高温作用后原煤、型煤力学及声发射特性对比试验研究

Experimental study on mechanical and acoustic emission characteristics of raw coal and briquette after high temperature action

利用单轴压缩试验仪器与声发射检测系统对煤样进行单轴压缩声发射试验,分析温度对原煤、型煤力学及声发射特性的影响规律。结果表明:同一温度下,型煤的峰值强度大于原煤,随着试验温度的升高,原煤的峰值强度与损伤强度逐渐降低,峰值应变也随之减小;型煤的峰值强度逐渐增大,但高温处理后型煤的损伤强度较常温相比降低,两者损伤强度数值在应力-应变曲线拐点附近。通过分析煤样不同阶段的声发射特征,相同温度下原煤、型煤的力学与声发射特性相吻合。原煤加载初期声发射计数出现一段"空白期",随着试验温度的升高,原煤最大振铃计数增大,200℃时达到最大值,型煤最大振铃计数先增大后减小,100℃时达到最大值;应力-时间曲线拐点附近,煤样声发射计数活跃,原煤激增现象明显,且高温处理后的煤样与常温煤样相比,拐点前移;原煤、型煤在加载过程中声发射信号的差异性间接表明了两者结构的差异,对比高温作用后两者力学及声发射特征规律上的不同,更加说明高温作用后原煤内部产生的热应力对结构破坏的剧烈程度。原煤、型煤高温处理后拐点的出现及附近声发射信号激增标志着煤岩内部裂纹大面积产生,据此可对矿井可能发生动力学灾害部位及时采取预防措施。

Uniaxial compression acoustic emission(AE)tests were carried out on coal samples using uniaxial compression test instruments and AE detection system.The effects of temperature on mechanics and AE characteristics of raw coal and briquette were analyzed.The results show that the peak strength of briquette is higher than that of raw coal at the same temperature.With the increase of test temperature,the peak strength and damage strength of raw coal decrease gradually,and the peak strain also decreases,but the peak strength of briquette increases gradually,and the damage strength of briquette after high temperature treatment is lower than that at normal temperature.By analyzing the AE characteristics of coal samples at different stages,the mechanical properties of raw coal and briquette at the same temperature coincide with the characteristics.There is a"blank period"in the initial stage of loading of raw coal.With the increase of test temperature,the maximum AE counts of raw coal increase,reach the maximum at 200℃,the maximum AE counts of briquette increase first and then decrease,and reach the maximum at 100℃.Near the inflection point of stress-time curve,the AE counts of coal samples are active and the raw coal is stimulated.The increase phenomenon is obvious,and the inflection point moves forward after high temperature treatment compared with normal temperature coal sample.The difference of AE signals between raw coal and briquette during loading indirectly indicates the difference of their structures.Compared with the difference of their laws after high temperature action,the difference of thermal stress produced after high temperature action on the internal knot of coal sample is more obvious.The severity of structural damage.The appearance of inflexion point and the sharp increase of AE signal after high temperature treatment of raw coal and briquette indicate the large area of internal cracks in coal and rock.Therefore,preventive measures can be taken in time for possible dynamic disasters in coal mines.