各向异性岩石纵、横波的波速比特性研究

通过对板岩、千枚岩、糜棱岩和变质砂岩等4种各向异性岩石在平行和垂直层理或板理的3个正交方向上进行大量的纵、横波波速试验，并结合对相关文献中已有岩石波速数据的深入分析，提出岩石介质纵、横波波速比的各向异性效应。这种效应广泛存在，其发育程度受到岩石类别的控制。在试验所用的4种岩石中，板岩和千枚岩的波速比的各向异性明显，而糜棱岩和变质砂岩则不甚发育。波速比的各向异性特征主要表现为垂直层理方向上的波速比普遍小于平行层理方向，且两方向波速比的相对增量还随着垂直层理方向上的波速比的增大而逐步减小。基于横观各向同性弹性介质的波速方程，还进一步通过具体算例对这一特征进行较好的理论分析。

CHARACTERISTICS OF VELOCITY RATIO OF P-WAVE AND S-WAVE FOR ANISOTROPIC ROCKS

By measuring the velocities of the P-wave and S-wave in three orthotropic directions including parallel and vertical directions to the stratum of the rock samples for slate, phyllite, mylonite and metasandstone, and based on the wave velocities of other rocks from the relevant studies, the anisotropic effect of wave velocity ratio of the P-wave and S-wave for most rocks is put forward. The anisotropic effect is controlled by the lithologic characteristics, and apparent for slate and phyllite, while not for the other two kinds of rocks, mylonite and metasandstone. The wave velocity ratio vertical to the stratum of the rock samples is usually less than that in parallel direction, and the relative increment of wave velocity ratio between the vertical direction and the parallel direction decreases as the wave velocity ratio in vertical direction gradually increases. By treating the rock as the transverse isotropic elastic medium and using numerical test of the wave velocity function, the property is theoretically validated.