Characteristics of energy evolution and acoustic emission response of concrete under the action of acidic drying-saturation processes cycle

Abstract

The continuous fluctuation in the acidic mine water level of the underground reservoir will affect the artificial dam's strength and stability. The uniaxial compression test of C25 concrete under different drying-saturation processes cycle (DSPC) numbers and pH solutions were performed. The degradation mechanism of mechanical properties of concrete under acidic DSPC was investigated; the calculation formula for the elastic strain energy at peak stress has been corrected and the energy evolution law has been obtained; besides, the evolution characteristics of acoustic emission (AE) parameters were studied using multi-fractal theory and the precursor characteristics of concrete failure were obtained. The results revealed that increasing the DSPC times or decreasing the pH caused an increase in the saturation moisture content of the concrete, the strain and elastic strain energy of the concrete at peak stress increased, a drop in the ultrasonic velocity, the uniaxial compressive strength (UCS), the elastic modulus (EM) and the overall input energy. The accumulated ringing count and accumulated energy of AE dramatically increased before the concrete was close to failure, and numerous low-frequency and high-amplitude signals started to appear. The information mentioned above might be considered a short-impending warning of concrete failure. During the plastic deformation, the large increase of the multi-fractal parameter Δα and the significant drop of Δf might be viewed as early warning for concrete failure. This research will offer some theoretical direction for artificial dam design and long-term stability monitoring in underground reservoirs.