Time-dependence of mechanical behavior of Shikotsu welded tuff at sub-zero temperatures

A series of uniaxial compression and creep tests were performed on dry and wet specimens of Shikotsu welded tuff at -20 degrees C (-4 degrees F) to examine the time-dependence of the mechanical behavior of frozen rock. The impact of the water content of the specimens on the time-dependence of mechanical behavior was also investigated. The uniaxial compressive strengths (UCSs) of the frozen wet specimens strongly depended on the loading rate, and were greater than those of the frozen dry specimens at strain rates greater than 4.2 x 10(-5) s(-1). However, the creep lives of the frozen wet specimens were shorter than those of the frozen dry specimens at stress levels of less than 13.4 MPa (52% of the UCSs of the frozen wet specimens). Deformation behavior induced by pore ice was observed in the frozen wet specimens. The stress-strain behavior transitioned from brittle to ductile as the strain rate increased, and the ratio of the tertiary creep region was relatively larger. The strains of the frozen wet specimens were significantly larger than the frozen dry specimens. These results demonstrated that understanding the time-dependent deformation of frozen rock is crucial for the assessment of the long-term stability of rock slopes in cold regions, as pore ice strongly affected the failure process of the frozen wet specimens.