Rock and Soil Mechanics ›› 2020, Vol. 41 ›› Issue (8): 2536-2546.doi: 10.16285/j.rsm.2019.7064

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Study on simulation method of mode I fracture toughness and its meso-influencing factors

WU Shun-chuan1, 2, SUN Wei1, LIU Yang1, CHENG Zi-qiao3, XU Xue-liang4   

  1. 1. Key Laboratory of Ministry of Education for Efficient Mining and Safety of Metal Mine, University of Science and Technology Beijing, Beijing 100083, China 2. Faculty of Land Resource Engineering, Kunming University of Science and Technology, Kunming, Yunnan 650093, China 3. PowerChina Roadbridge Group Co., Ltd., Beijing 100044, China 4. Railway Engineering Research Institute, China Academy of Railway Sciences, Beijing 100081, China
  • Online:2020-08-09 Published:2021-01-22
  • Contact: Sun Wei, male, born in 1987, PhD candidate, focusing on rock fracture mechanics and numerical simulation. E-mail:
  • About author:WU Shun-chuan, male, born in 1969, PhD, Professor, PhD supervisor, focusing on geotechnical disaster prevention and control.
  • Supported by:
    the National Natural Science Foundation of China(51774020, 51934003), the National Key Research and Development Program of China (2017YFC0805300) and the Science and Technology Project of Power China Road Bridge Group Co., Ltd. (LQKY2017-03).

Abstract: The discrete element numerical method has been usually used for some parameter sensitivity analysis of geo-materials in the compression test and the Brazilian splitting test. However, there have been limited studies systematically focusing on mesoscopic influencing factors and 3D fracture process in mode I fracture toughness tests. The 2D discrete element methods cannot reflect the real mechanical behavior of a 3D model. Therefore, a three-dimensional flat joint model (FJM3D) is used in this paper to investigate the effects of microstructure parameters and bond mesoscopic parameters on mode I fracture toughness tests with different notch shapes. The microstructure parameters include the square root of average particle radius ( ), model resolution ( ), and maximum/minimum particle diameter ( ). Bond meso-parameters include average coordination number (CN), slit element fraction ( ), bond tensile strength ( ), bond cohesion ( ), friction coefficient ( ) and friction angle ( ). Results of parameter sensitivity analysis show that the mode I fracture toughness ( ) is positively correlated with , CN, and , and negatively correlated with and . There are no obvious linear relationships between and , , , . In addition, suitable ranges of and are recommended to obtain an appropriate mode I fracture toughness with a low level of variation. Based on the results of parameter sensitivity analysis, the mechanical behaviors of the Kowloon granite with notched semi-circular bend (SCB) and cracked chevron notched semi-circular bend (CCNSCB) specimens are calibrated. The failure process of mode I fracture toughness tests with different notch shapes indicates that the pre-peak and post-peak behaviors of the SCB test is more consistent with the laboratory test.

Key words: mode I fracture toughness, flat-joint model, sensitivity analysis, SCB, CCNSCB