摘要
为了研究液氮循环冷冲击作用后煤体受拉破坏特征,分别针对0,2,4,6,8,10次液氮冷冲击煤样开展超声测试与巴西劈裂试验,对煤样的纵波波速、抗拉强度、破坏形态、裂隙密度、分形维数等相关物理参数进行分析,同时研究了液氮冷冲击次数对煤样受拉破坏应力场和声发射时域参数特征的影响.研究结果表明:随着冷冲击次数的增加,煤样的纵波波速及抗拉强度逐渐降低,经10次冷冲击后分别降为初始值的37%和30.72%;冷冲击后煤样出现分次破坏且呈现出较明显的屈服阶段.随着冷冲击次数的增加,煤样表面最大应变值逐渐增大,破坏形态从“直线型”逐渐向“网络型”演化,裂隙密度从32.11 m^(-1)逐渐增大至经10次冷冲击后的113.75 m^(-1),同时分形维数从1.15增大至1.49.液氮冷冲击后煤样缓增期内振铃计数出现突变点,且突变点数量随冷冲击次数的增加先升高后降低,第6次冷冲击时达到最大值,之后振铃计数峰值逐渐降低.冷冲击后煤样累计能量曲线呈现阶跃式增长,累计能量峰值随冷冲击次数的增加先升高后降低.弱结构区的存在可能是煤样产生分次破坏、破坏形态向网络型演化以及振铃计数出现突变点的根本原因.
In order to study the tensile failure characteristics of coal after the cyclic cold shock of liquid nitrogen(LN2),ultrasonic tests and Brazilian splitting tests were carried out on the coal samples with 0,2,4,6,8,and 10 times of LN2cold shocks. The related physical parameters such as longitudinal wave velocity,tensile strength,failure modes,crack density and fractal dimension of the coal samples were analyzed,and the influence of the cold shock times of LN2on the stress field and the characteristics of the acoustic emission time-domain parameters of the coal samples subjected to tensile failure was studied. The results indicate that the coal samples are broken in several stages and show a more obvious yield stage after cold shock. With the increase of the cold shock times,the longitudinal wave velocity and tensile strength of the coal samples gradually decrease,which drop to 37% and 30.72% of the initial values after 10 times of cold shocks,respectively. The maximum strain on the surface of the coal samples gradually increase with cold shock times,and the failure mode evolve from ‘line’ to ‘network’. In addition,the crack density increase from 32.11 m^(-1)to 113.75 m^(-1)after 10 times of cold shocks,while the fractal dimension increase from 1.15 to 1.49. There is a sudden change in the ringing count of acoustic emission during the slow increase period of the coal samples after cold shock. The number of the ringing count increase first and then drop with the increase of the cold shock times,reaching the maximum value after 6 times of cold shocks,and then the peak value of it decrease gradually. The cumulative energy curve of the coal samples shows a step increase after cold shock,and the cumulative energy peak increase first and then decrease with the cold shock times. The existence of the weak structural area may be the prime reason for the staged destruction of the coal samples,the evolution of the failure mode to the ‘network’ type and the sudden change of the ringing count of acoustic emission.
作者
陈爱坤
翟成
丛钰洲
孙勇
郑仰峰
CHEN Aikun;ZHAI Cheng;CONG Yuzhou;SUN Yong;ZHENG Yangfeng(School of Safety Engineering,China University of Mining and Technology,Xuzhou,Jiangsu 221l16,China;National Engineering Research Center for Coal Gas Control,China University of Mining and Technology,Xuzhou,Jiangsu 221116,China)
出处
《中国矿业大学学报》
EI
CAS
CSCD
北大核心
2023年第2期342-353,共12页
Journal of China University of Mining & Technology
基金
国家杰出青年科学基金项目(51925404)
国家自然科学基金项目(51774278)
中国矿业大学未来杰出人才助力计划项目(2022WLJCRCZL17)
江苏省研究生科研与实践创新计划项目(KYCX22_2662)。
关键词
煤体
液氮循环冷冲击
受拉破坏
声发射
数字图像相关
coal
cyclic cold shock of liquid nitrogen
tensile failure
acoustic emission
digital image correlation
