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Abstract In order to repair the collapsed shaft at the watery zone with fault fractures in a new mine in Yunnan province，the basic principles and the“sequence-combined”control method were put forward based on the callapsing mechanism of shaft rocks obtained through on-site research and numerical simulation. The fundamental reasons of the instability and slippage of shaft rocks were found to be the serious degradation of the surrounding rock by water，the low capability of self-supporting and the distinct plastic fluidity of loose rocks in the watery zone with fault fractures. Previous multiple unsuccessful repairing led to the increase of the caving height，the activation of the fault fractures and the unblocking of the local aquifers and caused large area collapses and water gushing in the broken section. The broken surrounding rock during the process of instability and slipping had a zone of quickly release of stress，a zone of transition of stress and a zone of stress concentration. The key measure of controlling the surrounding rock is to block water flow and to reinforce the rock in the zone of stress relieved and containing groundwater flows for improving support ability of the surrounding rock and decreasing the support loading in the following stage. Variation angle umbrella-like ahead grouting are proposed to carry out from a distance behind the deformed area. The temporary support can provide the space and the time for the first and/or the secondary support later. The integral supporting capacity of the surrounding rock can be improved by embedding grouting pipes so that the secondary grouting can be applied to backfill the cavities which may exist in fractured surrounding rock.
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Received: 28 June 2013
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2014, Vol. 33 
