A rational approach to railway track foundation design with clay subgrade

Abstract

In planning the railway line, crossing low-lying area of high plasticity clay formation soil for straight line alignment may become necessary either for cost efficiency or shorter travelling time. This paper describes the new approach, which served to rationalize and reformulate the current state of design and management process of rail track substructure involved clay subgrade. It puts forward the concept of “Managing current lower-bound threshold stress” for clay subgrade on the premise that lower-bound threshold stress which represents subgrade capacity of the most vulnerable state, is not necessarily a constant material parameter and can potentially increase two folds which should be taken into consideration for economical design. The readily use of proposed theoretical model and design charts for predicting and re-assessing threshold stress offers a key advantage for the new approach over current practices.