Study on the change law of temperature and mechanical properties of coal body in uncovering coal seam in low temperature freezing cross-cut
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摘要: 为研究低温冻结石门揭煤煤体温度及力学性能变化规律,制作煤样时将U形铜管预埋在内并进行注液氮冻结,通过温度测量、红外热成像、单轴压缩等试验分析了不同冻结时间下煤样内部及表面温度和应力-应变变化特征。试验结果表明:随着冻结时间的增加,煤样内部及表面温度呈下降趋势;煤样表面最低温度位于U形铜管附近,煤样表面最高温度位于煤样边界;在压密阶段,随着冻结时间的增加,煤样应变逐渐减小,压密阶段缩短;在弹性变形阶段和屈服阶段,随着冻结时间的增加,煤样最大应力和弹性模量均呈增大趋势。Abstract: In order to study the change law of temperature and mechanical properties of coal body in uncovering coal seam in low-temperature freezing cross-cut, U-shaped copper tubes are pre-buried and frozen with liquid nitrogen during the preparation of coal samples. The characteristics of internal and surface temperature and stress-strain changes of coal samples under different freezing times are analyzed by temperature measurement, infrared thermal imaging and uniaxial compression. The test results show that with the increase of freezing time, the internal and surface temperatures of coal samples show a decreasing trend. The lowest surface temperature of coal samples is located near the U-shaped copper tube, and the highest surface temperature of coal samples is located at the boundary of coal samples. In the compaction stage, with the increase of freezing time, the strain of coal samples gradually decreases and the compaction stage shortens. In the elastic deformation stage and yield stage, with the increase of freezing time, the maximum stress and elastic modulus of coal samples both increase.
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