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

Table 2

Physical and mechanical properties of similar materials.

Number	Lithology	Compressive strength (KPa)	Thickness (mm)	Material quality (kg)
				Sand	Calcium carbonate	Gypsum
23	Sandy mudstone	86.53	46	28.91	4.05	1.73
22	Medium-grain sandstone	150.97	84	50.25	6.28	6.28
21	Sandy mudstone	86.53	45	28.13	3.94	1.69
20	Medium-grain sandstone	150.97	91	54.75	6.84	6.84
19	Sandy mudstone	86.53	44	27.34	3.83	1.64
18	No.2-1 coal seam	28.5	91	59.88	5.99	2.57
17	Sandy mudstone	86.53	63	39.06	5.47	2.34
16	Medium-grain sandstone	150.97	58	34.5	4.31	4.31
15	Sandy mudstone	86.53	91	57.03	7.98	3.42
14	Medium-grain sandstone	150.97	38	22.5	2.81	2.81
13	Limestone 2	486.3	11	6.33	0.63	1.48
12	Sandy mudstone	86.53	19	11.72	1.64	0.7
11	Medium-grain sandstone	150.97	25	15	1.88	1.88
10	Sandy mudstone	86.53	25	15.63	2.19	0.94
9	Medium-grain sandstone	150.97	31	18.75	2.34	2.34
8	Sandy mudstone	86.53	63	39.06	5.47	2.34
7	Limestone 1	486.3	56	31.64	3.16	7.38
6	3307B protective layer	86.53	19	11.72	1.64	0.7
5	Sandy mudstone	86.53	23	14.06	1.97	0.84
4	No.1-8 coal seam	28.5	8	8.2	0.82	0.35
3	Medium-grain sandstone	150.97	20	12	1.5	1.5
2	Limestone	486.3	25	14.06	1.41	3.28
1	Sandy mudstone	86.53	21	13.28	1.86	0.8