爆炸荷载下含预裂缝的裂纹扩展实验研究
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摘要
预裂爆破技术目前广泛应用于爆破工程中,为了探究预裂爆破形成的预裂缝对爆生裂纹和原生裂纹动态断裂特性的影响,基于数字激光动态焦散线实验开展了一系列研究,获得了裂纹扩展的时实动力学参数。研究结果表明:预裂爆破形成的预裂缝可以阻挡爆生裂纹向保留岩体内扩展,加大被爆岩体的损伤;其两端产生的翼裂纹向保留岩体扩展,且扩展长度随着预裂缝长度的增加而增大;长度较短的预裂缝(L=20～80 mm),对保留岩体内原生裂纹扩展有促进作用,只有当预裂缝长度增加到一定程度(L=100 mm),才会对保留岩体内原生裂纹扩展有抑制作用,预裂缝A长度L=100 mm时,其B裂纹扩展长度为无预裂缝A模型时的21%,Bz和By扩展速度均值为无预裂缝A时的0和64. 8%;当有预裂缝存在时,原生裂纹两端翼裂纹的起裂时间随着预裂缝长度增加而增加,当预裂缝长度增加到一定程度(L=100 mm),迎爆侧翼裂纹没有起裂,By起裂时间推迟到和无预裂缝时一样的150μs;原生裂纹迎爆侧翼裂纹断裂韧度小于背爆侧断裂韧度;当有预裂缝存在时,原生裂纹两端起裂韧度均小于无预裂缝时的起裂韧度,且随着预裂缝长度增加迎爆侧翼裂纹起裂韧度降低;原生裂纹两端应力强度因子峰值随着预裂缝长度增加而减小。
Presplit blasting technology is currently widely used in blasting engineering.In order to investigate the effect of pre-crack formed by split blasting on the dynamic fracture behavior of blasting cracks and original cracks,a series of studies were carried out based on the digital laser dynamic caustic experiment.The real-time dynamic parameters of crack propagation were obtained.The results show that the pre-crack can stop blasting-cracks from expanding to the retained rock mass and increase the damage of the explosive rock mass.The wing cracks generated at the both ends of the pre-crack expand to the retained rock mass.As the pre-crack length increases,the wing crack propagation length increases.The shorter pre-crack( L = 20-80 mm) can promote the propagation of the original crack in the retained rock mass.Only when the pre-crack length increases to a certain degree( L = 100 mm),it can inhibit the expansion of the original crack in the retained rock mass. When the length of the pre-crack A is 100 mm,the crack propagation length of B is 21% comparing with no pre-crack A model,and the average speed of Bzand Byis 0 and 64.8% without pre-crack A.When the pre-crack exists,the crack time of the ends of the primary crack increases with the increase of pre-crack length.When the pre-crack length increases to a certain extent( L = 100 mm),explosive flank crack does not crack,Bycrack initiation time is delayed to the same 150 μs as without pre-crack.Fracture toughness of explosive flank crack is less than fracture toughness of backside flanking crack. When the pre-crack exists,the fracture toughness of the ends of the primary crack is less than that of the non-pre-crack,and the fracture toughness of explosive flank crack decreases with the increase of the pre-crack length.The peak of the ends of the primary crack stress intensity decreases with the increase of pre-crack length.
Presplit blasting technology is currently widely used in blasting engineering.In order to investigate the effect of pre-crack formed by split blasting on the dynamic fracture behavior of blasting cracks and original cracks,a series of studies were carried out based on the digital laser dynamic caustic experiment.The real-time dynamic parameters of crack propagation were obtained.The results show that the pre-crack can stop blasting-cracks from expanding to the retained rock mass and increase the damage of the explosive rock mass.The wing cracks generated at the both ends of the pre-crack expand to the retained rock mass.As the pre-crack length increases,the wing crack propagation length increases.The shorter pre-crack( L = 20-80 mm) can promote the propagation of the original crack in the retained rock mass.Only when the pre-crack length increases to a certain degree( L = 100 mm),it can inhibit the expansion of the original crack in the retained rock mass. When the length of the pre-crack A is 100 mm,the crack propagation length of B is 21% comparing with no pre-crack A model,and the average speed of Bzand Byis 0 and 64.8% without pre-crack A.When the pre-crack exists,the crack time of the ends of the primary crack increases with the increase of pre-crack length.When the pre-crack length increases to a certain extent( L = 100 mm),explosive flank crack does not crack,Bycrack initiation time is delayed to the same 150 μs as without pre-crack.Fracture toughness of explosive flank crack is less than fracture toughness of backside flanking crack. When the pre-crack exists,the fracture toughness of the ends of the primary crack is less than that of the non-pre-crack,and the fracture toughness of explosive flank crack decreases with the increase of the pre-crack length.The peak of the ends of the primary crack stress intensity decreases with the increase of pre-crack length.
引文
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[13]魏晨慧,朱万成,白羽,等.不同地应力条件下切缝药包爆破的数值模拟[J].爆炸与冲击,2011,32(12):3812-3820.WEI Chenhui,ZHU Wancheng,BAI Yu,et al.Numerical simulation on cutting seam cartridge blasting under different in-situ stress conditions[J].Explosion and Shock Waves,2011,32(12):3812-3820.
[14]杨立云,杨仁树,许鹏.新型数字激光动态焦散线实验系统及其应用[J].中国矿业大学学报,2013,42(2):188-194.YANG Liyun,YANG Renshu,XU Peng.Caustics method combined with laser&digital high-speed camera and its applications[J].Journal of China University of Mining&Technology,2013,42(2):188-194.
[15] MANOGG P. Anwendung der schattenoptik zur untersuchungdes zerreissvorgangs von platen[D]. West Germany:University of Freiburg,1964.
