饱和大理岩特征强度试验研究
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摘要
为了研究水对岩石裂纹扩展活动的影响规律和机制,通过单轴压缩声发射试验,采用声发射法和体应变(含裂纹体应变)法确定干燥和饱和大理岩的特征强度,探讨声发射法确定大理岩特征强度的适用性和水对特征强度值变化的影响规律。结合特征强度附近声发射波形信号的主频统计结果,分析讨论水影响特征强度值的内在机制。结果表明:声发射法确定的大理岩起裂强度均小于宏观体应变法,其用于确定饱和岩样起裂强度有较强的适用性,但不适用于损伤强度的确定。岩样饱和后,其归一化起裂强度减小,归一化损伤强度增大。影响机制主要是孔隙水压力作用的强弱和裂纹扩展"阻碍力"。起裂点附近,孔隙水压力作用明显,岩石内部产生较多微观拉破坏,使裂纹在较低应力水平发生稳定扩展。扩容点附近,孔隙水压力作用弱化,产生裂纹扩展"阻碍力",裂纹在较高应力水平发生非稳定性扩展。
The uniaxial compression acoustic emission(AE) tests of dry and saturated marble were carried out to study the effect mechanism of water on crack propagation. The characteristic strength of samples was determined by AE method and volumetric strain(crack volumetric strain) method. The applicability of AE method for determining the characteristic strength was discussed,and the effect mechanism of water on the characteristic strength was analyzed combining statistical analysis results of dominant frequency of AE waveforms in the vicinity of the characteristic strength. The results show that the strength threshold of crack initiation determined by AE method is lower than that by macro volumetric strain method. AE method can be suitably used to determine the strength threshold of crack initiation for saturated rock,whereas it is not appropriate to determine the damage strength threshold. The normalized crack initiation strength of samples decreases and the normalized damage strength increases after saturation. Effect factors of water on the normalized characteristic strength are the intensity of the pore water pressure and the crack growth resistance. Near the moment of crack initiation,the effect of the pore water pressure is obvious and there are many micro-tensile failures inside the rock,which makes crack develop stably at a lower stress level. Near the moment of volume dilation,the effect of the pore water pressure is weakened along with the existence of the crack growth resistance,which makes unstable crack propagation occur at a higher stress level.
The uniaxial compression acoustic emission(AE) tests of dry and saturated marble were carried out to study the effect mechanism of water on crack propagation. The characteristic strength of samples was determined by AE method and volumetric strain(crack volumetric strain) method. The applicability of AE method for determining the characteristic strength was discussed,and the effect mechanism of water on the characteristic strength was analyzed combining statistical analysis results of dominant frequency of AE waveforms in the vicinity of the characteristic strength. The results show that the strength threshold of crack initiation determined by AE method is lower than that by macro volumetric strain method. AE method can be suitably used to determine the strength threshold of crack initiation for saturated rock,whereas it is not appropriate to determine the damage strength threshold. The normalized crack initiation strength of samples decreases and the normalized damage strength increases after saturation. Effect factors of water on the normalized characteristic strength are the intensity of the pore water pressure and the crack growth resistance. Near the moment of crack initiation,the effect of the pore water pressure is obvious and there are many micro-tensile failures inside the rock,which makes crack develop stably at a lower stress level. Near the moment of volume dilation,the effect of the pore water pressure is weakened along with the existence of the crack growth resistance,which makes unstable crack propagation occur at a higher stress level.
引文
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[19]贾雪娜.应变岩爆实验的声发射本征频谱特征[博士学位论文][D].北京:中国矿业大学(北京),2013.(JIA Xuena.Experimental study on acoustic emission Eigen frequency spectrum features of strain bursts[Ph.D.Thesis][D].Beijing:China University of Mining and Technology(Beijing),2013.(in Chinese))
[20]CAI M,KAISER P K,MORIOKA H,et al.FLAC/PFC coupled numerical simulation of AE in large-scale underground excavations[J].International Journal of Rock Mechanics and Mining Sciences,2007,44(4):550-564.
[21]ZHOU Z L,CAI X,ZHAO Y,et al.Strength characteristics of dry and saturated rock at different strain rates[J].Transactions of Nonferrous Metals Society of China,2016,26(7):1 919-1 925.
[22]邓建辉,李林芮,陈菲,等.大理岩破坏的声发射双主频特征及其机制初探[J].工程科学与技术,2018,50(5):1-6.(DENGJianhui,LI Linrui,CHEN Fei,et al.Twin-peak frequencies of acoustic emission due to the fracture of marble and their possible mechanism[J].Advanced Engineering Sciences,2018,50(5):1-6.(in Chinese))
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[24]ZHENG D,LI Q.An explanation for rate effect of concrete strength based on fracture toughness including free water viscosity[J].Engineering Fracture Mechanics,2004,71(16):2 319-2 327.
[2]BIENIAWSKI Z T.Mechanism of brittle fracture of rock:Part I-theory of the fracture process[J].International Journal of Rock Mechanics and Mining Sciences and Geomechanics Abstracts,1967,4(4):395-406.
[3]BIENIAWSKI Z T.Mechanism of brittle rock fracture.Part II.Experimental studies[J].International Journal of Rock Mechanics and Mining Sciences,1967,4(4):407-423.
[4]MARTIN C D.The strength of massive Lac du Bonnet granite around underground openings[Ph.D.Thesis][D].Manitoba,Canada:University of Manitoba,1993.
[5]MARTIN C D.The progressive fracture of Lac du Bonnet granite[J].International Journal of Rock Mechanics and Mining Science and Geomechanics Abstracts,1994,31(6):643-659.
