超临界CO2-水-煤相互作用后冲击载荷下煤的动态响应

Dynamic response of coal under impact load after supercritical CO2-water-coal interaction

为研究CO2注入关闭/废弃矿井中煤的力学行为,利用?50 mm分离式Hopkinson压杆(SHPB)试验装置,对自然状态、饱水状态和超临界CO2-水-煤作用后煤样分别进行动态压缩试验,分析3种状态煤样试件在冲击载荷作用下的破坏形态、能量特征以及动态力学参数。试验结果表明:①随应变率增高,相对于自然和饱水状态煤样,超临界CO2-水-煤相互作用后煤样的破碎块度数量更多,碎块粒径更小;②随入射能增大,3种状态煤样的能量反射率、透射率及耗散率的线性变化趋势不同,超临界CO2-水-煤相互作用后煤样的能量反射率显著增高,能量耗散率显著降低;③超临界CO2-水-煤作用后煤岩材料性质发生弱化,在冲击载荷下通过微裂隙萌发扩展来提高耗散能密度,其动态抗压强度和动态弹性模量与耗散能密度间关系介于自然和饱水状态煤样之间。本次试验证实CO2-水-煤作用过程中发生的矿物化学反应、吸附膨胀诱导微观结构改变、裂隙表面能降低等因素能够明显影响煤样的动态响应特征。尽管本文的试验不能完全反映关闭/废弃封存CO2的真实情况,但为后续CO2-水-煤相互作用下煤样动态响应特征研究提供了借鉴。

In order to study the mechanical behavior of coal after CO2 injection in closed/abandoned mines,the ?50 mm split Hopkinson pressure bar(SHPB) test system was used.This dynamic compression tests were carried out on the natural state coal,saturated state and supercritical CO2-water-coal interacted coal samples.Thus,the failure modes,energy characteristics and dynamic mechanical parameters of three state coal samples under impact load were analyzed.The test results show that ① with the increase of strain rate,compared with the natural and saturated state coal samples,the coal samples treated by supercritical CO2-water-coal interaction have more fragments and smaller particles.② With the increase of incident energy,the linear trend of energy reflectance,transmittance and dissipation rate of three state coal samples are different.Coals after supercritical CO2-water-coal interaction show that if energy reflectivity significantly increase,the energy dissipation rate will significantly decrease.③ Compared with the natural and saturated state coal samples,the properties of coal are weakened after supercritical CO2-water-coal interaction,and the dissipated energy density is increased by the micro-crack germination expansion under impact load.Besides,the curves of dynamic compressive strength-dissipated energy and dynamic elastic modulus-dissipated energy density vibrate between natural state and saturated state.The experimental results show that the factors such as mineral chemical reaction,microstructure change induced by adsorption expansion,and surface energy reduction of cracks can significantly affect the dynamic response characteristics of coal samples.Although the experimental methods in this paper cannot fully reflect the real situation of CO2 storage in closed/abandoned,this study provides a relevant reference information for the further research of the dynamic response characteristics of coal samples under the CO2-water-coal interaction.