R A Jewell and M J Pedley, University of Oxford. This paper was first published in GE’s March 1990 edition.
This paper addresses a controversy that has arisen out of the paper by R J Bridle on soil nailing analysis and design, which was published in the September 1989 issue of Ground Engineering.
There appears to be a fundamental error of mechanics and a conceptual error in reinforced soil design theory that have become established in the French and American literature on soil nailing. Built upon these has been a sequence of development in soil nailing design which appears to have moved far away from what can actually occur in soil reinforced by bars. If true, this could seriously mislead designers. as this work has now been imported to UK literature by Bridle (1989), it is necessary that they be identified and discussed.
This paper draws attention to the apparent error concerning the role of reinforcement bending stiffness. The possible role of bending stiffness as a mechanismand source of improvement in soil reinforced by bars (soil nailing) is then investigated. The conclusion drawn from the analysis is that bending stiffness is only of marginal significance in soil nailing, and is the wrong focus for design.
A companion paper discusses the apparent error in reinforced soil design theory introduced with the use of logarithmic spirals as the limiting failure surface. A straightforward and more rational method of designfor soil nailing and associated design software is then described.