A number of instability problems in rock engineering projects are caused by crack
propagation. However, crack growth mechanisms from 3-dimentional flaw are not fully understood,
in particular for 3-D flaw case with varied dipping angle. This study focuses on 3-D surface flaw
using real rock specimens containing a flaw with varied inclination angle α from axial loading and
dipping angle γ from specimen surface under uniaxial compression. Acoustic emission technique
was used for tracing the initiation and growth of micro-cracks inside of specimen. It was found that
crack growth process is affected by the dipping angle γ of the 3-D flaw. When dipping angle γ ≠ 90º,
the thickness of rock above the flaw plane is thinner than that of below the flaw plane. As a result,
compressive crack and wing crack initiated easily from the thinner flaw tips. And, the normalized
stress for crack initiation σi /σc, AE events and the AE energy for crack growth decreases with the
dipping angle γ. However, for γ = 90º, the thickness of rock above and below of the flaw tips is the
same, it was observed that anti-wing crack (crack growth direction opposite to wing crack) initiated
first at a certain place away from the flaw tips, then wing crack and compressive crack emerged at
the late stage. For this case, the stress σi /σc, AE events and the AE energy for crack initiation and
propagation are at a high value. Thus, for rock mass contains flaws geometry with small dipping
angle, some problems of crack propagation may be induced easily during excavation.
Numerical modeling of wing crack propagation accounting for fracture contact mechanics
