Investigation on the Movement and Fracture Characteristics of an Extra-Thick Hard Roof during Longwall Panel Extraction in the Yima Mining Area, China

Table 1

The generalized stratigraphy and geotechnical parameters.

Rock strata	Thickness (m)			Density (kg·m^−3)	UCS (MPa)
	Max.	Min.	Mean
Conglomerate rock	580.50	96.35	550.00	2 700	45
Mudstone	42.20	4.40	24.00	2 170	30
Sandstone	27.00	0.00	10.00	2 200	27
No. 2 coal seam	37.48	5.59	9.60	1 440	16
Siltstone	32.81	0.30	26.00	2 600	30