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.
Highlights
Railway electrification offers benefits for both the environment (zero carbon dioxide (CO2) and particulate emissions at the point of use) and traction operation, but requires investment in fixed infrastructure
This paper focuses on moment at ground level (MGL); it does not address the vertical capacity check that would need to be carried out for design according to standard geotechnical engineering principles
A further point concerns the relationship between the surface zone soil of 1·5 times the pile diameter d and the UIC-Office for Research & Experiments (ORE) ineffective depth
Summary
Railway electrification offers benefits for both the environment (zero carbon dioxide (CO2) and particulate emissions at the point of use) and traction operation (reduced complexity and cost), but requires investment in fixed infrastructure. The simultaneous development of a revised approach to pile foundation design (Krechowiecki-Shaw and Alobaidi, 2015) led to an apparently significant increase in design foundation depths The development of both the HOPS and the revised foundation design process occurred in advance of the specification of the overhead line equipment (OLE) itself. The more massive ‘Series 1’ superstructure added to the problem by increasing the loads (compared with previous norms) that the foundations were required to carry. While all of these changes were individually well intentioned, aiming variously to. Published with permission by the ICE under the CC-BY license
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