Experimental Investigation on Sandstone Permeability under Plastic Flow: Permeability Evolution Law with Stress Increment

Table 4

Axial stress, confining pressure, axial strain, and circumferential strain.

State	(MPa)	(MPa)	(%)	(%)	State
A1	10.75	6	0.051	0.022	Pre-peak
A2	37.78	6	0.434	0.033	Pre-peak
A3	56.29	6	0.625	0.040	Pre-peak
A4	76.68	6	0.816	0.100	Pre-peak
A5	97.43	6	1.008	-0.189	Shear yielding
A6	32.92	6	1.372	-1.421	Plastic flow
A7	24.95	7.25	1.324	-1.353	Plastic flow
A8	28.19	5	1.419	-1.300	Plastic flow
A9	18.87	5.66	1.324	-1.307	Plastic flow
A10	23.51	5.9	1.372	-1.332	Plastic flow
A11	10.7	5.9	1.132	-1.123	Plastic flow