内试验研究黏土岩的水力耦合机制及长期蠕变特性。三轴压缩试验表明,黏土岩压缩强度、超孔隙水压力与围压正相关。渗透试验表明,黏土岩渗透性呈现显著的各向异性特征,围压增大使黏土岩渗透性显著降低。蠕变试验表明,黏土岩蠕变变形、蠕变变形速率与载荷密切相关,即:载荷越大,黏土岩蠕变变形越显著,蠕变变形速率达到稳定所需的时间越长,且相应的稳态蠕变速率越大;根据应力阈值和等时曲线法初步确定该黏土岩长期强度在1.0~1.2 MPa。研究结果将为我国未来黏土岩高放废物处置库的选址和安全性评估提供重要科学依据。

For the geological disposal of high-level radioactive waste,the geological barrier system,as an important defense,is the last barrier for hazardous substances to enter the environment.Clayey rock,in virtue of its properties,such as low permeability,self-healing,and strong adsorption capacity,is considered a reasonable geological barrier for the disposal of high-level radioactive waste.In this study,the hydro-mechanical coupling mechanism and long-term rheological properties of a clayey rock were studied through a series of laboratory experiments.Triaxial tests show that the compression strength and excess pore water pressure have a positive relation with confining pressure.Permeability tests show the anisotropic hydraulic properties of the clayey rock and the permeability notably decreases under high confining pressure.Creep tests show that creep deformation and creep deformation rate are closely related to the load level.That is to say the larger the load is,the more significant the creep deformation is,the longer it takes for the creep deformation rate to reach stability,and the larger the corresponding steady-state creep rate is.According to the stress threshold and isochronal curve method,the long-term strength of the clayey rock is preliminarily determined to be 1.0-1.2 MPa.The results of this study will be of great significance to the geological disposal and safety assessment of high-level radioactive waste in clayey rock in China.