Research of the Backfill Body Compaction Ratio Based on Upward Backfill Safety Mining of the Close-Distance Coal Seam Group

Table 1

Method for judging the feasibility of upward backfill.

Method	Formula	Variable	Meaning	Literature source	Comparison index
I			The ratio of the distance between the upper and lower coal seams to the thickness of the lower coal seam	Zhang [14], Xu [20]
II			Height of the caving zone
III			Seam spacing necessary for upward mining
IV			Seam spacing necessary for upward mining