Sayedali Badsar

The use of the SASW method to determine the shear wave velocity and the material damping ratio of shallow soil layers

This paper focuses on the Spectral Analysis of Surface Waves (SASW) method for the determination of stiffness and damping parameters of shallow soil layers. The paper consists of three parts, addressing (1) the in situ SASW test, (2) the determination of the dispersion and attenuation curves from the measurement data, and (3) the inverse problem where the soil profile is identified. The existing practice is critically reviewed, and a number of improvements to the SASW method are presented. These include a technique to improve the efficiency of the in situ test, and a new method to determine the experimental attenuation curve. The efficiency of the test is improved by monitoring the signal-to-noise ratio during the experiment. The experimental attenuation curve is determined by means of a frequencywavenumber analysis, using the half-power bandwidth method.

Determination of the dynamic soil characteristics at the NGES

Analysis of the field data collected at the National Geotechnical Experimentation Site (NGES) at Texas A&M University (TAMU) is outlined. Data have been collected along two measurement lines from two and multi-sensor arrays using a variety of sources. The data from each measurement line are processed separately. The STA/LTA procedure is applied in order to determine the P- waves arrival time. The P-wave velocity profile is determined by solving an inverse problem, where the difference between the theoretical arrival time, corresponding to a horizontally layered halfspace, with the experimental arrival time is minimized. The classical SASW method as well as the frequency- wavenumber analysis are used to determine the experimental dispersion curve. The dispersion curve is subsequently inverted to determine the S-wave velocity profile, using the a priori determined P-wave velocity profile. The width of peaks of the response in the frequency-wavenumber domain is used to determine the experimental attenuation curve. The attenuation curve is finally inverted to give the material damping ratio profile, while the already determined P- and S-wave velocity profiles are fixed in the inversion procedure. The determined soil profile is finally used to make a comparison between the theoretical and experimental frequency-wavenumber spectrum. The correspondence with experimental results is good. INTRODUCTION A data set collected at the National Geotechnical Experimentation Site (NGES) at Texas A&M University (TAMU) is made available to the community for interpretation. In this paper, the Seismic Refraction (SR) method, the classical Spectral Analysis of Surface Waves (SASW) method, and the Multi-channel Analysis of Surface Waves (MASW) method are used to determine dynamic soil properties. The SR method gives the P-wave arrival time from which the P-wave velocity profile of the soil is determined. The classical SASW method results in a composite dispersion curve and subsequently the S-wave velocity profile. The MASW method gives both the dispersion and attenuation curve. The material damping ratio profile is determined from the attenuation curve. Finally, the identified soil profiles are used to simulate the wave field recorded in the SASW test to verify the accuracy of the results. DETERMINATION OF THE P-WAVE VELOCITY Measurements were performed using two measurement lines A and B at the NGES. For each setup, waves were generated by means of sledgehammer impacts at the soils surface. The response was recorded by means of a set of 62 receivers spaced at 0.61 m along a straight measurement line. The position of the source was

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

This paper focuses on the determination of the material damping in the soil by means of the SASW test. Two new methods are proposed. The first method is based on the half-power bandwidth method applied to the width of the peaks in the

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

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The robustness of ground vibration predictions based on SASW tests

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Robust ground vibration predictions based on SASW tests

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Determination of the material damping ratio in the soil from SASW test using the half-power bandwidth method and the Arias intensity

spectrum to determine the attenuation of Rayleigh waves. The second method uses the spatial decay of the Arias intensity at the surface to determine the material damping ratio. Both methods are used to determine the material damping ratio in the soil at a site in Belgium. The identified soil profiles are used to simulate the wave field registered in the SASW test, which is confronted with the experimental data. Good results are obtained with both methods, the second method performing slightly better than the first.