EXPERIMENTAL STUDY OF FACTORS AFFECTING THE SPECTRAL-ANALYSIS-OF-SURFACE-WAVES METHOD. INTERIM REPORT
Three series of seismic tests were performed to investigate factors which affect the Spectral-Analysis-of-Surface-Waves (SASW) test method. In the first series, the source of seismic waves was studied. Until recently, transient input motion has been used almost exclusively as the source with often unpredictable results. Random and sinusoidal input motions were investigated to evaluate if either could provide more consistent results. The investigation revealed that sinusoidal input attained substantially higher signal-to-noise ratios than either transient or random motions. The improved signal-to-noise ratio may be very helpful in situations where transient motion fails to provide acceptable results. A basic assumption of the SASW method is that only fundamental mode surface waves exist in the field. This assumption was investigated in the second series of tests using measurements of particle motion versus depth to calculate the relative contribution of the first several modes of surface wave propagation. The results were somewhat inconclusive because of the inability to model the subsurface accurately. However, theoretical results indicated that fundamental-mode surface waves comprised between 72 and 86% of the total motion. In addition, a qualitative comparison of theoretical mode shapes and experimental displacements also indicated that fundamental-mode motion dominates. Finally, the third series of surface wave tests was performed on a concrete test slab to assess the influence of the relative stiffness of adjacent layers and the relative spacing of source and receivers on measured dispersion. Results of this test series indicated that a large stiffness ratio between adjacent layers can adversely affect measured dispersion curves for wavelengths which are between approximately 0.7 and 1.8 times the thickness of the slab. The influence of the relative source-receiver spacing was more difficult to determine because of the lack of a "true" dispersion curve with which to compare results. Based on selected records, receiver spacings with a ratio of d2/d1 greater than two appeared to yield improved dispersion curves.
- Research study title: Non-Destructive Test Procedures for Analyzing the Structural Conditions of Pavements.
University of Texas, AustinCenter for Transportation Research, 3208 Red River Street
Austin, TX United States 78705
Texas Department of TransportationTransportation Planning Division, P.O. Box 5051
Austin, TX United States 78763
Federal Highway Administration1200 New Jersey Avenue, SE
Washington, DC United States 20590
- Rix, G J
- Stokoe II, K H
- Roesset, J M
- Publication Date: 1991-2
- Features: Appendices; Figures; References; Tables;
- Pagination: 188 p.
- TRT Terms: Concrete; Elastic waves; Nondestructive tests; Pavements; Rayleigh waves; Signal to noise ratio; Slabs; Spectrum analysis; Stiffness; Subgrade (Pavements); Thickness
- Candidate Terms: Spectral analysis of surface waves
- Subject Areas: Design; Highways; Pavements; I22: Design of Pavements, Railways and Guideways;
- Accession Number: 00625441
- Record Type: Publication
- Report/Paper Numbers: FHWA/TX-91+1123-5, Res Rept 1123-5, CTR 2/3-18-87/9-1123-5
- Contract Numbers: Study 2/3-18-87/9-1123
- Files: TRIS, USDOT, STATEDOT
- Created Date: Dec 3 1996 12:00AM