Influence of Valleys Terrain on Pressure of Fully Mechanized Working Faces in Shallow Coal Seams

Table 2

Missing statistics of the main key stratum in the overlying strata of the No. 3 Panel from the Huojitu Coal Mine.

Working face	Valley no.	Relative position of interface between bottom of key stratum and valley bottom (m)	Condition
21304	1	+22.36	Missing
	2	+27.13	Missing
	3	+26.11	Missing
21305	1	+30.01	Missing
	2	+12.97	Missing
	3	+2.91	Missing
	4	−2.87	Not missing
21306	1	−4.12	Not missing
	2	+5.01	Missing