A Nonlinear Creep Damage Model of Layered Rock under Unloading Condition

Table 1

Triaxial unloading creep test scheme.

Series	/MPa	/MPa	Unloading rate/(MPa/min)
Level 1	60	40	0.5
Level 2	60	35	0.5
Level 3	60	30	0.5
⋯	60	⋯	0.5
Level 7	60	10 (destroy)	0.5