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| Research on the range of fracture process zone of granite based on
DIC and acoustic emission |
| FU Shuaiyang1，2，LI Haibo1，2，LI Xiaofeng3 |
| (1. State Key Laboratory of Geomechanics and Geotechnical Engineering，Institute of Rock and Soil Mechanics，Chinese Academy of Sciences，Wuhan，Hubei 430071，China；2. University of Chinese Academy of Sciences，Beijing 100049，China；
3. Department of Civil and Mineral Engineering，University of Toronto，Toronto M5S1A4，Canada) |
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Abstract Fracture process zone(FPZ) is easily generated at the crack tip during the fracture process of rock. The geometry feature of FPZ determines the fracture properties and macro-mechanical behavior of rock. It significantly influences the safety and stability of the rock mass in practical engineering. Mode I three-point bending tests using notched semi-circular bend specimens were performed on MTS testing machine to study the nucleation characteristics and evolution process of the FPZ in granites. To understand the FPZ nucleation process at the tip of the mode I crack，the digital image correlation method(DIC) and the acoustic emission(AE) localization were employed. Micro and macro failure behaviors in rocks were obtained. According to the self-programmed acoustic emission signal identification and localization method，the spatial distribution density of AE events and AE energy were obtained. Then the zone and boundary of the micro-scale FPZ were determined. After which the critical strain value εFPZ of the FPZ was obtained in cooperation with the DIC method. The Irwin-Bazant model was utilized to determine the fully developed FPZ length of the sample，and the experimental value was compared with the theoretical one. Combining the wave velocity of the sample，the theoretical solution of the critical crack opening displacement(COD) at the crack end is obtained and compared with the experimental results. The results indicated that：(1) the critical strain value of FPZ of the rocks used in the experiment is about 1.8‰. (2) The theoretical value of the length of FPZ is in good agreement with the experimental value. For the rocks used in the experiment，the theoretical length of the FPZ is 5.2–8.7 mm，and the experimental result is 5–8 mm. (3) The boundary of FPZ can be regarded as the position where the AE energy suddenly changes from high to low along the crack propagation direction and remains at low energy.
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2022, Vol. 41 
