预制平行双节理类岩石材料板动态破坏试验研究
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摘要
大型土木工程选址通常会遇到较复杂的地质结构.在工程建设或运营期间,往往受到地震、爆破等动态荷载作用,动载下其基础坐落的岩体内蕴含的节理裂隙会被激活发展,严重威胁着大型岩体工程的安全,因此,研究含节理岩体在动荷载作用下裂纹的起裂及扩展机理十分必要.试验基于断裂力学理论,取含平行双节理的类岩体材料作为研究对象,以节理角度作为变量,制作水泥砂浆试块,利用分离式霍普金森杆(SHPB)加载系统和数字图像相关(DIC)技术,动态捕捉节理的起始扩展及动态传播过程,分析其破坏形态、位移场和应力场,结果表明:①随着节理角度从0°至90°逐渐变化,样品强度呈现出先增大再减小,最后再增大的变化规律;②不同角度双裂纹试样均呈现X型主裂纹分布破坏,试样中心部位出现应变集中,岩桥连通破坏.岩桥破坏类型主要有两种,一种为两条节理尖端斜对角线相连的Z型破坏,另一种为口字形破坏.此外,高加载率会改变Z型岩桥破坏的连通位置;③同等加载条件下,0°节理试样裂纹尖端应力较小;15°～45°节理试样裂纹尖端应力略高,呈现出随加载率先增大后减小的形态;60°节理试样组受压明显导致节理面摩擦增大,使得Ⅱ型应力强度因子KⅡ持续增大;75°～90°试样组应力场由于相对加载方向垂直度较高,导致KⅡ相对较小,变化幅度也较小,破坏形态基本对称,不同裂纹尖端的KⅡ差值也较小.试验结果反映了节理岩体在动态荷载下的扩展机理,为工程建设及地质灾害防治等领域提供了一定的理论支撑.
Major civil infrastructure sites are usually located in high-altitude gorge areas with complex geological structures.When subjected to dynamic loads such as earthquakes and blasting,the development of rock mass fractures is particularly intense,which seriously threatens the safety of rock mass projects.Therefore,it is necessary to study the crack initiation and propagation mechanism of rock mass under impact loads.Herein,based on theory of fracture mechanics,the experiment is designed to study the fracturing behavior of cement mortar specimens with parallel double joint angle as a variable using the split Hopkinson pressure bar(SHPB)system together with an ultrahigh-speed camera and digital image correlation(DIC)technology.The initiation and expansion of the joint cracks are captured,the failure mode is monitored,and the displacement and strain fields are analyzed.The results show that ①As the joint angle changes gradually from 0° to 90°,the strength of the specimens exhibits an increasedecrease-increase trend.②All the specimens with parallel double cracks present an X-type failure pattern with strain concentration occurred at the specimen center.The rock bridge connects through the fracture phenomenon. There are two main types of rock bridge failures,one is the Z type damage connected by two flaw tips diagonally,and the other is the "mouth" shape damage. In addition,the high loading rate will change the connected position of the Z type rock bridge failure. ③The stress is low at the joint tip for 0° specimens;for specimens with 15°—45° joint angles,the stress at the joint tip is slightly high,showing an increase-decrease-increase trend with similar loading rate;in the 60° joint angle group,the surfaces friction of flaws is obviously increased,which increases the type Ⅱintensity factor KⅡ;and for 75°—90° joint angle group,KⅡ is relatively lower owing to the loading direction,with a small magnitude of KⅡ difference and symmetrical damage morphology,the KⅡ difference at different crack tips is also small.The study reveals the failure pattern and failure mechanism of jointed rock mass under dynamic load,which provides certain theoretical support as a reference for engineering construction and geological disaster prevention and control.
Major civil infrastructure sites are usually located in high-altitude gorge areas with complex geological structures.When subjected to dynamic loads such as earthquakes and blasting,the development of rock mass fractures is particularly intense,which seriously threatens the safety of rock mass projects.Therefore,it is necessary to study the crack initiation and propagation mechanism of rock mass under impact loads.Herein,based on theory of fracture mechanics,the experiment is designed to study the fracturing behavior of cement mortar specimens with parallel double joint angle as a variable using the split Hopkinson pressure bar(SHPB)system together with an ultrahigh-speed camera and digital image correlation(DIC)technology.The initiation and expansion of the joint cracks are captured,the failure mode is monitored,and the displacement and strain fields are analyzed.The results show that ①As the joint angle changes gradually from 0° to 90°,the strength of the specimens exhibits an increasedecrease-increase trend.②All the specimens with parallel double cracks present an X-type failure pattern with strain concentration occurred at the specimen center.The rock bridge connects through the fracture phenomenon. There are two main types of rock bridge failures,one is the Z type damage connected by two flaw tips diagonally,and the other is the "mouth" shape damage. In addition,the high loading rate will change the connected position of the Z type rock bridge failure. ③The stress is low at the joint tip for 0° specimens;for specimens with 15°—45° joint angles,the stress at the joint tip is slightly high,showing an increase-decrease-increase trend with similar loading rate;in the 60° joint angle group,the surfaces friction of flaws is obviously increased,which increases the type Ⅱintensity factor KⅡ;and for 75°—90° joint angle group,KⅡ is relatively lower owing to the loading direction,with a small magnitude of KⅡ difference and symmetrical damage morphology,the KⅡ difference at different crack tips is also small.The study reveals the failure pattern and failure mechanism of jointed rock mass under dynamic load,which provides certain theoretical support as a reference for engineering construction and geological disaster prevention and control.
