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| Research on the size effect of rock dynamic fracture toughness considering the influence of space-time domain |
| ZHANG Sheng1，2，AN Dingchao1，ZHANG Xulong1，CHEN Zhao1，WANG Zheng1 |
| (1. School of Energy Science and Engineering，Henan Polytechnic University，Jiaozuo，Henan 454001，China；2. Collaborative Innovation Center of Coal Work Safety and Clean High Efficiency Utilization，Jiaozuo，Henan 454001，China) |
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Abstract In order to explore the size effect of rock dynamic fracture toughness，the dynamic split loading test was carried out using the split Hopkinson pressure bar(SHPB) system on the cracked straight-through Brazilian disc(CSTBD) specimens with diameters of 50，100，150 and 205 mm，respectively. The variation of the dynamic fracture toughness with the size of the specimens was analyzed. The length of fracture process zone，the incubation time and the fracture energy of the specimens with different sizes were determined by virtual crack model，theoretical analysis and dynamic finite element method. A method for determining rock dynamic fracture toughness considering space(length of fracture process zone)-time(incubation time of fracture process zone) domain was proposed. At the same time，the digital image correlation method(DICM) was used to monitor the surface of the specimens，and the failure process of the specimens was explored. The results show that the test values of the fracture toughness increase with the size，showing an obvious size effect. The length of fracture process zone and the incubation time increase with the size，indicating that the contribution of the stored energy increases with the size，which is consistent with the size effect of the fracture energy and indirectly explains the reason of the size effect of the fracture toughness. Considering the space-time domain，the size effect of the fracture toughness of larger size specimens(D = 150 mm，D = 205 mm) is reduced. The method to eliminate the size effect from the overall size needs to be further explored. The crack propagation direction of the specimens is from the crack tip to the loading end，and a wedge-shaped failure zone is formed at the loading end.
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2022, Vol. 41 
