Stability Analysis and Fracture Patterns of Hard Main Roof in Longwall Top Coal Caving with Large Mining Height

Table 1

Physical properties of coal and roof in No. 8100 longwall face.

Number		Lithology	Thickness (m)	Volume weight (kg/m3)	Compressive strength (MPa)	Tensile strength (MPa)	Elastic modulus (GPa)	Remark
Roof	17	Sandy conglomerates	80	2520	27.0	7.9	35.2	Key stratum
	16	Fine sandstone	80	2650	107.8	7.9	36.0	Key stratum
	15	Medium sandstone	20	2500	92.6	4.2	28.6
	14	Fine sandstone	40	2650	107.8	7.9	35.2
	13	Coarse sandstone	40	2700	62.3	5.2	20.0
	12	Fine sandstone	40	2650	107.8	7.9	35.2	Key stratum
	11	Siltstone	16	2400	40.7	4.5	23.5
	10	Coarse sandstone	16	2700	62.3	5.2	20.0
	9	Granule conglomerate	4	2600	96.5	4.3	28.7
	8	Fine sandstone	24	2650	107.8	8.2	35.6	Key stratum
	7	Medium-grained sandstone	4	2670	90.2	6.1	29.6
	6	Granule conglomerate	16	2600	96.5	4.3	28.4
	5	Coarse sandstone	8	2700	62.3	4.8	20.3
	4	Fine sandstone	12	2650	107.8	7.8	35.5	Key stratum
	3	Siltstone	6	2400	40.7	5.0	23.6
	2	Pebble conglomerate	8	2500	92.6	7.7	36.2	Key stratum
	1	Sandy mudstone	4	2580	18.5	5.5	18.4
Coal seam		3–5 coal seam	15	1430	14.4	1.5	1.7