加载条件下软砂岩声波传播特性实验研究
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摘要
软砂岩是红层软岩乃至砂岩中工程力学性质较差的一类岩石,对其超声波传播特性实验研究无论对工程的快速勘察还是岩石特性的理论研究都具有重大意义。因此,实验研究以力学测试系统为基本平台,集成超声波测试系统,同步同向地采集了软砂岩单轴压缩过程中的力学和声学数据,据此讨论了压缩过程中软砂岩不同变形阶段的声波传播特性与应力、岩石内部裂隙发育的相关性及其相互作用机理。研究发现:1纵横波波速、振幅、波形和频谱都随应变表现出阶段性变化特征且与岩石所处的应力-应变阶段相对应;2纵波横波速度都与瞬时弹性模量(应力应变曲线斜率)正相关,振幅与应力正相关;3纵波对岩石内裂隙的闭合紧密程度较为敏感,而横波对岩石内的裂隙数量较为敏感;4通过纵横波波形和频谱对比分析,可以辨别岩石所处的应力应变阶段。
Soft sandstone(SS) is such a kind of sandstone with poor engineering mechanical properties among sandstones and red-bed soft rock.Study on the acoustic wave propagation characteristics of the SS has significant application of rapid survey for engineering and theory research of the rock properties.Therefore,the experiment,which based on the integration of mechanical test system and ultrasonic testing system,synchronously and cordirectionally collected the mechanical and acoustic data of SS in the compression process,pursuant to discuss the correlations and interactive mechanisms between acoustic wave propagation and such factors as stress and internal fracture in different deformation stage of compression process.Researches indicated that:1 Velocity,amplitude of first arriving waves,waveforms and frequency spectrum are changed with the SS deformation corresponding to each stage under the SS being compressed; 2 Both of the velocities of P-wave and S-wave are performance of positive correlations to the instantaneous elastic modulus gradient of the stress-strain curve,amplitude and stress; 3 The Pwave is relatively sensitive to the close degree of the crack closure of the SS,while the S-wave is relatively sensitive to the mumber of cracks; 4 By the study,the NSS deformation stage can be identified by waveforms and frequency spectrum of the acoustic data.
Soft sandstone(SS) is such a kind of sandstone with poor engineering mechanical properties among sandstones and red-bed soft rock.Study on the acoustic wave propagation characteristics of the SS has significant application of rapid survey for engineering and theory research of the rock properties.Therefore,the experiment,which based on the integration of mechanical test system and ultrasonic testing system,synchronously and cordirectionally collected the mechanical and acoustic data of SS in the compression process,pursuant to discuss the correlations and interactive mechanisms between acoustic wave propagation and such factors as stress and internal fracture in different deformation stage of compression process.Researches indicated that:1 Velocity,amplitude of first arriving waves,waveforms and frequency spectrum are changed with the SS deformation corresponding to each stage under the SS being compressed; 2 Both of the velocities of P-wave and S-wave are performance of positive correlations to the instantaneous elastic modulus gradient of the stress-strain curve,amplitude and stress; 3 The Pwave is relatively sensitive to the close degree of the crack closure of the SS,while the S-wave is relatively sensitive to the mumber of cracks; 4 By the study,the NSS deformation stage can be identified by waveforms and frequency spectrum of the acoustic data.
引文
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3 Freund D.Ultrasonic compressional and shear velocities in dry clastics rocks as a function of porosity clay content and confining pressure.Geophysical Journal International,1992;108:125—135
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7 蔡忠理,刘克,吴绵拔,等.单轴压缩过程中花岗岩声学特性的研究.岩土力学,1986;7(2):27—36Cai Zhongli,Liu Ke,Wu Jingba,et al.The research on acoustic properties of granite under uni-axial compression condition.Rock and Siol Mechanics,1989;7(2):27—36
8 罗津辉,蔡忠理.用声波参数确定岩石加载破坏过程的不同阶段.岩土力学,1992;13(1):51—56Luo Jinhui,Cai Zhongli.Determination of the various stages in the process of rock failure under loading by the acoustic parameters.Rock and Soil Mechanics,1989;7(2):51—56
9 刘向君,刘洪,徐晓雷,等.低孔低渗砂岩加载条件下的声波传播特性实验研究.岩石力学与工程学报,2009;28(3):560—567Liu Xiangjun,Liu Hong,XüXiaolei,et al.Experimenal research on acoustic wave propagation charicteristics of low porosity and permeability sandstone under loading conditions.Chinese Journal Rock Mechanics and Engineering,2009;28(3):560—567
10 刘维国,单钰铭,刘荣和.砂岩扩容过程中超声波衰减的实验研究.成都理工大学学报(自然科学版),2006;33(6):611 —616Liu Weiguo,Shan Yuming,Liu Ronghe.Study on ultrasonic attenuation in the process of rock dilatancy by amplitude spectrum ratio.Journal Chengdu University of Technology(Science&Technology Edition),2006;33(6):611—616
2 罗运军,秦本东,何军.3种条件下砂岩超声波波速的实验研究.中国矿业大学学报,2012;41(1):153—158He Yunjun,Qing Ben dong,He Jun.Experimental study of the longitudinal wave velocity sandstone under three different constraints.Journal China University of Ming&Technology,2012;41(1):153—158
3 Freund D.Ultrasonic compressional and shear velocities in dry clastics rocks as a function of porosity clay content and confining pressure.Geophysical Journal International,1992;108:125—135
4 Mckenzie C K,Stacey G P,Gladwin M T.Ultrasonic characteristics of a rock mass.International Journal Rock Mechanics and Mining Sciences&Geomechanics Abstracts,1982;19(1):25—30
5 Toksoz,et al.Attenuation of seismic waves in dry and saturation rocks.Laboratory Meophysics,2000;44(4):681—690
6 Nur A.Effect of stress on velocity anisotropy in rock with cracks.Journal of geophysical research,1971;76(8):2022—2034
7 蔡忠理,刘克,吴绵拔,等.单轴压缩过程中花岗岩声学特性的研究.岩土力学,1986;7(2):27—36Cai Zhongli,Liu Ke,Wu Jingba,et al.The research on acoustic properties of granite under uni-axial compression condition.Rock and Siol Mechanics,1989;7(2):27—36
8 罗津辉,蔡忠理.用声波参数确定岩石加载破坏过程的不同阶段.岩土力学,1992;13(1):51—56Luo Jinhui,Cai Zhongli.Determination of the various stages in the process of rock failure under loading by the acoustic parameters.Rock and Soil Mechanics,1989;7(2):51—56
9 刘向君,刘洪,徐晓雷,等.低孔低渗砂岩加载条件下的声波传播特性实验研究.岩石力学与工程学报,2009;28(3):560—567Liu Xiangjun,Liu Hong,XüXiaolei,et al.Experimenal research on acoustic wave propagation charicteristics of low porosity and permeability sandstone under loading conditions.Chinese Journal Rock Mechanics and Engineering,2009;28(3):560—567
10 刘维国,单钰铭,刘荣和.砂岩扩容过程中超声波衰减的实验研究.成都理工大学学报(自然科学版),2006;33(6):611 —616Liu Weiguo,Shan Yuming,Liu Ronghe.Study on ultrasonic attenuation in the process of rock dilatancy by amplitude spectrum ratio.Journal Chengdu University of Technology(Science&Technology Edition),2006;33(6):611—616