基于声学测试和摄像技术的单裂隙岩石裂纹扩展特征研究
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摘要
为研究裂隙岩石破坏强度及裂纹扩展特征,采用MTS岩石力学试验机对单裂隙岩石进行单轴压缩试验,同步进行声发射、声波及摄像测试,研究裂隙岩石应力应变行为、声波及声发射特征与裂纹扩展、聚结的变化关系。结果表明,起裂应力、峰值强度及模量随裂隙倾角α变化一致,均先减小后增大,起裂应力和强度受α影响较大;裂纹间断性加速扩展引起的应力转移和释放(应力降),导致裂隙岩石应力-应变曲线呈阶梯状上升;应力降伴随着能量释放、刚度劣化和AE振铃计数的激增,随着α的增大,首次应力降和振铃计数陡增对应的应力逐渐增大,且振铃分布向峰值强度附近集中;裂纹起裂、扩展引起波幅和波速衰减,且波幅下降早于应力降的发生。α=0o岩样峰前波速降高达50%,随α的增大,波速下降点的应力逐渐增大,峰前波速降幅不断减小,α较小时峰前裂纹发育程度高,随着α的增大,峰前裂纹发育程度减弱,裂纹加速扩展、聚合向峰后转移;裂纹长度扩展到临界值时扩展速率会发生快速增大,随着α的增大,裂纹临界长度逐渐降低。
In order to study the failure strength and crack propagation characteristics of fractured rocks, the uniaxial compression experiments on rocks with single fissure were carried out by MTS rock mechanics system. Acoustic emission(AE), ultrasonic testing and camera recording were monitored simultaneously to study the relationships between stress-strain behaviors, acoustic emission characteristics, the propagation and coalescence of cracks. The results show that the variations of crack initiation stress, peak strength(PS) and modulus are consistent with the inclination angle α of fissure, which decreases firstly then increases later. Crack initiation stress and peak strength are affected greatly by α. The stress-strain curves of fractured rocks rise stepwise before peak strength attributed to the stress transference and stress release(stress drop) induced by intermittent accelerated propagation of cracks.The stress drop is accompanied with energy release, modulus deterioration and sharp increase in ring counts of acoustic emission.With the increase in α, the stress corresponding to the first stress drop and sharp increase in ring counts of α coustic emission gradually increases. Besides, the ring distribution gradually shifts to peak strength. The initiation and propagation of cracks result in the attenuation of wave amplitude and velocity, and the amplitude decrease occurs earlier than that of stress drop. The velocity decrease of rock sample with α = 0o reaches up to 50% before peak strength. With the increase in α, the stress increases at the moment corresponding to the velocity drop, and the drop rate of wave velocity before peak strength decreases gradually. When α is small,crack propagation is highly developed before peak strength of rock. It shows that with the increase in α, crack development before peak strength subsides. Thus the accelerated crack propagation and convergence transfer to post-peak stage. When the crack length is extended to a critical value, the expansion rate will increase rapidly. The threshold of crack length gradually decreases as α increases.
In order to study the failure strength and crack propagation characteristics of fractured rocks, the uniaxial compression experiments on rocks with single fissure were carried out by MTS rock mechanics system. Acoustic emission(AE), ultrasonic testing and camera recording were monitored simultaneously to study the relationships between stress-strain behaviors, acoustic emission characteristics, the propagation and coalescence of cracks. The results show that the variations of crack initiation stress, peak strength(PS) and modulus are consistent with the inclination angle α of fissure, which decreases firstly then increases later. Crack initiation stress and peak strength are affected greatly by α. The stress-strain curves of fractured rocks rise stepwise before peak strength attributed to the stress transference and stress release(stress drop) induced by intermittent accelerated propagation of cracks.The stress drop is accompanied with energy release, modulus deterioration and sharp increase in ring counts of acoustic emission.With the increase in α, the stress corresponding to the first stress drop and sharp increase in ring counts of α coustic emission gradually increases. Besides, the ring distribution gradually shifts to peak strength. The initiation and propagation of cracks result in the attenuation of wave amplitude and velocity, and the amplitude decrease occurs earlier than that of stress drop. The velocity decrease of rock sample with α = 0o reaches up to 50% before peak strength. With the increase in α, the stress increases at the moment corresponding to the velocity drop, and the drop rate of wave velocity before peak strength decreases gradually. When α is small,crack propagation is highly developed before peak strength of rock. It shows that with the increase in α, crack development before peak strength subsides. Thus the accelerated crack propagation and convergence transfer to post-peak stage. When the crack length is extended to a critical value, the expansion rate will increase rapidly. The threshold of crack length gradually decreases as α increases.
