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 5

Mechanical parameters of contact surface of strata in the model.

Rock type	Normal stiffness (GPa)	Shear stiffness (GPa)	Cohesion (MPa)	Frictional angle (°)	Tensile strength (MPa)
Mudstone	1.0	2.2	0	10	0
Sandstone	2.6	5.8	0	22	0
Mudstone	0.8	2.0	0	10	0
Fine sandstone	3.5	7.4	0	23	0
Mudstone	0.8	2.2	0	10	0
Siltite	3.4	7.0	0	22	0
Mudstone	1.0	2.2	0	12	0
Medium-grained stone	3.6	7.4	0	22	0
Siltite	3.4	7.0	0	20	0
Medium-grained stone	3.6	7.4	0	22	0
Fine sandstone	3.5	7.0	0	23	0
Coal	0.5	2.0	0	16	0
Mudstone	1.0	2.2	0	12	0
Sandstone	3.2	6.8	0	22	0