A Study on the Mechanism of Dynamic Pressure during the Combinatorial Key Strata Rock Column Instability in Shallow Multi-coal Seams

Table 1

Rock mechanical parameters in numerical simulation.

		Material properties of rock layers					Joint properties of rock layers
Lithology	Thickness (m)	ρ kN (m^3)	K (GPa)	G (GPa)	C (MPa)	φ (°)	σT (MPa)	Kn (GPa)	Ks (GPa)	φ (°)
Loess soil	34	1800	3.1	1.78	0.06	12	0.04	3.6	2.2	5
Red soil	43	1800	3.1	1.78	0.06	12	0.04	3.6	2.2	5
Bedrock	6	2400	8.3	5.4	0.9	30	0.6	6.2	4.3	15
Basic roof	8	2550	10.5	7.4	2.2	38	0.7	9.4	6.3	30
Immediate roof	2	2400	6.8	3.9	0.6	30	0.44	5.4	3.5	15
No. 2^–2 seam	2	1300	5.7	3.2	0.4	25	0.5	4.8	3.3	20
Bedrock	20	2400	8.9	6.2	0.9	30	0.6	8.4	5.1	15
Basic roof	8	2550	12.5	8.4	2.2	38	0.7	9.4	6.3	30
Immediate roof	4	2450	6.5	3.9	0.6	30	0.44	5.4	3.5	15
No. 3^−1 seam	2	1350	5.7	3.5	0.4	25	0.5	4.8	3.3	20
Floor strata	16	2500	10.33	8.17	0.9	30	0.6	8.4	5.1	15