单轴条件下砂岩三维破裂过程的CT观测
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摘要
岩石破裂过程研究一直是岩石力学专家关注的重要问题。本文采用特制的三轴压力仪与医用西门子SOMATOM -plusCT扫描仪结合 ,对砂岩进行了室内单轴压缩试验。通过对砂岩的CT图像和密度损伤增量与应力关系曲线分析 ,结果显示 ,砂岩的破裂演化过程可分为初始损伤的压密、裂纹出现—扩展、裂纹归并—分岔、裂纹重分岔—扩展以及裂纹惯通—宏观破坏等五个阶段。在初始损伤的压密阶段 ,砂岩的密度损伤增量为正值 ,速率也为正 ;在裂纹出现—扩展阶段 ,砂岩出现局部密度损伤增量减小 ,并随应力增加而由正值转为负值 ,速率也由正变负 ;在裂纹归并—分岔阶段 ,砂岩的密度损伤增量全为负值 ,速率也变快 ;在裂纹重分岔—扩展阶段 ,砂岩的密度损伤增量继续变负 ,但速率变慢 ;在裂纹惯通—宏观破坏阶段 ,砂岩的密度损伤增量继续变负 ,速率变的更快。
Fracturing process of rock caused by loading is an important problem in study of failure mechanism of rock. In order to analyze quantitatively the fracturing process of rock, sandstone specimen was tested under uniaxial and triaxial compressions and observed by X-ray . From the result the formula of rock damage variable and its increment and the calculation of rock initial damage variable are proposed. Analyzed CT images and relational curves between stress and density damage increment of sandstone, we found that the fracturing process of sandstone occurred in five stages,i.e. the compaction by initial damage, crack extension, the crack merging and forking of crack, the continuos forking and extension of crack, and the connection of cracks and failure of rock. In the stage of compaction by initial damage, density damage increment of sandstone is positive and the rate ia positive. In the stage of crack extension, local density damage increment of sandstone decreased and changed from positive to negative, and the rates changed also from positive to negative with increasing stress. In the stage of merging and forking of crack, density damage increment of sandstone is negative and the rate became higher. In the stage of continuous forking and extension of crack, density damage increment of sandstone is continuously negative, but the rate became slower. In the stage of connection of cracks and failure of rock, the density damage increment of sandstone is continuously negative and the rate became higher.
Fracturing process of rock caused by loading is an important problem in study of failure mechanism of rock. In order to analyze quantitatively the fracturing process of rock, sandstone specimen was tested under uniaxial and triaxial compressions and observed by X-ray . From the result the formula of rock damage variable and its increment and the calculation of rock initial damage variable are proposed. Analyzed CT images and relational curves between stress and density damage increment of sandstone, we found that the fracturing process of sandstone occurred in five stages,i.e. the compaction by initial damage, crack extension, the crack merging and forking of crack, the continuos forking and extension of crack, and the connection of cracks and failure of rock. In the stage of compaction by initial damage, density damage increment of sandstone is positive and the rate ia positive. In the stage of crack extension, local density damage increment of sandstone decreased and changed from positive to negative, and the rates changed also from positive to negative with increasing stress. In the stage of merging and forking of crack, density damage increment of sandstone is negative and the rate became higher. In the stage of continuous forking and extension of crack, density damage increment of sandstone is continuously negative, but the rate became slower. In the stage of connection of cracks and failure of rock, the density damage increment of sandstone is continuously negative and the rate became higher.
引文
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[18] 张强勇,向文,朱维申.节理岩体能量损伤本构模型与工程应用[J].工程地质学报,1999,7(4):310～314.ZhangQiangyong,XiangWenandZhuWeishen.Constitutivemodelforenergydamageofjointedrockmassanditsengineeringapplication.JournalofEngineeringGeology,1999,7(4):310～314.
[2] 陈忠辉,唐春安,傅宇方.岩石微破裂演化诱致突变的数值模拟[J].岩土工程学报,1998,20(6):9～15.ChenZhonghui,TangChunan,FuYufang.Numericalmodelingofsaltationinducedbymicro-fracturingevolutionofrock.JournalofChineseGeotechnicalEngineering,1998,20(6):9～15.
[3] 谢强,姜崇喜,凌建明.岩石细观力学实验与分析[M ].成都:西南交通大学出版社,1997,50～55.XieQiang,etal..Analysisandtestofrockmeso-mechanics.Chengdu:SouthwestJiaotongUniversityPress,1997,50～55.