引文
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[13]张盛,王启智,梁亚磊.裂缝长度对岩石动态断裂韧度测试值影响的研究[J].岩石力学与工程学报,2009,28(8):1691-1696.Zhang Sheng,Wang Qizhi,Liang Yalei.Research on influence of crack length on test values of rock dynamic fracture toughness[J].Chinese Journal of Rock Mechanics and Engineering,2009,28(8):1691-1696(in Chinese).
[14]Wang Q Z,Zhang S,Xie H P.Rock dynamic fracture toughness tested with holed-cracked flattened brazilian discs diametrically impacted by SHPB and its size effect[J].Experimental Mechanics,2010,50(7):877-885.
[15]Dai F,Chen R,Iqbal M J,et al.Dynamic cracked chevron notched Brazilian disc method for measuring rock fracture parameters[J].International Journal of Rock Mechanics and Mining Sciences,2010,47(4):606-613.
[16]Dai F,Xia K,Zheng H,et al.Determination of dynamic rock mode-Ⅰfracture parameters using cracked chevron notched semi-circular bend specimen[J].Engineering Fracture Mechanics,2011,78(15):2633-2644.
[17]Dai F,Xia K.Characterization of dynamic rock fracture parameters using notched semi-circular bend(NSCB)method and cracked chevron notched brazilian disc(CCNBD)method[C]//Proceedings of the 12th ISRMInternational Congress on Rock Mechanics.Beijing,China,2012:1183-1188.
[18]Wang Q Z,Feng F,Ni M,et al.Measurement of modeⅠand modeⅡrock dynamic fracture toughness with cracked straight through flattened brazilian disc impacted by split hopkinson pressure bar[J].Engineering Fracture Mechanics,2011,78(12):2455-2469.
[19]Wang Q Z,Yang J R,Zhang C G,et al.Determination of dynamic crack initiation and propagation toughness of a rock using a hybrid experimental-numerical approach[J].Journal of Engineering Mechanics,2016,142(12):04016097.
[20]Zou C J,Wong L N Y.Experimental studies on cracking processes and failure in marble under dynamic loading[J].Engineering Geology,2014,173:19-31.
[21]Zou C J,Wong L N Y,Loo J J,et al.Different mechanical and cracking behaviors of single-flawed brittle gypsum specimens under dynamic and quasi-static loadings[J].Engineering Geology,2016,201:71-84.
[22]Gao G,Yao W,Xia K,et al.Investigation of the rate dependence of fracture propagation in rocks using digital image correlation(DIC)method[J].Engineering Fracture Mechanics,2015,138:146-155.
[23]Gao G,Huang S,Xia K,et al.Application of digital image correlation(DIC)in dynamic notched semi-circular bend(NSCB)tests[J].Experimental Mechanics,2015,55(1):95-104.
[24]Gao G Y,Zhou J,Li Z.Experimental investigation of dynamic fracture behaviors of polymethyl methacrylate[J].Macromolecular Symposia,2016,365(1):180-190.
[25]Liu F,Zheng H,Du X.Hybrid analytical and MLS-based NMM for the determination of generalized stress intensity factors[J].Mathematical Problems in Engineering,2015(1):219657.
[2]Brace W F,Bombolakis E G.A note on brittle crack growth in compression[J].Journal of Geophysical Research,1963,68(12):3709-3713.
[3]Wong L N Y,Einstein H H.Systematic evaluation of cracking behavior in specimens containing single flaws under uniaxial compression[J].International Journal of Rock Mechanics and Mining Sciences,2009,46(2):239-249.
[4]Bobet A,Einstein H H.Fracture coalescence in rocktype materials under uniaxial and biaxial compression[J].International Journal of Rock Mechanics and Mining Sciences,1998,35(7):863-888.
[5]杨圣奇,戴永浩,韩立军,等.断续预制裂隙脆性大理岩变形破坏特性单轴压缩试验研究[J].岩石力学与工程学报,2009,28(12):2391-2404.Yang Shengqi,Dai Yonghao,Han Lijun,et al.Uniaxial compression experimental research ondeformation and failure properties of brittle marblespecimen with pre-existing fissures[J].Chinese Journal of Rock Mechanics and Engineering,2009,28(12):2391-2404(in Chinese).
[6]张伟,周国庆,张海波,等.倾角对裂隙岩体力学特性影响试验模拟研究[J].中国矿业大学学报,2009,38(1):30-33.Zhang Wei,Zhou Guoqing,Zhang Haibo,et al.Experimental research on the influence of obliquity on the mechanical characteristics of a factured rock mass[J].Journal of China University of Mining&Technology,2009,38(1):30-33(in Chinese).
