Study on the Acoustic Emission Characteristics and Failure Precursors of Water-Rich Frozen Sandstone under Different Lateral Unloading Rates

The artificial freezing method is used to cross the water-rich soft rock strata in order exploit deep coal resources. At present, studies that consider both effect and unloading rate are insufficient. To study influences of excavation using on deformation failure surrounding rock, we carry out mechanical synchronous acoustic emission (AE) tests frozen (−10 °C) sandstone samples under different lateral rates. Combined with AE signals, stress, strain process analysed determine behaviours damage difference between normal temperature during studied. According relationships among amplitude, energy, cumulative energy (CAEE), stress were compared analyzed. In this paper, 3D positioning system monitor fracture propagation trajectory confining pressure sandstone. results show peak about 2.5 times at 20 °C. More than 2 amplitudes per second regarded as precursor (FP), point FP taken first level warning. CAEE °C shows same change law over time, increasing slowly before exponentially after point. Peak increases axial decreases increase sample. (AEE) time when sample increases. Principal component analysis was extract key characteristic obtain a clearer AEE concentration area, which defined second-level early research can provide guidance for shaft construction reduce occurrence disasters.