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When residual pillars are extracted in a short time in room and pillar mining, the load 10 transferred from the removed pillar acts on neighbouring pillar workings in a dynamic manner. This 11 study aims to investigate the instability of large mined-out areas triggered by dynamic disturbance 12 resulting from residual pillar recovery. A mechanical model combining the pressure arch theory (PAT) 13 based method and structural dynamics was first established to assess the stress state and deformation 14 of a pillar subjected to combined effects of static and dynamic loads. The process of residual pillar 15 recovery and potential induced instability of neighbouring pillar workings in a five-pillar system was 16 further numerically simulated in both static and dynamic modes, and the response of adjacent pillars 17 was investigated. It was found that the induced disturbance to a pillar can be characterised by the 18 dynamic amplification coefficient R, the ratio of the increased vertical pillar load to the transferred 19 load. Rmax can exceed 1.5 or even approach 2 in practical pillar recovery using the blasting method. 20Modelling results showed that while pillar workings adjacent to a removed pillar remain stable in 21 static analysis, violent and large-scale pillar collapses can be triggered in the event of quick pillar 22 recovery of blasting method. Results indicated that when the dynamic effect of pillar recovery is not 23 considered, the load undertaken by adjacent pillar workings would be largely underestimated. To 24 ensure mining safety, the induced dynamic effect should be accounted for in the design of the pillar 25 recovery method.

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