Design guidance on the use of a row of spaced piles to stabilise clay highway slopes. Prepared for Highways Agency.

A single row of bored piles spaced at intervals along a clay slope provides an effective remedial measure to improve the stability of slopes that have either failed or are showing incipient signs of failure. The technique can also be used to steepen slopes so that highway corridors can be widened within existing boundaries to accommodate extra vehicular lanes or other modes of transport. Although the piling technique is now becoming more frequently used on the highway network, further design guidance is needed to ensure economy of design and safe practice. This report provides additional guidance based on a programme of research which has included a review of current practice, centrifuge and analytical modelling, and a full scale instrumented trial on the network. (Author/publisher)