Field Test Of Surface Wave Spectrum Analysis And Dynamic Parameters Inversion Of Foundation Soil

In this paper, the field SASW tests(the transient surface wave test by cross spectrum analysis) are carried out in Jining, Inner Mongolia and the free field of Beijing Jiaotong University, which is based on the theory of Rayleigh surface wave and its testing principle. The acceleration sensors are used to record the vertical ground vibration under the vertical action of force hammer, and then the experimental data is analyzed by the method of cross spectrum, cross power spectrum, the coherent function and the actual phase difference, respectively. The measured dispersion curve is finally calculated out. Furthermore, the measured dispersion curve is compared with the theoretical dispersion curve and the results show that the field test is feasibility and rationality.In the dynamic parameters inversion of foundation soil, the mathematical model of inversion is introduced and the inversion program is compiled on the basis of the genetic algorithm by utilizing the measured dispersion curve. The calculated results are compared with the experimental data to validate that the program is correct and effective.Due to the restrictions of many factors in the field SASW, it is difficult to get the complete dispersion curve, and therefore the inversion error is inevitable. The error analysis of the dispersion curve inversion of the missing medium, high or low frequency is carried out in this paper. Moreover, the results of the error analysis are compared with the results of the sensitivity analysis of the frequency dispersion curves for the shear wave velocity in different soil layers and it is proved that the error analysis is right. According to the error analysis, the precise inversion results of the target soil layer can be obtained, in which the effects of the lack of different frequency on the inversion results of different soil layers are taken into account.