Static and coupled dynamic testing of granite for geological disposal of high-level waste

Abstract

The Tianhu area of Xinjiang Province has been pre-selected for the geological disposal of high-level radioactive waste. To engineer the design of the disposal site, one must understand the static and dynamic properties of the granite in the borehole. In the present study, rock was sampled at the same depth in the same borehole, and its tensile and uniaxial-compression strengths were evaluated. Both strengths were steady and representative. The dynamic tensile and dynamic compression strengths increased with loading rate, confirming the loading rate effect on the brittle material. A coupled static-and-dynamic tension test was then carried out. Under increasing axial static stress, the dynamic tensile strength first increased and then decreased in a stable manner. The dynamic tensile strength was maximized when the static axial pre-pressure reached approximately 50% of the static-tensile strength. Meanwhile, the coupled static-and-dynamic strength increased under increasing axial static pressure, reaching approximately three times the static tension strength, and 1.5 times the dynamic tension strength. The failure model in the dynamic test was mainly tension failure, consistent with the static tension test. Therefore, the rock in this area is mechanically stable and putatively suitable for the geo-disposal of high-level waste (HLW). For a complete assessment, the rock should be tested by other methods such as seepage and in situ stress testing. After a detailed analysis of the rock in this area, the testing results and theoretical knowledge will become available for deep geo-engineering blasting and excavation, and HLW geo-disposal.