Mechanical Response of Castlegate Sandstone under Hydrostatic Cyclic Loading

Table 3

Values of the bulk modulus measured during hydrostatic loading at test inception and unloading at test ending. Unloading is the volumetric strain calculated from a third-degree polynomial best fit of the unloading curve. Test duration indicates the number of days each test lasted. Cycle loading rate represents the rate of effective stress change during cyclic loading.

Sample number	Loading (GPa)	Unloading (GPa)	Cycle loading rate (MPa/hr)	Unloading (%)
CG_001	2.38	3.18	0.86	0.179
CG_003	2.88	4.50	0.86	0.540
CG_004	2.61	5.24	0.86	0.449
CG_005	2.14	5.03	1.21	0.752
CG_006	2.27	4.40	2.42	0.652
CG_007	2.21	3.40	2.41	0.282
CG_009	2.64	5.52	—	0.025
CG_010	2.27	4.94	4.14	0.266