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Aiming at the shortcomings of crow search algorithm ( CSA), this paper proposed a crow search algorithm using multi-mode flight ( MFCSA) . Based on the strength of foraging ability, the algorithm divided the population into two groups: strong and weak foraging ability. Those with strong foraging ability adopted the strategy of trailing and tracking the optimal target of the current group, and flied to the vicinity of the current optimal position of the group under the guidance of the group information to carry out search activities, which enhanced the local exploitation ability of the algorithm. Those with weaker foraging ability adopted the two strategies of observing and learning the foraging methods of the strong, and flying away quickly when encountering danger, the former could improve the global exploration ability of the algorithm, and the latter could maintain the diversity of the population. Through the numerical experiment simulation of 15 benchmark test functions and 2 engineering application problems, the results show that the MFCSA has better performance in optimization accuracy, convergence speed, etc., enhances the ability to avoid falling into the local optimum, and has better stability. [ABSTRACT FROM AUTHOR]

This paper took Haishiwan coalfield as the background and CO2 in the No. 2 coal seam of Haishiwan mine area as the main study object, systematically carrying out study of various aspects on the causes of CO2, CO2 enrichment regularity, CO2 occurrence in coal seam of Yaojie coalfield, adsorption and desorption of CO2 in coal, numerical simulation and engineering practice applied to eliminate the risk of coal and CO2 outburst regionally, making some innovations. During the researches, the authors adopted all kinds of research methods that multi-disciplinary theory includes geochemistry, petrology, structural geology, surface chemistry, rock mechanics, mining engineering, mechanics, numerical simulation, theoretical analysis, laboratory experiments and field engineering practice. The main research content and conclusions are as follows: (1) The CO2 concentration range in the eastern coalfield is 18.79% to 96.6%. The δ13Cco2 values are mainly in the range of -5.0‰ to + 1.0‰ ( PDB ), suggesting an inorganic origin of CO2. The ³He/4 He ratios are (0.6 ~ 25.9) x 108, and the R/Ra is 0. 004 2 ~ 0. 185 0, which is a characteristic of crust-derived CO2 gas. The dynamic-thermal metamorphism of the F19 ductile-brittle shear zone is believed to result in the release of CO2 from basement marble formations, which shows an inorganic source of CO2 in the Haishiwan coalfield. The regional geological evolution and multi-periodical F19 fault movement control the formation, migration, and accumulation of CO2. The F19 fault plays multiple roles in the generation, transport, and sequestration of gas during the CO2 formation. (2) The studies on the characteristics of coal absorbing CO2 or CO2 and CH4 mixed gas are carried out under low pressure. The D-A model can fit the adsorption isotherms of CO2 well under low pressure. At the same time, the authors establish the modified D-A, which fit the present high-pressure adsorption data well. The modified model is applied to analyze the supercritical CO2 adsorption isotherms of Haishiwan coal field and abnormal adsorption isotherms introducing free volume theory of polymer. The result is preliminarily verified by desorption curve. (3) The mining depth of the Haishiwan mine coal is 600 to 1 000 m, where the coal reservoir temperature is in the range of 31.72 to 43.88 °C. The measured mixture gas pressure is not less than 7.3 MPa;the CO2 concentration range in the eastern coalfield exceeded 90%; statistical gas content is in the range of 50 to 60 m³/t. Supercritical CO2 is likely to exist in the No. 2 coal seam of the Haishiwan coalfield according to in situ measurement, experimental determination and theoretical analysis. (4) The numerical simulation results indicate that the range of pressure-relief and dilatational strain of lower coal-rock mass increases along with the pore pressure increases, the maximum absolute and the maximum relative amount of deformity reach 328 mm and 0.5 % under pore pressure of 9 MPa respectively. At the same time, the plastic area also increases along with pore pressure enlargement. It is indicated that the pore pressure plays strengthen role in the protected coal seam pressure relief according to plate theory. (5) High pore pressure acts on pressure relief of coal seam, which has been verified in practice of remote protective coal seam mining and pressure-relief gas drainage. The singe gas drainage flow reaches more than 2 m³/min. The coal seam permeability increases by 878 times. The gas content decreases from 53 m³/t to 12 m³/t. The risk of outburst has been eliminated with regard to the No. 2 coal seam. [ABSTRACT FROM AUTHOR]