Characteristics and spatial differences of pressure-stimulated rock potential in diorite partly loaded to fracturing

Abstract

The spatial differences of pressure-stimulated rock potential (PSRP) and its correlation with crack development and distribution were poorly studied, despite their importance in understanding seismic anomalies and monitoring engineering rock mass. In this study, compressive stresses were partly applied to specially designed diorite specimens in shape of composite cuboid-platform, which make the specimens being comprised of loaded cuboid and free platform. The PSRP differences between each end of the free platform and the loaded cuboid were monitored separately, and acoustic emission was monitored simultaneously to observe crack development. Results revealed distinct stage-specific PSRP characteristics: exponential drop during initial loading, rapid rise with local macro failure, pulse appear with instability failure, and large fluctuation rise occur with post-peak loading. Preceding the instability failure phase, the PSRPs variation across different regions exhibited consistent trend with differences in amplitude and timing. At instability failure phase, however, significant spatial differences emerged, with opposite polarity pulses observed. The detected PSRP could be attributed to the fluid electrokinetic effect and the activation of positive holes (P-holes). The PSRP corresponds to crack development, as larger accumulated crack areas activate more P-holes and consequently generate higher PSRP rises. Spatial distribution in macro fracture surfaces further governed the spatial differences of PSRP, where open fractures blocked the upward transmission of P-holes, affecting the response of P-holes in PSRP. The revealed relationship between PSRP and crack development/distribution provides novel insights for monitoring and early warning of engineering rock mass instability and earthquakes.