Detection of Underground Obstacles by the SASW Test

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9622140 The objective of the proposed research program is to develop practical procedures for detection of underground obstacles in the field by the Spectral-Analysis-of-Surface-Waves (SASW) technique. Such a development is important for two major reasons: 1) In urban areas where subsurface right-of-way is congested, the ability to detect the position and characteristics of underground obstacles or voids is important for maintenance, repair, and rehabilitation. 2) This research will provide guidelines for minimization of the effects of underground obstacles in SASW site characterization. Existing experimental and numerical studies indicate that underground obstacles and soil heterogeneity have significant effects on Rayleigh wave dispersion evaluated by the SASW test. This research will encompass a refinement of the numerical model for obstacle detection, verification of the developed procedures in detection of obstacles in soil systems and below pavements, and integration of the procedures into packages for an automated SASW test. The refinement involves optimization of the procedure with respect to the number, spacing and placement of receivers, and more accurate evaluation of some of the obstacle parameters. Verification and implementation of the procedure will be done in the laboratory and in the field. Test sites will be selected and prepared in cooperation with the New Jersey Department of Transportation. ***