引文
[1] WONG R H C, CHAU K T. Crack coalescence in a rock-likematerialcontainingtwocracks[J].International Journal of Rock Mechanics&Mining Sciences, 1998, 35(2):147-164.
[2]刘红岩,邓正定,王新生,等.节理岩体动态破坏的SHPB相似材料试验研究[J].岩土力学, 2014, 35(3):659-665.LIU Hong-yan, DENG Zheng-ding, WANG Xin-sheng,et al. Similar material test study of dynamic failure of jointed rock mass with SHPB[J]. Rock and Soil Mechanics, 2014, 35(3):659-665.
[3]刘欣宇,刘爱华,李夕兵.充填柱状节理类岩石材料的试验研究[J].岩石力学与工程学报, 2014, 33(4):772-777.LIU Xin-yu, LIU Ai-hua, LI Xi-bing. Experimental study of columnar jointed sandstone-like material with preset filling[J]. Chinese Journal of Rock Mechanics and Engineering, 2014, 33(4):772-777.
[4] LAJTAI E Z. Brittle fracture in compression[J].International Journal of Fracture, 1974, 10(4):525-536.
[5] INGRAFFEA A R, HEUZE F E. Finite element models for rock fracture mechanics[J]. International Journal for Numerical&Analytical Methods in Geo-mechanics,1980, 4(1):25-43.
[6]陈新,廖志红,李德建.节理倾角及连通率对岩体强度、变形影响的单轴压缩试验研究[J].岩石力学与工程学报, 2011, 30(4):781-789.CHEN Xin, LIAO Zhi-hong, LI De-jian. Experimental study of effects of joint inclination angle and connectivity rate on strength and deformation properties of rock masses under uniaxial compression[J]. Chinese Journal of Rock Mechanics and Engineering, 2011, 30(4):781-789.
[7] SHEN B, STEPHANSSON O, EINSTEIN H H, et al.Coalescence of fractures under shear stresses in experiments[J]. Journal of Geophysical Research Solid Earth, 1995, 100(B4):5975-5990.
[8] BOBET A, EINSTEIN H H. Fracture coalescence in rock-type materials under uniaxial and biaxial compression[J]. International Journal of Rock Mechanics&Mining Sciences, 1998, 35(7):863-888.
[9] PRUDENCIO M, JAN M V S. Strength and failure modes of rock mass models with non-persistent joints[J].International Journal of Rock Mechanics&Mining Sciences, 2007, 44(6):890-902.
[10]赵程,田加深,松田浩,等.单轴压缩下基于全局应变场分析的岩石裂纹扩展及其损伤演化特性研究[J].岩石力学与工程学报, 2015, 34(4):763-769.ZHAO Cheng, TIAN Jia-shen, MATSUDA Hiroshi, et al.Crack propagation and damage of rock under uniaxial compression based on global strain field analysis[J].Chinese Journal of Rock Mechanics and Engineering,2015, 34(4):763-769.
[11]赵延林,万文,王卫军,等.类岩石材料有序多裂纹体单轴压缩破断试验与翼形断裂数值模拟[J].岩土工程学报, 2013, 35(11):2097-2109.ZHAO Yan-lin, WAN Wen, WANG Wei-jun, et al.Fracture experiments on ordered multi-crack body in rock-like materials under uniaxial compression and numerical simulation of wing cracks[J]. Chinese Journal of Geotechnical Engineering, 2013, 35(11):2097-2109.
