Experimental and numerical study on the fracture process zone and fracture toughness determination for ISRM-suggested semi-circular bend rock specimen

The semi-circular bend (SCB) method suggested by International Society for Rock Mechanics (ISRM) is demonstrated to yield much conservative mode I fracture toughness. A large fracture process zone observed by both acoustic emission (AE) monitoring and numerical modeling is analyzed to be responsible for that phenomenon. Using numerically simulated effective crack lengths at the peak-load stage in the experiments, the measured toughness values are close to the level I fracture toughness. In addition, numerically simulated K-resistance curves are demonstrated to have great potential for determining the fracture toughness at the level II. (C) 2016 Elsevier Ltd. All rights reserved.