Acoustic emission response and rupture evolution analysis of triaxial compression damage of hot dry rock under seawater fatigue dissolution

Abstract

Analyzing the fatigue damage characteristics of hot dry rock (HDR) affected by seawater thermal shock cycles is required for the efficient exploitation of HDR and the conservation of freshwater resources. Mechanical and acoustic emission (AE) monitoring tests were conducted during the triaxial compression of HDR at different confining pressures, temperatures, and numbers of seawater thermal shocks to investigate the seawater damage of HDR. The test results indicated an increase in the cumulative AE counts with increasing temperature and number of seawater thermal shocks, and a decrease in AE counts with increasing confining pressure. The effect of the number of seawater thermal shocks was significant. The AE counts were 276% higher at 15 than at 0 seawater thermal shocks. The b-value increased with the number of thermal shocks and stabilized after 5 shocks. Most of the damage was small fractures, which reduced the rock’s damage resistance. The AE time series under HDR triaxial compression exhibited multifractal features. High-energy AE events dominated the damage mechanism of HDR, indicating shear damage to the HDR. Therefore, this study can provide a reference for seawater as a heat transfer fluid in the design of geothermal energy resource extraction.

Keywords

fatigue damage / hot dry rock / seawater thermal shocks / triaxial compression / acoustic emission

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