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煤损伤演化过程中的红外辐射响应特征研究

Characteristics of infrared radiation response during coal damage evolution

  • 摘要: 为揭示煤样损伤破坏机制,为煤岩动力灾害红外辐射遥感监测预警提供理论基础与技术支持,采用红外热成像技术和应变监测技术联合观测煤样单轴加载过程,分析了煤样损伤演化各个阶段其表面平均红外辐射温度(AIRT)和红外热像的响应特征,并尝试揭示煤样损伤演化过程中的红外辐射响应机制。研究结果表明:煤样的红外辐射响应特征与其破坏形式有关,剪切破坏煤样AIRT总体呈上升趋势,张拉破坏煤样AIRT总体呈下降趋势。将煤样损伤演化全过程划分为压密阶段、弹性阶段、裂纹稳定扩展阶段、裂纹非稳定扩展阶段和破坏阶段,发现AIRT在裂纹非稳定扩展阶段变化幅度最小(剪切破坏煤样平均增幅0.03 ℃;张拉破坏煤样平均降幅0.02 ℃),在破坏阶段变化幅度最大。张剪煤样破坏失稳前,其红外热像图中2种趋势相反的热效应(升温热效应和降温热效应)相互抵消,导致AIRT曲线出现“沉寂期”,这种现象可作为煤样破坏失稳的红外辐射前兆。煤样损伤演化不同阶段,红外辐射信息红外辐射响应机制不同:弹性阶段,煤样红外辐射信息变化是由热弹效应主导;裂纹稳定扩展阶段和裂纹非稳定扩展阶段,剪切破坏煤样红外辐射信息变化由摩擦热效应和裂纹扩展热效应主导、张拉破坏煤样红外辐射信息变化由张性变形产生的吸热效应主导。

     

    Abstract: In order to reveal the damage and failure mechanism of coal samples and provide theoretical basis and technical support for infrared radiation remote sensing monitoring and early warning of coal-rock dynamic disasters, the uniaxial loading process of coal samples was observed by using infrared thermal imaging technology and strain monitoring technology, and the damage evolution of coal samples was analyzed. The response characteristics of the surface average infrared radiation temperature (AIRT) and infrared thermal images at each stage were analyzed, and the infrared radiation response mechanism during the evolution of coal sample damage was attempted to be revealed. The research results show that the infrared radiation response characteristics of coal samples are related to their failure modes, and the shear failure of coal AIRT generally shows an upward trend, while the tensile failure of coal AIRT generally shows a downward trend. The whole process of damage evolution of coal samples was divided into compaction stage, elastic stage, stable crack propagation stage, unstable crack growth stage and failure stage. It was found that the variation amplitude of AIRT in the unsteady crack growth stage was the smallest (average increase rate of shear failure coal sample was 0.03 ℃. The average decrease rate of tensile failure coal sample is 0.02 ℃), and the variation amplitude is the largest in the failure stage. Before the failure and instability of the sheared coal sample, the thermal effects of the two opposite trends in the infrared thermal image cancel each other, resulting in the “quiet period” of the AIRT curve, which can be used as the infrared radiation precursor of the failure and instability of the coal sample. The response mechanism of infrared radiation is different in different stages of coal damage evolution. In the elastic stage, the infrared radiation information of coal is dominated by thermal elastic effect. In the stable crack propagation stage and the unstable crack propagation stage, the infrared radiation information of shear failure of coal is dominated by the frictional thermal effect and the thermal effect of crack propagation, while the infrared radiation information of tensile failure of coal is dominated by the endothermic effect of tensile deformation.

     

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