Characterization of railway subgrade using an elastic wave full-waveform inversion method

Abstract

Using field measurements of railroad responses to probing waves originating from ballast surface, this study presents a two-dimensional elastic wave full-waveform inversion (FWI) method for characterization of high-speed railway subgrade. Full-waveform inversion is implemented based on a PDE-constrained optimization approach, which seeks optimal values of elastic moduli for the domain of investigation while minimizing a Lagrangian functional. The Lagrangian consists of a least-squares objective functional and regularization terms, augmented by weak imposition of governing wave equations via Lagrange multipliers. The load data and measured surficial responses for high-speed railway subgrade are used in the FWI framework. Numerical results show that the elastic moduli of the high-speed railway subgrade can be reconstructed fairly well. Shear wave velocities of the ballast layer reconstructed by FWI method are comparable to results obtained by spectral analysis of surface waves (SASW) method. © 2020 The Korean Society for Railway.