Study On Optimization Of Section Pillar Rational Size In Fully Mechanized Caving Face Of Zhaozhuang No.2 Mine

With the development of science and technology,comprehensive mechanized top coal mining has been widely used in the production of thick coal seams.In view of the comprehensive mechanized caving mining in thick coal seams,how to increase the recovery rate,reduce the waste of coal resources,and achieve the high output and high efficiency of mines are the subject of continuous research by coal industry workers.Based on the engineering background of the Zhaozhuang No.2 mine of the Jinmei Coal Group,the reasonable coal pillar parameters of the fully mechanized top-coal caving face of the No.3 coal seam of this mine have been optimized and combined with numerical simulation.The actual size of the coal pillars in the section of the mine was determined by field measurements.The research results provide certain reference and guidance for the research on the coal pillar width of the thick coal seam fully mechanized top-coal caving mining section.Finally achieved the following results:?1?Analyze the surrounding rock structure of coal pillars and their stress characteristics,failure mechanism and damage patterns.In the basic theoretical research,the basic issues closely related to the dissertation are mainly studied:the structure formed by the section pillars and the roof,the factors affecting the strength of the section pillars,the load and stress distribution of the section pillars,deformation and damage of section pillars,stability of section pillars.We will try to clarify the basic rules and the influencing factors of the above issues,and lay the foundation for the paper to study and ultimately determine the reasonable size of the section pillars.Through research,we have further defined a series of important viewpoints and regular understandings of basic issues.These viewpoints and understanding can explain some of the phenomena on the ground.?2?Considering the influence of the intermediate principal stress,the SMP is used to destroy the yield criterion,and the stress variation of the coal pillar under three-dimensional stress is analyzed.The theoretical mathematical formula of the ultimate strength of the coal pillar is given.In the different stress environments of roadway surrounding rock,the theoretical calculation formula for the plastic zone width of coal pillars under plane strain is introduced using the limit equilibrium theory.According to the distribution law of support pressure on coal pillars,combined with the Airy stress function and the maximum principal stress formula,The SMP yield criterion gives the critical width formula for the elastic zone in the middle of the roadway pillar:The Mohr-Coulomb criterion and AH Wilson were compared by analyzing the internal friction angle and cohesion of the coal body and the ultimate strength of the coal pillar obtained by the ultimate strength of the coal column under the Mohr-Coulomb criterion and the simplified AH Wilson formula.Because the formula ignores the influence of the principal stress of the middle pillar,the ultimate strength obtained is low,making the pillar size design more conservative,and the width of the pillar calculated based on the SMP criterion can be mine in line with reality.?3?Apply the theoretical research results to Zhaozhuang No.2 mine.According to the physical and mechanical test results of No.3 coal seam roof and bottom,combined with the theoretical research results,the theoretical calculation values of the reasonable pillar size of the Zhaozhuang No.2 mine section have been determined.?4?Using FLAC^3D numerical simulation software to further study the reasonable width of the section coal pillars.Firstly,according to the specific engineering geological conditions of the fully mechanized top-coal caving face of the Zhaozhuang No.2 mine,the model scheme is designed according to the width of the coal pillar,the mining phase and the monitoring index.Secondly,the yield failure and stress distribution of the coal pillar under different schemes are simulated.According to the analysis of the simulation results,the reasonable coal pillar width of fully mechanized top-coal caving face of No.3 mine No.2 in Zhaozhuang No.2 mine should be greater than or equal to 25m,and the correctness of the theory is verified.?5?Through field measurement of deformation of the roadway surrounding rock pillar under the condition of coal face width variation and coal pillar stress variation law,the measured data in field measurement environment are basically consistent with the numerical simulation results,indicating that the numerical simulation of this paper has a better Accuracy strongly supports the results of numerical simulation.Initially solved the problem of the reasonable size of coal pillars in the section of Zhaozhuang No.2 mine.