Numerical Simulation Analysis On The Dispersion Characteristics Of Rayleigh Wave In Complicated Stratum

The exploring method of transient Rayleigh wave compared with other physical exploring methods has some virtues, which are simple, no boring sampling, having very high distinguishable ratio in the shallow stratum and economy and so on. However, to realize propagation characteristic of Rayleigh wave will have instructional function for analyzing complex stratum. Therefore, the aim of this paper is to look for the consistency between factual measuring results of Rayleigh wave and the numerical simulation results calculated by the finite element method under modeling impulse loading, and then using the response of ground surface calculated by the dynamic finite element method is to investigate the dispersion characteristic of Rayleigh wave in complex stratum and utilize it to analyze complex stratum in practice.Rayleigh wave had the disperse characteristic in the stratification ground, so the engineer just utilized it to qualitatively investigate the factual stratum conditions of the project site. In this paper, the response of ground surface subjected by impulse loading was obtained by the dynamic finite element method to model axisymmetric stratum condition that possibly existed in the actual field, and then the propagation characteristic of Rayleigh wave in the stratification groundsill was analyzed by the vertical displacement with time at two'testing point'. Hereby, the dispersion characteristic of Rayleigh wave in the different stratum conditions can be simulated by the numerical method. The main conclusions are as follow:(1) The dispersion characteristic of Rayleigh wave can be explored by the numerical simulation method which model stratification ground. The velocity of Rayleigh wave would increase with wavelength for the stratification stratum in which the super-stratum is soft and the under-layer is hard. When the thickness of strata appears different, the curve Rayleigh wave velocity with depth is also different. When the thickness of super-stratum increases, the Rayleigh wave velocity is lower on the same wavelength.(2)When weak interlayer exists under ground, Rayleigh wave velocity should decrease obviously and inflexion should appear on the dispersion curve. Assumed 0.8 times of wavelength for determined the depth, the dispersion curve can investigate the structure of strata.(3)When inanition exists under ground, sawtooth shape should appear on the dispersion curve. If we assume1.0 times of wavelength for its testing depth, we could get hold of its depth and thickness basically. It is obvious that half-wavelength method on the project can not be used in numerical computation analysis.When weak interlayer or inanition exits in the stratum, its judgment is also different. Finally, the result of numerical computation compared with the testing result validates feasibility of numerical method which studies the propagation characteristic of Rayleigh wave. It would set out foreground to investigate Rayleigh wave of the complex stratum. On this point of view, the numerical simulation analysis of 3D model will be developed in order to offer much more reliable knowledge on the dispersion characteristics of Rayleigh wave.