Maximum Allowable Gas Content Threshold Model Of Coal And Coalbed Methane Co-Mining In Chengzhuang Mine And Its Space-Time Optimization

The relationship between coal mining and coalbed methane(gas)extraction is a kind of mutual promotion and mutual restriction.The two systems interfere with each other in the actual production process,and are far from achieving the state of space-time coordination at the macro level.Taking Chengzhuang Coal Mine in Jincheng Mining Area as the research object,this thesis studies the variation law of pores and fissures in coal during coal mining and the influence of pore structure on coalbed methane desorption,analyzes the main influencing factors affecting coal production,establishes constraint boundary conditions for coal mining and gas extraction in combination with safety regulations,optimizes the establishment of the highest allowable gas content model for coal mine safety mining and calculates and analyzes the actual parameters of 4308 working face in the study area,and finally completes the space-time optimal allocation of coal and coalbed methane co-mining.The main understanding is as follows:Firstly,The pore change law and promoting desorption of coal rock during mining are described.By comparing the changes of pore and fracture in coal seam before and after mining,it is found that the transition pore and middle pore in coal are subjected to stress compression,and some of the transition pore and middle pore expansion pore size are connected with adjacent pores to form macropores or cracks.Each form of microfracture extends through each other and develops into a more complex network fracture group,which provides a broader channel for the desorption and diffusion of coalbed methane.Secondly,the maximum allowable gas content model in coal mining process is constructed.Considering the four factors of coalbed methane geological conditions,mine gas conditions,coal mining intensity and coal mine ventilation safety measures.In the process of coal mining and gas extraction,scientific and reasonable mining and extraction constraints are established.Through the mathematical relationship between various factors,the maximum allowable gas content model in the process of safe coal mining is optimized.Taking the 4308 working face of Chengzhuang Mine as an example,the maximum allowable gas content is calculated to be 6.78m~3/t,and the minimum pre-drainage rate of coal mine safety production is 54%.Thirdly,the’four zones’division method is improved,and the space-time optimization of coal and coalbed methane co-mining is completed.Based on the occurrence conditions of coal resources and the occurrence characteristics of coalbed methane resources,the space-time optimization method is improved.According to the maximum allowable gas content and the original gas content,the distribution of each zone under the original state and the current mining stage of the mine is divided and the pre-drainage time limit of each zone is calculated.The space-time optimization of coal and coalbed methane co-mining is completed.Finally,the technical system of coal and coalbed methane co-mining in each zone is studied and analyzed.