Under extra compressive stress, some phenomena of rock spallings and fractures often
exist on rock mass located in sidewalls of underground house and tunnels. It is the reason that the
crack growth and coalescence initiation from original flaws (or faults) in rock mass. In the previous
studies, many researchers took a flaw as a through flaw (2-dimentional model), but the flaws are not
always through the whole rock mass in fact, most of them are only near the surface of rock mass,
These are so named as surface flaws. They belong to three dimensional (2-D) flaws. Now, the
reports on initiation and growth of 3-D surface flaw are few. So, for the investigation on growth
patterns of 3-D surface flaw, a series of samples containing a surface flaw were carried out using
frozen casting resin material at about -30°C temperatures. The surface flaw was made of a polyester
film was used to model a single closed flaw on rock mass. The experimental results show that the
wrapping wing crack (Mode I) initiated at the ends (or tips) of surface flaw first, and then formed a
kinking zone (mixed crack zone) at a certain place at the middle of surface flaw region. Some petal
cracks (Mode III) and shell-shaped cracks (Mode III) would grow at the middle place of flaw. A big
fin crack (Mixed Mode) also emerged in middle of flaw and grown along loading direction. Finally,
a team of large cracking curved faces deformed inside the resin specimen; the whole specimen
would be splitted off by the initiation and growth of the cracks. The reasons lead to the fracture
patterns of 3-D closed surface flaw were provided with brittle fracture mechanics theory in the
article, preliminarily.