Creep Mechanical Properties of Granite under Combined Axial Compression and Water Pressure and Support Characteristics of Surrounding Rock

Table 3

Reduction coefficient of external water pressure [13].

Level	Groundwater activity state	Influence of groundwater on surrounding rock stability	βe value
1	The cavern is dry or wet	No effect	0∼0.20
2	There is water seepage or dripping along the structural surface	There is filling material on the weathered structural plane, which reduces the shear strength of the structural plane	0.10∼0.40
3	There is a large amount of dripping water, linear water, or water spray along the crack or weak structural plane	Argillaceous weak structural plane has filling material, which reduces its shear strength and softens medium hard rock mass	0.25∼0.60
4	Serious dripping and small amount of water gushing along the weak structural plane	Groundwater washes the filling material in the structural plane, which can bulge out a thin weak layer	0.40∼0.80
5	There is a large amount of water gushing in weak zones such as severe strand water and faults	Groundwater scouring brings out the filling material in the structural plane and separates the rock mass, which can lead to surrounding rock collapse	0.65∼1.00