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.
On the Application of PDS-FEM for Simulating 3D Wing Crack Growth in Brittle Elastic Solids
