13th International Conference on Fracture June 16–21, 2013, Beijing, China -1- A experimental study of I-II-III mixed mode crack fracture of rock under different temperature LI Li-yun1, *, XU Zhi-qiang1, LI Ming-xiu1, LIU Yi1, FAN Chen1, TANG Tie-Wu1, LIU Da-an2 1China University of Mining and Technology, Beijing 100083, China; 2Institute of Geology and Geophysics, Chinese Academy of Science, Beijing 100029, China * Corresponding author: lly@cumtb.edu.cn Abstract A series of critical fracture toughness of two kinds of rock materials under different temperature which varied from -50oC to 240 oC are measured by I-II-III mixed mode fracture experiments adopting atypical three point bending specimens. Relative stress intensity factors of crack initiation are calculated by finite element method. Combining with calculated values, the experiment result shows that, the mixed mode fracture toughness of the rocks decreases with the increase of temperature. The experimental and calculated results can be used in the design of deep underground engineering and disaster prevention and mitigation engineering。 Key words rock crack fracture, I-II-III mixed mode , temperature, experiments, finite element method. 1. Introduction The rock mass whole structure failure in underground engineering is the process of damage, crack fracture and propagation. Deep mining engineering and geological disposal engineering such as nuclear waste, carbon dioxide and garbage deeply buried belong to the underground geotechnical engineering combining with temperature variation. Therefore, the investigation of the propagation behavior of rock crack under different temperature will be very important. Preliminary studies on temperature effect are mainly concentrated in mode I rock crack[1-3], a small amount of studies are concentrated in mixed-mode I-II rock crack[4-7]. About three-dimensional propagation behavior of rock crack which containing mode III stress intensity factor, the authors have done some researches under the room temperature in the recent time [8-9]. But the research about mixed mode I-II-III rock crack fracture coupling with temperature effect, there is almost no published paper, but it has important significance in deep underground engineering, for this mixed mode crack coupling with temperature is the basic existence in deep underground engineering. Consider of this, three point bending I-II-III mixed mode fracture experiments of two kinds of granite were carried out under 6 temperature levels in this paper. The variation law of critical fracture load v.s. temperature was measured. Combined with finite element method (FEM) calculation, the stress intensity factors in crack tip line under the critical load were got. The results of the paper both in experiments and in numerical calculation can provide a valuable reference for the deep underground engineering design and disaster prevention engineering design. 2. Experimental investigation
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