To investigate the effects of the relative orientation between a sample's principal axes of anisotropy and the principal stress axes on the dynamic behaviour of undisturbed loess, samples with axial inclinations 30° and 90° relative to the horizontal were prepared. The effects of confining pressure and depth of soil also were examined to investigate variations in the dynamic behaviour of loess. The results showed an obvious effect of intrinsic anisotropy on the dynamic behaviour of loess. With all other conditions constant, the higher the confining pressure, the greater the dynamic stress to generate the same dynamic strain. The dynamic stresses of the 90° samples were always greater than those of the 30° samples. The effect of intrinsic anisotropy on the backbone curves was more obvious for the 2 m depth samples than for the 6 m depth samples. The damping ratio was within a certain range and initially increased as the dynamic strain increased and then gradually levelled off. The 2 m samples exhibited higher damping ratios than the 6 m samples. Finally it was found that the intrinsic anisotropy of loess might weaken the sample during the loading process and a confining pressure of 300 kPa was sufficient to nearly eliminate the effects of intrinsic anisotropy.

中文翻译：

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固有各向异性对原状黄土动力特性的影响

为了研究样品的各向异性主轴和主应力轴之间的相对取向对原状黄土动力特性的影响，制备了相对于水平方向呈30°和90°轴向倾斜的样品。还研究了围压和土壤深度的影响，以研究黄土动力特性的变化。结果表明，固有各向异性对黄土动力特性具有明显的影响。在所有其他条件不变的情况下，围压越高，产生相同动态应变的动应力就越大。90°样品的动应力始终大于30°样品的动应力。固有各向异性对主干曲线的影响在深度为2 m的样本中比在深度为6 m的样本中更为明显。阻尼比在一定范围内，最初随着动态应变的增加而增加，然后逐渐趋于平稳。2 m样品比6 m样品具有更高的阻尼比。最终发现，黄土的固有各向异性可能会在加载过程中削弱样品，而300 kPa的围压足以几乎消除固有各向异性的影响。