The Stability Evaluation of Shaft during Drastic Drawdown Dewatering of Alluvium

Table 5

Prediction results of strata compression a month near the main and auxiliary shafts in the Zhuxianzhuang Coal Mine.

Location	Lithology	Buried depth (m)	Thickness (m)	Water level drop (m)	Formation compression ratio (mm·m^−2)	Formation compression (mm)	Strata compression (mm)
Main shaft	Silt	231.60–236.50	4.90	114	0.081	45.25	241.22
	Clay sand	236.50–242.80	6.30	114	0.081	58.17
	Clay	242.80–246.20	3.40	114	0.032	12.40
	Gravel	246.20–257.20	11.00	114	0.100	125.40
Auxiliary shaft	Clay sand	237.51–243.03	5.52	114	0.081	50.97	292.48
	Clay sand	243.03–251.11	8.08	114	0.081	74.61
	Gravel	251.11–265.75	14.64	114	0.100	166.90