A study of fracture toughness of granite under impact load using three-dimensional reconstruction and high-speed photogr
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ORIGINAL PAPER
A study of fracture toughness of granite under impact load using three-dimensional reconstruction and high-speed photography techniques Xin Yang 1 & Bo Wu 2,3 & Zhenya Zhang 4 Received: 28 December 2018 / Accepted: 27 October 2020 # Saudi Society for Geosciences 2020
Abstract To study the dynamic fracture toughness of granite under impact load, the dynamic stress intensity factor of I-type cracks was calculated based on a bending test for straight cut grooves in semi-circular discs. With the help of high-speed photography, the process of dynamic fracture failure was studied, and it was found that the cracks propagated rapidly in the dynamic fracture toughness test; initiation of cracks occurred at the crystal boundaries; then, the cracks propagated rapidly, accompanied by intracrystalline and cleavage cracks, followed by convergence, penetration, and ultimately failure. By performing surface three-dimensional reconstruction of sample cross-sections using the LM740 laser confocal microscope, the surface coarseness and surface three-dimensional reconstruction of the granite were determined, and relationships between the surface coarseness and crack propagation velocity and between the dynamic propagation toughness and crack propagation velocity were determined. The research results show that the average value of dynamic fracture toughness of the granite was 4.12 MPa m1/2, the crack propagation velocity during dynamic loading was 400–600 m/s, the maximum dynamic propagation toughness was 14.88 MPa m1/2, and the crack surface coarseness and crack dynamic propagation toughness exhibited exponential increasing trends with the increase in crack propagation velocity. Keywords Dynamic fracture . Semi-circular disc bending . Three-dimensional reconstruction . Granite . High-speed photography
Introduction Dynamic fracture has research significance in geoscience, physics, and engineering science, such as studies of earthquakes, aircraft impact, projectile invasion, rock stratum Responsible Editor: Amjad Kallel * Xin Yang [email protected] * Bo Wu [email protected] 1
School of Civil Engineering, Fujian University of Technology, Fuzhou 350108, China
2
College of Civil Engineering and Architecture, Guangxi University, Nanning 530004, China
3
Key laboratory of Disaster Prevention and Structural Safety of China Ministry of Education, Guangxi University, Nanning 540004, China
4
School of Architecture and Transportation Engineering, Ningbo University of Technology, Ningbo 315211, China
protrusion, and rockburst. All of these involve typical cases of dynamic fracture. It is very difficult to accurately measure dynamic fracture parameters. The fracture mechanism must be sufficiently understood. The parameters measured in such a manner can only be applied in engineering practice. Many scholars have studied the fracture characteristics of rock and attained some achievements. Gao et al. (Gao et al. 2015) studied the dynamic fracture characteristics of rock using the data image correlation technique. Zhou et al. (Z
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