• The deadman root exhibits a 'curved' shape and a distinct 'floating' state, with a central floating height of ~0.45 m increasing toward the hearth edge.
• Image analysis revealed average deadman voidage of 54.75% (±0.85%) and coke particle size of 21.47 mm (±0.53 mm), with vertical division into slag–coke, iron–coke, and coke–free zones.
• A 'slag + CaS isolation layer' suppresses carburization and is the most limiting factor for deadman coke renewal; renewal time was calculated as 14.74 days.
• The findings provide scientific guidance for low-carbon BF operation and fuel optimization, enabling better control of deadman conditions.