Study on the mechanical properties of coal under the adsorption of CO2 in different phase states
In order to investigate the effect of different phases of CO2 injected into difficult-to-mining coal seams on the mechanical properties of coal bodies.Taking the mining area of Inner Mongolia Mindong I Mine as an example,coal samples were put into a homemade triaxial adsorption and permeation apparatus,and the adsorption test of different phases of CO2 on the coal samples was carried out by regulating the temperature and pressure,so as to simulate the adsorption process of different phases of CO2 on the difficult-to-explore coal seams under the complex ground stress conditions.The uniaxial compression test was carried out on adsorbed coal samples,supplemented by an acoustic emission device.Changes in compressive strength,modulus of elasticity and acoustic emission energy of the coal body were obtained.Define the degradation of compressive strength and modulus of elasticity of the coal body,and take the cumulative energy of rupture acoustic emission of coal samples without CO2 adsorption as the baseline,and divide the high-energy zone and low-energy zone to get the evolution law of rupture behaviours and damage characteristics of coal samples after CO2 adsorption in different phases.The results show that:(1)CO2 adsorption weakens the mechanical parameters of coal samples,leading to changes in the macroscopic damage characteristics of the coal body and reducing its mechanical properties,and the total deterioration of the compressive strength of the coal body under the effect of CO2 adsorption ranges from 11.72％to 70.89％.(2)The total degradation of the elastic modulus of the coal body under CO2 adsorption ranges from 8.42％to 43.07％,and the total degradation of the coal body under CO2 adsorption in different phases is as follows:supercritical state adsorption group＞liquid state adsorption group＞gas state adsorption group.(3)After CO2 adsorption,more pores and fissures were formed inside the coal samples,resulting in a longer initial compaction time,and at the same time,the elastic deformation ability of the coal samples was weakened,and the elasticity stage of the coal samples adsorbed by gaseous CO2 lasted twice as long as that of the coal samples adsorbed by liquid CO2,and four times as long as that of the coal samples adsorbed by supercritical CO2.(4)Coal samples adsorbed by CO2,without CO2 adsorption of the total acoustic emission energy of the coal samples as a baseline,the division of high-energy and low-energy areas acoustic emission cumulative energy are in the high-energy area,compared with the unadsorbed coal samples,are produced to a certain extent of the rupture.
mining engineeringadsorption of carbon dioxide in different phasesuniaxial compressionacoustic emission energydeterioration degree
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