Study on Mechanical Properties and Damage Evolution Law of Secondary Destruction Induced by Simultaneous Unloading after the Peak of the Curve of Sandstone

Table 1

Basic information of yellow sandstone.

Numbering	Diameter × height (mm)	Mass m ()	Confining pressure σ3 (MPa)	P wave speed (m/s)	Loading and unloading speed (MPa/min)
SZ-24	49.22 × 100.09	438.2	5	3910	1
SZ-5	50.30 × 100.10	434.7	10	3895	1
SZ-10	50.02 × 100.02	436.2	20	3927	1
SZ-21	50.20 × 101.30	436.6	30	3896	1
SZ-18	50.19 × 101.61	436.4	40	3908	1