Study On Support Optimization And Stability Of Broken Soft Rock Roadway In Yangla Copper Mine

Yangla Copper Mine is located in Yangla Township,Deqin County,Yunnan Province.It is difficult to support the soft rock roadway at the 3390 middle level.In order to solve the problem of supporting the fractured soft-rock roadway in the mine,the on-site investigation and laboratory test are carried out.The research results have a great practical significance to the normal production of the mine,and have certain reference value to other soft rock underground construction.Based on the on-site investigation and rock mechanics test,mineral composition analysis,water test,weathering test and free expansion rate test,it is concluded that the main reasons for the instability of the roadway are as follows:the weak of rock strength and rock mass structure is loose and broken,the second reasons are the support structure can’t separate roadway from water and air,water,weathering,cyclic drying-wetting effect make the rock weakened,the last reason is that the stress change leads to the decrease of shear strength of the rock.Based on the analysis of the roadway instability mechanism,the bolting and shotcreting with wire mesh supporting scheme is proposed.The radius of the plastic zone were calculated basing on the Elastic-plastic theory,which is 2.94m,then based on the suspension theory and loosen circle theory the support parameters is optimized.The stability of roadway in unsupporting,lining supporting,bolting and shotcreting with wire mesh supporting has been simulated through numerical analysis software 3DEC,and the results of numerical simulation show:the relative convergent ratios of wall under this three supporting before exploiting are 4.71%,1.35%and 2.03%,and the convergent ratios of roof and floor are 4.55%,1.60%and 1.80%.Under the influence of exploit,the relative convergent ratios of wall under this three supporting are 8.68%,1.87%and 3.62%,and the relative convergent ratios of roof and floor are 8.51%,2.58%and 3.45%.The relative convergent ratios of unsupporting is always greater than 4%,indicating the unsupporting roadway is unstable.The relative convergent ratio of optimized supporting scheme is always less than 4%,expounding the roadway under bolting and shotcreting with wire mesh supporting is stable.Finally,economic benefit comparison between bolting and shotcreting with wire mesh supporting and lining supporting is obtained.As with the per meter supporting cost,the former is less than the latter ￥1288.4.Based on the comprehensive evaluation of the support effect and economic benefit,the bolting and shotcreting with wire mesh supporting is better.