Mechanical behavior of Tamusu mudstone under elevated temperatures

Tamusu mudstone is a potential geological medium for high-level radioactive waste disposal in China. In this study, the mechanical behavior of Tamusu mudstone was examined through a series of triaxial compression experiments conducted under varying confining pressures (5, 10, 15, and 20 MPa) at two temperatures: 22 degrees C and 80 degrees C. The experimental findings revealed that heating strengthened the mechanical properties of Tamusu mudstone when compared under the same hydro-mechanical conditions. The strength, elastic modulus, cohesion, and friction angle of Tamusu mudstone increased after being subjected to elevated temperatures. However, the brittleness of Tamusu mudstone was also enhanced compared to its behavior at room temperature. The investigation into the post-peak deformation properties of Tamusu mudstone indicated a gradual failure process, which possibly involved multiple stress drops. As the number of stress drops increased, the rate of deviatoric stress reduction gradually decreased, while the corresponding plastic deformation progressively increased. This behavior was attributed to the weakened cohesion and strengthened friction of the Tamusu mudstone. This study contributes to the understanding of thermomechanical phenomena in argillaceous rocks and provides important input parameters for theoretical and numerical modeling in the safety assessment of HLW repositories.