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Determination of the material damping ratio in the soil from SASW tests using the half-power bandwidth method

SA Badsar, M Schevenels, Wim Haegeman UGent and G Degrande (2010) GEOPHYSICAL JOURNAL INTERNATIONAL. 182(3). p.1493-1508
abstract
This paper presents a novel technique for the determination of the material damping ratio in shallow soil layers. It is based on the spectral analysis of surface waves (SASW) test. The technique is an alternative to existing methods, where the damping ratio is determined from the spatial decay of the Rayleigh wave. These methods rely on the knowledge of the geometric damping, and may lead to incorrect results if the geometric damping is calculated based on an inaccurate shear wave velocity profile. The existing methods may also lead to incorrect results when higher modes contribute to the wavefield in the soil. In the proposed technique, the wavefield is transformed to the frequency-wavenumber domain. The resulting frequency-wavenumber spectrum exhibits a peak that corresponds to the fundamental Rayleigh wave. The dispersion curve is derived from the peak's position, whereas the attenuation curve is derived from its width, using the half-power bandwidth method. Due to the use of the appropriate wavenumber transformation, this method does not require the calculation of the geometric damping. In addition, the occurrence of higher Rayleigh modes does not affect the attenuation curve associated with the fundamental Rayleigh wave, as higher modes appear as separate peaks in the frequency-wavenumber spectrum that do not interfere with the peak corresponding to the fundamental Rayleigh wave (except at the osculation points). Three benchmark problems are considered to validate the outlined technique; the results are compared with those obtained using existing methods. All methods perform well when applied to a regular soil profile, where the stiffness of the soil increases with depth. For soil profiles with a soft layer trapped between two stiffer layers, or where the soil properties vary smoothly with depth, the proposed technique yields more accurate results than the existing methods. The practical applicability of the new method is finally illustrated using experimental data collected from a test site in Belgium.
Please use this url to cite or link to this publication:
author
organization
year
type
journalArticle (original)
publication status
published
subject
keyword
Inverse theory, Fourier analysis, Surface waves and free oscillations, Seismic attenuation, Wave propagation, WAVE-FIELD TRANSFORMATION, INDUCED VIBRATIONS, PREDICTION, INVERSION, VALIDATION, DISPERSION, MODEL
journal title
GEOPHYSICAL JOURNAL INTERNATIONAL
Geophys. J. Int.
volume
182
issue
3
pages
1493 - 1508
Web of Science type
Article
Web of Science id
000280997700027
JCR category
GEOCHEMISTRY & GEOPHYSICS
JCR impact factor
2.411 (2010)
JCR rank
21/77 (2010)
JCR quartile
2 (2010)
ISSN
0956-540X
DOI
10.1111/j.1365-246X.2010.04690.x
language
English
UGent publication?
yes
classification
A1
copyright statement
I have transferred the copyright for this publication to the publisher
id
1225938
handle
http://hdl.handle.net/1854/LU-1225938
date created
2011-05-18 10:38:40
date last changed
2011-06-22 09:25:49
@article{1225938,
  abstract     = {This paper presents a novel technique for the determination of the material damping ratio in shallow soil layers. It is based on the spectral analysis of surface waves (SASW) test. The technique is an alternative to existing methods, where the damping ratio is determined from the spatial decay of the Rayleigh wave. These methods rely on the knowledge of the geometric damping, and may lead to incorrect results if the geometric damping is calculated based on an inaccurate shear wave velocity profile. The existing methods may also lead to incorrect results when higher modes contribute to the wavefield in the soil.
In the proposed technique, the wavefield is transformed to the frequency-wavenumber domain. The resulting frequency-wavenumber spectrum exhibits a peak that corresponds to the fundamental Rayleigh wave. The dispersion curve is derived from the peak's position, whereas the attenuation curve is derived from its width, using the half-power bandwidth method. Due to the use of the appropriate wavenumber transformation, this method does not require the calculation of the geometric damping. In addition, the occurrence of higher Rayleigh modes does not affect the attenuation curve associated with the fundamental Rayleigh wave, as higher modes appear as separate peaks in the frequency-wavenumber spectrum that do not interfere with the peak corresponding to the fundamental Rayleigh wave (except at the osculation points).
Three benchmark problems are considered to validate the outlined technique; the results are compared with those obtained using existing methods. All methods perform well when applied to a regular soil profile, where the stiffness of the soil increases with depth. For soil profiles with a soft layer trapped between two stiffer layers, or where the soil properties vary smoothly with depth, the proposed technique yields more accurate results than the existing methods.
The practical applicability of the new method is finally illustrated using experimental data collected from a test site in Belgium.},
  author       = {Badsar, SA and Schevenels, M and Haegeman, Wim and Degrande, G},
  issn         = {0956-540X},
  journal      = {GEOPHYSICAL JOURNAL INTERNATIONAL},
  keyword      = {Inverse theory,Fourier analysis,Surface waves and free oscillations,Seismic attenuation,Wave propagation,WAVE-FIELD TRANSFORMATION,INDUCED VIBRATIONS,PREDICTION,INVERSION,VALIDATION,DISPERSION,MODEL},
  language     = {eng},
  number       = {3},
  pages        = {1493--1508},
  title        = {Determination of the material damping ratio in the soil from SASW tests using the half-power bandwidth method},
  url          = {http://dx.doi.org/10.1111/j.1365-246X.2010.04690.x},
  volume       = {182},
  year         = {2010},
}

Chicago
Badsar, SA, M Schevenels, Wim Haegeman, and G Degrande. 2010. “Determination of the Material Damping Ratio in the Soil from SASW Tests Using the Half-power Bandwidth Method.” Geophysical Journal International 182 (3): 1493–1508.
APA
Badsar, S., Schevenels, M., Haegeman, W., & Degrande, G. (2010). Determination of the material damping ratio in the soil from SASW tests using the half-power bandwidth method. GEOPHYSICAL JOURNAL INTERNATIONAL, 182(3), 1493–1508.
Vancouver
1.
Badsar S, Schevenels M, Haegeman W, Degrande G. Determination of the material damping ratio in the soil from SASW tests using the half-power bandwidth method. GEOPHYSICAL JOURNAL INTERNATIONAL. 2010;182(3):1493–508.
MLA
Badsar, SA, M Schevenels, Wim Haegeman, et al. “Determination of the Material Damping Ratio in the Soil from SASW Tests Using the Half-power Bandwidth Method.” GEOPHYSICAL JOURNAL INTERNATIONAL 182.3 (2010): 1493–1508. Print.