Seismic Surface Wave Testing for Track Substructure Assessment

This paper presents some results of a Federal Railroad Administration (FRA) sponsored research project on using seismic surface waves to evaluate track substructure (ballast and subgrade) condition and performance. The main objective of this project is to develop a system for rapidly, nondestructively, and quantitatively assessing the engineering properties of the track substructure (ballast and subgrade). These engineering properties — shear modulus, Young’s modulus, and shear strength — are derived from measurement of the shear wave velocity profile and can be used to evaluate track safety and to predict inspection and maintenance intervals. This paper describes the seismic testing, results of field measurements, and numerical modeling of the seismic wave propagation in the track substructure. Procedural issues addressed by the numerical models and presented herein include the size and location of the excitation source and orientation and spacing of the receiving accelerometers.