[12]肖桃李,李新平,郭运华.三轴压缩条件下单裂隙岩石的破坏特性研究[J].岩土力学, 2012, 33(11):3251-3256.XIAO Tao-li, LI Xin-ping, GUO Yun-hua, et al.Experimental study of failure characteristic of single jointed rock mass under triaxial compression tests[J].Rock and Soil Mechanics, 2012, 33(11):3251-3256.
[13] LEE H, JEON S. An experimental and numerical study of fracture coalescence in pre-cracked specimens under uniaxial compression[J]. International Journal of Solids&Structures, 2011, 48(6):979-999.
[14] WONG L N Y, EINSTEIN H H. Crack coalescence in molded gypsum and carrara marble:part 1. Macroscopic observations and interpretation[J]. Rock Mechanics and Rock Engineering, 2009, 42(3):475-511.
[15] WONG L NY, EINSTEIN H H. Crack coalescence in molded gypsum and carrara marble. part 2. Microscopic observations and interpretation[J]. Rock Mechanics and Rock Engineering, 2009, 42(3):513-545.
[16]李浩然,杨春和,刘玉刚,等.单轴荷载作用下盐岩声波与声发射特征试验研究[J].岩石力学与工程学报,2014, 33(10):2107-2116.LI Hao-ran, YANG Chun-he, LIU Yu-gang, et al.Experimental study of ultrasonic velocity and acoustic emission properties of salt rock under uniaxial compression load[J]. Chinese Journal of Rock Mechanics and Engineering, 2014, 33(10):2107-2116.
[17]张国凯,李海波,夏祥,等.单轴加载条件下花岗岩声发射及波传播特性研究[J].岩石力学与工程学报,2017, 36(5):1133-1144.ZHANG Guo-kai, LI Hai-bo, XIA Xiang, et al.Experiment study on acoustic emission and wave propagation in granite under uniaxial compression[J].Chinese Journal of Rock Mechanics and Engineering,2017, 36(5):1133-1144.
[18]冯夏庭,吴世勇,李邵军,等.中国锦屏地下实验室二期工程安全原位综合监测与分析[J].岩石力学与工程学报, 2016, 35(4):649-657.FENG Xia-ting, WU Shi-yong, LI Shao-jun, et al.Comprehensive field monitoring of deep tunnels at Jinping underground laboratory(CJPL–II)in China[J].Chinese Journal of Rock Mechanics and Engineering,2016, 35(4):649-657.
[19]中华人民共和国国家发展和改革委员会. DL/T 5389-2007水工建筑物岩石基础开挖工程施工技术规范[S].北京:中国电力出版社, 2007.National Development and Reform Commission. DL/T5389-2007 Construction technical specifications on rock-foundation excavating engineering of hydraulic structures[S]. Beijing:China Electric Power Press, 2007.
[20]李新平,赵航,罗忆,等.深部裂隙岩体中弹性波传播与衰减规律试验研究[J].岩石力学与工程学报, 2015,34(11):2319-2326.LI Xin-ping, ZHAO Hang, LUO Yi, et al. Experimental study of propagation and attenuation of Elastic wave in deep rock mass with joints[J]. Chinese Journal of Rock Mechanics and Engineering, 2015, 34(11):2319-2326.
[21] CHOW T M, MEGLIS I L, YOUNG R P. Progressive microcrack development in tests on Lac du Bonnet granite. II. Ultrasonic tomographic imaging[J]. International Journal of Rock Mechanics&Mining Sciences&Geomechanics Abstracts, 1995, 32(8):751-761.
[22] GANNE P, VERVOORT A. Effect of stress path on pre-peak damage in rock induced by macro-compressive and-tensile stress fields[J]. International Journal of Fracture, 2007, 144(2):77-89.
[23] YANG S Q, JING H W. Strength failure and crack coalescence behavior of brittle sandstone samples containing a single fissure under uniaxial compression[J].International Journal of Fracture, 2011, 168(2):227-250.
