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It Is a pleasure to acknowledge the patient guidance offered by Dr. Eugene Zwoyer, Director of the Eric H. Wang Civil Engineering Research Facility where the work was performed. Dr. George E. Trlandafilldls, Supervisor of Soil Dynamics Research at the facility, was of inestimable help In his review of the work, and his editing of the drafts. Messrs. W.J. Baker and P.M. Babcock, Research Engineers at the facility, assisted greatly in both the experimental and theoretical work. Messrs. Robert Fä.sher and Bert Wilkinson designed and assembled the experimental equipment, and performed many of the tests. The assistance of other personnel at the facility was inviluable and is gratefully acknowledged. This report has been reviewed and is approved.