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

Table 6

Parameters of the improved Nishihara model for rock-concrete composite specimens under the confining pressure of 7 MPa.

Axial stress (MPa)	E0 (MPa)	E1 (MPa)	η1 (MPa·h)	η2 (MPa·h)	η3 (MPa·h)	n	R^2
6.60	95.69	1811.38	3266.33				0.954
13.20	102.54	2955.27	7695.78				0.972
19.79	120.30	2744.09	4171.33	39367.41			0.949
26.39	131.99	2883.72	4981.11	51656.32			0.985
32.99	136.86	1786.77	2391.15	56471.60	44143.79		0.986
39.59	156.95	3578.24	5794.31	49782.37	48671.23	1.4	0.945