Influences of sub-zero temperature on dynamic tensile behavior of rhyolite porphyry

Abstract

The mechanical behavior of rock materials in cold regions undergoes significant alterations under sub-zero temperatures. To understand the dynamic tensile properties of rhyolite porphyry (RP) under cryogenic conditions, a series of dynamic Brazilian disc tests were carried out on RP specimens within a temperature range from 10 °C to −40 °C covering a wide range of loading rate utilizing a split Hopkinson pressure bar. The test results demonstrate that, under sub-zero temperature conditions, the dynamic tensile strength (DTS) of RP is dependent on loading rate, increasing exponentially with loading rate across all temperatures. Additionally, at a given loading rate, the DTS initially increases and subsequently declines with decreasing temperature. Scanning electronic microscope (SEM) analysis reveals that the extreme cooling (−20 °C to −40 °C) induces inconsistent mineral shrinkage, generating microcracks that degrade macroscopic strength. The skeleton contraction stress theory is incorporated to computationally quantify freezing-induced contraction stress among distinct mineral constituents within RP specimens, theoretically confirming significant contraction stress differentials between compositional phases. Furthermore, a predictive model for rock strength, integrating temperature and loading rate effects, was developed through response surface methodology. The predicted values from this model showed good agreement with the experimental data, indicating its reliability for rock strength prediction.