The Study On Treatment Technology Of The Mined-out Area In Qiyugou Gold Mine

The Qiyugou Gold mine is located in the territory of Chengguan town in Henan Province. J5 ore body is the main mining ore body. After many years of extraction,J5 ore body form into two mined area which includes one large and one small and the two mined-out area was divided by the transport tunnel as the boundary. Besides, the large mined-out area and the below level mined-out area communicated with each other. In this condition, For the sake of ensure the safety in production lower level.and eliminate mined-out area damage, the treatment scheme urgent needed to be research.In this article, on-site investigation, theoretical analysis, numerical simulation and engineering analogy are combined to study Qiyugou gold mined-out area treatment scheme. First, by investigation the mined-out area status of 580m mine level, the length of the big mined-out area is about 76m,the wideness is about 36m. And the small mined-out area’s length is about 36m, wideness is about 6.5m～10m. It is also found out that there is no distinct surface appearance around tunnels which means the mined-out area is remaining stable.Secondly, though structural plane survey of the mined area surrounding rock and point load strength tests, the stability of rock mass is classified and analysis the caving ability of the rock of mined area. According to the specific form of mined area and combined with the rock mechanical parameters, the critical caving span was calculated is 63m; By using engineering analogy, the continuing caving span was calculated is 79 meters. Due to the presence of the mined-out area roof for many years,the surface strength of the roof was seriously weakened which unstable rock may occur at any local caving. So the technical measures which dispersions taken isolate at the bottom of mined-out area to ensure production safety was presented, and the technical solutions that caving the pillar of mined-out area, at the same time,caving part of the footwall rock to induce the mined-out area caving were presented. Thirdly, the effects of treatment on mined-out area were numerical simulated by FLAC3D software, and calculated by the simulation, after caving pillar,the roof of mined-out area destroyed mainly caused by the tensile break,which the side wall was the shear break, in addition,the plastic unit would be extended to ground surface which indicated that the roof near the ground surface of the plastic deformation also occurred. The results show that caving the pillar, which can effectively induce mined-out area natural caving. Fourthly, through analysis control methods of caving blast damage, surface subsidence damage and rockfall damage, these security measures, such as isolate dispersion on the bottom of mined-out area; prohibited to enter the mined-out area when pillar mining; delineated surface collapse scope were proposed.Analysis shows that Induction caving treatment of mined-out area, by the obvious advantages like production safety,simple in construction,small investment, will well adapt the mined-out area conditions of Qiyugou gold mine.