This project involved the stabilisation of the base of a natural slope comprising granular soils overlying chalk. Whilst the stability of the embankment as a whole had not reached the point of failure, the toe condition was causing concern as the brick retaining wall had failed owing to the pressure from debris accumulation and tree action, and if this had been left it would have led to progressive erosion and ultimately embankment failure.

Harrison Geotechnical was engaged by the local authority client to analyse and design a suitable solution to the problem, and to procure and supervise the construction. On investigation the soils concerned were found to be dilatent and thus suitable for soil nailing, which in the right conditions is an economic stabilisation method. The angle –steel nails were driven pneumatically, and the old brick retaining wall was replaced with a gunited mesh facing to minimise the risk of erosion.

It is estimated that this solution saved the client 50% of the cost of alternative methods.