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Computers and Concrete
  Volume 20, Number 1, July 2017, pages 039-47

Direct and indirect methods for determination of mode I fracture toughness using PFC2D
Vahab Sarfarazi, Hadi Haeri and Alireza Bagher Shemirani

    In this paper, mode I fracture toughness of rock was determined by direct and indirect methods using Particle Flow Code simulation. Direct methods are compaction tension (CT) test and hollow centre cracked quadratic sample (HCCQS). Indirect methods are notched Brazilian disk (NBD) specimen, the semi-circular bend (SCB) specimen, hollow centre cracked disc (HCCD), the single edge-notched round bar in bending (SENRBB) specimen and edge notched disk (END). It was determined that which one of indirect fracture toughness values is close to direct one. For this purpose, initially calibration of PFC was undertaken with respect to data obtained from Brazilian laboratory tests to ensure the conformity of the simulated numerical models response. Furthermore, the simulated models in five introduced indirect tests were cross checked with the results from direct tests. By using numerical testing, the failure process was visually observed. Discrete element simulations demonstrated that the macro fractures in models are caused by microscopic tensile breakages on large numbers of bonded discs. Mode I fracture toughness of rock in direct test was less than other tests results. Fracture toughness resulted from semi-circular bend specimen test was close to direct test results. Therefore semi-circular bend specimen can be a proper test for determination of Mode I fracture toughness of rock in absence of direct test.
Key Words
    tensile strength; direct test; flexural test; double punch tensile test and ring test
Vahab Sarfarazi: Department of Mining Engineering, Hamedan University of Technology, Hamedan, Iran
Hadi Haeri: Department of Civil Engineering, Aria University of Sciences and Sustainability, Tehran, Iran
Alireza Bagher Shemirani:
1) Department of Civil Engineering, SADRA Institute of Higher Education, Tehran, Iran
2) Department of Civil Engineering, Sharif University of Technology, Tehran, Iran

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