Macroscopic and Mesoscopic Damage Characteristics and Energy Evolution Laws of Rock Mass With Double Arcuate Fractures Under Uniaxial Compression

In order to reveal the influence of double arc-shaped fissure dip angles on the macro-micro failure and energy evolution laws of rock masses, a numerical model of red sandstone was firstly established using the PFC2D. Moreover, mesoscopic parameters of the numerical model were calibrated based on the uniaxial compression tests on intact and single straight fissure red sandstone specimens. Then, particle flow simulation tests of red sandstone with different arc-shaped fissure dip angles were carried out. The results show that the peak strength and elastic modulus both increase with the increase of arc-shaped fissure dip angle alpha, exhibiting an oblique shear-tensile failure pattern. Six types of cracks evolved during the instability and rupture of the rock mass with double arc-shaped fissures. The macroscopic fissures in the rock mass ultimately penetrate along the extension direction of the arc-shaped fissures. As the arc-shaped fissure dip angle alpha increases, the crack evolution is positively correlated with the acoustic emission (AE) of the specimen. When approaching instability failure, the AE ringing count rapidly increases. There is a critical angle limit inflection point for the total energy absorbed by the rock between 60 degrees and 75 degrees, with a total energy increase of about 54%. During instability failure, it is dominated by dissipative energy, with elastic energy as a supplement. This article derived a damage constitutive model of red sandstone with different arc-shaped fissure dip angles, revealing the damage laws of red sandstone under different arc-shaped fissure dip angles.