Abstract
The experimental system of 3D digital image correlation (3D-DIC) is set up to eliminate a certain extent of out-of-plane motion for accurate measuring the full-field strain field during crack propagation, and the effect of blast loading rates of fracture behavior of granite rectangle plate with a crack (GRPC) is investigated. The experimental results indicated that the maximum values of the strain concentration zone do not fully represent the crack tip during the whole process of crack propagation. The axial strain threshold value tip (ASTVT) plotting with lines and coordinate contours corresponding with the actual crack at the shooting area can be used to describe the position of the crack. The axial strain 1.3% is more practical to obtain crack velocity and average crack velocity, and the average crack velocity decreases as the blast loading rates increase. Through observing the relationship between crack width and time, it can be found that there are three stages, and the crack width increases as the blast loading rates increase.
Highlights
Blasting is one of the main rock breaking methods that is widely used in rock excavation, and rock blasting fragmentation time is an important component of the delay time of differential blasting, which is related to the fracture velocity and fracture process of rock [1]
Based on the International Society for Rock Mechanics (ISRM) standards, parallelism and perpendicularity of two end planes are smaller than 0.2 mm, cylindrical specimens cut into 50 × 100 mm and 50 × 25 mm for uniaxial static compressive strength tests and static tensile strength tests are cored from the same rock block without obvious joint
It can be found that axial strain threshold value tip (ASTVT) plotting with lines in test 3 matches well with the actual crack position, and the trajectory of ASTVT is consistent with the crack morphology for test 1 and test 3
Summary
Blasting is one of the main rock breaking methods that is widely used in rock excavation, and rock blasting fragmentation time is an important component of the delay time of differential blasting, which is related to the fracture velocity and fracture process of rock [1]. Granites are a common rock type in the open bench blasting, and thermal shocks, frost action, and salt crystallization leading to cracking of granites are widely studied [2,3,4,5]; on the other hand, the fracture characteristics of granite under explosive dynamic loading are one of the core problems of rock dynamic mechanics, and the research in this area has practical application significance [6]. Liu et al [9] proposed a single internal crack circular disc (SICCD) specimen with poly methyl methacrylatemethacrylic acid (PMMA) to investigate the fracture toughness parameters and propagation behavior of mode-I crack under blasting load by using crack propagation gauges (CPGs); the crack propagation velocity, dynamic initiation toughness, propagation toughness, and fracture parameters of mode-I crack were obtained through the experimental-numerical method. Sun et al [7] introduced symmetry experimental model with PMMA to implement the visualized positioning of the crack tip and obtained the more accurate record of full-field strain, and it is concluded that the maximum strain value point in
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