Numerical Simulation Of Layered Roadway Floor Burst Under Impact Loads

Rock burst is a mine dynamic phenomenon characterized by sudden and drastic destructions of coal and rock mass.The floor burst occurs frequently and has great influence on the safety of mining.However,research on the mechanism of floor burst is still in its infancy.In this paper,based on a large number of floor burst examples,the characteristics of floor burst are summarized and the failure model of layered floor is established.Taking the coal mine of Yuejin as an example,physical and mechanical parameters of coal and rock are tested.Besides,the mechanism of floor burst under actual working conditions are analyzed by numerical simulation method and compared to field results.Characteristic rules of different influencing factors(internal and external)on floor burst are studied and discussed.Main research results of this paper are as follows:(1)The stability of the layered floor is mainly determined by the critical stress and the relative magnitude of dynamic and static load values on the layered floor.The critical stress of the layered floor is related to the lithology of rock and bed thickness ratio of rock.The relative magnitude of dynamic and static load values is not only related to the dynamic load strength,but also related to the lateral pressure coefficient and the horizontal stress caused by gravity in the upper strata under the actual working condition of the mine.Under the impact stress,the layered floor are severely buckled,which subsequently leads to the serious bulging of the floor and the failure of the mine.(2)Develop the attenuation curve equation of impact load by analyzing the mine monitoring impact data.Test the physical and mechanical property of rock layer in coal by finete element analysis software that can simulate the development principle of the floor burst under dynamic impact load at Yuejin mine.The mining of Yuejin mine caused massive movement of the top plate of the heavy and hard conglomerate.Influencd by impact load,the surrounding rock in the tunel is under the limiting condition due to the high horizontal stress in the layered floor.The external dynamic disturbance disequilibrate the balance of limiting condition of stress,which resulted in layered fracture,release of massive energy,and the impact appeared.With the constant influence of dynamic impact load,the stress peak moves to the bottom of the plate,which results in the release of the elastic energy of the bottom plate and the deeper plastic failure becoming.Under the action of static and dynamic loads,the vertical displacement is the main driving force of layered roadway floor burst.The simulation results are consistent with the actual rock burst disaster.(3)The main inducing factors of floor burst include dynamic load strength,lateral pressurecoefficient,as well as the lithology and bed thickness ratio of the layered floor.Numerical simulation results show that the vertical displacement of roadway floor increases non-linearly due to the increase of dynamic load strength.With the increase of the lateral pressure coefficient,the horizontal stress of the layered floor under static load increases,and the horizontal stress value required for failure decreases.Under impact load,it is easier to exceed the limit stress state for failure.With the increase of the lateral pressure coefficient,the vertical displacement of roadway floor increases non-linearly.Under certain working conditions,lithology and bed thickness ratio of layered floor have a range that is more prone to rock burst when applied with the same dynamic load strength.The stronger lithologic strength and the thicker hard layer lead to stronger resistance to the impact load.There are 62 Figures,7 Tables and 73 References in the dissertation.