Using the characteristics of infrared radiation during the process of strain energy evolution in saturated rock as a precursor for violent failure

Abstract

Water saturated rock strain energy evolution was measured using infrared radiation (IR) under uniaxial load of sandstone samples. The variation in the characteristics of total strain, elastic strain, dissipated strain energies and maximum IR of saturated rock under stress were analyzed. The results reveal the degree of saturation has a significant effect on rock strain energy. The total strain and elastic strain energies correlated linearly negatively, dissipative strain energy were correlated exponentially negatively, and maximum infrared radiation variance (IRV) correlated quadratically at peak stress point with different degree of saturation of rock samples. The relationship between total strain, elastic strain energies, and ΔIRV was a linear function under different saturated conditions. It was found that there was a linear energy transfer and linear energy storage function in the rock. Based on linear energy transfer and storage, two coefficient in the presence of IR were introduced, i.e., the Total Energy Infrared Radiation Coefficient (TEIRC) and Energy Storage Infrared Radiation Coefficient (ESIRC). These can be used with variation in infrared radiation variance (ΔIRV) to determine total strain and elastic strain energies of saturated rock. Furthermore, a quantitative analysis index of energy dissipation infrared radiation ratio (EDIRR), i.e. the ratio of dissipative strain energy to ΔIRV, has been proposed which can be used to predict and identify the failures of saturated rock. The inflection point of rock EDIRR from horizontal to rapid growth can be regarded as the precursor point for rock failure, and the EDIRR mutation after the precursor point can be used as the new criterion to monitor rock failure and instability.