[6]EVERITT R A,LAJTAI E Z.The influence of rock fabric on excavation damage in the Lac du Bonnett granite[J].International Journal of Rock Mechanics and Mining Sciences,2004,41(8):1 277-1 303.
[7]刘宁,张春生,褚卫江.锦屏深埋大理岩破裂特征与损伤演化规律[J].岩石力学与工程学报,2012,31(8):1 606-1 613.(LIU Ning,ZHANG Chunsheng,CHU Weijiang.Fracture characteristics and damage evolution law of Jinping deep marble[J].Chinese Journal of Rock Mechanics and Engineering,2012,31(8):1 606-1 613.(in Chinese))
[8]刘宁,张春生,褚卫江.深埋隧洞开挖损伤区的检测及特征分析[J].岩土力学,2011,32(增2):526-531.(LIU Ning,ZHANGChunsheng,CHU Weijiang.Detection and analysis of excavation damage zone of deep tunnel[J].Rock and Soil Mechanics,2011,32(Supp.2):526-531.(in Chinese))
[9]汪斌,朱杰兵,严鹏,等.大理岩损伤强度的识别及基于损伤控制的参数演化规律[J].岩石力学与工程学报,2012,31(增2):3 967-3 973.(WANG Bin,ZHU Jiebing,YAN Peng,et al.Damage strength determination of marble and its parameters evaluation based on damage control test[J].Chinese Journal of Rock Mechanics and Engineering,2012,31(Supp.2):3 967-3 973.(in Chinese))
[10]王洪亮,范鹏贤,王明洋,等.应变率对红砂岩渐进破坏过程和特征应力的影响[J].岩土力学,2011,32(5):1 340-1 346.(WANGHongliang,FAN Pengxian,WANG Mingyang,et al.Influence of strain rate on progressive failure process and characteristic stresses of red sandstone[J].Rock and Soil Mechanics,2011,32(5):1 340-1 346.(in Chinese))
[11]NING J,WANG J,JIANG J,et al.Estimation of crack initiation and propagation thresholds of confined brittle coal specimens based on energy dissipation theory[J].Rock Mechanics and Rock Engineering,2017,51(5):1-16.
[12]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.
[13]EBERHARDT E,STEAD D,STIMPSON B.Quantifying progressive pre-peak brittle fracture damage in rock during uniaxial compression[J].International Journal of Rock Mechanics and Mining Sciences,1999,36(3):361-380.
[14]周辉,孟凡震,卢景景,等.硬岩裂纹起裂强度和损伤强度取值方法探讨[J].岩土力学,2014,35(4):913-918.(ZHOU Hui,MENGFanzhen,LU Jingjing,et al.Discussion on methods for calculating crack initiation strength and crack damage strength for hard rock[J].Rock and Soil Mechanics,2014,35(4):913-918.(in Chinese))
[15]YAO Q,CHEN T,JU M,et al.Effects of water intrusion on mechanical properties of and crack propagation in coal[J].Rock Mechanics and Rock Engineering,2016,49(12):1-11.
[16]CHEN T,YAO Q L,WEI F,et al.Effects of water intrusion and loading rate on mechanical properties of and crack propagation in coal-rock combinations[J].Journal of Central South University,2017,24(2):423-431.
[17]VISHAL V,RANJITH P G,SINGH T N.An experimental investigation on behaviour of coal under fluid saturation,using acoustic emission[J].Journal of Natural Gas Science and Engineering,2015,22:428-436.
[18]唐鸥玲,李天斌,陈国庆.含水率对砂岩渐进破裂过程影响的试验研究[J].实验力学,2016,31(4):503-510.(TANG Ouling,LITianbin,CHEN Guoqing.Experimental study of the effect of moisture content on progressive failure process of sandstone[J].Journal of Experimental Mechanics,2016,31(4):503-510.(in Chinese))
[19]贾雪娜.应变岩爆实验的声发射本征频谱特征[博士学位论文][D].北京:中国矿业大学(北京),2013.(JIA Xuena.Experimental study on acoustic emission Eigen frequency spectrum features of strain bursts[Ph.D.Thesis][D].Beijing:China University of Mining and Technology(Beijing),2013.(in Chinese))
[20]CAI M,KAISER P K,MORIOKA H,et al.FLAC/PFC coupled numerical simulation of AE in large-scale underground excavations[J].International Journal of Rock Mechanics and Mining Sciences,2007,44(4):550-564.
[21]ZHOU Z L,CAI X,ZHAO Y,et al.Strength characteristics of dry and saturated rock at different strain rates[J].Transactions of Nonferrous Metals Society of China,2016,26(7):1 919-1 925.
[22]邓建辉,李林芮,陈菲,等.大理岩破坏的声发射双主频特征及其机制初探[J].工程科学与技术,2018,50(5):1-6.(DENGJianhui,LI Linrui,CHEN Fei,et al.Twin-peak frequencies of acoustic emission due to the fracture of marble and their possible mechanism[J].Advanced Engineering Sciences,2018,50(5):1-6.(in Chinese))
[23]李林芮.岩石破坏的声发射主频特征与力学机制[博士学位论文][D].成都:四川大学,2017.(LI Linrui.Dominant frequencies and their mechanical mechanism of acoustic emissions in rock failures[Ph.D.Thesis][D].Chengdu:Sichuan University,2017.(in Chinese))
[24]ZHENG D,LI Q.An explanation for rate effect of concrete strength based on fracture toughness including free water viscosity[J].Engineering Fracture Mechanics,2004,71(16):2 319-2 327.