[4] LocknerD .Theroleofacousticemissioninthestudyofrockfracture[J].Int.J.RockMech.Min.Sci.&Geomech.Ab str.1993,30(7):883～900.
[5] 雷兴林,马瑾等.三轴压缩条件下粗晶花岗闪长岩声发射三维分布及其分形特征[J].地震地质,1991,13(2):97～114.LeiXinglin,MaJin,etal.Threedimensionaldistributionandfractalstructureofacousticemissionincoarsedioriterockundertriaxialcompressionconditions.SeismologyandGeology,1991,13(2):97～114.
[6] TakashiIKEDA ,KoichiKOTANI,YuichiroMAEDA ,etal.,PreliminarystudyonapplicationofX -rayCTscannertomea surementofvoidfractionsinsteadystatetwo-phaseflows[J].JournalofNuclearScienceandTechnology,1983,20(1):1～12.
[7] KanakataH ,etal.Three-dimensionalobservationsoffaultingprocessinWesterlygraniteunderuniaxialconditionsbyX -rayCTscan[J].Tectonophysics,313,1999:293～305.
[8] 杨更社,张长庆.岩体损伤及检测[M ].西安:陕西科学技术出版社,1998,76～79.YangGengsheandZhangChangqing.Rockmassdamageanditsdetecting.Xi’an:ShaanxiScienceandTechnologyPress,1998,76～79.
[9] 葛修润,任建喜,蒲毅彬,等.岩石细观损伤扩展规律的CT时实试验[J].中国科学(E辑),2000,30(2):104～110.GeXiurun,RenJianxi,etal.Areal-in-timeCTtestingofmeso-damageevolutionlawofrock.ScienceInChina(SeriesE),2000,30(2):104～110.
[10] 仵彦卿,丁卫华.等.压缩条件下岩石密度损伤增量的CT动态观测[J].自然科学进展,2000,10(9):830～835.WuYanqingetal.Real-timeobservationofrockdensitydam ageincrementsundercompressionconditionsbyX -rayCTscan.ProgressinNaturalScience,2000,10(9):830～835.
[11] 丁卫华,仵彦卿,等.受力岩石密度损伤增量及其数字图像[J].西安理工大学学报,2000,16(1):45～48.DingWeihua,WuYanqing,etal.Thedensitydamageincre mentanditsdigitalimageofrockincompression.JournalofXi’anUniversityofTechnology,2000,16(1):45～48.
[12] 丁卫华,仵彦卿,蒲毅彬,廖全荣,CT技术应用于岩石实验动态观测的新进展[J].冰川冻土,2000,22(3):218～222.DingWeihua,WuYanqing,etal.Newprogressinreal-timedetectingofgeotechnicalexperimentbyuseofX -raycomput edtomography.JournalofGlaciologyandGeocryology,2000,22(3):218～222.
[13] 仵彦卿、柴军瑞.作用在岩体裂隙网络中的渗透力分析[J].工程地质学报,2001,9(1):24～28.WuYanqing,ChaiJunrui.Analysisofseepageforcesexertedonfracturenetworkofrockmass.JournalofEngineeringGeol ogy,2001,9(1):24～28.
[14] 柴军瑞,仵彦卿.作用在裂隙中的渗透力分析[J].工程地质学报,2001,9(1):29～31.ChaiJunrui,WuYanqing.Analysisofseepageforcesactingonsingle-fissurewalls.JournalofEngineeringGeology,2001,9(1):29～31.
[15] 仵彦卿、张倬元.岩体水力学导论.[M ].成都:西南交通大学出版社,1995.WuYanqing,ZhangZhuoyuan.IntroductiontoRockMassHydraulics.Chengdu:SouthwestJiaotongUniversityPublish er,1995.
[16] 李云鹏、王芝银.岩体裂隙扩展过程的数值模拟[J].工程地质学报,1995,3(4):48～53.LiYunpeng,WangZhiyin.NumericalSimulationoftheCrackExtensionProcessinRockMasses.JournalofEngineeringGe ology,1995,3(4):48～53.
[18] 张强勇,向文,朱维申.节理岩体能量损伤本构模型与工程应用[J].工程地质学报,1999,7(4):310～314.ZhangQiangyong,XiangWenandZhuWeishen.Constitutivemodelforenergydamageofjointedrockmassanditsengineeringapplication.JournalofEngineeringGeology,1999,7(4):310～314.
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