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Determination of dynamic rock Mode-I fracture parameters using cracked chevron notched semi-circular bend specimen
Authors:F Dai  K Xia  H Zheng  YX Wang
Affiliation:aDepartment of Civil Engineering and Lassonde Institute, University of Toronto, ON, Canada M5S 1A4;bState Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, China
Abstract:Rock dynamic fractures are common in many geophysical processes and engineering applications. Characterization of rock dynamic fracture properties such as the initiation fracture toughness, the fracture energy, and the fracture velocity, is thus of great importance in rock mechanics. A novel method is proposed in this work to measure dynamic Mode-I rock fracture parameters using a cracked chevron notched semi-circular bend (CCNSCB) specimen loaded by a split Hopkinson pressure bar (SHPB) apparatus. A strain gauge is mounted on the sample surface near the chevron notch to detect the fracture onset, and a laser gap gauge (LGG) is used to monitor the crack surface opening distance (CSOD) during the dynamic test. With dynamic force balance achieved in the tests, the stable–unstable transition of the crack propagation crack is observed and the initiation fracture toughness is calculated from the dynamic peak load. The average dynamic fracture energy as well as the fracture propagation toughness are calculated based on the first law of thermodynamics. The measured dynamic fracture properties of Laurentian granite using CCNSCB method are consistent with those reported in the literature using other methods.
Keywords:Dynamic rock fracture  CCNSCB  Dynamic initiation toughness  Dynamic propagation toughness  Fracture energy  Stable&ndash  unstable crack transition
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