A METHOD OF ESTIMATION OF ELASTIC PROPERTIES AND THICKNESSES OF SOIL LAYERS USING VERTICAL HARMONIC LOADING ON GROUND SURFACE AND ITS NUMERICAL VERIFICATION

摘要

This paper presents a new method that may achieve a more accurate and lower cost estimation of elastic properties and thicknesses of soil deposits. The kernel of the proposed method, being independent of the usually adopted assumption that only one Rayleigh wave mode is dominant, is to use the near field characteristics of all types of P-SV wave motions on the surface of elastic multi-layered half space generated by the vertical harmonic load applied on its surface. The near field wave motions are accurately simulated by the stiffness matrix method as one of more powerful numerical solutions, and then the following two physical quantities, which can be observable in the field, are used in inversion analysis: (1) the predominant frequency for which the dynamic vertical displacement on the soil surface takes a maximum value, and (2) the frequency variation of the phase velocity at a point on the soil surface near the vertical harmonic load. The phase velocity used in the proposed method is a local quantity varying with the location from the vertical load, because of using all types of waves and their modes. To demonstrate the capability and reliability of the proposed method, the numerical examples are presented by using regular and irregular soil profiles.