Abstract：Direct tensile experiments of rock-like materials with surface crack have been carried out. And the influences of the inclination angle of the surface crack on the peak strength and fracture process have been analyzed. Because the inclined surface cracks are under the mixed mode I，II，III loading conditions，in order to study the fracture criterion of the surface crack the stress intensity factors of the front of half-circular surface crack are calculated according to fracture analysis code–3D(FRANC3D). And the law between I，II，III mode stress intensity factors and the orientation angle are analyzed. Then the initial angles are predicted according to the minimum strain energy density criterion，the maximum circumferential stress criterion and the revised maximum circumferential stress criterion. The contrast with the experimental results show that the revised maximum circumference stress criterion，which included mode–III stress intensity factor is fit to predict the initial angle of the inclined surface crack.
2011, Vol. 30 
