Mechanical properties and fracture behavior of flawed granite under dynamic loading: Fid-Bau Portal

Mechanical properties and fracture behavior of flawed granite under dynamic loading

Xu, Jinhui / Kang, Yong / Liu, Feng / Liu, Yiwei / Wang, Zuan / Wang, Xiaochuan

Abstract The dynamic mechanical properties and fracture process of rock materials with pre-existing flaws are crucial for explaining the failure mechanisms of deeply buried constructions. To investigate the mechanical properties and fracture behavior of flawed granite subjected to dynamic loading, dynamic experiments were conducted on granite specimens by using a split-Hopkinson pressure bar test system. The effects of strain rate and flaw inclination angle on granite strength and deformation properties were investigated. The white patch initiation, micro-crack propagation, and failure mode were analyzed using a high-speed camera and digital image correlation technology. The fracture mechanism was revealed by quantitatively analyzing the localized strain field and fractal features. The results demonstrated that the dynamic strength and deformation of the flawed specimen compared to an intact specimen had more obvious strain rate effects. The development of white patches determined the direction and path of crack propagation. The fracture process and shear-tensile failure mode were closely correlated with the evolution of the strain field. Furthermore, the fractal characteristics indicated that a larger fractal dimension resulted in a more complex fracture distribution and mixed failure modes. These results provide a reference for the construction design and safety control of deep rock engineering.

Highlights • Dynamic properties of flawed specimens are more strain rate dependent than the intact specimens. • The number and complexity of white patches increase with increasing inclination angle. • The white patch is the sign of crack initiation, and it determines the direction and path of crack propagation. • The strain concentration zone is closely correlated with the fracture process and failure mode. • The fracture distribution is positively relative to the fractal dimension, and it is more complicated at high strain rates.