黏弹TI煤层介质3层模型Love槽波频散与衰减特征

煤层是典型的黏弹各向异性介质,将黏弹性和各向异性两种性质结合起来的槽波研究较少。以弱各向异性煤层为研究对象,应用Thomsen等效介质理论,采用Kelvin-Voigt黏弹性模型,研究了黏弹TI(Transverse Isotropy)介质3层水平层状模型Love槽波频散与衰减特征;推导了3层水平介质的Love槽波频散方程解,可以计算品质因子随频率变化的情况;分析了各向异性参数γ、煤层横波品质因子Qs值变化及煤层Qs随频率变化对Love槽波频散、品质因子和衰减曲线的影响;模拟了煤层Qs=10和Qs=20时三维槽波波场传播过程。结果表明:TI介质和各向同性介质的槽波品质因子和衰减系数基阶曲线差别小,各向异性参数γ对Love槽波品质因子和衰减系数影响较小;煤层Qs对Love槽波频散曲线影响很小,主要影响槽波品质因子和衰减系数曲线,煤层Qs=10时槽波衰减系数值比Qs=20和30时大很多;目前煤层Qs在0～1 000 Hz内是否随频率变化尚无定论,假设煤层Qs随频率线性减小,各阶槽波品质因子曲线低频部分差异很小,高频部分差异变大,当Qs减小到10时,槽波衰减系数随频率增长很快;对于三维槽波波...

Dispersion and attenuation characteristics of Love channel waves in the three-layer model of viscoelastic TI coal seam media

The coal seam is a typical viscoelastic anisotropic medium.At present,there is little research on channel waves that combine viscoelasticity and anisotropy.By taking weakly anisotropic coal seams as the research object,applying the Thomsen equivalent medium theory,and adopting the Kelvin-Voigt viscoelastic model,the frequency dispersion and attenuation characteristics of the Love channel waves in the horizontal three-layer model of viscoelastic TI(Transverse Isotropy)medium is studied.The solution of dispersion equation of the Love channel waves for the horizontal three-layer model is derived,which can calculate the case that the quality factor parameter changes with frequency.The influence of the anisotropic parametersγ,the change of coal seam Q_s(shear wave quality factor)and the change of Q_swith frequency on the dispersion and attenuation characteristics of Love channel waves is analyzed.The propagation process of 3D(three dimensional)channel wave field with coal seam Q_sof 10 and 20 is simulated.The following conclusions can be obtained.The difference between the quality factor and attenuation coefficient curves of the fundamental-mode Love channel waves of TI and isotropic medium is small.The anisotropic parameterγhas little effect on the quality factor and attenuation coefficient of the Love channel waves.The Q_sof the coal seam has little influence on the velocity dispersion curves of the Love channel waves,and it mainly affects the quality factor and attenuation coefficient curves of the Love channel waves.When the Q_sof the coal seam is 10,the value of attenuation coefficient of the love channel waves is much larger than that the Q_sis 20 and 30.Whether the Q_sof the coal seam changes with frequency within the range of 0-1000 Hz is not yet definitive at present.Assuming that the Q_sof coal seam decreases linearly with frequency,the difference of the low-frequency part of the quality factor curves is small,the difference in the low-frequency part of the quality factor curves of different mode Love channel waves is small,and the difference in the high-frequency part becomes larger.When the Q_sis reduced to 10,the attenuation coefficient of Love channel waves increases rapidly with the frequency.For the 3D channel wave field,when the Q_sof the coal seam is 20,the energy of the transmission Love channel waves and the transmission fundamental-mode Rayleigh channel waves is strong,and when the Q_sis 10,these waves attenuate quickly and cannot be received by the opposite roadway.It shows that the reason why these waves cannot be received in practical engineering is probably that the Q_sof coal seam is very small.When the Love channel waves and the fundamental-mode Rayleigh channel waves cannot be received in the field working surface detection,the high-mode Rayleigh channel waves with high speed and relatively small attenuation can be used.