| With the steady improvement of the modernization of China's mining industry,the electrification of mining equipment has led to the rapid development of mining technology and the continuous expansion of mining scale.And the combination of different intelligent mining methods of new information technologies such as big data,cloud computing,artificial intelligence and industrial 5G not only can achieve the goal of "unmanned" mining,but also become a new opportunity to ensure China's energy security and promote high-quality economic development.Although the maturity of information technology has been continuously improved and the fully mechanized top coal caving technology has made great progress in China after more than 40 years of development,there are still some problems to be solved in intelligent fully mechanized top coal caving mining,which are mainly manifested in its basic theory and the insufficient support of intelligent equipment for technology development.The key problem of intelligent fully mechanized top coal caving mining in thick coal seam is the intellectualization of coal drawing process.It is requested that the law of top coal crushing and drawing is mastered.And combined with intelligent detection and control technology,the intelligent coal caving control system is established.Based on the background of the intelligent construction of working surface in Wangjialing Coal Mine 12309,this paper focuses on the whole process of fully mechanized top coal caving mining and takes the evolution law of top coal mining stress field as the breakthrough point to reveal its crushing mechanism and clarify the release characteristics of loose top coal discharged by the rear scraper conveyor,so as to put forward the reasonable coal drawing method,which provides theoretical support for increasing production and efficiency of intelligent caving in thick coal seam.Through the theoretical analysis,the key technologies that are necessary to realize intelligent coal caving are refined and the integrative application of which provides important technical support for the realization of intelligent coal caving in thick coal seam.The main conclusions are as follows:(1)Based on the main stress space,the evolution law of main stress field of top coal stress unit in the process of fully mechanized top coal caving mining in thick coal seam is studied.And Based on the finite differential numerical simulation method and the supporting effect of the hydraulic support working resistance on the top coal,the variation of the main stress and the direction deflection characteristics under the condition of high-level stress are clarified.On this basis,the top coal is divided into five zones: the original rock stress zone,the middle main stress rising zone,the stress significantly increased zone,the stress peak reduction zone and the hydraulic support top zone.So,the main stress driving path of top coal under high-level stress condition is obtained,which provides the stress boundary for the subsequent research on progressive crushing mechanism of top coal.(2)Based on the theory of elastic-plastic mechanics,the evolution processes of average stress,deviatoric stress and Lode angle of stress in fully mechanized top coal caving are analyzed,which are the three parameters that describe the stress state of top coal,and then their own evolution characteristics in each top coal zone are revealed.And the 3D numerical model of fractured coal body is reconstructed by means of the high-precision industrial CT scanning technology and the synthetic rock mass(SRM)numerical modeling method.This paper also establishes a "continuous-discontinuous" coupling true triaxial numerical model to simulate the progressive crushing process of top coal under the condition of specified main stress boundary by using the "finite difference particle flow" coupling numerical method.On this basis,the fracture developmental trace and the law of fragmentation distribution are clarified,and the fragmentation distribution characteristics of top coal caving are measured.And then through the comparation with the numerical simulation results,the reliability of the numerical method is proved,which provides data support for the follow-up study of the movement and release law of loose top coal.(3)Based on the "finite difference particle flow" coupling algorithm,the numerical model of "continuous-discontinuous" coupling of fully mechanized top coal caving is established,and the coupling modeling method of "random free fall step by step servo compaction" is developed.And the whole process of fully mechanized top coal caving is inversed from equipment installation to stable coal caving.Through the above operations,three characteristics of the evolution of the coal gangue boundary shape are obtained so that the "hook" function is improved to be suitable for describing the coal gangue boundary shape.The fitting of them reveals the evolution law of coal gangue boundary shape from primary caving to periodic caving,which is divided into three stages: Primary Mining influence stage,transitional caving stage and periodic caving stage.And it provides the top coal displacement boundary conditions for the following selection of caving process based on intelligent caving control technology.(4)The whole coal drawing process is divided into three stages: before coal drawing,during coal drawing and after coal drawing,and the intelligent control technology in each stage is analyzed,including: top coal thickness detection and shearer inertial navigation positioning before coal drawing;accurate monitoring and control of coal drawing mechanism and coal gangue identification during coal drawing,and real-time monitoring of coal production after coal drawing.With the combination of the above intelligent technologies,an intelligent coal drawing control technology system is established.And from self-perception,self-learning,selfdetermination and self-executing four levels,the internal relationship among the intelligent coal caving control technologies is revealed.Finally,the basic logic of intelligent coal caving control software is constructed,which provides the technical basis for the selection of intelligent coal caving process parameters and the realization of intelligent coal caving control in the future.(5)Based on the system of the intelligent coal caving control technology and the research results of evolution characteristics of coal gangue boundary as the top coal displacement boundary condition,the Bergmark-Roos theory is improved,the theoretical model of periodic coal caving time prediction is established,the comprehensive judgement method of the opening or closing of the coal drawing point is proposed,and the "finite difference particle flow" coupling numerical model including multiple hydraulic supports is established.On this basis,the parameters of the rational coal drawing process that are applicable to the current intelligent integrated drawing working surface are optimized,and finally the intelligent fully mechanized top coal caving demonstration working surface is established in Wangjialing Coal Mine 12309,where the main production equipment and organization relationship of the working surface are upgraded,and the reliability of intelligent top coal caving control technology is verified,which makes the better economic and social benefits achieved. |
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