Mechanical properties and failure behaviour of anchored granite containing two filled edge-notched fissures in triaxial compression

Abstract

High in-situ stress commonly exists in deep rock engineering and causes great difficulties in underground mining support systems. To elucidate the relationship between the anchoring effect of bolts and confining pressures, triaxial compression tests were performed to study the deformation characteristics, mechanical properties, and failure behaviour of anchored granite with two pre-existing fissures. The results demonstrated that the deformation characteristics or mechanical properties of anchored granite, including triaxial compressive strength, elastic modulus, and stored or dissipated energy, increased with increasing confining pressure under low confining pressures. Rockbolt boreholes significantly weaken the mechanical properties and failure behaviour under high confining pressures and have a negative impact on the peak axial strength and stored or dissipated energy of the anchored granite. The fissure angle and confining pressure have a direct impact on the failure mode of anchored granite. With increasing confining pressures or fissure angles, shear cracks and anti-wing cracks instead of tensile wing cracks are more likely to cause ultimate failure. In addition, four modes of crack coalescence were identified: no coalescence, two types of direct crack coalescence, and indirect crack coalescence.