循环载荷下煤样能量转化与碎块分布特征
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摘要
煤矿开采中煤体常处于反复加卸载过程,研究煤体在不同加载速率重复载荷作用下的能量转化与破坏机制对认清煤矿动力灾害本质具有指导意义。利用MTS815.03伺服实验系统,通过单轴循环加卸载试验,结合能量和分形理论,获得了不同加载速率下煤样变形破坏各阶段能量积聚、耗散和释放的转化机制及其与煤样碎块块度分布规律的内在关系,为开展重复载荷作用下煤岩破裂响应及破坏机制的研究提供依据。试验结果表明:煤样能量转化具有明显的阶段性特征,可分为能量初始积累阶段、能量加速积累阶段和能量快速耗散阶段。煤样破坏前耗散能所占比例经历了高—低—高的过程,而弹性能则相反,加载后期弹性能比例下降或耗散能比例的升高,预示着煤样进入加速破坏阶段;能量集聚和释放与加载速率密切相关,随着加载速率的增大,峰值前弹性能所占比例逐渐增加,煤样破坏前更多的能量以弹性能形式储存在煤样体内,岩石破坏后,更多的能量被释放出来,煤样破坏越剧烈,其宏观破坏形态由剪切张拉和劈裂破坏向弹射破坏过渡;循环加卸载下煤样碎块分形特征具有明显的分段性,在小于尺寸阈值范围内具有较好的自相似性特征,不同加载速率下碎块分形维数为2～3,且随加载速率的增加成线性增长;加载速率越大碎块分形维数越大,煤样破碎程度越高,大块碎块所占比例越小,煤样碎块越破碎且单块碎块质量越小,煤样发生动力灾害的危险性越大。
Coal mass is often affected by consecutive loading-unloading cycles in coal mining,so the study of energy conversion and failure mechanism of coal mass under repeated loads has a guiding significance for understanding the mine dynamic disasters. By using MTS815. 03 servo experimental system,the uniaxial loading cycle tests were performed for the mechanism of energy accumulation,dissipation,and release in the failure process of coal sample under different loading rates,and the fragmentation distribution was also analyzed based on the theoretical analysis of energy and fractal. It provides a basis for the study of burst response and failure mechanism of coal and rock under cyclic loading. The experimental results show that the phasic characteristics of energy conversion are obvious,which can be divided into three stages:initial energy accumulation stage,accelerated energy accumulation stage and fast energy dissipation stage. The proportion of energy dissipation of coal samples encounters the course from high to low again to high. The elastic energy has an opposite trend of change,the proportion of elastic energy drops or the proportion dissipated energy increases at the later stage of loading,the coal samples enter the accelerated failure stage. The energy dissipation and the energy release are closely related with the loading rate. With the increase of loading rate,the proportion of elastic energy increases before the peak stress,sample is damaged severely after the peak stress and its macro failure mode transits from shear tension and splitting failure to ejection failure. Because more energy is stored in the coal sample body in the form of elastic energy before the coal sample is destroyed,and more energy is released after the rock is destroyed,which makes the coal sample destroyed more severely. The phasic characteristics of fractal features of coal samples are obvious under cycling loading and unloading and the self-similarity characteristics are obvious within the range of threshold,the fractal dimension is between 2-3,which increases linearly with the loading rate. The fractal dimension of fragments increases with the increase of loading rate,and the higher the broken degree of coal samples,the smaller the proportion of large fragments. In this case,the higher of the broken level of more fragments and the smaller the mass of single fragments is,the greater the risk of dynamic disasters of coal samples.
Coal mass is often affected by consecutive loading-unloading cycles in coal mining,so the study of energy conversion and failure mechanism of coal mass under repeated loads has a guiding significance for understanding the mine dynamic disasters. By using MTS815. 03 servo experimental system,the uniaxial loading cycle tests were performed for the mechanism of energy accumulation,dissipation,and release in the failure process of coal sample under different loading rates,and the fragmentation distribution was also analyzed based on the theoretical analysis of energy and fractal. It provides a basis for the study of burst response and failure mechanism of coal and rock under cyclic loading. The experimental results show that the phasic characteristics of energy conversion are obvious,which can be divided into three stages:initial energy accumulation stage,accelerated energy accumulation stage and fast energy dissipation stage. The proportion of energy dissipation of coal samples encounters the course from high to low again to high. The elastic energy has an opposite trend of change,the proportion of elastic energy drops or the proportion dissipated energy increases at the later stage of loading,the coal samples enter the accelerated failure stage. The energy dissipation and the energy release are closely related with the loading rate. With the increase of loading rate,the proportion of elastic energy increases before the peak stress,sample is damaged severely after the peak stress and its macro failure mode transits from shear tension and splitting failure to ejection failure. Because more energy is stored in the coal sample body in the form of elastic energy before the coal sample is destroyed,and more energy is released after the rock is destroyed,which makes the coal sample destroyed more severely. The phasic characteristics of fractal features of coal samples are obvious under cycling loading and unloading and the self-similarity characteristics are obvious within the range of threshold,the fractal dimension is between 2-3,which increases linearly with the loading rate. The fractal dimension of fragments increases with the increase of loading rate,and the higher the broken degree of coal samples,the smaller the proportion of large fragments. In this case,the higher of the broken level of more fragments and the smaller the mass of single fragments is,the greater the risk of dynamic disasters of coal samples.
