Study on Fracture and Stress Evolution Characteristics of Ultra-Thick Hard Sandstone Roof in the Fully Mechanized Mining Face with Large Mining Height: A Case Study of Xiaojihan Coal Mine in Western China

Table 4

Mechanical parameters of coal and rock mass in numerical model.

Rock type	Thickness (m)	Density (KN/m^3)	Elastic module (GPa)	Poisson’s ratio	Cohesion (MPa)	Fractional angle (°)
Mudstone	6	18	9.8	0.32	1.4	20
Sandstone	14	22	15	0.28	11.4	23
Mudstone	12	19	10.2	0.32	1.4	20
Fine sandstone	12	20	16	0.29	5.9	30
Mudstone	3	19	10.2	0.32	1.4	20
Siltite	7	21	14.4	0.29	10.2	31
Mudstone	5	19	9.6	0.32	1.4	19
Medium-grained stone	23	26	15.2	0.30	7.9	30
Siltite	8	23	14.4	0.29	10.2	29
Medium-grained stone	19.8	25	15.2	0.33	7.9	31
Fine sandstone	7	23	16	0.33	5.9	31
Coal	4.5	14	2.2	0.30	4.8	13
Mudstone	3	18	9.8	0.32	1.4	20
Sandstone	11	24	14.2	0.28	11.0	23