Experimental monitoring of geotechnical response of railway track systems.

摘要

An important issue that compromises rail track operations and safety is ballast fouling. Ballast fouling may lead to track deformation, reduction of track load capacity and train speed, and ultimately train derailment. This problem is quite costly for the railway industry thus, assessing and controlling ballast fouling and then preventing train derailment while optimizing maintenance operation is very important for reducing the overall cost of freight and passenger transportation. This study presents a proposed holistic methodology that extends assessing fouling while monitoring rail track deformation. The techniques uses deformation monitoring instruments (e.g., fiber optic (FO) sensors and LVDTs) coupled with Electromagnetic (EM) surveying: Ground penetrating radar (GPR) and a time domain reflectometry (TDR). The methodology aims at gathering data to create an early warning system that would allow railway engineers to develop a symptomatic approach to ballast maintenance procedures. This proposed methodology was tested on a full scale track model (FSTM). This model comprises 2.45 m rail supported by five ties embedded in ballast layer that was fouled under controlled conditions. The testing program considered three common types of fouling: mineral fouling, clay fouling, and silica sand fouling. A comparison between rail settlement measurements measured by LVDTs and rail bending strain measurement measured by FO sensors showed that FO sensors do not provide an indication of track deterioration due to cyclic loading, moisture content, and fouling depth. In addition, results showed a high correlation between rate of plastic settlement and amount of fouling detected by EM survey. Experimental results also showed that EM survey results can be used to determine depth and type of fouling.