Non-contact measurement of vertical deflections of rail trackbeds and performance testing of stabilized sub-ballasts using a novel micropiling system

Trackbed stabilization (TBS) refers to engineering works to improve the railway trackbed stiffness in areas affected by poor load bearing capacity from soft subgrade. There are a variety of TBS techniques available to improve soft subgrades; however, many conventional approaches require a full renewal of the ballast which is disruptive and requires lengthy track possession time. This paper documents the improvements of a soft subgrade site in the UK using micropiles, installed between sleepers during overnight possession methods, thus allowing daytime rail traffic to run as normal. A non-contact vision-based monitoring (VBM) system developed by the authors and consisting of a high-speed camera was used to quantify the track bed deflection before and after the remedial works. The VBM system records displacement-Time response of the rail and its foundation system during train passage. The results obtained from the experiments indicate that the post-rehabilitation trackbed modulus was increased.