Stability Analysis Of Mining Of Roof And Bottom Pillars Under The Backfill In Xinli Area Of Sanshandao Gold Mine

Abstract:Xinli area of Sanshandao Gold Mine firstly adopts decentralization pointed prop mechanical slice stopping and backfilling mining method based on complicated mining conditions that the ore body is located under the seaside for the mine’s safety. With the mining method there are a considerable number of residual pillars in the top and bottom in the various intermediate sections.According to the mine design, the average height of roof and bottom pillars is7.0m, there are2.0-2.5m cemented backfill, with cement-sand ratio1:6, at the bottom of the mining room or over the roof and bottom pillars. the ore grade is higher and gold reserves is substantial. There are many technical problems for resource recovery, such as the roof is too thin, the filling body strength over the roof is too low, the safety hazards of the remnant ore mining is serious. Therefore, it is critical.for recycling the top and bottom pillar resources to analyze the overall stability of the mine after the pillar mining and the stope stabilityduring the pillar mining.Making use of YEUNG Sum granular pressure theory to analysis the loose backfill pressure distribution characteristics and establish the mechanical equilibrium expression to get the distribution formula of the loose backfill pressure along the depth direction. ANSYS finite element numerical simulation method was used to calculate and analyze quantitatively the distribution of the stress and plastic zone of the remaining roof and bottom pillars, backfill and rib pillar, and the deformation and the Y direction displacement variation of the surrounding rock with the mining of roof and bottom pillars. The security recovery area and reasonable recovery steps of the top and bottom residue pillars is put forward based on the variation of the stress and strain with the step mining. The method provides the technical support for Sanshandao Gold Mine’s safety and efficient exploitation of the top and bottom residue pillars in under-sea mining, and extends Sanshandao Gold Mine’s service life.The upward horizontal slice stoping and backfilling method is applicated to the roof and bottom mining based on on the occurrence and mining conditions. The different supporting ways are applicated to provide protection for the safety of the stope based on the stability of the pillar itself and cemented backfill which is considered as the bear er layer.The combination of theoretical mechanics and numerical is used to analysis stope stability.Firstly, mechanical mode is established to analysis stress and strain of the mining approach’s roof based on simply supported "beam" theory, the approach width influencing the stope stability is analyzed when carrying layer thickness is unchanged, the safety factor of the roof with different carrying layer thickness and different approach width is calculated based on safety factor method. ABAQUS is applicated to simulate the mining process of roof and bottom pillar, the stress and strain of the mining approach’s roof is calculated, the settlement, the location of the maximum principal stress and the Mises equivalent bias stress of the approach’s roof. The safe, reasonable and stable approach parameters is draw based on the result of comprehensive theoretical mechanics calculations and numerical simulation, which provide technical reference for recoving the roof and bottom pillar safely and effectively.