The design of railway overhead line equipment mast foundations

Abstract

Railway electrification offers significant benefits in terms of decarbonisation at the point of use and reduced traction costs. However, to realise these benefits, the fixed infrastructure must be provided at an affordable cost. Recent schemes in the UK have seen the cost of railway electrification soar: one of a number of reasons for this has been the substantial increase in mast foundation pile lengths compared with historic practice. The paper explores this through a comparative review of traditional and modern pile design methods. In addressing the ultimate limit state, the various approaches are shown to give broadly consistent results in terms of pile length. However, increased pile lengths will be calculated if three-dimensional effects are not allowed for in limit equilibrium (ultimate limit state) calculations, or if a serviceability limit state calculation is carried out using unrealistically low soil stiffness. The results of the comparative analyses should give designers the confidence to use the traditional empirical approach, or a limit equilibrium calculation without the need for an explicit serviceability limit state check (as permitted by Eurocode 7) using potentially inappropriate soil stiffness parameters.