Study on Reasonable Layout of Upper Protective Layer for Prevention Rock Burst under Coal Seam Group with Close Quarters Conditions

Table 1

The coal seam and strata assignment parameters of this 3D model.

Types	Density (kg·m^−3)	Bulk modulus (GPa)	Shear modulus (GPa)	Cohesion (MPa)	Internal friction angle (°)	Thickness (m)
Mudstone fine sandstone	2600	16.3	13.8	9.8	26	18.5
Gritstone	2690	19.5	20.5	14.3	31	23.0
Sandy mudstone	2730	13.4	13.1	28.8	20	15.5
Fine sandstone	2800	22.5	21.6	18.7	32	16.0
Mudstone	2600	16.3	13.8	9.8	26	5.0
Coal seam #1	1360	1.6	1.7	1.1	35	1.3
Sandy mudstone	2730	13.4	13.1	28.8	20	10.3
Coal seam #2	1360	1.6	1.7	1.1	35	2.2
Siltstone	2650	17.8	18.1	15.2	27	9.5
Mudstone	2600	16.3	13.8	9.8	26	15.5
Siltstone	2650	17.8	18.1	15.2	27	13.2