| Yushen mining area is an important energy base in our country.The coal seam in the mining area is simple in structure,hard in coal quality,and the top coal is not easy to run,the periodic pressure load coefficient is large and the support often is crushed to death,which seriously affects the safe and efficient production of the working face.Therefor,combined with the existing conditions of coal seam in Yushen mining area,mining practice and requirements of safe and efficient mining,this paper had researched the science problems that the coupling relationship between support and top coal in fully mechanized top coal caving with large mining height,the dynamic load response and structural optimization design of hydraulic support for large mining height caving by using a variety of research methods such as theoretical model calculation,numerical simulation analysis and field experiment synthetically.Base on the study the technical scheme and the way to realize the fully mechanized caving mining of high mining height in the working face of extra thick coal seam was put forward.The main research work of this thesis is as follows:(1)According to the characteristics of fully mechanized caving mining in hard and thick coal seam,the fluidity model of loose body of top coal was established,the mechanism of arch formation in the flow of coal and gangue was revealed,and the block degree of top coal and the size of caving mouth were studied.The influence of inclined angle of shield beam and supporting force of tail beam on the arch formation in the coal gangue flow process,a new three-stage caving mechanism was designed,which effectively improves the caving property of top coal.(2)Based on the theory of the coupling between support and surrounding rock,the coupling relationship between support and top coal under the condition of hard and thick coal seam was established,and the working point of combined force of hydraulic support,mining height and supporting strength were studied.According to the research results,the breakage and caving state of top coal can be changed by changing the structure of hydraulic support for top coal caving,so as to improve the recovery rate of working face.(3)The dynamic equation of rigid body and dynamic load model of hydraulic support were established,the stiffness and dynamic load of hydraulic support were tested,and the dynamic bearing characteristics of hydraulic support were analyzed.It is found that the response characteristic of the hydraulic support under dynamic load is about 1.5 times of that of the static load,which provides a reference for the strength check of the hydraulic support design.(4)The optimization design and precision control method of four-bar connecting rod of hydraulic support based on genetic algorithm are put forward.The key factors affecting the stability of hydraulic support are studied,and the plane and spatial mechanics models of two-pillar caving hydraulic support are established.The spatial analytical results of support force in the position of roof beam are obtained.The load-bearing performance of two pillar caving hydraulic support and four pillar top-coal caving hydraulic support is compared and analyzed,and it is found that under the condition of hard top coal,the performance of two-pillar top coal caving hydraulic support is better.(5)The hydraulic support of ZFY18000 / 27 / 50 D two-column shield caving top coal caving is developed,and the engineering practice is carried out in Shenshupan Coal Mine.The matching cross side unloading and large gradient transition technology are put forward.Through monitoring the mine pressure in the super-high mining face,The feasibility and reliability of the above theoretical results are verified. |
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