Research On The Dynamic And Static Stability Of The Roof Of The Goaf Group

The partition roof of goaf group belongs to the relatively weak part of the mine,and is also one of the most important hazard sources in metal underground mines.It usually shows roof caving,serious or even goaf penetration.If an accident occurs,it will often cause a large number of casualties and property losses.There are many factors affecting the stability of goaf.The two most important factors are the self-weight stress load of surrounding rock and blasting vibration caused by blasting operation.Therefore,this paper mainly studies the stability of the roof of No.2 goaf under the action of gravity stress of rock mass and blasting vibration dynamic load by combining theoretical analysis with numerical simulation from two aspects of static and dynamic impact.The main research contents are as follows:(1)By consulting a large number of literatures,this paper summarizes the failure types,instability mechanism and stability influencing factors of the goaf roof under gravity condition,establishes the mechanics model of the goaf roof instability and failure,and discusses its influence on the stability of the goaf on the formation,propagation and mechanism of blasting seismic wave in dynamic aspect.(2)Based on the theory of elasticity and the practice of mine engineering,the roof is simplified as a fixed fixed fixed beam model,and the stress,strain and displacement of the fixed beam under uniform load are calculated by theoretical analysis.On this basis,combined with the software of MATLAB,the change law of the deflection and stress surface of the roof is analyzed,and the influence law of the thickness-span ratio of the roof on the deflection and stress is discussed.Finally,the appropriate roof thickness of the mine is obtained by combining the calculation results of the roof thickness with the engineering examples.(3)After completing the calculation of the physical model of the elastic fixed beam,the three-dimensional mechanical numerical calculation model of the complex goaf is established by using the coupling technology of 3D MINE-MIDAS/GTS-FLAC 3D and other software.The first and second goafs are excavated by simulation.The displacement,stress,plastic area,surface subsidence and the stability of the goaf caused by the thickness of the roof are calculated and analyzed under the condition of self-weight.Influence.(4)On the basis of simulating the static load after the excavation of the orebody,a simple harmonic dynamic load is applied to the floor of each layer of the goaf in No.2 mined-out area.The displacement,stress and particle velocity of the roof in the goaf are analyzed under the dynamic load,and compared with the static load to illustrate the influence of dynamic load on the stability of the roof.