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Geomechanics and Engineering
  Volume 15, Number 4, July20 2018, pages 927-935

Direct shear testing of brittle material samples with non-persistent cracks
Hadi Haeri, Vahab Sarfarazi, Alireza Bagher Shemirani and Zheming Zhu

    The mechanical behavior of the brittle material samples containing the internal and edge cracks are studied under direct shear tests. It is tried to investigate the effects of stress interactions and stress intensity factors at the tips of the pre-existing cracks on the failure mechanism of the bridge areas within these cracks. The direct shear tests are carried out on more than 30 various modeled samples each containing the internal cracks (S models) and edge cracks (E models). The visual inspection and a low power microscope are used to monitor the failure mechanisms of the tested samples. The cracks initiation, propagation and coalescences are being visualized in each test and the detected failure surfaces are used to study and measure the characteristics of each surface. These investigations show that as the ratio of the crack area to the total shear surface increases the shear failure mode changes to that of the tensile. When the bridge areas are fixed, the bridge areas in between the edge cracks have less strength than those of internal cracks. However, the results of this study show that for the case of internal cracks as the bridge area is increased, the strength of the material within the bridge area is decreased. It has been shown that the failure mechanism and fracture pattern of the samples depend on the bridge areas because as the bridge area decreases the interactions between the crack tip stress fields increases.
Key Words
    bridge area; failure mechanism; crack propagation; direct shear test
Hadi Haeri and Zheming Zhu: College of Architecture and Environment, Sichuan University, Chengdu 610065, China

Vahab Sarfarazi: Department of Mining Engineering, Hamedan University of Technology, Hamedan, Iran

Alireza Bagher Shemirani: Department of Civil, Water and Environmental Engineering, Shahid Beheshti University, Tehran, Iran

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