Characterization of Electrical Parameter Response and Energy Evolution Law of Coal Sandstone Loaded Process Under Different Water Contents

This study conducts uniaxial compression tests on sandstone under four water content states using the MTS 816 rock mechanics testing system to investigate the response law of electrical parameters, mechanical properties, and energy evolution of coal sandstone under the influence of water. It also establishes a real-time monitoring system for electrical parameters during sandstone loading by installing an electrode spatial matrix on the surface of the sandstone. The findings indicate that the presence of water softens the sandstone. As the water content increases from 0% to 1.325%, the sandstone's peak stress and apparent resistivity gradually decrease. The maximum values of excitation currents at peak stress are 3.8, 4.1, 5.0, and 9.7 mA, respectively, demonstrating an exponential function correlation between the water content and the maximum excitation current. The energy evolution process of sandstones with varying water contents shows similarities; the elastic energy increases gradually before the peak, the dissipation energy increases and then decreases, and the elastic energy decreases sharply after the peak while the dissipation energy surges. The value of K exceeds 1 in the postpeak stage of compression and density and falls below 1 during the elastic and plastic deformation stage, indicating that K =1 is the critical threshold for sandstone destabilization. The changes in elastic energy consumption ratio and energy dissipation rate reflect the transition from the sandstone damage deformation stage to damage progression. As water content increases, the elastic energy consumption ratio and the energy dissipation rate increase. This study demonstrated that the synergistic analysis of mechanical, electrical, and energy parameters can finely detect the various stages of deformation and damage in sandstone specimens under load and clarify the local rupture of the specimens. This provides a novel approach for evaluating rock damage.