Extended Ultimate-Pit-Limit Methodology for Optimizing Surface-to-Underground Mining Transition in Metal Mines

Table 3

Alternative optimal design for surface-to-underground transition in the Dagushan iron mine.

Size of crown pillar (m)	Depth of open-pit limit (m)	Depth of underground stope roof (m)	Total benefit (million CNY)
55	−330	−385	2733.43
54	−351	−405	3300.66
53	−367	−420	3643.94
52	−383	−435	3888.00
51	−409	−460	4114.02
52	−428	−480	4170.73
51	−459	−510	4058.11
50	−480	−530	3859.73
50	−485 (original design)	−535	3794.52