Experimental Investigations on Electrical Charge of Precracked Rock Specimens under Uniaxial Compression

Table 1

Mechanical and electric charging parameters for precracked sandstone samples.

Sample	Precrack inclination angle	Peak strength (MPa)	First charge (pC)	Time at first charge (s)	Stress at first charge (MPa)	Maximum charge (pC)	Secondary crack growth angle
Sample 1	0	34.01	8	253	7.5	50	−70°
Sample 2		37.35	12	263	7.8	52	−62°
Sample 3		38.05	11	272	7.6	48	−50°
Sample 4		44.56	6	277	10.3	51	−52°
Sample 5		44.88	11	283	12.32	49	−90°