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Although the capabilities of engineering surface wave methods have improved in recent years due to several advances, a number of issues still require study to further improve the capabilities of modern surface wave methods. Near-field effects, which are one of these issues, have been studied for traditional surface wave methods with two receivers, and several criteria to mitigate the effects have been recommended. However, these criteria are not applicable to surface wave methods with multiple receivers. Moreover, the criteria are not quantitatively based and do not account for different types of soil profiles, which strongly influence near-field effects. A new study of near-field effects on surface wave methods with multiple receivers was conducted via numerical simulations, laboratory simulations, and field tests. Quantitatively based criteria for near-field effects in different soil profiles are presented using two normalized parameters developed in this study. There was excellent agreement between numerical and experimental results, and it was found that underestimation of measured Rayleigh phase velocities was the major symptom of near-field effects. CE Database subject headings: Surface waves; Rayleigh waves; Simulation; Parameters.

Analysis of seismic surface waves offers a noninvasive method to estimate the dynamic engineering properties of the near-surface earth. Traditional two-sensor spectral analysis of surface waves (SASW) techniques suffer from several limitations that impede their use in practice, including poor resolution, inability to properly account for multiple modes, and an imprecise understanding of near-field effects. Current multichannel and array analysis of surface waves resolve several of these limitations, but still suffer from a near-field model incompatibility, i.e., estimating plane wave parameters in a cylindrically spreading wave field. This paper introduces cylindrical beamforming, an array processing method to overcome the limitations of plane wave processing methods. To aide in motivating the cylindrical beamformer, the paper discusses the near-field effects and explains some of the underlying physical reasons for previous observations regarding the near-field. The cylindrical beamformer is then introduced to more accurately model the wave field, allowing better estimates of phase velocity from point sources. The results from measured data taken with a linear array on a site in Atlanta are used to compare the methods. DOI: 10.1061/(ASCE) 1090-0241 (2005) 131:8(970) CE Database subject headings: Spectral analysis; Surface waves; Seismic analysis; Signal processing; Nondestructive tests; Velocity.

Measurements of surface wave attenuation provide a means to determine the in situ material damping ratio profile of near-surface soils. Frequency-dependent surface wave attenuation coefficients are determined from measurements of seismic wave amplitudes at various offsets from a swept-sine source. The accuracy of the measured attenuation coefficients is improved by properly accounting for the geometric attenuation of multimode Rayleigh waves. Once the frequency-dependent attenuation coefficients are determined, the shear damping ratio profile is calculated using a constrained inversion analysis. Application of the method is illustrated at the Treasure Island National Geotechnical Experimentation Site. Values of shear damping ratio, obtained using surface wave measurements, were less than those measured using cross hole tests, possibly because the higher frequencies used in cross hole tests result in more apparent attenuation due to scattering and because fluid losses contribute to damping at higher frequencies. Damping ratios from surface wave tests agree more closely with resonant column and torsional shear test results.

A comment on a study on the interpretation of the results of steady-state (Rayleigh wave) surface vibration tests is presented. Another procedure, however, is more effective when considering deposits with stiff upper layers underlain by softer soils. The other method is bulkier, though. The procedure is an iterative numerical inversion scheme that is utilized in spectral analysis of surface waves methods.

Two surveys examining computing education in civil engineering courses and the use of computing in engineering firms reveal that engineering education does not provide students with sufficient computer skills needed to practice engineering. Numerous computer software and hardware are available for practicing engineers. The inclusion of computing education in the engineering curricula will, therefore, benefit not only the students, but the practicing engineering community as well. Specific recommendations for upgrading computing education and facilities are discussed.