致密岩石纵横波波速各向异性的比较研究

Anisotropy comparison of P wave and S wave velocity for compacted rocks

通过对板岩、千枚岩、糜棱岩和变质砂岩等4种岩石在平行和垂直层理、板理的3个正交方向上的纵、横波波速试验,提出了致密岩石纵波波速的各向异性与横波波速的各向异性普遍存在着一致性和差异性两种特征。一致性特征主要表现为致密岩石的横波各向异性随纵波各向异性的增强而增强;差异性特征主要表现为在平行和垂直层理、板理的两个方向上,纵波波速的各向异性指数大于横波,亦即纵波波速的各向异性比横波更为显著。从横观各向同性弹性介质的波速方程出发,通过具体的算例对这两种特征进行了较好的理论分析。

By measuring the velocity of the P wave and S wave on the three orthotropic different directions including parallel and vertical direction to the stratum of the compacted rock samples including slate, phyllite, mylonite and metasandstone, the two obvious anisotropy effects of P wave and S wave velocity are put forward. One is the conformity of the anisotropy of P wave and S wave velocity expressed by that the anisotropic indexes of S wave velocity would linearly increase as the P wave anisotropic indexes increase in a great degree, namely the anisotropy of S wave velocity is statistically proportional to that of P wave; the other effect is the variation between P wave and S wave velocity anisotropy, which is mainly expressed by that the anisotropic index of the P wave velocity is usually greater than S wave in the parallel and vertical directions to the stratum of the rock samples which means that the anisotropy of S wave velocity is inferior to that of P wave. Using numerical value test based on the wave velocity function of the transverse isotropic elastic medium, the two effects are validated.