A study of new screw soil nail

This dissertation is based on the study of a new soil nail called screw nail. The research is focused on the design, fabrication and analysis of a new screw nail and its interaction mechanisms between the soil and nail in two cohesive and non-cohesive soil materials that are compacted in a suitably fabricated large box. The interaction behaviour of the nail was investigated by a series of fully instrumented pullout tests that were carried under different surcharge load conditions and the observed behaviours were compared with the results of pullout tests by various other investigators. Numerical modelling was also carried out in an attempt to investigate and understand the performance and the shear mechanism of the screw nail under different boundary conditions. For this purpose, a full three-dimensional finite element computer program was used to study the soil and nail displacements associated with the axial loading. Comprehensive laboratory soil tests were carried out prior and after the pullout tests to fully characterise the soils conditions. The box was instrumented with load cells and LVDTs and strain gauges were adhered to the screw nail. For the non-cohesive soil, thin vertical sand bands were cast to analyse the soil deformation patterns after the completion of the pullout tests. The pullout tests of the screw nail show that its performance is better when compared to the results of other investigators due to the efficient geometry of the screw nail and its interaction with the surrounding soil.