Study On The Stability Of Return Air Drift Above The Goaf Of Xijikeng Lead-Zine Mine

With the gradual depletion of shallow and easily mined mineral resources,mineral resource development will face more complex mining environments.When mining the ore bodies near the openings,the tunnel will inevitably be arranged near the openings,and the existence of the openings increases the complexity of the tunnel excavation project and has a certain impact on the stability of the tunnel,which can seriously destabilize the tunnel and endanger the lives of underground operators.The stability of adjacent goaf tunnels is closely related to factors such as surrounding rock properties and goaf characteristics.There are still technical bottlenecks in how tunnels can safely pass through goaf groups and ensure the smooth development of mineral resources in the lower part.Relevant research content has become a focus of attention for engineering and scientific researchers at home and abroad.The paper takes the underground mining system of the east wing of the Xijikeng lead-zinc mine in Guiping City as the engineering background,and uses three research methods,namely theoretical analysis,numerical simulation calculation and indoor mechanical test,to study the stability of the 0m middle section of the level tunnel located in the upper part of the Goaf-2:（1）Rock mechanics tests were carried out on ore rock samples taken from the mine,and mechanical parameters of ore rock were obtained.The paper calculates the mechanical parameters of the mining rock mass using evaluation methods that are suitable for the mining engineering environment,analyzes the reduction effect of rock mass strength under mining water filling environment.In the end,we concluded that the mechanical properties of the ore rock mass in the water filled environment have decreased to varying degrees.（2）Basing on the theory of elastic mechanics small thin plate,combined with the actual engineering conditions of the underground mining area in the east wing section of Xijikeng lead-zinc mine,the solution formula for the safe thickness of the top plate of the upper compartment of the mining hollow area is derived;using FLAC^3Dnumerical simulation software,a solid three-dimensional model of the 0m middle section tunnel and Goaf-2 is established,and the stability parameters of the tunnel under different conditions of the top plate thickness of the compartment are calculated,and through the numerical The results obtained from the simulations were used to verify the feasibility of the elastodynamic small thin plate theory for the stability analysis of the tunnel above the goaf.（3）Using Bieniawski’s pillar strength formula to calculate the pillar safety factor in the Goaf-2,the unstable pillars were identified;based on the theory of unstable pillar chain collapse effect,the safety thickness of the compartment roof after the unstable pillar collapse was calculated by using FLAC^3D,the unstable pillar collapse process was simulated and the effect of unstable pillar chain collapse on the 0m middle return was obtained.The influence law of the unstable pillar chain collapse on the 0m middle section tunnel.（4）Basing on the impact of goaf on the stability of the upper roadway,a goaf treatment plan of constructing artificial pillars in the early stage and filling with waste rock cementation in the later stage is proposed,as well as a combined ground pressure monitoring method of installing borehole stress gauges and portable mobile acoustic emission.Through verification,it can be concluded that the above treatment measures can ensure the long-term stability of the 0m middle section return air level roadway.The research results of the paper can provide reference for mines in the layout and excavation construction of near-goaf tunnel,which is of positive significance in reducing mine production costs and ensuring mine safety,and also can provide reference for similar mines in the design and excavation construction of shaft engineering and ground pressure control above the goaf.