Strong Ground Pressure Mechanism and Control at the Longwall Top Coal Caving with a Single Key Stratum in Goaf

Table 2

Physical-mechanical parameters of coal rocks and mix ratios of rock similar materials.

Name	Strata thickness (m)	Tensile strength (MPa)	Elastic modulus (GPa)	Cohesion (MPa)	Compressive strength		Bulk density		Mix ratio
					Prototype (MPa)	Model (MPa)	Prototype (kg/m^3)	Model (kg/m^3)	Sand : gypsum : lime
Sandy mudstone	50.0	1.57	6.34	3.6	32.63	0.21	2100	1350	7 : 7 : 3
Siltstone	8.0	4.31	10.52	5.4	86.34	0.55	2550	1640	9 : 5 : 5
Sandy mudstone	12.0	1.57	6.34	3.6	32.63	0.21	2100	1350	7 : 7 : 3
2-2# coal	3.5	1.25	5.44	2.8	10.78	0.07	1300	1300	10 : 5 : 5
Sandy mudstone	19.0	1.57	6.34	3.6	32.63	0.21	2100	1350	7 : 7 : 3
Siltstone	22.0	4.31	10.52	5.4	86.34	0.55	2550	1640	9 : 5 : 5
Sandy mudstone	24.0	1.57	6.34	3.6	32.63	0.21	2100	1350	7 : 7 : 3
4-2# coal	6.5	1.25	5.44	2.8	10.78	0.07	1300	1300	10 : 5 : 5
Sandy mudstone	5.0	1.57	6.34	3.6	32.63	0.21	2100	1350	7 : 7 : 3