HTI煤层介质槽波波场与频散特征初步研究

Preliminary study on wave field and dispersion characteristics of channel waves in HTI coal seam medium

煤层内裂隙较为发育,具有明显的各向异性.目前槽波理论研究以各向同性介质为主,对HTI介质中槽波及其频散性质研究很少.本文以弱各向异性、含垂直裂隙HTI煤层介质为研究对象,研究了HTI煤层介质中的三维槽波波场,采用交错网格高阶有限差分法模拟槽波,推导了三层水平层状HTI煤层介质的Love型槽波理论频散公式和振幅深度分布,分析了HTI各弹性参数对频散曲线的影响.HTI介质和各向同性介质基阶Love槽波频散曲线差异较小,高阶较大;煤厚主要影响Airy相频率,而Airy相速度不变;煤层vs对Airy相速度影响很大;煤层γ对基阶Love槽波影响很小,高阶稍大.各波偏振方向不再与波的传播方向平行或垂直,而是呈一定夹角.利用基阶Love槽波频散曲线推测裂隙发育较为困难,可利用高阶频散曲线.

Cracks in the coal seam are relatively developed, with obvious anisotropy. However, the theory of channel wave is mainly isotropic medium at present, and there are few studies on the channel wave field and dispersion properties of HTI medium. Taking HTI medium with weak anisotropy and vertical cracks as the research object, we study the three-dimensional channel wave field in the HTI coal seam medium, and the staggered grid high order finite difference method is used to simulate the channel wave. The theoretical dispersion formula and amplitude depth distribution of the Love channel wave in three horizontal layers of HTI coal seam medium is derived, and the influence of the HTI elastic parameters on the dispersion curve is analyzed. The difference between HTI medium and isotropic medium of fundamental mode Love channel wave dispersion curve is small, and the high order is larger. Coal thickness mainly affects Airy phase frequency, while Airy phase velocity remains unchanged. The coal seam vs has a great influence on the Airy phase velocity. The coal seam γ has little effect on the fundamental mode Love channel wave, and the high order is slightly larger. The polarization direction of each wave is no longer parallel or perpendicular to the direction of wave propagation, but there is an angle between them. It is difficult to predict crack development by using fundamental Love channel wave dispersion curve. However, we can use high order channel wave to detect cracks.