NUMERICAL INVESTIGATION OF UNKNOWN FOUNDATION GEOMETRY USING FULL WAVEFORM INVERSION OF SURFACE WAVES

Abstract

As interest in foundation reuse increases, there has been renewed emphasis on methodologies to characterize existing foundations for determination of unknown geometry, material properties, integrity, and load-carrying capacity. Geophysical and non-destructive testing efforts provide an efficient manner by which to evaluate these parameters. Stiffness information from these methods can be used to evaluate foundation geometry as well as load carrying capabilities based on reverse engineering concepts. The use of surface waves as in the Multichannel Analysis of Surface Waves (MASW) method has been largely neglected for this purpose. MASW offers a number of advantages over other seismic methods due to its robustness, speed, and high signal strength. However, lack of case histories means there is limited information regarding the capabilities of MASW for the purposes of foundation evaluation. Recent efforts have highlighted deficiencies in typical MASW inversion analysis when applied for evaluating unknown foundations. The objective of this study was therefore to examine the effectiveness of MASW when applied using a full waveform inversion (FWI) technique for analysis. Numerical testing was performed on a model representing an in-service foundation system. This paper presents the numerical model followed by a discussion of data analysis and interpretation.