Numerical and Similarity Simulation Study on the Protection Effect of Composite Protective Layer Mining with Gently Inclined Thick Coal Seam

Table 1

Mechanical parameters for the prototype coal-rock seam.

Lithology	Compressive strength (MPa)	Cohesion (MPa)	Friction angle (°)	Poisson’s ratio	Elastic modulus (GPa)
Sandy mudstone	11.56	3.71	24.6	0.31	1.57
Medium-course sandstone	20.17	6.35	25.6	0.27	1.23
Sandy mudstone	11.56	3.71	24.6	0.31	1.57
Medium-course sandstone	20.17	6.35	25.6	0.27	1.23
Sandy mudstone	11.56	3.71	24.6	0.31	1.57
Mudstone	6.27	2	24.9	0.14	1.07
No. 2-1 coal seam	3.8	1.27	22.3	0.21	0.86
Sandy mudstone	11.56	3.71	24.6	0.31	1.57
Medium-course sandstone	20.17	6.35	25.6	0.27	1.23
Sandy mudstone	11.56	3.71	24.6	0.31	1.57
Medium-course sandstone	20.17	6.35	25.6	0.27	1.23
Limestone 2	64.97	17.97	32.1	0.2	6.05
No. 1-7 coal seam	3.04	1.02	22.3	0.21	0.86
Sandy mudstone	7.17	2.3	24.6	0.31	1.57
Medium-course sandstone	20.17	6.35	25.6	0.27	1.23
Sandy mudstone	11.56	3.71	24.6	0.31	1.57
Medium-course sandstone	20.17	6.35	25.6	0.27	1.23
Sandy mudstone	11.56	3.71	24.6	0.31	1.57
Limestone 1	64.97	17.97	32.1	0.2	6.05
3307B protective layer	11.56	3.71	24.6	0.31	1.57
Sandy mudstone	11.56	3.71	24.6	0.31	1.57
No. 1-8 coal seam	3.8	1.27	22.3	0.21	0.86
Medium-course sandstone	20.17	6.35	25.6	0.27	1.23
Sandy mudstone	11.56	3.71	24.6	0.31	1.57
Limestone	64.97	17.97	32.1	0.2	6.05
Sandy mudstone	11.56	3.71	24.6	0.31	1.57