四种典型地层的瑞雷波“之”字型频散曲线数值模拟研究

Numerical simulation of Rayleigh wave zigzag dispersion curves of four typical strata

虽然MASW技术已经广泛地应用于地基榆测中,但由于缺少大量理论指导,特别是数值模拟方面的研究,其应用受到限制.本文基于有限元软件LS-DYNA,通过数值模拟研究了四种典型地层(递增型地层、含软弱下伏层地层、含软弱夹层地层和硬夹层地层)由MASW方法提取的瑞雷波频散曲线的"之"字型特征.发现对于递增型地层,频散曲线不会出现"之"字型,对于其他三种地层,频散曲线则会出现不同类型的"之"字型,其中含软弱夹层地层"之"字型的位置和尺寸与软夹层的位置和层厚有较好的对应关系,本文的研究结果为实际工程中利用瑞雷波频散曲线的形状判定地层类型和软弱夹层位置提供了重要参考.

MASW technology is widely used in stratum exploration, but its application is limited because of insufficient theoretical guidance, especially numerical simulation research .This article used the finite element software LS-DYNA to study the characteristics of Rayleigh wave zigzag dispersion curves （extracted by MASW method） of four typical strata （stratum of Rayleigh wave velocity increasing with wavelength, stratum with a soft under-layer, with a weak interlayer, and with a hard interlayer） by numerical simulation method. We found that the Rayleigh wave dispersion curve of the first stratum does not show zigzag, however, the Rayleigh wave dispersion curves of the other strata display different zigzag types. Among the four strata, the zigzag position and size of the stratum including a weak interlayer matches well with the position and layer thickness of the weak interlayer. The results of the article offer important reference for using dispersion curve shape to determine stratum types and position of weak interlayer in actual engineering.