Rock Burst Mechanism In Bearing Coal Pillar Under Hard Roof-Coal-Floor Structure And Its Application

Rockburst is a destructive coal mine dynamic disaster.As a bearing structure between hard roof-coal-floor structure,coal pillar was widely used in coal mine production process.It always led to stress concentration excessive and induced the coal pillar type burst.Therefore,it is of great significance to study stress distribution and rockburst rules as well as control methods of bearing pillar composite structure under hard roof-coal-flor under static and dynamic load.This paper has been studied by means of laboratory test,mechanical analysis,numerical simulation and field engineering practice.The main achievements are as follows:Experiment of damage as well as AE response characteristics of hard roof-coal-floor structure under cycle dynamic load was developed,rules of crack and energy evolution were also analysed.The result shows that the pertubance and damage to roof-coal-floor strcuture will be the highest in the first moment of dynamic load,the damage whereafter the influence to roof-coal-floor structure was rapidly decreased due to the attenuation of dynamic load.In an instant of instability of roof-coal-floor structure,AE rings count,accumulate AE rings count,AE energy,accumulate AE energy have a obvious peak abnormal.Hence,aboved four indexs can be monitoring indexs for failure of coal-rocl composite structure.In the meantime also find that AE location result have a close relation with fracture type and energy evolution of coal-rock composite structure.The higher strength and thicker of rock is,the more energy accumulate in the interior of composite structure will be,and the more burst dangerous of composite structure will be.Respectively established mechanical models of hard roof-coal-floor structure under pure static load and cicle dynamic load.Instability catastrophe criterion under static and dynamic load was derived by means of cusp catastrophe,result shows that the bigger of the height ratio between roof and coal,the smaller of the elastic modulus in roof and floor,the bigger of the elastic modulus in coal,the more easily instability the composite structure will be.the smaller of release energy,respresents the lower violent stage and the bigger amount subsidence of roof will be.Through analyzing the formula find that bursting criterion condition and violent stage as well as amount subsidence of roof are closely releated to physical and mechanical properties.Numberical simulation studied the influence of stress evolution of coal-rock composite structure.it also studied dynamic response characteristics of bearing pillar under different degree strength dynamic load.Simulation result shows that stress concentrate in bearing pillar as well as range of plastic zone resulted by mining is increasing with the increase thickness and strength of roof,and more eaisly cause rockburst.Above-mentioned study result have been successfully applied in burst control work of W1103 working face in Yutian coal mine.Burst dangerous have been effectively pre-evaluation and control of bearing pillar by put into effect pre-evaluation and prevention methods,which ensure safety and high efficient production of working face,can provide guidance for which have simliar conditions in bearing pillar under hard roof-coal-floor structure.