Influence of Key Strata on the Gas Downward Leakage Law in Dual-System of Coal Seam

Table 1

Physical and mechanical parameters of 1# drill hole column and coal seams.

	Lithology	Thickness (m)	Buried depth (m)	Unit weight (kN·m^-3)	Tensile strength (MPa)	Elastic modulus (GPa)	Key strata location
Jurassic system	Fine-grained sandstone	6.44	346.13	27.00	6.40	44.65
	Siltstone	8.21	354.34	26.04	4.89	37.29
	Coal seam 14	2.90	357.24	14.26	4.20	4.20
	Siltstone	8.57	365.81	26.04	4.89	37.29
	Sandy mudstone	6.48	372.29	26.81	4.40	38.07
	Medium-grained sandstone	4.30	376.59	26.54	5.72	38.90
	Mudstone	4.20	380.79	27.52	2.72	29.40
	Coarse-grained sandstone	3.64	384.43	25.40	2.56	18.28
	Medium-grained sandstone	3.35	387.78	26.54	5.72	38.90
	Mudstone	9.06	396.84	27.52	2.72	29.40
	Fine-grained sandstone	1.60	398.44	27.00	6.40	44.65
	Mudstone	2.03	400.47	27.52	2.72	29.40
	Fine-grained sandstone	4.30	404.77	27.00	6.40	44.65
	Mudstone	17.31	422.08	27.52	2.72	29.40
	Fine-grained sandstone	5.27	427.35	27.00	6.40	44.65
	Siltstone	42.01	469.36	27.52	2.72	29.40	Higher key strata
	Sandy mudstone	7.27	476.63	26.81	4.40	38.07
	Fine-grained sandstone	3.00	479.63	27.00	6.40	44.65
	Sandy mudstone	2.04	481.67	26.81	4.40	38.07
	Coarse-grained sandstone	6.37	488.04	25.40	2.56	18.28
	Coarse sandstone with gravel	4.57	492.61	25.28	3.20	15.33
	Coarse-grained sandstone	3.23	495.84	25.40	2.56	18.28
	Coarse sandstone with gravel	2.80	498.64	25.28	3.20	15.33
	Coarse-grained sandstone	5.54	504.18	25.40	2.56	18.28
	Coarse sandstone with gravel	12.74	516.92	25.28	3.20	15.33	Lower key strata
	Coarse-grained sandstone	5.84	522.76	25.40	2.56	18.28
	Coarse sandstone with gravel	6.97	529.73	25.28	3.20	15.33
	Mudstone	5.20	534.93	27.52	2.72	29.40
Dyas system	Sandy mudstone	3.57	538.50	26.81	4.40	38.07
	Coarse-grained sandstone	6.17	544.67	25.40	2.56	18.28
	Sandy mudstone	4.10	548.77	26.81	4.40	38.07
	Medium-grained sandstone	2.37	551.14	26.54	5.72	38.90
	Coarse-grained sandstone	2.40	553.54	25.40	2.56	18.28
	Sandy mudstone	5.94	559.48	26.81	4.40	38.07
	Coarse-grained sandstone	3.10	562.58	25.40	2.56	18.28
	Mudstone	6.74	569.32	27.52	2.72	29.40
	Sandy mudstone	1.87	571.19	26.81	4.40	38.07
	Coarse-grained sandstone	5.34	576.53	25.40	2.56	18.28
Carboniferous system	Sandy mudstone	1.60	578.13	26.81	4.40	38.07
	Coal seams 3-5	14.05	592.18	14.26	4.20	4.20
	Sandy mudstone	4.00	596.18	26.81	4.40	38.07