$K_{\mathrm{IC}}, K_{\mathrm{IIC}}$	Mode I and mode II fracture toughness
${\rho }_{\mathrm{r}}, E_{\mathrm{r}},{\nu }_{\mathrm{r}}$	Density, elastic modulus, and Poisson’s ratio of rock
${\rho }_{\mathrm{s}}, E_{\mathrm{s}}, {\nu }_{\mathrm{s}}$	Density, elastic modulus, and Poisson’s ratio of steel
$a, W, B$	Notch depth, side length, and thickness of specimen
$\beta$	Loading angle of specimen
$2a/W$	Initial notch length ratio
$P_{\mathrm{n}}, P_{\mathrm{s}}, P_{\mathrm{c}}$	Normal force, tangential force, and peak load
$\theta$	Angle of potential fracture plane
$u_1, v_1$	Normal displacement perpendicular and tangential displacement parallel to fracture
${\epsilon }_{\mathrm{xy}}, {\epsilon }_{\mathrm{yy}}, {\epsilon }_{\mathrm{xx}}$	Strain components in cartesian coordinate system
$K_{\mathrm{I}}, K_{\mathrm{II}}$	Mode I and mode II stress intensity factor on the original crack plane
$Y_{\mathrm{I}}, Y_{\mathrm{II}}$	Mode I and mode II dimensionless shape factor
${\sigma }_r, {\sigma }_{\theta }, {\tau }_{r\theta }$	Stress components in polar coordinate system around crack tip
$K_{\mathrm{I}}\left(\theta \right), K_{\mathrm{II}}\left(\theta \right)$	Mode I and mode II stress intensity factors on θ plane
$k_{\alpha }$	Loading ratio, $K_{\mathrm{I}}/K_{\mathrm{II}}$
${\sigma }_{\mathrm{xx}}, {\sigma }_{\mathrm{yy}}, {\tau }_{\mathrm{xy}}$	Stress components in cartesian coordinate system
${\sigma }_{\mathrm{n}}$	Normal stress on θ plane
$c$	Shear strength when the compressive stress is zero
$f$	Friction coefficient
$\varphi$	Fracture angle under uniaxial compression
$K_{\mathrm{IIC}}^{\prime }\left(\theta \right)$	Fracture toughness considering the effect of normal compressive stress
${\theta }_{\mathrm{MC}}$	Initiation angle of compressive-shear fracture
$Q_{\mathrm{e}}$	Equivalent shear load
$Q_{\mathrm{e}}^{\prime }$	Modified equivalent shear load