Study on ductile fracture mechanism of coal and rock mass based on cohesive crack model
YANG Jianfeng1，2，CHAI Jing1，2，ZHANG Dingding1，2，MA Zhe1，LIU Yongliang1
(1. College of Energy Engineering，Xi?an University of Science and Technology，Xi?an，Shaanxi 710054，China；2. Key Laboratory of Western Mine Exploitation and Hazard Prevention，Ministry of Education，Xi?an University of Science and Technology，Xi?an，Shaanxi 710054，China)
Abstract：Due to the traditional linear elastic fracture theory is no longer applicable to characterize the ductile fracture characteristics of coal and rock mass，the PPR unified potential-based cohesive crack model for mixed mode I/II fractures in mudstones and coals by using semi-circular specimen under three-point bending(SCB) tests and punch-through shear(PTS) tests to describe the I/II mixed crack propagation behavior in coal and rock mass. The experimental results show that the increase of crack tip opening displacement(CTOD) in the nonlinear damage process after load peak of the coal SCB specimen was 3.48 times that of the mudstone specimen. Meanwhile，the digital image correlation method(DIC) was used to measure the length of fracture process zone(FPZ) in the coal and mudstone specimens. The FPZ length of the coal SCB specimen was about 6.21 mm，which was 2.75 times that of the mudstone specimen. And the FPZ length of the coal SCB specimen can significantly cause a ductile fracture failure of the coal body. During the punch-through shear(PTS) experiments，the average maximum tangential displacement of PTS coal specimen is 0.055 mm，which is significantly larger than that of mudstone specimen，and the characteristics of the type II ductile fracture of PTS coal specimen are significantly higher than that of mudstone specimen. In addition，the pure mode II fracture energy of the two types of samples is higher than that of the pure mode I fracture energy，indicating that the occurrence of mode II shear fracture consumes more energy. Finally，the mixed mode I/II single-edge notched beam(SENB) through three-point bending test. And the corresponding numerical simulation were carried out for the coal and mudstone，which the numerical simulation process is based on the PPR cohesive crack model and the linear elastic fracture theory，respectively. Through a comparison with the linear elastic fracture theory，the numerical simulation results based on the PPR cohesive crack model are more in line with the experimental results. Therefore，the cohesive crack model that built in the study is suitable for characterizing the mixed mode I/II ductile fracture behavior of coal-rock mass.
杨健锋1，2，柴 敬1，2，张丁丁1，2，马 哲1，刘永亮1. 基于黏聚裂纹模型的煤岩体韧性断裂机制研究[J]. 岩石力学与工程学报, 2021, 40(S2): 3014-3023.
YANG Jianfeng1，2，CHAI Jing1，2，ZHANG Dingding1，2，MA Zhe1，LIU Yongliang1. Study on ductile fracture mechanism of coal and rock mass based on cohesive crack model. , 2021, 40(S2): 3014-3023.
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2021, Vol. 40 
