The initiation criterion for open-crack considering fissured water under biaxial compression

Abstract

Fissured rock is under compression-shear load for a long time in the geotechnical engineering, while the blunt crack tip and fissured water also make the compression-shear fracture mechanism of the open-crack more complicated. So, the profound study on the distribution of the stress at the open-crack tip is made and the open-crack initiation criterion under hydrostatic and confining pressure is also established. First of all, according to Muskhelishvili's tensile stress hypothesis, the stress intensity factor KI under compression is studied and the stress field at the open-crack tip is modified, which involves the curvature radius ρ, high-order and non-singular terms, then the revised maximum tangential stress (MTS) criterion is proposed. Second, the effect of the curvature radius ρ and half-length a on KI and the initiation angle θ are discussed respectively. It is found that KI increases with increasing ρ and decreasing a. It is also found that when the loading angle β = 0 ∼ 45°, the initiation angle θ increases with decreasing ρ and increasing a. In the range of β = 45 ∼ 90°, the initiation angle θ is insensitive to ρ, a and tends to converge. The initiation stress goes down firstly in the range of β = 0 ∼ 50° and then gradually goes up with increasing β. Third, the model for the open-crack filled with fissured water under biaxial compression is discussed. The trend of the wing-crack initiation angle θ is similar to that under uniaxial compression with increasing β and a, but the upper limit of θ decreases with increasing the hydrostatic pressure pw. Finally, the revised criterion is preliminarily verified with the indoor test.