引文
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[11]赵永川,杨天鸿,肖福坤,等.西部弱胶结砂岩循环载荷作用下塑性应变能变化规律[J].煤炭学报,2015,40(8):1813-1819.ZHAO Yongchuan,YANG Tianhong,XIAO Fukun,et al.The variation law of plastic strain energy of western weak cemented sandstone during cyclic loading experiment[J].Journal of China Coal Society,2015,40(8):1813-1819.
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[13]MANDELBROT B B.The fractal geometry of nature[M].San Francisco:W H Freeman,1983.
[14]谢和平.分形-岩石力学导论[M].北京:科学出版社.1997.
[15]谢和平,高峰,周宏伟,等.岩石断裂和破碎的分形研究[J].防灾减灾工程学报,2003,23(4):1-9.XIE Heping,GAO Feng,ZHOU Hongwei,et al.Fractal fracture and fragmentation in rocks[J].Journal of Disaster Prevention and Mitigation Engineering,2003,23(4):1-9.
[16]高峰,谢和平,赵鹏.岩石块度分布的分形性质及细观结构效应[J].岩石力学与工程学报1994,13(13):240.GAO Feng,XIE Heping,ZHAO Peng.Fractal properties of size-frequency distribution of rock fragments and the influence of mesostructure[J].Chinese Journal of Rock Mechanics and Engineering,1994,13(13):240.
[17]高峰,谢和平,巫静波.岩石损伤和破碎相关性的分形分析[J].岩石力学与工程学报1999,18(5):503.GAO Feng,XIE Heping,WU Jingbo.Fractal analysis of the relation between rock damage and rock fragmentation[J].Chinese Journal of Rock Mechanics and Engineering,1999,18(5):503.
[18]邓涛,杨林德,韩文峰.加载方式对大理岩碎块分布影响的试验研究[J].同济大学学报(自然科学版),2007,35(1):10-14.DENG Tao,YANG Linde,HAN Wenfeng.Influence of loading form on distribution of marble fragments[J].Journal of Tong Ji University(Natural Science),2007,35(1):10-14.
[19]何满潮,杨国兴,苗金丽,等.岩爆实验碎屑分类及其研究方法[J].岩石力学与工程学报,2009,28(8):1522-1529.HE Manchao,YANG Guoxing,MIAO Jinli,et al.Classification and research methods of rock burst experimental fragments[J].Chinese Journal of Rock Mechanics and Engineering,2009,28(8):1522-1529.
[20]刘石,许金余,白二雷.基于分形理论的岩石冲击破坏研究[J].振动与冲击,2013,32(5):163-166.LIU Shi,XU Jinyu,BAI Erlei,et al.Research on impact fracture of rock based on fractal theory[J].Journal of Vibration and Shock,2013,32(5):163-166.
[21]张文清,石必明,穆朝民.冲击载荷作用下煤样破碎与耗能规律实验研究[J].采矿与安全工程学报,2016,3(2):375-380.ZHANG Wenqing,SHI Biming,MU Chaomin.Experimental research on failure and energy dissipation law of coal under impact load[J].Journal of Mining&Safety Engineering,2016,3(2):375-380.
[22]王登科,刘淑敏,魏建平,等.冲击载荷作用下煤的破坏特性试验研究[J].采矿与安全工程学报,2017,34(3):594-600.WANG Dengke,LIU Shumin,WEI Jianping,et al.The failure characteristics of coal under impact load in laboratory[J].Journal of Mining&Safety Engineering,2017,34(3):594-600.
[23]乔兰,周明,杨建明,等.高阻尼橡胶用于岩石动载冲击防护的吸能特性试验研究[J].岩石力学与工程学报,2018,37(4):961-968.QIAO Lan,ZHOU Ming,YANG Jianming,et al.Experimental study on energy absorption of high damping rubber for rock under dynamic loads[J].Chinese Journal of Rock Mechanics and Engineering,2018,37(4):961-968.
[24]苏海健,靖洪文,赵洪辉.高温后砂岩单轴压缩加载速率效应的试验研究[J].岩土工程学报,2014,36(6):1064-1071.SU Haijian,JING Hongwen,ZHAO Honghui.Experimental investigation on loading rate effect of sandstone after high temperature under uniaxial compression[J].Chinese Journal of Geotechnical Engineering,2014,36(6):1064-1071.
