Impact of ground surface movements on ventilation shaft No. 5 of Taimyrsky Mine at Oktyabrsky deposit

Abstract

The main resources of Taimyrsky Mine represent the high-grade and impregnated ore. The mine field holds some high-grade massive ore bodies and many impregnated ore bodies which occur everywhere except for the south wing of the deposit. The hydrogeological regime of the deposit is governed by the thick permafrost layer. The accesses to the ore bodies is got via vertical shafts: cage shaft KS-3, skip shaft SS-3, ventilation shafts VS-5, VS-6 and VS-7, a backfill shaft (BS) and an air feed shaft (AFS). In the influence zone of mining operations, there are service shafts SS-5, SS-6 and SS-7, BS and AFS, accordingly, shaft headgears, shaft top works and other facilities. The authors estimate the impact of ground surface movements in the course of mining operations on the behavior of ventilation shaft No. 5. The data of the in-situ, as well as geophysical and geodetic survey observations of the study object are presented. All data analyzed, it is possible to reach a conclusion that all damages detected result from the movements and over-weathering of rocks in the space behind the shaft lining. The incorrect engineering estimate of water influx and seasonal watering during the shaft construction led to a drop in the load-bearing capacity of the lining and to suspension of the lining string in rock mass, which created an extra load and induced partial failure of the lining. At the present time, shaft VS-5 is in the process of the lining reconstruction, complete grating of the space behind the lining and erection of segmental lining from top downward. Based on the research findings, the detected movements are also typical of neighbor shaft VS-6. It is required to undertake a fully integrated survey of the shaft and make provisions for its loadbearing capacity recovery to avoid an adverse situation.