Study on the AE Characteristics and Energy Evolution Mechanism of Sandstone with Different Aspect Ratios Under Biaxial Compression

With the increase of mining depth, frequent disasters in roadway pose a significant threat to the safe mining of coal resources. Studying the fracture characteristics and deformation evolution process of excavated unloading rock mass can provide important basis for controlling deep mine roadways and preventing rock burst. To reveal the strength and fracture characteristics of deep rock masses under different aspect ratios, biaxial compression tests were conducted on 7 kinds of sandstones with the same height and different widths. The time—frequency domain of acoustic emission (AE) characteristics in the rock failure were comprehensively analyzed, and the correlation mechanism between energy evolution and strength failure of rocks was explored. The research results indicate that with the increase of aspect ratio, the rock strength decreases gradually, and the shear angle decreases first and then increases. The macroscopic failure mode gradually changes from the complex multi crack failure dominated by tensile-shear mixed cracks to the single tensile crack failure. The proportion of dissipative energy gradually increases at low stress level, and as the axial load increases to the elastic limit of rocks, the proportion of dissipative energy gradually decreases. When the rock approaches failure, the ratio of elastic strain energy to dissipative energy tends to stabilize. The total energy of AE is positively proportional to its size. The peak frequency of AE presents obvious zoning characteristics. With the decrease of the aspect ratios, the cumulative energy of AE increases in a stepped curve, and the concentration of the cumulative energy is gradually obvious.

Highlights

Biaxial compression tests on sandstones with different aspect ratios.