[25]黄达,谭清,黄润秋.高围压卸荷条件下大理岩破碎块度分形特征及其与能量相关性研究[J].岩石力学与工程学报,2012,31(7):1379-1389.HUANG Da,TAN Qing,HUANG Runqiu.Fractal characteristics of fragmentation and correlation with energy of marble under unloading with high confining pressure[J].Chinese Journal of Rock Mechanics and Engineering,2012,31(7):1379-1389.
[26]许金余,刘石.大理岩冲击加载试验碎块的分形特征分析[J].岩土力学,2012,33(11):3225-3229.XU Jinyu,LIU Shi.Research on fractal characteristics of marble fragments subjected to impact loading[J].Rock and Soil Mechanics,2012,33(11):3225-3229.
[2]马本堃,高尚惠,孙煜.热力学与统计物理学(第二版)[M].北京:高等教育出版社,1995.
[3]彭瑞东,鞠杨,高峰,等.三轴循环加卸载下煤样损伤的能量机制分析[J].煤炭学报,2014,39(2):245-252.PENG Ruidong,JU Yang,GAO Feng,et al.Energy analysis on damage of coal under cyclical triaxial loading and unloading conditions[J].Journal of China Coal Society,2014,39(2):245-252.
[4]宋大钊,王恩元,刘晓斐,等.煤样循环加载破坏电磁辐射能与耗散能的关系[J].中国矿业大学学报,2012,41(2):175-181.SONG Dazhao,WANG Enyuan,LIU Xiaofei,et al.Correlation between electromagnetic radiation and dissipated energy of coal rock during cyclic loading[J].Journal of China University of Mining&Technology,2012,41(2):175-181.
[5]张志镇,高峰.单轴压缩下岩石能量演化的非线性特性研究[J].岩石力学与工程学报,2012,31(6):1198-1207.ZHANG Zhizhen,GAO Feng.Research on nonlinear characteristics of rock energy evolution under uniaxial compression[J].Chinese Journal of Rock Mechanics and Engineering,2012,31(6):1198-1207.
[6]AMMER I B,KARRA C,MAHI A E I,et al.Mechanical behavior and acoustic emission technique for detecting damage in sandwich structures[J].Applied Acoustic,2014,86(86):106-117.
[7]左建平,谢和平,孟冰冰,等.煤岩组合体分级加卸载特性的试验研究[J].岩土力学,2011,32(5):1287-1296.ZUO Jianping,XIE Heping,MENG Bingbing,et al.Experimental research on loading-unloading behavior of coal-rock combination bodies at different stress levels[J].Rock and Soil Mechanics,2011,32(5):1287-1296.
[8]陈岩,左建平,宋洪强,等.煤岩组合体循环加卸载变形及裂纹演化规律研究[J].采矿与安全工程学报,2018,35(4):826-833.CHEN Yan,ZUO Jianping,SONG Hongqiang,et al.Deformation and crack evolution of coal-rock combined body under cyclic loading-unloading effects[J].Journal of Mining&Safety Engineering,2018,35(4):826-833.
[9]赵闯,武科,李术才,等.循环荷载作用下岩石损伤变形与能量特征分析[J].岩土工程学报,2013,35(5):890-896.ZHAO Chuang,WU Ke,LI Shucai,et al.Energy characteristics and damage deformation of rock subjected to cyclic loading[J].Chinese Journal of Geotechnical Engineering,2013,35(5):890-896.
[10]肖福坤,申志亮,刘刚,等.循环加卸载中滞回环与弹塑性应变能关系研究[J].岩石力学与工程学报,2014,33(9):1791-1797.XIAO Fukun,SHEN Zhiliang,LIU Gang,et al.Relationship between hysteresis loop and elastoplastic strain energy during cyclic loading and unloading[J].Chinese Journal of Rock Mechanics and Engineering,2014,33(9):1791-1797.
[11]赵永川,杨天鸿,肖福坤,等.西部弱胶结砂岩循环载荷作用下塑性应变能变化规律[J].煤炭学报,2015,40(8):1813-1819.ZHAO Yongchuan,YANG Tianhong,XIAO Fukun,et al.The variation law of plastic strain energy of western weak cemented sandstone during cyclic loading experiment[J].Journal of China Coal Society,2015,40(8):1813-1819.
[12]肖福坤,刘刚,申志亮,等.循环载荷作用下煤样能量转化规律和声发射变化特征[J].岩石力学与工程学报,2016,35(10):1954-1964.XIAO Fukun,LIU Gang,SHEN Zhiliang,et al.Energy conversion and acoustic emission(AE)characteristics of coal samples under cyclic loading[J].Chinese Journal of Rock Mechanics and Engineering,2016,35(10):1954-1964.
