A Study on the Instability Mechanisms of Coal Pillars in Shallow Coal Seams Group Mining

Table 2

Similar simulation material parameters of the physical model.

Lithology	Strata thickness (m)	Model thickness (cm)	Mix ratio	Material consumption (kg/cm): each layer
				Sand	Gypsum	Calcium carbonate	Coal ash
Aeolian sand	18	9	Aeolian sand	9.6
Loess	2	1	Sand : loess	3.2	6.4
Red clay	64	32	Sand : red clay	3.2	6.4
Fine sandstone	16	8	837	8.53	0.32	0.747
Medium-grained sandstone	6	3	837	8.53	0.32	0.747
Medium-grained sandstone	8	4	828	8.53	0.213	0.853
Coal no. 3^−1	3	1.5	20 : 1 : 5 : 20	3.39	0.17	0.17	3.39
Silty fine sand	4	2	937	8.64	0.288	0.672
Silty fine sand	5	2.5	937	8.64	0.288	0.672
Fine sandstone	10	5	837	8.53	0.32	0.747
Silty fine sand	7	3.5	937	8.64	0.288	0.672
Mud-sandstone	10	5	928	8.64	0.192	0.768
Silty fine sand	4	2	937	8.64	0.288	0.672
Coal no. 4^−2	4	2	20 : 1 : 5 : 20	3.39	0.17	0.17	3.39
Mud-sandstone	5	2.5	928	8.64	0.192	0.768
Silty fine sand	8	4	937	8.64	0.288	0.672
Mud-sandstone	5	2.5	928	8.64	0.192	0.768
Silty fine sand	12	6	937	8.64	0.288	0.672
Fine sandstone	6	3	837	8.53	0.32	0.747
Medium-grained sandstone	16	8	837	8.53	0.32	0.747
Silty fine sand	8	4	937	8.64	0.288	0.672
Medium-grained sandstone	3	1.5	837	8.53	0.32	0.747
Coal no. 5^−2	6	3	20 : 1:5 : 20	3.39	0.17	0.17	3.39
Fine sandstone	18	9	837	8.53	0.32	0.747
Silty fine sand	12	6	937	8.64	0.288	0.672
Medium-grained sandstone	9	4.5	837	8.53	0.32	0.747