Failure Mechanism and Control Technology of Thick and Soft Coal Fully Mechanized Caving Roadway under Double Gobs in Close Coal Seams

Table 1

Rock strata properties used in the numerical model.

Rock strata	D (kg·m^−3)	K (GPa)	G (GPa)	Φm (°)	Cm (MPa)	σtm (MPa)
Overlying strata	2600	8.5	6.3	30	1.8	0.7
Sandy mudstone	1800	5.5	3.3	18	1.1	0.4
Fine sandstone	2650	11.5	7.3	33	2.1	0.8
Mudstone	1600	4.5	2.3	16	1	0.3
Limestone	2850	14.5	9.3	38	2.4	1.2
No. 9 coal seam	1400	2.6	1.5	20	0.8	0.4
Mudstone	1600	4.5	2.3	16	1	0.3
No. 10 + 11 coal seam	1400	2.6	1.5	20	0.8	0.4
Sandy mudstone	1800	5.5	3.3	18	1.1	0.4
No. 12 coal seam	1400	2.6	1.5	20	0.8	0.4
Mudstone	1600	4.5	2.3	16	1	0.3
Fine sandstone	2650	11.5	7.3	33	2.1	0.8
Underlying strata	2600	8.5	6.3	30	1.8	0.7

D is the density; K is the bulk modulus; G is the shear modulus; Φ_m is the friction angle; C_m is the cohesion; σ_tm is the tensile strength.