Estimate of Small Stiffness and Damping Ratio in Residual Soil Using Spectral Analysis of Surface Wave Method

Nor Faizah Bawadi,Noor Adila Omar,Khairul Anuar Mohd Nayan,Mohd Raihan Taha,N Abd Rahman,R Yunus,Z Mohd Jaini,S.N Rahmat

doi:10.1051/matecconf/20164703017

Nor Faizah Bawadi, Noor Adila Omar + Show 6 more

Open Access

https://doi.org/10.1051/matecconf/20164703017

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Abstract

Research in the important parameters for modeling the dynamic behavior of soils has led to rapid development of the small strain stiffness and damping ratio for use in the seismic method. It is because, the experimental determination of the damping ratio is problematic, especially for hard soils sample. Many researchers have proved that the surface wave method is a reliable tool to determine shear wave velocity and damping ratio profiles at a site with very small strains level. Surface wave methods based on Rayleigh waves propagation and the resulting attenuation curve can become erroneous when higher modes contribute to the soil’s response. In this study, two approaches has been used to determine the shear strain amplitude and damping ratio of residual soils at small strain level using Spectral Analysis of Surface Wave (SASW) method. One is to derive shear strain amplitude from the frequency-response curve and the other is to derive damping ratio from travel-time data. Then, the results are compared to the conventional method.

Highlights

In many geotechnical engineering applications, the level of strains in the soil is small [9, 11], especially when dealing with normal functionality of the structures
Many researchers have proved that the surface wave method is a reliable tool to determine shear wave velocity and damping ratio profiles at a site with very small strains level
Prediction on characteristic of strain amplitudes and damping in Spectral Analysis of Surface Wave (SASW) method will decreases with depth of soil

Summary

Introduction

In many geotechnical engineering applications, the level of strains in the soil is small [9, 11], especially when dealing with normal functionality of the structures. Within the range of small strain (10-4% or less), [17], the mechanical behavior of the ground can be properly modeled by means of viscoelasticity [3]. The shear modulus and damping ratio profiles at a site can be determined by means of Rayleigh waves propagation [14], by assuming a layered half-space with horizontal, mono-phase, homogeneous and isotropic layers. Rayleigh waves propagate on the free surface of a medium and during propagation they are subjected to dispersion and attenuation. Viscoelasticity dispersion and attenuation phenomena are correlated [8], so that shear modulus and damping ratio are coupled dynamic properties of the soil. At very small deformations uncoupling dispersion and attenuation phenomena may represent a good approximation of soil behavior

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