Abstract: The No.1 section of No.3 mining stope in An iron mine is located at the bottom of two open pits.For this reason，its overlying rock is thin，and there exists certain risks when implementing pillar recovery.On the basis of a full investigation on the current situation，through the equivalent exposed area method，the stope limits span is determined to be 160 m in this region.An overall pillar recovery program of 'every three mining two" has been put forward with ore capacity of 196 000 tons.Based on the disaster mechanism analysis of goaf collapse ripple effect，The Wang Jin`an roof-pillar rheological model is adopted to simplify the roof-permanent pillar system as an elastic sheet supported by four groups of Buegers body.A dynamic stability analysis system of pillar-roof is set up，and the mined-out area' survival time was predicted by this system.Roof displacement monitoring shows that pillar' stress and strain are in good condition during pillar recovery.Practice indicates that with combination of the equivalent exposed area method and the Wang Jin'an roof-pillar rheological models，it's easy to determine the stope limits span and mined-out area' survival time，with a certain reference value.

Key words: Pillar recovery, Mined-out area handling, Ground pressure monitoring, Equivalent exposed area, Rheological model