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[17] ROSSMANITH H P,DAEHNKE A,KNASMILLNER R E K,et al.Fracture mechanics applications to drilling and blasting[J].Fatigue and Fracture Engineering Materials and Structures,1997,20(11):1617-1636.
[18]张晓敏,万玲,严波,等.断裂力学[M].北京:清华大学出版社,2012.
[2]龚敏,黄毅华,王德胜,等.松软煤层深孔预裂爆破力学特性的数值分析[J].岩石力学与工程学报,2008,27(8):1674-1681.GONG Min,HUANG Yihua,WANG Desheng,et al.Numerical simulation on mechanical characteristics of deep-holf presplitting blasting soft coal bed[J].Chinese Journal of Rock Mechanics and Engineering,2008,27(8):1674-1681.
[3]王建国,高全臣,吴浩,等.预裂爆破成缝机理的数值模拟研究[J].有色金属(矿山部分),2014,66(2):80-84.WANG Jianguo,GAO Quanchen,WU Hao,et al. Numerical simulation analvsis on mechanism of the crack formation induced by presplit blasting[J]. Nonferrous Metals(Mining Section),2014,66(2):80-84.
[4] BADAL R. Controlled blasting in jointed rocks[J]. International Journal of Rock Mechanics and Mining Sciences,1994,31(1):79-84.
[5]饶宇,夏元友,胡英国,等.预裂缝对爆破振动频谱分布特征的影响[J].振动与冲击,2017,36(7):191-198.RAO Yu,XIA Yuanyou,HU Yingguo,et al. Influence of pre-splitting crack on spectrum distribution characteristics of blasting vibration[J].Journal of Vibration and Shock,2017,36(7):191-198.
[6]杨风威,李海波,刘亚群,等.台阶与预裂爆破岩体振动特征的对比研究[J].煤炭学报,2012,37(8):1285-1291.YANG Fengwei,LI Haibo,LIU Yaqun,et al. Comparative study on vibration characteristics of rock mass induced by bench blasting and pre-splitting blasting[J]. Journal of China Coal Society,2012,37(8):1285-1291.
[7]杨仁树,佟强,杨国梁.聚能管装药预裂爆破模拟试验研究[J].中国矿业大学学报,2010,39(5):631-635.YANG Renshu,TONG Qiang,YANG Guoliang. Pre-splitting Blasting with binding energy tube charges:Simulations and experimental research[J]. Journal of China University of Mining&Technology,2010,39(5):631-635.
[8]杨仁树,王雁冰,杨立云,等.双孔切槽爆破裂纹扩展的动焦散实验[J].中国矿业大学学报,2012,41(6):868-872.YANG Renshu,WANG Yanbing,YANG Liyun,et al.Dynamic caustic experimental in two borehole study of crack propagation cut blasting[J].Journal of China University of Mining&Technology,2012,41(6):868-872.
[9]杨仁树,车玉龙,冯栋凯,等.切缝药包预裂爆破减振技术试验研究[J].振动与冲击,2014,33(12):7-14.YANG Renshu,CHE Yulong,FENG Dongkai,et al.Tests for blasting vibration reduction technique with presplitting blasting of a slotted cartridge[J].Journal of Vibration and Shock,2014,33(12):7-14.
[10]蔡峰,刘泽功,张朝举,等.高瓦斯低透气性煤层深孔预裂爆破增透数值模拟[J].煤炭学报,2007,32(5):499-503.CAI Feng,LIU Zegong,ZHANG Chaoju,et al.Numerical simulation of improving permeability by deep-hole presplitting explosion in loose-soft and low permeability coal seam[J]. Journal of China Coal Society,2007,32(5):499-503.
[11]徐颖,孟益平,宗琦,等.断层带爆炸裂隙区范围及裂纹扩展长度的研究[J].岩土力学,2002,23(1):81-84.XU Ying,MENG Yiping,ZONG Qi,et al.Study on range of cranny and length of fissure expansion in fault zone[J].Rock and Soil Mechanics,2002,23(1):81-84.
[12]谢冰,李海波,王长柏,等.节理几何特征对预裂爆破效果影响的数值模拟[J].岩土力学,2011,32(12):3812-3820.XIE Bing,LI Haibo,WANG Changbai,et al. Numerical simulation of presplit blasting influenced by geometrical characteristics of joints[J].Rock and Soil Mechanics,2011,32(12):3812-3820.
[13]魏晨慧,朱万成,白羽,等.不同地应力条件下切缝药包爆破的数值模拟[J].爆炸与冲击,2011,32(12):3812-3820.WEI Chenhui,ZHU Wancheng,BAI Yu,et al.Numerical simulation on cutting seam cartridge blasting under different in-situ stress conditions[J].Explosion and Shock Waves,2011,32(12):3812-3820.
[14]杨立云,杨仁树,许鹏.新型数字激光动态焦散线实验系统及其应用[J].中国矿业大学学报,2013,42(2):188-194.YANG Liyun,YANG Renshu,XU Peng.Caustics method combined with laser&digital high-speed camera and its applications[J].Journal of China University of Mining&Technology,2013,42(2):188-194.
[15] MANOGG P. Anwendung der schattenoptik zur untersuchungdes zerreissvorgangs von platen[D]. West Germany:University of Freiburg,1964.
[16] THEOCARIS P S,GDOUTOS E E.The modified Dugdale-Barenblatt modelad apted to various fracture configurations in metals[J].International Journal of Fracture,1974,10:549-564.
[17] ROSSMANITH H P,DAEHNKE A,KNASMILLNER R E K,et al.Fracture mechanics applications to drilling and blasting[J].Fatigue and Fracture Engineering Materials and Structures,1997,20(11):1617-1636.
[18]张晓敏,万玲,严波,等.断裂力学[M].北京:清华大学出版社,2012.