[24] EBERHARDT E, STEAD D, STIMPSON B, et al.Identifying crack initiation and propagation thresholds in brittle rock[J]. Canadian Geotechnical Journal, 1998,35(2):222-233.
[25] LOKAJí?EK T, GOEL R K, RUDAJEV V, et al.Assessment of velocity anisotropy in rocks[J].International Journal of Rock Mechanics&Mining Sciences, 2013, 57:142-152.
[2]刘红岩,邓正定,王新生,等.节理岩体动态破坏的SHPB相似材料试验研究[J].岩土力学, 2014, 35(3):659-665.LIU Hong-yan, DENG Zheng-ding, WANG Xin-sheng,et al. Similar material test study of dynamic failure of jointed rock mass with SHPB[J]. Rock and Soil Mechanics, 2014, 35(3):659-665.
[3]刘欣宇,刘爱华,李夕兵.充填柱状节理类岩石材料的试验研究[J].岩石力学与工程学报, 2014, 33(4):772-777.LIU Xin-yu, LIU Ai-hua, LI Xi-bing. Experimental study of columnar jointed sandstone-like material with preset filling[J]. Chinese Journal of Rock Mechanics and Engineering, 2014, 33(4):772-777.
[4] LAJTAI E Z. Brittle fracture in compression[J].International Journal of Fracture, 1974, 10(4):525-536.
[5] INGRAFFEA A R, HEUZE F E. Finite element models for rock fracture mechanics[J]. International Journal for Numerical&Analytical Methods in Geo-mechanics,1980, 4(1):25-43.
[6]陈新,廖志红,李德建.节理倾角及连通率对岩体强度、变形影响的单轴压缩试验研究[J].岩石力学与工程学报, 2011, 30(4):781-789.CHEN Xin, LIAO Zhi-hong, LI De-jian. Experimental study of effects of joint inclination angle and connectivity rate on strength and deformation properties of rock masses under uniaxial compression[J]. Chinese Journal of Rock Mechanics and Engineering, 2011, 30(4):781-789.
[7] SHEN B, STEPHANSSON O, EINSTEIN H H, et al.Coalescence of fractures under shear stresses in experiments[J]. Journal of Geophysical Research Solid Earth, 1995, 100(B4):5975-5990.
[8] BOBET A, EINSTEIN H H. Fracture coalescence in rock-type materials under uniaxial and biaxial compression[J]. International Journal of Rock Mechanics&Mining Sciences, 1998, 35(7):863-888.
[9] PRUDENCIO M, JAN M V S. Strength and failure modes of rock mass models with non-persistent joints[J].International Journal of Rock Mechanics&Mining Sciences, 2007, 44(6):890-902.
[10]赵程,田加深,松田浩,等.单轴压缩下基于全局应变场分析的岩石裂纹扩展及其损伤演化特性研究[J].岩石力学与工程学报, 2015, 34(4):763-769.ZHAO Cheng, TIAN Jia-shen, MATSUDA Hiroshi, et al.Crack propagation and damage of rock under uniaxial compression based on global strain field analysis[J].Chinese Journal of Rock Mechanics and Engineering,2015, 34(4):763-769.
[11]赵延林,万文,王卫军,等.类岩石材料有序多裂纹体单轴压缩破断试验与翼形断裂数值模拟[J].岩土工程学报, 2013, 35(11):2097-2109.ZHAO Yan-lin, WAN Wen, WANG Wei-jun, et al.Fracture experiments on ordered multi-crack body in rock-like materials under uniaxial compression and numerical simulation of wing cracks[J]. Chinese Journal of Geotechnical Engineering, 2013, 35(11):2097-2109.
[12]肖桃李,李新平,郭运华.三轴压缩条件下单裂隙岩石的破坏特性研究[J].岩土力学, 2012, 33(11):3251-3256.XIAO Tao-li, LI Xin-ping, GUO Yun-hua, et al.Experimental study of failure characteristic of single jointed rock mass under triaxial compression tests[J].Rock and Soil Mechanics, 2012, 33(11):3251-3256.
