Study On The Dynamic Characteristics Of Tail Beam Under The Impact And Slippage Effect Of Coal Gangue

Coal is an important energy source in China and it plays an irreplaceable role in the process of China’s modernization.As one of the main mining methods of thick coal seam and extra thick coal seam in China,the fully mechanized top coal caving mining makes safe and efficient mining of coal a reality.Due to the problem of coal gangue identification in the coal caving department of hydraulic support for fully mechanized top coal caving has not been effectively solved so far,the automatic control level of coal caving department has not been able to achieve substantive breakthrough,which hinders the further improvement of coal mining efficiency and economic benefits of coal enterprises.The vibration identification method can automatically identify the degree of coal caving by monitoring the mechanical vibration of tail beam,which is a widely popular method of coal gangue identification.After the preliminary investigation and research,it can be found that the impact and slippage of coal and gangue are the main reasons for the vibration behavior of tail beam when the coal is discharged in the coal caving department.In order to explore the vibration mechanism of the tail beam and the impact slippage effect of coal gangue on the dynamic characteristics of the tail beam,this paper bases on the National Nature Science Foundation of China(Grant No.51674155)and focuses on the dynamic characteristics of the tail beam of top coal caving hydraulic support to carry out some research as follows.First of all,this paper introduces the research background of the project and describes the research status of coal gangue identification method,contact mechanics and friction mechanics at home and abroad in detail.After that,this paper introduces the research content of the subject,summarizes the research significance of the subject and arranges the research contents of each chapter.By introducing the basic models of contact and friction commonly used in engineering problems,the Hertz contact theory and Coulomb friction model are selected as the theoretical models to define the contact and slippage behavior between tail beam and coal gangue.Then this paper takes the tail beam of top coal caving hydraulic support as the research object,analyzes the impact characteristics of the bearing area and researches the dynamic response of the tail beam under different coal caving gestures.The 3-D model of the coal caving department is established by Solidworks,and the tail beam and coal gangue particles are treated as flexible body files by Hypermesh.Finishing this,this paper establishes the rigid-flexible coupling model of coal caving mechanism in Adams and determines the contact stiffness and equivalent spring stiffness through the Hertz contact theory and solid-liquid coupling spring model.This paper takes single grain coal rock as the breakthrough point,uses the method of coal rock’s direct impact to add load to tail beam and simulates the dynamic process of coal rock impacting the tail beam at different positions and different coal caving angles to study the dynamic response and stress of tail beam after being impacted by coal rock.By comparing the simulation results of multi-rigid body model and rigid-flexible coupling model,the reliability of the research method of rigid-flexible coupling dynamic simulation is verified.Through analyzing the dynamic change process of the velocity,acceleration,displacement,contact force at the hinge point and spring force in the tail beam vibration system after the impact excitation of coal gangue particles,this paper selects the maximum values of these dynamic responses as the characteristic values to describe the dynamic change process of tail beam and to measure the strength of impact excitation.Around the influence of character difference between coal and sandstone on the vibration characteristics of tail beam,this paper simulates the transient impact of coal gangue particles on the tail beam under different impact height,different particle size and the same impact energy these three basic impact conditions.After that,this paper summarizes the changing law of dynamic responses in the tail beam vibration system under different impact conditions,compares the difference in the dynamic responses of tail beam caused by coal and gangue and discusses the dynamic feedback quantity which can be used to identify the caving state of top coal.At last,this paper puts forward the point that the slippage effect of coal gangue is an important factor that causes the mechanical vibration of the tail beam during the process of coal caving and establishes the slippage model of coal gangue to study the slippage mechanism of coal gangue and the influence on the vibration behavior of tail beam caused by coal gangue’s slippage effect.By simulating the slippage of single coal gangue under the conditions of different coal release attitude and different particle size based on this slippage model,this paper obtains the stress state of tail beam,analyzes the influence of slippage effect on the dynamic characteristics of tail beam and compares the results of coal and sandstone’s slippage action.This paper also carry out the research of massive coal gangue’s slippage effect under the condition of different sizes,compares the slippage results of spherical and massive coal gangue and analyzes the difference in dynamic responses of tail beam caused by coal and sandstone.In addition,this paper studies the slippage process of multi-particle coal gangue under different conditions and the changing situation of tail beam’s dynamic responses caused by multi-particle’s slippage action,which can provide a research basis for the study of group particle coal gangue’s slippage.By simulating the impact and slippage effect of coal gangue in the coal caving department,this paper analyzes the influence of impact and slippage effect from coal gangue on the vibration behavior of tail beam,summarizes the changing situations of stress state and dynamic responses of the tail beam under the working condition of impact and slippage and compares the difference of tail beam’s dynamic responses caused by coal and gangue.The research content provides the research basis for the application of coal gangue recognition technology based on tail beam’vibration signals,which can promote the improvement of automation control level of fully mechanized coal caving face.