The modelling of railway subgrade strengthening foundation on weak soils

Abstract

Abstract As a consequence of increased axle loads and speeds of trains on modernised railway lines, there may occur problems with bearing capacity and stability of the subgrade in some sections of the railway network. This is the situation we are dealing with right now on the Polish State Railways network. Therefore, as a case study, a fragment of an existing railway embankment based on a weak foundation was chosen for the analysis of train–track–subgrade interaction. A two-stage train–track–subgrade model has been developed. The model consists of the upper part (train–track) and the lower part (subgrade-foundation). The first part is modelled as a self-contained system of differential equations which are solved by means of finite difference method and yield the stress levels on the subgrade. These stresses are treated as a load for the lower system modelled using FEM. The model has been validated using experimental data from literature, authors’ measurements, and railway staff measurements of the track geometry. Several cases of strengthening methods were calculated and compared with measurements on the railway section under consideration. Good agreement between the prediction and the measurement was found. The novelty of the model is including the heterogeneity of the subgrade, the strengthening methods, and very deep layers of its foundation as well as adding the influence of vibration on the weakening of soils. It was found that this influence is noticeable and should be included in the prediction of railway subgrade behaviour