Dynamic mechanical behavior and failure evolution of water-bearing grotto sandstone under cyclic loading and unloading

Abstract

To further investigate the dynamic mechanical behavior and failure evolution of grotto sandstone in water-rich environments, a series of uniaxial cyclic loading and unloading tests were conducted on water-bearing grotto sandstone, with simultaneous acoustic emission (AE) signal monitoring. The results show that a critical water content range of 2.63–3.93 % was identified, within which significant shifts occur in both the hysteresis curve and the fatigue characteristics of sandstone. The proportion of shear and tensile cracks gradually transfers from a low-frequency ordered zone to a high-frequency disordered zone, with a critical transition point occurring at an axial stress of σ₁ = 12 MPa and a cycle number N = 4. Total energy, dissipated energy, and elastic energy demonstrate exponential growth as the number of cycles increases. With increasing water content, the rate of dissipated energy increases, leading to a more significant rise in irreversible damage. The evolution of the correlation dimension of water-bearing sandstone during fatigue failure follows three stages: initial decrease stage, stable change stage, and gradual increase stage. Based on the evolution of the correlation dimension of AE absolute energy, the instability precursor information for the water-bearing sandstone can be determined. The weakening effect of water reduces the instability time of grotto sandstone under cyclic loading. This research holds significant implications for prediction of rock failure in grotto heritage of rock masses.