Slope stabilization of an embankment on the West Coast Main Line, UK

Abstract

A site inspection of an embankment on the West Coast Main Line (UK) revealed a general de-terioration of the embankment, significant movement of the trackside services and waterlogging and bulging along the embankment toe. The medium-height embankment, with side slopes at about 30 degrees to the hori-zontal, was constructed on natural sidelong ground and the site had been an area of previous instability (for-mer ash and slag tip). Site investigation, ground monitoring and analytical modelling indicated that the em-bankment was at limiting equilibrium and that recent progressive movement was occurring along a rotational slip surface located within the embankment core (ash and slag materials overlying reworked glacial till). The upgrade works comprised the installation of a row of stabilizing piles along the mid-height of the embank-ment side slope (facilitating Green Zone working); regrading to prevent shallower slips near the embankment crest and the installation of a toe drain that discharged to a nearby stream.