On the effect of freeze-thaw on fracture and instability of hole-fissure-contained granite under uniaxial variable frequency- amplitude cyclic loads

Abstract

This work aims at investigating the fracture and instability behaviors of Xinjiang granite containing hole and fissures under freeze-thaw (FT) and cyclic loads using acoustic emission (AE) monitoring and X-ray computed tomography (CT) imaging. The stress path is sinusoidal load with decreasing frequency and increasing amplitude pattern. The experimental results reveal a sudden increase of volumetric strain and a sudden decrease of AE-b value. Their increasing rate becomes quick as cycle increases reflecting the rapid propagation of damage. The frequency of AE activities displays different proportions that is impacted by the FT cycle. The percentage of the low-frequency and high-frequency signals is relatively high and low respectively for a rock experiencing more FT cycles. The theoretical description of F-T influence coupled with mechanical performance are performed. Based on acoustic emission energy, a damage evolution model considering the coupling effect of freezing-thawing cycle and cyclic load is proposed, which can fit the experimental data well. A series of CT images reveal the influence of freeze-thaw on rock failure modes. Typical failure modes of double shear coalescence, single shear coalescence and single tensile coalescence failure modes were identified from the reconstructured CT images.