TI介质Love型槽波频散曲线特性

Characteristics of dispersion curves for Love channel waves in transversely isotropic media

煤层层理结构显著,裂隙较为发育,具有明显的各向异性,但目前对各向异性煤层的槽波频散性质研究很少。本文以VTI介质和HTI介质为模型,采用广义反射-透射系数法求解Love槽波频散曲线数值解,分析了TI介质中几种典型模型的Love槽波频散特征。结果表明:各向同性介质和VTI介质频散曲线差异较大,VTI介质相速度和Airy相速度均大于各向同性介质,在实际槽波探测中忽略此差异会造成较大探测误差;各向同性介质和HTI介质频散曲线差异相对较小,各阶Airy相速度接近;含夹矸煤层模型群速度曲线极不规则,基阶Airy相不明显,一阶Airy相凸显,适合选用一阶槽波探测夹矸。

Coal seams have a pronounced bedding structure with developed cracks and exhibit signifi cant anisotropy.However,few studies have examined the frequency dispersion properties of channel waves in anisotropic coal seams.In this study,numerical solutions are calculated using the generalized reflection–transmission coefficient method for the dispersion curves of Love channel waves in vertical transversely isotropic(VTI)and horizontal transversely isotropic(HTI)medium models.Moreover,the frequency dispersion characteristics of Love channel waves in several typical transversely isotropic models are analyzed.We fi nd that the dispersion curves for isotropic and VTI media diff er signifi cantly.In addition,the phase and Airy-phase velocities in VTI media are higher than those in isotropic media.Thus,neglecting this difference in practical channel wave detection will result in large detection errors.The dispersion curves for the isotropic and HTI media do not differ signifi cantly,and the Airy-phase velocities of various modes are similar.The group-velocity curve for a coal seam model containing a dirt band is found to be extremely irregular.The fundamental-mode Airy phase is not pronounced,but the fi rst-mode Airy phase can be clearly observed.Hence,fi rst-mode channel waves are suitable for detecting dirt bands.