Trackbed Deflection under Combined Freight and High Speed Passenger Service

An instrumentation program was undertaken to evaluate the relative damage to railway track from various classes of traffic: loaded freight, empty freight, passenger, and high-speed intercity. As part of this investigation, the roadbed deflection was targeted for measurement since the roadbed deflection is the main characteristic differentiating track performance for these classes of traffic. The project involved installation and calibration of the sensors, measuring the track response under a test freight train, measuring the deflection from passing traffic, and analyzing the data to determine the deflection distribution in the track structure and the damage induced by the different classes of traffic. Based on the analysis, a traffic based track condition deterioration model was developed and applied to the test section. The results of the analysis were confirmed with a program to monitor the overall track settlement and deformation of the roadbed. The monitoring program indicated that the predictive model estimated the track deterioration rate relatively accurately and could be applied to other sites with the addition of site specific traffic volume, maintenance records, and local site geology or field tests to estimate roadbed and subgrade characteristics. This paper describes the test, summarizes the results and analysis, and provides an example of the application of the results.