Investigation on Fracture Properties of Surface Cracked Rocks Based on Finite Fracture Mechanics

Abstract

Surface crack, as a major cause of failure, is one of the most common defects for rocks in civil and building engineering structures. It is significant to investigate the fracture properties of surface cracked rocks for the integrity assessment of cracked rock structures. This paper focuses on the fracture behaviors and loads of Brazilian disc rock specimens weakened by a semi-circular surface crack under uniaxial compressive loading. Firstly, three-dimensional (3D) finite element (FE) analysis is conducted to compute the stress intensity factor (SIF) along the front of the semi-circular surface crack in Brazilian disc specimen. Various crack radii and disc thicknesses are considered, and a mathematical relationship between the compressive load and the SIF is established using non-dimensional analysis. Secondly, uniaxial compression tests are conducted to study the effects of crack size and specimen geometry on the fracture properties of surface cracked Brazilian disc rock specimens. Both acoustic emission (AE) and digital image correlation (DIC) techniques are employed to visualize the interior and surface fracture processes of the rock specimen. Finally, a novel theoretical model is proposed to describe the relationship between the fracture load and geometrical parameters of rock specimens based on finite fracture mechanics (FFM). The fracture loads of surface cracked rocks predicted by FFM are compared to those determined by AE and DIC to verify the feasibility and accuracy of the proposed theoretical model. This research provides a significant guidance for fracture assessment of rock structures containing numerous complex surface cracks.

Keywords: Semi-circular surface crack, Brazilian disc, Acoustic emission, Finite fracture mechanics