Identification of Initial Crack and Fracture Development Monitoring under Uniaxial Compression of Coal with High Bump Proneness

Table 2

The initial surface crack of each coal sample.

	Crack no.	Position (mm)	Direction	Length (mm)	Width (mm)	Thickness (mm)
1	1	Top 5.2	Horizontal	23.8	13.2	0.25
2	1	Bottom 12.3	Horizontal 30°	25.8	9.5	0.96
3	1	Bottom 38	Horizontal 45°	27.6	13.8	0.62
	2	Inclined	Vertical	25.3	19.3	0.78
4	1	Bottom 5	Horizontal	19.2	17	0.36
5	1	Top 45	Horizontal	33.1	16.4	0.40
	2	Top	Vertical	24.3	13.2	0.42
6	1	Top 55	Horizontal	19.5	17.9	1.00
	2	Top 50	Horizontal	27.4	16.3	0.3
	3	Top 10	Vertical	21.3	10.1	0.22
7	1	Top-middle	Vertical	38.3	15.3	0.1
8	1	Top-middle	Vertical	48.3	9.3	0.3
	2	Middle	Horizontal 80°	30.1	18.2	0.25
9	1	Bottom 10	Horizontal	26.3	16.1	0.5
	2	Bottom 20	Horizontal	28.4	15.0	0.5
	3	Bottom 35	Horizontal	23.4	21.5	0.52
	2	Bottom	Vertical	51.3	22.4	0.28
	3	Top 15	Horizontal	18.4	16.7	0.4
	4	Top 17	Vertical	23.4	8.4	0.23