Effects of Voiding on the Performance of Fixed Diamond Railway Crossings

Switches and Crossings (S&C) are an important component of a railway track system, used to direct trains between different paths. They constitute approximately 2% of UK track, but account for 23% of annual track renewals and consume 24% of the annual track maintenance budget. One of the contributing factors is the effect of poor or variable geotechnical support from the underlying substructure (the ballast/and or underlying geology), which can lead to amplified dynamic and impact loads and voiding beneath the track. This paper presents an initial assessment of the history of track geometrical performance of two S&C suspected of underlying geotechnical issues. The initial assessment is based on historical data from the Linear Asset Decision System (LADS) of the UK railway infrastructure owner and operator Network Rail (NR), supplemented by evidence from on-track inspections. The aim is to identify features and behaviour linked to possible underlying geotechnical issues for targeted and detailed investigation, including strategic on-track monitoring. The study is based on an historically problematic junction and a recently renewed junction on the UK railway network. A qualitative assessment of the evidenced behaviour of each asset is used to identify areas of suspected voiding beneath the track. This will assist in future investigation of crossing behaviour in relation to the importance and benefits of consistent geotechnical support for optimal S&C performance.