Infrared radiation and acoustic emission characteristics of sandstone with different granularities under uniaxial compression

The mechanical properties and deformation characteristics of sandstone are significantly influenced by granularity. To characterize the deformation and failure of sandstone with different granularities, sandstone specimens were subjected to uniaxial compression tests, and infrared radiation temperature (IRT) and acoustic emission (AE) events were monitored simultaneously. The results show that the AE energy evolution is similar for the sandstone with different granularities, and AE energy decreases with the granularity during the crack closure stage. The values of average infrared radiation temperature (AIRT) of the middle part are higher than those in the upper and lower parts, and the trends are different in various regions of the sample. The spatial evolution of AE and AIRT is similar for the sandstone with different granularities, and the high-temperature area is consistent with the AE concentration area. The higher the granularity of sandstone is, the more AE events are detected during the deformation and failure stage. The failure precursors for sandstone range from 0.76 sigma(c) to 0.98 sigma(c). The AIRT precursor of the upper part is earlier than those in the middle and lower parts, and the AIRT precursors of different regions are earlier than the overall AIRT precursor. Moreover, the precursors of AE and IRT for sandstone get earlier with the granularity. The dissipated energies in medium sandstone, fine sandstone, and siltstone are 0.25, 0.27, and 0.34 J/cm(3), and the dissipated energy is negatively correlated with granularity. This study is of significance for the effective monitoring of sandstone instability and failure using IRT and AE.