[13]MANDELBROT B B.The fractal geometry of nature[M].San Francisco:W H Freeman,1983.
[14]谢和平.分形-岩石力学导论[M].北京:科学出版社.1997.
[15]谢和平,高峰,周宏伟,等.岩石断裂和破碎的分形研究[J].防灾减灾工程学报,2003,23(4):1-9.XIE Heping,GAO Feng,ZHOU Hongwei,et al.Fractal fracture and fragmentation in rocks[J].Journal of Disaster Prevention and Mitigation Engineering,2003,23(4):1-9.
[16]高峰,谢和平,赵鹏.岩石块度分布的分形性质及细观结构效应[J].岩石力学与工程学报1994,13(13):240.GAO Feng,XIE Heping,ZHAO Peng.Fractal properties of size-frequency distribution of rock fragments and the influence of mesostructure[J].Chinese Journal of Rock Mechanics and Engineering,1994,13(13):240.
[17]高峰,谢和平,巫静波.岩石损伤和破碎相关性的分形分析[J].岩石力学与工程学报1999,18(5):503.GAO Feng,XIE Heping,WU Jingbo.Fractal analysis of the relation between rock damage and rock fragmentation[J].Chinese Journal of Rock Mechanics and Engineering,1999,18(5):503.
[18]邓涛,杨林德,韩文峰.加载方式对大理岩碎块分布影响的试验研究[J].同济大学学报(自然科学版),2007,35(1):10-14.DENG Tao,YANG Linde,HAN Wenfeng.Influence of loading form on distribution of marble fragments[J].Journal of Tong Ji University(Natural Science),2007,35(1):10-14.
[19]何满潮,杨国兴,苗金丽,等.岩爆实验碎屑分类及其研究方法[J].岩石力学与工程学报,2009,28(8):1522-1529.HE Manchao,YANG Guoxing,MIAO Jinli,et al.Classification and research methods of rock burst experimental fragments[J].Chinese Journal of Rock Mechanics and Engineering,2009,28(8):1522-1529.
[20]刘石,许金余,白二雷.基于分形理论的岩石冲击破坏研究[J].振动与冲击,2013,32(5):163-166.LIU Shi,XU Jinyu,BAI Erlei,et al.Research on impact fracture of rock based on fractal theory[J].Journal of Vibration and Shock,2013,32(5):163-166.
[21]张文清,石必明,穆朝民.冲击载荷作用下煤样破碎与耗能规律实验研究[J].采矿与安全工程学报,2016,3(2):375-380.ZHANG Wenqing,SHI Biming,MU Chaomin.Experimental research on failure and energy dissipation law of coal under impact load[J].Journal of Mining&Safety Engineering,2016,3(2):375-380.
[22]王登科,刘淑敏,魏建平,等.冲击载荷作用下煤的破坏特性试验研究[J].采矿与安全工程学报,2017,34(3):594-600.WANG Dengke,LIU Shumin,WEI Jianping,et al.The failure characteristics of coal under impact load in laboratory[J].Journal of Mining&Safety Engineering,2017,34(3):594-600.
[23]乔兰,周明,杨建明,等.高阻尼橡胶用于岩石动载冲击防护的吸能特性试验研究[J].岩石力学与工程学报,2018,37(4):961-968.QIAO Lan,ZHOU Ming,YANG Jianming,et al.Experimental study on energy absorption of high damping rubber for rock under dynamic loads[J].Chinese Journal of Rock Mechanics and Engineering,2018,37(4):961-968.
[24]苏海健,靖洪文,赵洪辉.高温后砂岩单轴压缩加载速率效应的试验研究[J].岩土工程学报,2014,36(6):1064-1071.SU Haijian,JING Hongwen,ZHAO Honghui.Experimental investigation on loading rate effect of sandstone after high temperature under uniaxial compression[J].Chinese Journal of Geotechnical Engineering,2014,36(6):1064-1071.
[25]黄达,谭清,黄润秋.高围压卸荷条件下大理岩破碎块度分形特征及其与能量相关性研究[J].岩石力学与工程学报,2012,31(7):1379-1389.HUANG Da,TAN Qing,HUANG Runqiu.Fractal characteristics of fragmentation and correlation with energy of marble under unloading with high confining pressure[J].Chinese Journal of Rock Mechanics and Engineering,2012,31(7):1379-1389.
[26]许金余,刘石.大理岩冲击加载试验碎块的分形特征分析[J].岩土力学,2012,33(11):3225-3229.XU Jinyu,LIU Shi.Research on fractal characteristics of marble fragments subjected to impact loading[J].Rock and Soil Mechanics,2012,33(11):3225-3229.
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