Evolution Mechanism of Interconnected Vertical Fractures in the Overburden of Longwall Coal Mining

Table 2

Compression-tension ratio of common rocks [37].

Test no.	Field naming	Uniaxial compressive strength			Uniaxial tensile strength			Compression-tension ratio
		Natural	Dry	Saturated	Natural	Dry	Saturated	Natural	Dry	Saturated
		MPa						/
ZK33	Granite	/	88.6	44.9	/	8.51	4.14		10.4	10.8
ZK34	Granite	/	82.3	39.6	/	6.27	4.59		13.1	8.6
ZK35	Granite	/	85.4	44.7	/	9.14	5.22		9.3	8.6
ZK36	Granite	/	83.1	36	/	8.93	5.96		9.3	6.0
ZK1	Coarse sandstone	72.6	83.1	25.7	4.75	6.43	2.94	15.3	12.9	8.7
ZK2	Carboniferous coarse sandstone	43.5	52.8	37.4	4.21	5.22	3.26	10.3	10.1	11.5
ZK3	Fine sandstone	21.4	39.1	20.4	4.03	5.12	2.01	5.3	7.6	10.1
ZK4	Carbonaceous fine sandstone	37.3	53.9	32.8	3.18	5.64	1.68	11.7	9.6	19.5
ZK5	Coarse sandstone	76.3	99.3	51.8	7.52	8.79	4.59	10.1	11.3	11.3
ZK6	Carbonaceous siltstone	27.9	37.2	2.18	2.14	3.21	0.71	13.0	11.6	3.1
ZK7	Siltstone	25.3	43.7	12.7	2.83	4.36	1.97	8.9	10.0	6.4
ZK8	Fine sandstone	92.7	97.8	20.6	6.56	9.54	3.02	14.1	10.3	6.8
ZK9	Coarse sandstone	49.1	84.1	26.5	3.48	6.37	2	14.1	13.2	13.3
ZK10	Conglomerate	43.8	85.1	36.4	5	6.65	2.41	8.8	12.8	15.1
ZK11	Carboniferous siltstone	44.6	87.2	28.9	6.26	8.86	3.55	7.1	9.8	8.1
ZK12	Siltstone	32.9	52.7	21.5	3.9	4.93	2.17	8.4	10.7	9.9
ZK13	Carbonous siltstone	24.5	45	21.8	3.51	4.47	2.79	7.0	10.1	7.8
ZK14	Carbonous siltstone	9.09	13.3	5.09	1.03	1.32	0.59	8.8	10.1	8.6
ZK15	Carbonous siltstone	7.63	35.2	2.12	1.75	2.98	0.32	4.4	11.8	6.6
ZK16	Coarse sandstone	69.6	87.3	43.5	4.88	7.66	4.13	14.3	11.4	10.5