[13] LEE H, JEON S. An experimental and numerical study of fracture coalescence in pre-cracked specimens under uniaxial compression[J]. International Journal of Solids&Structures, 2011, 48(6):979-999.
[14] WONG L N Y, EINSTEIN H H. Crack coalescence in molded gypsum and carrara marble:part 1. Macroscopic observations and interpretation[J]. Rock Mechanics and Rock Engineering, 2009, 42(3):475-511.
[15] WONG L NY, EINSTEIN H H. Crack coalescence in molded gypsum and carrara marble. part 2. Microscopic observations and interpretation[J]. Rock Mechanics and Rock Engineering, 2009, 42(3):513-545.
[16]李浩然,杨春和,刘玉刚,等.单轴荷载作用下盐岩声波与声发射特征试验研究[J].岩石力学与工程学报,2014, 33(10):2107-2116.LI Hao-ran, YANG Chun-he, LIU Yu-gang, et al.Experimental study of ultrasonic velocity and acoustic emission properties of salt rock under uniaxial compression load[J]. Chinese Journal of Rock Mechanics and Engineering, 2014, 33(10):2107-2116.
[17]张国凯,李海波,夏祥,等.单轴加载条件下花岗岩声发射及波传播特性研究[J].岩石力学与工程学报,2017, 36(5):1133-1144.ZHANG Guo-kai, LI Hai-bo, XIA Xiang, et al.Experiment study on acoustic emission and wave propagation in granite under uniaxial compression[J].Chinese Journal of Rock Mechanics and Engineering,2017, 36(5):1133-1144.
[18]冯夏庭,吴世勇,李邵军,等.中国锦屏地下实验室二期工程安全原位综合监测与分析[J].岩石力学与工程学报, 2016, 35(4):649-657.FENG Xia-ting, WU Shi-yong, LI Shao-jun, et al.Comprehensive field monitoring of deep tunnels at Jinping underground laboratory(CJPL–II)in China[J].Chinese Journal of Rock Mechanics and Engineering,2016, 35(4):649-657.
[19]中华人民共和国国家发展和改革委员会. DL/T 5389-2007水工建筑物岩石基础开挖工程施工技术规范[S].北京:中国电力出版社, 2007.National Development and Reform Commission. DL/T5389-2007 Construction technical specifications on rock-foundation excavating engineering of hydraulic structures[S]. Beijing:China Electric Power Press, 2007.
[20]李新平,赵航,罗忆,等.深部裂隙岩体中弹性波传播与衰减规律试验研究[J].岩石力学与工程学报, 2015,34(11):2319-2326.LI Xin-ping, ZHAO Hang, LUO Yi, et al. Experimental study of propagation and attenuation of Elastic wave in deep rock mass with joints[J]. Chinese Journal of Rock Mechanics and Engineering, 2015, 34(11):2319-2326.
[21] CHOW T M, MEGLIS I L, YOUNG R P. Progressive microcrack development in tests on Lac du Bonnet granite. II. Ultrasonic tomographic imaging[J]. International Journal of Rock Mechanics&Mining Sciences&Geomechanics Abstracts, 1995, 32(8):751-761.
[22] GANNE P, VERVOORT A. Effect of stress path on pre-peak damage in rock induced by macro-compressive and-tensile stress fields[J]. International Journal of Fracture, 2007, 144(2):77-89.
[23] YANG S Q, JING H W. Strength failure and crack coalescence behavior of brittle sandstone samples containing a single fissure under uniaxial compression[J].International Journal of Fracture, 2011, 168(2):227-250.
[24] EBERHARDT E, STEAD D, STIMPSON B, et al.Identifying crack initiation and propagation thresholds in brittle rock[J]. Canadian Geotechnical Journal, 1998,35(2):222-233.
[25] LOKAJí?EK T, GOEL R K, RUDAJEV V, et al.Assessment of velocity anisotropy in rocks[J].International Journal of Rock Mechanics&Mining Sciences, 2013, 57:142-152.