Abstract: Constructing the artificial roof is the key and precondition of safe and efficient cut-and-fill mining in underhand drift stoping.Filling strength and reinforcement ratio of the artificial roof are correlative and related to the safety and economics of ore extraction directly.The method of computing the bearing load of the artificial roof is optimized by constructing a multi-layered pressure-arch model.Based on thin plate theory,elastic mechanics theory and the mining technology of underhand drift cut-and-fill stoping,the strength of the backfilling artificial roof is resolved.The design method of reinforced concrete structure is applied to compute the reinforcement ratio of the bearing layer of underhand drift cut-and-fill stoping.The whole scheme design of the artificial roof's strength and reinforcement ratio is presented,and for one gold-silver mine that applied large structural parameter (5 m×5 m),the strength and reinforcement ratio are determined.The thickness of the artificial roof is 2 m,the strength is no less than5 Mpa,bar-mat reinforcement (12mm HRB335) is 300 mm×300 mm,the ratio of reinforcement is 0.106%.The research is instructive and meaningful to constructing the artificial roof and applying underhand drift cut-and-fill mining method safely and efficiently.

Key words: Artificial roof of underhand drift cut-and-fill stopping,Filling strength,Reinforcement ratio, Multi-layered pressure-arch model, Thin plate theory, Reinforced concrete structure