Study On Deformation And Support Technology Of Crossheading Surrounding Rock In Deep And Thick Coal Seam Under Impact Load

It is of great value to ensure the safe construction of the crossheading and caving face,which carry out research on deformation and support technology of crossheading surrounding rock at combined mining face in deep and thick coal seam under impact load.The paper takes crossheading of Hujiahe number 4 coal seam at combined mining face as the research object,and uses the combination of theoretical analysis,laboratory experiment,FLAC3n numerical simulation and field condition analysis to carry out research work.The main conclusions are as follows:(1)Rock burst of Hujiahe number 4 coal seam crossheading surrounding rock at combined mining face induced factors mainly include:coal rock characteristics of physical and mechanical,high groud stress,faults and foldS,dynamic load disturbance of ground pressure and support method.The dynamic load disturbance under high stress is the dominant factor.The hard roof and extra thick coal pillar are the energy storage conditions.The bottom plate is easily release part of the rock burst energy.(2)The dynamic and static load triaxial or single tests of coal rock are combined with acoustic emission detection to study the deformation and failure mechanism of coal rock.Results show that the coal rock appear un,idirectional shear failure under static load,and the peak strength and strain increase significantly with the increase of confining pressure.The reduction of strength of coal rock after dynamic load is obvious,from shear failure to transverse tensile failure;the peak intensity has a nonlinear negative correlation with frequency at a certain amplitude.There is a static load critical load of coal rock.When the critical value is not reached,the fracture development of coal rock is gradually stable under long time dynamic load.After exceeding the critical value,rapid damage occurred under dynamic load.The coal rock acoustic emission event mainly occurs in the initial stage of dynamic load and peak failure stage.The Kaiser effect is obvious after dynamic loading.The acoustic emission point is mainly concentrated near the shear and tensile failure surface of coal rock and extends from the center to the periphery,which can better reflect its failure evolution trend.(3)Based on the FLAC3D finite difference method,the crossheading analysis model of excavation and support process for deep and thick coal seams was established,which research the deformation mechanism of high stress and under dynamic load.The results show thatthe displacement of the crossheading is obviously asymmetric deformation,and the deformation amount increases sharply with the increase of dynamic load strength under the dynamic load.The crossheading can be divided into three periods under dynamic loads:deformation vibration period,deformation recovery period and deformation stability period.(4)According to the deformation law of the crossheading surrounding rock in the deep and thick coal seam under the impact load,it is proposed that the fully mechanized caving face adopts the support concept of“strong support and unload",and completes the support design of crossheading at the deep and thick coal seam.The field condition shows that the deformation of the crossheading surrounding rock after the dynamic load disturbance is increased without excessive instability failure,and the support measures can effectively prevent the phenomenon of sudden instability to occur rapid destruction of the surrounding rock under the dynamic loading,the support method is reasonable and effective.