Research on Characteristic Stress and Constitutive Equation of Confined Sandstone during Damage Evolution Based on Energy Evolution Analysis

Table 1

Comparison of characteristic stress determined by the three methods.

Confining stress (MPa)	Peak stress σp (MPa)	Characteristic stress (MPa)						Difference (MPa)			Ratio of characteristic stress to σci (%)
		EPM			LSM		VSM				EPM			LSM		VSM
		σcc	σci	σcd	σcc	σci	σcd	σcc	σci	σcd	σcc/σp	σci/σp	σcd/σp	σcc/σp	σci/σp	σcd/σp
5	126.00	26.80	52.15	87.80	28.40	52.25	85.80	1.60	0.10	−2.0	21.27	41.39	69.68	22.54	41.47	68.10
10	160.00	20.35	62.70	100.00	22.40	65.30	105.00	2.05	2.60	5.00	12.72	39.19	62.50	14.00	40.81	65.63
20	194.00	18.70	77.00	135.50	21.82	77.50	137.00	3.12	0.50	1.50	9.64	39.69	69.85	11.25	39.95	70.62
30	234.00	12.15	90.00	165.50	15.80	91.00	170.00	3.65	1.00	4.50	5.19	38.46	70.73	6.75	38.89	72.65
Mean	—	—	—	—	—	—	—	2.61	1.05	2.25	—	39.68	68.19	—	40.28	69.25