岩石三阶弹性模量的高精度测定研究
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摘要
基于岩石的声弹理论,通过脉冲回波方法测量双轴加载条件下沿薄板岩样厚度方向传播的超声纵、横波波速变化,来测定岩石的三阶弹性模量。试验结果表明:将横波和纵波传感器放置于岩样中心部位的相对表面上,测量同一地点的纵、横波波速,不仅减弱了双向加载端部效应,而且克服了岩石的非均质性对测量结果的影响。此外,通过脉冲回波方法测量多次回波信号的时间差,来克服耦合剂和测量电路对走时差的影响。该方法可以实现岩石三阶弹性模量的高精度测定,从而为地应力测量声弹法的实现提供技术保障。
Based on the acoustoelastic theory of rock,velocity variation of longitudinal and transverse ultrasonic waves propagating along the thickness direction of plate rock samples under biaxial loading condition is measured by the pulse echo method to investigate the third-order elastic modulus for rock. The test results indicate that sensors of transversal wave and longitudinal wave are set at the relative surface of the central portion of rock specimen to measure the transversal wave and longitudinal wave at the same position,which not only can weaken the biaxial loading end effect,but also overcome the influence of rock anisotropy on the measured results. Furthermore,time difference between multi-echo signals is measured by pulse-echo method to overcome the influence of couplant and measured circuit on the travel-time difference of echo signals. The pulse-echo method can implement the high-precision measurement of third-order elastic modulus for rock,which provides technical support for the measurement of in-situ crustal stresses.
Based on the acoustoelastic theory of rock,velocity variation of longitudinal and transverse ultrasonic waves propagating along the thickness direction of plate rock samples under biaxial loading condition is measured by the pulse echo method to investigate the third-order elastic modulus for rock. The test results indicate that sensors of transversal wave and longitudinal wave are set at the relative surface of the central portion of rock specimen to measure the transversal wave and longitudinal wave at the same position,which not only can weaken the biaxial loading end effect,but also overcome the influence of rock anisotropy on the measured results. Furthermore,time difference between multi-echo signals is measured by pulse-echo method to overcome the influence of couplant and measured circuit on the travel-time difference of echo signals. The pulse-echo method can implement the high-precision measurement of third-order elastic modulus for rock,which provides technical support for the measurement of in-situ crustal stresses.
引文
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[12]TIAN J Y,MAN Y P,XIE Z M,et al.Influence of stress on elastic wave velocity around a borehole in rocks[C]//Proceedings of the14th World Conference on Earthquake Engineering,Beijing:[s.n.],2008:12–17.
[13]THURSTON R N,BRUGGER K.Third-order elastic constants and the velocity of small amplitude elastic waves in homogeneously stressed media[J].Physical Review,1964,(6A):1604–1610.
[14]BREAZEALE M A,PHILIP J.Determination of third order elastic constants from ultrasonic harmonic generation measurements[M].Orlands:Academic Press,1984:1–60.
[15]PAO Y,SACHSE W,FUKUOKA H.Acoustoelastic and ultrasonic measurement of residual stress[M].Orlando:Academic Press,1984:61–143.
[16]MURNAGHAN F D.Finite deformation of an elastic solid[J].American Journal of Mathematics,1937,59(2):235–260.
[2]蔡美峰.地应力测量原理和技术[M].北京:科学出版社,2000.(CAI Meifeng.The measurement principle and technology of in-situ crustal stress[M].Beijing:Science Press,2000.(in Chinese))
[3]苏恺之.地应力测量方法[M].北京:地震出版社,1985.(SU Kaizhi.The measurement method of in-situ crustal stress[M].Beijing:EarthquakePress,1985.(in Chinese))
[4]BIRCH F.The velocity of compressional waves in rocks to10kilobars,part1[J].Journal of Geophysical Research,1960,65(4):1083–1102.
[5]BIRCH F.The velocity of compressional waves in rocks to10kilobars,part2[J].Journal of Geophysical Research,1961,66(7):2199–2224.
[6]HUANG X J,BURNS D R,TOKSOZ M N,et al.The effect of stresses on the sound velocity in rocks:theory of acoustoelasticity and experimental measurements[R].Cambridge:ERL,Massachusetts Institute of Technology,2001.
[7]SAYERS C M,MUNSTER J G,KING M S.Stress-induced ultrasonic anisotropy in Berea sandstone[J].International Journal of Rock Mechanics and Mining Sciences,1990,27(5):429–436.
[8]JOHNSON P A,RASOLOFOSAON P N J.Nonlinear elasticity and stress-induced anisotropy in rock[J].Journal of Geophysical Research,1996,101(B2):3113–3124.
[9]SINHA B K,KOSTEK S,NORRIS A N.Stoneley and flxual modes in pressurized boreholes[J].Journal of Geophysical Research,1995,100(B11):22375–22381.
[10]SINHA B K,KOSTEK S.Stress-induced azimuthal anisotropy in borehole flexural waves[J].Geophysics,1996,(6):1899–1907.
[11]田家勇,王恩福.基于声弹理论的地应力超声测量方法[J].岩石力学与工程学报,2006,25(增2):3719–3724.(TIAN Jiayong,WANG Enfu.Ultrasonic method for measuring in-situ stress based on acoustoelasticity theory[J].Chinese Journal of Rock Mechanics and Engineering,2006,25(Supp.2):3719–3724.(in Chinese))
[12]TIAN J Y,MAN Y P,XIE Z M,et al.Influence of stress on elastic wave velocity around a borehole in rocks[C]//Proceedings of the14th World Conference on Earthquake Engineering,Beijing:[s.n.],2008:12–17.
[13]THURSTON R N,BRUGGER K.Third-order elastic constants and the velocity of small amplitude elastic waves in homogeneously stressed media[J].Physical Review,1964,(6A):1604–1610.
[14]BREAZEALE M A,PHILIP J.Determination of third order elastic constants from ultrasonic harmonic generation measurements[M].Orlands:Academic Press,1984:1–60.
[15]PAO Y,SACHSE W,FUKUOKA H.Acoustoelastic and ultrasonic measurement of residual stress[M].Orlando:Academic Press,1984:61–143.
[16]MURNAGHAN F D.Finite deformation of an elastic solid[J].American Journal of Mathematics,1937,59(2):235–260.
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