Nonlinear Creep Behavior and Viscoelastic-Plastic Constitutive Model of Rock-Concrete Composite Mass

Table 5

Step loading initial creep rate of rock-concrete composite specimens under different confining pressures.

Confining pressure (MPa)	Axial initial creep rate (10^−2/h)
	Instantaneous creep rate	Step 2	Step 3	Step 4	Step 5	Step 6	Step 7
0	15.11	8.93	7.66	5.88	4.42	2.03	27.75 ()
7	24.47	15.85	9.27	7.68	5.86	4.21	30.52 ()
15	38.99	14.2	8.22	6.47	38.82 ()
22	46.32	9.83	8.66	59.27 ()

() is the maximum creep rate of the rock-concrete composite specimen when failure happens.