Railway embankment stabilisation: economical asset management

Ashdon Way railway embankment in Basildon, Essex, is an 8 m high, 500 m long embankment founded on the London Clay Formation and predominantly comprising reworked London Clay fill. The embankment has a history of slope instability problems that have led to continued regular track maintenance requirements and associated imposition of temporary speed restrictions. This paper discusses how detailed slope monitoring, track performance data and site investigation were used to target and value engineered slope stabilisation measures at the site using soil nails and/or cess retention, resulting in cost savings of £5·8 million compared with a traditional sheet piled wall solution. Slope monitoring was undertaken by means of borehole inclinometers (including automated inclinometers), which allowed detailed interrogation of slope movement before, during and after construction. A progressive failure mechanism was identified from the monitoring data. The slope monitoring allowed for post-construction assessments of the success of the scheme and management of the residual risk for adjacent untreated areas.