Study of Subcritical Crack Growth and Long-Term Strength for Rock and Cementitious Material for Radioactive Waste Disposal

Abstract

Information and knowledge of the time-dependent fracturing of rock are essential to ensure the long-term stability of structures in a rock mass, such as repositories of radioactive wastes underground. Additionally, it is planned that high-strength and ultra low-permeability concrete (HSULPC) is used for a radioactive waste package for geological disposal of waste containing transuranic radionuclides (TRU waste). Therefore, it is important to investigate slow crack growth (subcritical crack growth) in rock and HSULPC. In this study, subcritical crack growth in rock and HSULPC was investigated. Andesite was used for the rock sample. In air, the crack velocity in andesite increased when the temperature was higher. On the other hand, the temperature had little effect on the crack velocity for HSULPC in air. In water, the crack velocity increased when the temperature was higher for both andesite and HSULPC. By using the experimental results of subcritical crack growth, the long-term strength was estimated. It was shown that the long-term strength of HSULPC was higher than that of andesite even though the Brazilian tensile strength was similar for both materials.