Offshore Technology Research Center

 

OTRC Project Summary

Project Title:

Theoretical Investigation of the Spectral Analysis of Surface Waves (SASW) Technique for Application Offshore

Prinicipal Investigators:

Stephen Wright and Jose Roesset

Sponsor:

National Science Foundation

Completion Date:

January, 1993

Final Report ID#

B41(Click to view final report abstract)

The objective of this project is to develop a fundamental understanding of wave propagation along a soil-water interface and to investigate theoretically the potential of the SASW technique for application offshore.

Theoretical solutions to compute dispersion curves for a soil-water system are developed.  Both two-and three-dimensional models are considered.  The models account for compressible water and soil-water interaction.  The so-called “counter-buoyancy effect” due to the counterbalancing forces of gravity caused by vertical displacements of the seafloor has been considered in the two-dimensional solution.  Computer programs implementing theoretical solutions for two- and three- dimensional models are developed.  The effects of gravity, wavelength, water depth and seafloor stiffness on dispersion curves for a half-space have been studied using the two-dimensional solution.  To verify the validity of two-dimensional solution, comparisons have been made with the experimental results obtained from a companion study by Gauer (1990).  The dispersion curves obtained from the two-dimensional solution have also been compared with the results obtained from three-dimensional formulation for the case of a half-space overlaid by water.  This comparison allows the applicability of the simplified plane wave solution for determining the stiffness profiles of the ocean-bottom materials to be evaluated.

Related Publications: Sedighi-Manesh, M., Wright, S.G., Roesset, J.M. and Stokoe, K.H., II, "Interpretation of Seismic Wave Measurements for Detection of Gas Hydrates Offshore," Proceedings, Offshore Technology Conference, Houston, Texas, Paper No. 6852, 1992.

Wright, S.G., Roesset, J.M., and Stokoe, K.H., II, “Analytical and Experimental Studies of Surface Wave Measurements to Detect Gas Hydrates Offshore,“ Proceedings, Offshore Technology Conference, Houston, Texas, 1991, OTC Paper No. 6535, pp. 317-324.

Roesset, J.M., Stokoe, K.H., II, Wright, S.G. and Sedighi-Manesh, M., "Analytical Investigation of Seismic Surface Waves in the Seafloor," Proceedings, Shear Waves in Marine Sediments, LaSpezia, Italy, 1990.

Stokoe, K.H., II, Wright, S.G., Roesset, J.M., Gauer, R. and Sedighi-Manesh M., "In Situ Measurement of Stiffness Profiles in Ocean Bottom Materials Using the SASW Method," Proceedings, Offshore Technology Conference, Houston, Texas, 1990, OTC Paper No. 6234, pp. 299-305.

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