Predictions and evaluations of settlement were made for revenue and the Facility for Accelerated Service Testing (FAST) track, both containing concrete and wood tie sections. The ballast physical states were investigated by field tests done before and after track maintenance. Borings were also taken to identify the subgrade conditions. The stress-dependent elastic and inelastic ballast behaviors were derived from repeated load triaxial tests and ballast box device. Triaxial tests were also performed on the subgrade soils.
A computer model, GEOTRACK, was used to estimate the stresses and deformations in the track foundations. In addition, revenue site track modulus values predicted with GEOTRACK were compared to measured values. Predictions of track settlement were then made based upon the laboratory test results and stresses estimated using the computer model. The predicted values were compared to field measurements obtained using ballast instrumentation and surveying from benchmarks. The predicted settlements were of the same order as the measured values, however, some differences in trends were observed. A discussion of the factors that were not included in the methodology is presented, along with the implications of these factors on track performance.