Experimental study for subcritical crack growth of transverse isotropy rock

Subcritical crack growth in transverse isotropy slate was investigated experimentally using constant displacement load relaxation method on MTS insight electronic tensile testing machine. The relationship between the stress intensity factor KI and the crack velocity v and the fracture toughness KIC were obtained by the test. The growth behavior of subcritical crack was connected with different joint inclination angles. The results show that lgKI-lgv relationships are in accordance with linear rule, i.e. when the joint inclination angle α is in the range of 0° to 45°,the regression parameter a increases with the increase of α and the regression parameter b decreases with the increase of α, and when the joint inclination angle α is in the range of 45° to 90°, a decreases with the increase of α and the regression parameter b is just the opposite. The change laws of subcritical crack growth parameters A and n are the same with those of the factors a and b, respectively. Both the fracture toughness KIC and the relaxation maximum load Pmax obey the "U"shaped parabolic distribution. When α is in the range of 0° to 45°, these two factors decrease with the increase of α,and when α is in the range of 45° to 90°,these two factors increase with the increase of α. In addition, the two factors reach the maximum value when the angle is 0° and reach the minimum when the angle is 45. © 2017, Central South University Press. All right reserved.