Effect Of Blasting Impact On Microstructure Of High-low Rank Coal

The pores in coal directly affect the adsorption,desorption,diffusion and seepage of gas.The adsorption and diffusion behavior of coal is also closely related to the change of microcrystalline structure.Therefore,it is of great significance to study the change characteristics of coal microstructure before and after the impact of coal.In order to explore the influence of blasting impact on the microstructure of coal,the low rank coal of Yima Qianqiu Coal Mine in Henan Province and the high rank coal of Chengzhuang Coal Mine in Jincheng,Shanxi Province were taken as the research objects.The blasting impact test was carried out on the coal samples by using explosives.The size of the impact load was controlled by changing the amount of explosives.The low temperature liquid nitrogen adsorption test and X-ray diffraction test were carried out on the coal samples after the impact.The change law of the microstructure of the coal samples under different strength impact loads was analyzed.The results show that:（1）With the increase of impact load,the peak stress of coal samples also increases.When the explosive amount is 50 g,the peak stress of the two coal samples reaches the maximum,respectively.Under the same explosive amount,the peak stress of high-order coal is greater than that of low-order coal.（2）The response of micro pore structure of high rank coal and low rank coal to blasting impact is different.When the impact load of low rank coal is 319.8 MPa,the micro pore is the most developed,and when the impact load of high rank coal is 285.6MPa,the micro pore is the most developed;whether high rank coal or low rank coal,the specific surface area of coal samples is most affected by micropores,and the total pore volume is most affected by micropores.The pore surface of high-rank coal and low-rank coal is rougher,the pore structure is more complex and the adsorption capacity is stronger after blasting impact.（3）After the impact load,the diffraction peak of low-rank coal becomes higher and steeper.The position of diffraction peak shifts to the side with largeθvalue,and the microcrystalline structure parameters change regularly.The surface layer spacing(d₀₀₂)shows a decreasing trend,and the unit stacking degree（L_c）and unit ductility（L_a）show an increasing trend.However,after the impact load,the high-rank coal shows different changes.The diffraction peak and microcrystalline parameters of high-rank coal begin to decrease after reaching the peak.