Use of surface waves for ground characterization via wavelength-depth method
Tham, Lai Shan.
Date of Issue2010
School of Civil and Environmental Engineering
In the past, geotechnical engineers use field tests such as Cone Penetration Test (CPT) to measure the stiffness of the ground. These methods are invasive and require lengthy testing time. Seismic methods can overcome these problems. Surface wave method is one of such seismic methods. The purpose of this project is obtain the soil profile from dispersion curve obtained via surface wave test through the wavelength-depth inversion method and then compared it with the actual soil profile. Through the comparison, improvement is made to the wavelength-depth method. There are a few inversion methods that are used to invert the dispersion curve from surface wave test to obtain the soil profile. Two methods, the linear elastic inversion and wavelength depth inversion method, are discussed in this report. Wavelength-depth inversion method is the main focus of this project. Fifty sets of dispersion curve and soil profile data are collated from the literature ranging from numerical to field data. These data are used to evaluate the wavelength-depth inversion method to determine the soil profile. The wavelength depth inversion method is dependent on (landa) / z , where landa is the wavelength and z is the depth. A chart for determining (landa) / z from frequency and wavelength of the last point on the dispersion curve is evaluated. The main findings are the development of a suitable formula for the shear wave velocity and the use of appropriate scale to determine the layer thickness. These two findings help to ensure that the best soil profile is being identified.
Final Year Project (FYP)
Nanyang Technological University