Study on Acoustic Emission Response and Failure Characteristics of Rock–Proppant–Rock Composite Constructions Under Uniaxial Compression

To reveal the bearing and instability mechanisms after filling proppants in the blasting pressure-relief fracture, four types of proppant-containing sandstone composite construction with interface inclinations of 0°, 4°, 8°, and 12° were prepared. A uniaxial compression test was conducted by combining Acoustic Emission (AE) monitoring and camera observation to analyze the variation patterns of peak strength, AE ringing count, b-value, critical slowing down indicators and failure mode. The results show that the average peak stress decreased from 48.55 MPa to 39.30 MPa as the inclination increased from 0°to 12°, corresponding to a reduction of approximately 19.0%. AE ringing counts remained low during the compaction and elastic stages but developed into concentrated bursts before peak stress. The b-value as a whole exhibited the characteristics of "high-level fluctuation—phased decline—low value before peak stress", reflecting the transformation of the crack scale from microcrack initiation to macroscopic penetration. The variance and autocorrelation of AE ringing counts increased before the peak stress and provided warning windows for the instability of specimens. The failure mode gradually transformed from axial splitting to compression–shear failure with increasing inclination.