A Study On Substitution Of Barrier Pillars Extracted By Open-pit And Underground Joint Mining

Abstract:Gold Mine of Guizhou is an underground and open pit combined mining project, the open pit will be closed in2015, at that time, the project will become a single underground pit. The mine is located in a heavy rain area, engineering geological condition is very complex, and the boundary barrier pillar which is20meters thick is mainly sandstone and thin layer of clay rock, its strength is low, performance of anti-moisture and anti-weather is rather weak. The water catchment in the open pit will permeate into roof pillar, and the interstitial flow will apply a normal seepage pressure and tangent hauling force on fissure wall, seepage field so formed will affect stability of the boundary barrier pillar. In addition, the open pit will be backfilled with the stripped wastes from Rongban. Take the pressure of backfilled body into account, keeping the existing boundary barrier pillar will cause many security risk. Moreover,20m security pillar kept at bottom of the open pit, of which the reserve is29.73×104t, with grade of4.3g/t and amount of metal of1.28t, which is with high economic value.Therefore, this paper carry technical study for substitution of barrier pillars between OP and UG mine with cemented backfill through numerical simulation method and evaluation and analysis means.The main results are as follows:(1) Demonstrate the feasibility and necessity of substitution for barrier pillars between OP and UG with cement filling body by numerical simulation, and make detailed study separately and risk analysis assessment for man-made substitution for20m barrier pillar.(2) Proposed reinforcement program of the substitution on the basis of the risk assessment, and prove the reliability of the reinforcement program by stability analysis of the reinforced substitution.(3) Propsed drainage plan by studying the risk of penetration of open pit running water downwards underground, ensure the catchment in the open pit can be drained timely, and reduce the damage to the underground filling body (4) Established the economical and feasible monitoring system with high degree of automation, and ensure safe underground mining during the period of waste backfill and after waste backfill.The result of this study is applied in the mine. The experiences and results of the appliction will contribute to other similar domestic mines...