Investigation on the Ground Pressure Induced by Hard Roof Fracturing at Different Layers during Extra Thick Coal Seam Mining

Table 5

Range of stress influence before and after strata fracturing.

	Before breaking		After breaking
	Peak stress (MPa)	Influence range (m)	Action range (m)	Stress variation (MPa)
KS1	30	45	﹥0	24 ⟶ 28
KS2	33	60	﹤15	—
KS3	25	60	﹥15	36 ⟶ 43
KS4	34	120	﹤30	—
KS5	33	105	﹥15	—