[7]Ashby M F,Hallam S D.The failure of brittle solids containing small cracks under compressive stress states[J].Acta Metallurgica,1986,34(3):497-510.
[8]Ramamurthy T.Shear strength response of some geological materials in triaxial compression[J].International Journal of Rock Mechanics and Mining Sciences,2001,38(5):683-697.
[9]陈卫忠,李术才,邱祥波,等.岩石裂纹扩展的试验与数值分析研究[J].岩石力学与工程学报,2003,22(1):18-23.Chen Weizhong,Li Shucai,Qiu Xiangbo,et al.Experimental and numberial research on crack propagation in rock under compression[J].Chinese Journal of Rock Mechanics and Engineering,2003,22(1):18-23(in Chinese).
[10]张波,李术才,杨学英,等.含交叉裂隙岩体相似材料试件力学性能单轴压缩试验[J].岩土力学,2012,33(12):3674-3679.Zhang Bo,Li Shucai,Yang Xueying,et al.Uniaxial compression tests on mechanical properties of rock masssimilar material with cross-cracks[J].Rock and Soil Mechanics,2012,33(12):3674-3679(in Chinese).
[11]张波,李术才,杨学英,等.含交叉裂隙节理岩体单轴压缩破坏机制研究[J].岩土力学,2014,35(7):1863-1870.Zhang Bo,Li Shucai,Yang Xueying,et al.Uniaxial compression failure mechanism of jointed rock mass with cross-cracks[J].Rock and Soil Mechanics,2014,35(7):1863-1870(in Chinese).
[12]张波,李术才,杨学英,等.含交叉多裂隙类岩石材料单轴压缩力学性能研究[J].岩石力学与工程学报,2015,34(9):1777-1785.Zhang Bo,Li Shucai,Yang Xueying,et al.Mechanical property of rock-like material with intersecting multi-flaws under uniaxial compression[J].Rock and Soil Mechanics,2015,34(9):1777-1785(in Chinese).
[13]张盛,王启智,梁亚磊.裂缝长度对岩石动态断裂韧度测试值影响的研究[J].岩石力学与工程学报,2009,28(8):1691-1696.Zhang Sheng,Wang Qizhi,Liang Yalei.Research on influence of crack length on test values of rock dynamic fracture toughness[J].Chinese Journal of Rock Mechanics and Engineering,2009,28(8):1691-1696(in Chinese).
[14]Wang Q Z,Zhang S,Xie H P.Rock dynamic fracture toughness tested with holed-cracked flattened brazilian discs diametrically impacted by SHPB and its size effect[J].Experimental Mechanics,2010,50(7):877-885.
[15]Dai F,Chen R,Iqbal M J,et al.Dynamic cracked chevron notched Brazilian disc method for measuring rock fracture parameters[J].International Journal of Rock Mechanics and Mining Sciences,2010,47(4):606-613.
[16]Dai F,Xia K,Zheng H,et al.Determination of dynamic rock mode-Ⅰfracture parameters using cracked chevron notched semi-circular bend specimen[J].Engineering Fracture Mechanics,2011,78(15):2633-2644.
[17]Dai F,Xia K.Characterization of dynamic rock fracture parameters using notched semi-circular bend(NSCB)method and cracked chevron notched brazilian disc(CCNBD)method[C]//Proceedings of the 12th ISRMInternational Congress on Rock Mechanics.Beijing,China,2012:1183-1188.
[18]Wang Q Z,Feng F,Ni M,et al.Measurement of modeⅠand modeⅡrock dynamic fracture toughness with cracked straight through flattened brazilian disc impacted by split hopkinson pressure bar[J].Engineering Fracture Mechanics,2011,78(12):2455-2469.
[19]Wang Q Z,Yang J R,Zhang C G,et al.Determination of dynamic crack initiation and propagation toughness of a rock using a hybrid experimental-numerical approach[J].Journal of Engineering Mechanics,2016,142(12):04016097.
[20]Zou C J,Wong L N Y.Experimental studies on cracking processes and failure in marble under dynamic loading[J].Engineering Geology,2014,173:19-31.
[21]Zou C J,Wong L N Y,Loo J J,et al.Different mechanical and cracking behaviors of single-flawed brittle gypsum specimens under dynamic and quasi-static loadings[J].Engineering Geology,2016,201:71-84.
[22]Gao G,Yao W,Xia K,et al.Investigation of the rate dependence of fracture propagation in rocks using digital image correlation(DIC)method[J].Engineering Fracture Mechanics,2015,138:146-155.
[23]Gao G,Huang S,Xia K,et al.Application of digital image correlation(DIC)in dynamic notched semi-circular bend(NSCB)tests[J].Experimental Mechanics,2015,55(1):95-104.
[24]Gao G Y,Zhou J,Li Z.Experimental investigation of dynamic fracture behaviors of polymethyl methacrylate[J].Macromolecular Symposia,2016,365(1):180-190.
[25]Liu F,Zheng H,Du X.Hybrid analytical and MLS-based NMM for the determination of generalized stress intensity factors[J].Mathematical Problems in Engineering,2015(1):219657.
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