Analysis of the Critical Safety Thickness for Pretreatment of Mined-Out Areas Underlying the Final Slopes of Open-Pit Mines and the Effects of Treatment

Table 3

Statistics of boundary pillar thickness in comparable mines.

Name of mines	Span of mined-out; area/m	Area of mined-out; area/m^2	Safety thickness of crown; pillar/m
Krivoy Rog Mine	15–25	200–600	20–30
Haydargangski Mine	25–30	100–500	15–20
Nuosisiji Chai Mine	—	200–2100	14–16
Niki Torfs Ki Mine	20–25	—	15–30
Datang Mine	20	—	15
Chuanyandong Mine	20–25	—	24
Jinchangyu Mine	>20	—	25
Shirengou iron Mine	20	—	20