Testing of self-drilled hollow bar soil nails

Current standards and best practice guidance recognise that testing of self-drilled soil nails can be problematic as conventional packers and debonded lengths cannot be constructed. As a result, this provides difficulty in testing and confirming the ultimate bond resistance within the passive zone of a soil nailed slope, and thus the soil nail lengths determined within the design. This paper provides a summary and review of the various testing procedures adopted for a recent soil nail construction project in Scotland. Approximately 1,500
self-drilled hollow bar soil nails were installed to depths between 7 m and 24 m to stabilise a 40 m high coastal slope with a history of instability.
Fifty six sacrificial test nails were installed and tested at the site by various methods to validate the soil nail lengths determined within the design. These methods, the associated construction issues and design assumptions, and the subsequent test results have been discussed in this paper.