Effect of Geocell Inclusion on Railway Ballast Stability

Railway foundations need a relatively strong ballast to reduce track settlement induced due to heavy wheel loads from trains. Geocell inclusions have shown to improve subgrade conditions by providing lateral confinement to the ballast. In this study, a numerical model of a plate load test followed by a railway foundation model was developed using a commercially available finite element software ABAQUS. After successful validation of the plate load numerical model with existing finite element (FE) model data and experimental data, the scope of the study was extended in developing a railway model with realistic railroad conditions. Models with and without geocell inclusion were simulated, and results were obtained in terms of vertical settlement and stresses. To model the elastoplastic behavior of the ballast, the Drucker Prager yield criterion was used, while the diamond shaped geocells were modelled as a linear elastic material. To mimic the real-life train wheel load effects, cyclic loading up to 80,000 cycles were simulated. The cyclic load was applied in a stress-controlled manner over a frequency of 16 Hz using a haversine amplitude function corresponding to the speed of fast and heavy haul trains reaching a velocity of 120 km/hr. The results showed a substantial performance improvement with geocell reinforcement. The vertical deformation reduced by 12% at the track level and 45% at the subgrade interface after 80,000 cycles due to the geocell reinforcement. There was a substantial reduction in vertical stresses up to a maximum of 40% at the track level. The geocell reinforcement model also shows a more uniform stress distribution compared to a rapidly fluctuating stress response for the unreinforced model.