Experimental investigation on the transmissivity of fractured granite filled with different materials.

The disposal of high-level radioactive waste (HLW) is one of the most challenging issues globally, and granite is considered an ideal host rock. In this paper, we present an experimental study on the transmissivity of fractured granite filled with different materials. A series of tests were carried out to study the effects of different factors (filling material, confining stress, and fracture roughness) on fracture transmissivity. Our results show that the properties of the filling material play a critical role in the transmissivity of fractured granite. Specifically, quartz sand significantly increases the transmissivity of the fractured granite, but the larger the sand particle size, the slower the transmissivity increases. Conversely, compared with fractured samples without any filling material, bentonite as a filling material decreases fracture transmissivity. Furthermore, confining stress also exhibits a great effect on transmissivity, and high stress compresses the filling material, resulting in a reduction in transmissivity. In addition, confining stress has a larger impact on the transmissivity of sand-filled fractured samples than others. We quantify the roughness of the fractures to examine its impact on the transmissivity. The results show that larger roughness reduces transmissivity for the unfilled fractures, but has an opposite effect on sand-filled fractures, while the results of bentonite-filled fractures are scattered. This study could provide an important guidance for evaluating the safety of HLW repositories. [ABSTRACT FROM AUTHOR]