Creep Behavior of Frozen Shikotsu Welded Tuff

Surfaces of rock slopes in a cold region often get frozen in winter. Therefore, understanding time-dependent behavior of frozen rock as well as that of unfrozen rock is significant for long-term stability assessment of the rock slopes. In this study, creep tests were carried out on Shikotsu welded tuff under dry and wet conditions at –20 °C (253 K) to clarify effect of water content on the time-dependent behavior of frozen rock. The results showed that deformation of frozen wet specimens was much more than that of frozen dry specimens. It was also found that axial strain rate-axial creep strain curves of the frozen wet specimens were different from those of the frozen dry specimens. Ratio of tertiary creep region of frozen wet specimens was relatively longer. These differences can be explained by existence of pore ice. Furthermore, creep life of un-failure specimens could be estimated with axial strain rate because creep life showed negative correlation with the axial strain rate in the early stage. Based on both observed creep life of rupture specimens and estimated creep life of un-failure specimens, the creep life of frozen wet specimens was expected to be shorter than that of frozen dry specimens at creep stress below about 50% of uniaxial compressive strength of frozen wet specimens. This result indicates that the effect of water content should be investigated for long-term stability assessment of rock slopes in a cold region.