Reliability of FTA general vibration assessment model in prediction of subway induced ground borne vibrations

Abstract

One of the main factors in the design of subways is the level of subway-induced vibrations. The ground borne vibrations are usually estimated by prediction models among which the FTA (Federal Transportation Association) general vibration assessment model is the most popular one. Although FTA approach/model is vastly used in the design and operation of underground railway systems, its reliability has not been sufficiently evaluated in the available literatures. This is addressed in this research. For this purpose, a comprehensive experimental investigation (both in the time and frequency domains) was conducted in three newly constructed subway lines in the Iranian underground railway (subway) network. The track and soil characteristics as well as ground borne vibrations were measured. The reliability and accuracy of the FTA model was assessed through comparisons of the experimental results obtained here with the FTA predictions. Contrary to the current belief, considerable underestimations of subway ground borne vibrations in the FTA model predictions were shown in this research. The results obtained indicate up to 20 dB differences between the experimental results and those of FTA predictions. Based on the field measurements obtained here and the theoretical background, the FTA model was improved/optimized, leading to increase the reliability of FTA model predictions in subway systems.