Pull-out resistance of soil nails in sand and clay

Pull out tests of elements of grouted soil nails from fine sand and medium-plasticity clay are being undertaken using large-scale laboratory apparatus. Formation of the nails follows site installation procedures as closely as possible, while instrumentation incorporated into the nails allows direct measurement of grout/soil normal and shear stresses during pull-out. The test programme is investigating the effects of initial stresses in the ground and grouting pressure, and the contribution to pull out resistance of soil dilatancy. Tests in clay will also investigate rate effects and the possible use of lime rather than cement grout. The tests aim to improve the fundamental understanding of soil-nail bond behaviour of grouted nails to allow more rational design for pull out conditions.