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Abstract Taking Guoluolongwa gold mining for engineering background，based on the elastoplastic theory，the roof of steep thin ore-body stope using medium-deep hole was simplified as high statically indeterminate beam which clamped at both ends，and the mechanics analysis model was established. The roof deformation process was divided into four stages，including elastic stage，the stage plastic zone occurring in the region close to both fixed ends，the stage of both fixed ends broken and becoming simple-support and the stage entire roof becoming plastic flow. The limit span of each stage were 7.38，9.27，9.53 and 10.43 m. Based on Kachanov creep damage theories，this paper made a prediction for the roof fracture time of different stages which were 51.8，15.3 and 14.5 d，and given the function relation between fracture time and roof span which presented substantially cubic function relationships. Finally，according to the on-site stress monitoring，the surrounding rock stress variation in the mining process was analyzed. Surrounding rock stress experienced four stages of slow increase，sharp increase，sharp reduce and slow recovery.
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Received: 25 December 2012
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2014, Vol. 33 
