Dynamic Compressive Test of Saturated Sandstones Under Ambient Sub-Zero Temperature

Background Dynamic compressive strength (DCS) of frozen rocks is significant in improving the impact design of rock engineering in cold regions. However, the existing dynamic low temperature testing systems generally cannot achieve a controllable cooling rate or maintain a stable freezing temperature environment, which induces undesirable damage in rocks due to the rapid cooling rate and leads to inaccurate measurement results. Objective The objective of this study is to develop a valid dynamic low temperature testing system capable of testing frozen rocks and investigate the effect of ambient sub-zero temperature on the dynamic compressive behaviors of rocks. Methods The T-2 spectrums obtained by NMR (Nuclear Magnetic Resonance) of two freezing conditions are adopted to prove the necessity of ambient sub-zero temperature for dynamic tests of frozen rocks. A valid dynamic low temperature testing system is developed to perform the dynamic rock test under the ambient sub-zero temperature of dry and saturated white sandstone specimens at 20 degrees C, -10 degrees C, and -20 degrees C. The DCSs (dynamic compressive strength) of dry and saturated porous white sandstones at 20 degrees C, -10 degrees C, and -20 degrees C are obtained and compared. Results The dynamic low temperature testing system is valid for performing the dynamic rock test under ambient sub-zero temperature and capturing the dynamic failure process of frozen rock specimens. At 20 degrees C, -10 degrees C, and -20 degrees C, the DCSs of dry sandstones are higher than those of saturated sandstones, and the sub-zero temperature has a different influence on the DCSs of dry and saturated sandstones, indicating that both the phase transition of water and the shrinkage of minerals contribute to the DCS deterioration. Conclusions Ambient sub-zero temperature of dynamic testing frozen rocks is necessary to evaluate the significant temperature influence on the dynamic compressive behavior of sandstone.