Numerical Simulation Of Multi-factor Influence On Goaf Stability In Gongchangling Open-pit Mine

Due to large-scale disorderly mining and illegal mining,there are a large number of goafs in the slope of Gongchangling Open-pit Mine.In the mining process,with the continuous stripping of bench mining,the safety thickness of each bench and the stolen goaf in the mining boundary is getting thinner and thinner.Under the action of the blasting disturbance of the upper bench,the internal damage of the lower rock mass is caused,and the water accumulation causes the softening of the surrounding rock of the goaf.In addition,the creep effect of itself may induce the instability and failure of the roof of the goaf,and even cause the sudden collapse of the surface,resulting in casualties and permanent damage to the ground equipment.Therefore,the comprehensive evaluation of goaf stability in Gongchangling Open-pit Mine has become an urgent problem to be solved in production.In this paper,the goaf of Gongchangling open-pit iron mine is taken as the research object.Combined with the previous similar simulation test and field monitoring work of the team,the numerical simulation method is used to study the influence of blasting disturbance,creep effect and goaf water accumulation on the stability of the goaf,and the stability of the goaf of Gongchangling open-pit mine is comprehensively evaluated.The following studies are carried out:(1)Determination of mechanical parameters of similar materials:According to the similarity criterion,the selection and proportion of similar materials are deduced.The similar material samples are made to complete uniaxial compression,Brazilian splitting and uniaxial compression tests.The basic physical and mechanical parameters and creep parameters of similar materials are measured,which provide parameters for the numerical simulation of similar simulation experiments of goaf failure under blasting disturbance.(2)Numerical simulation verification based on blasting test:Based on similar simulation blasting test,a numerical model with the same size as the test is constructed,and the blasting,excavation,ash cleaning and creep processes are simulated according to the similar simulation plan.The correctness of the program is verified by comparing the calculation results with the similar simulation test results.(3)Study on the stability of mined-out area under the influence of blasting vibration:The geological model,lithologic segmentation surface and mined-out area of Gongchangling Open-pit Mine are established.The griddle software is used to mesh the solid model of Gongchangling Open-pit Mine.The influence of blasting disturbance on the stability of goaf is studied and analyzed by using blasting disturbance program.After the blasting disturbance is applied,the deformation of the goaf roof increases,and the closer the blasting disturbance is applied to the goaf,the greater the deformation of the roof increases.When the blasting disturbance is applied 75 m away from the goaf,the goaf roof has the risk of instability and failure.(4)Study on the stability of mined-out area under the influence of multiple factors:A three-dimensional model of 100 million degrees of freedom in Gongchangling open-pit mine goaf was established.FLAC3 D numerical simulation software was used to simulate the softening effect of water on surrounding rock of goaf by reducing parameters,and the hydrostatic pressure was applied,and the creep effect of surrounding rock was also considered to carry out the numerical simulation of goaf stability.With the rise of water level line,the deformation of goaf roof increases and the stability of goaf decreases.The numerical simulation results are consistent with the monitoring results of the surface level.The roof settlement of the goaf is millimeter level,and the stability of the goaf is good under the current conditions.