Mechanical behavior and damage constitutive model of fractured granite after high-temperature treatment based on 3D digital image correlation

Abstract

A high-temperature environment, cracks, and surface pressure of the rock affect the deep mining of rock masses and nuclear waste disposal. We used the Muskhelishvili theory of fracture mechanics to deduce the fracture stress intensity K of granite samples affected by compressive stress, fractures, and gas–vapor pressure. We established a high-temperature damage constitutive model based on the Burr distribution with an effective stress invariant and the Hoek-Brown (H-B) criterion. Uniaxial mechanical loading and axial compression tests were conducted on granite samples with prefabricated cracks after different high-temperature treatments. Three-dimensional digital image correlation (3D-DIC) was used to analyze the mechanical behavior and strain localization of the fractured rock samples affected by temperature and stress. The results showed that the elastic modulus reached the maximum at the largest inclination angle at different heat treatment temperatures. The surface principal strain increased uniformly before the stress–strain peak, strain localization increased, and the macroscopic cracks in the post-peak region expanded rapidly at different temperatures. The dominant failure mechanism of the granite samples was tensile shear failure at different temperatures and fracture angles. The strain data obtained by placing virtual extenders in different positions and directions on the rock surface are in good agreement with the experimental data. The predicted results of the high-temperature damage constitutive model aligned well with the experimental results, indicating the model accurately predicted the evolution of axial compression fracture of heat-damaged fractured rock. The results provide new insights into the instability mechanism of rock masses in different environments.