Laboratory pullout resistance of a new screw soil nail in residual soil

The ultimate shear strength at the interface between the soil nail and surrounding soil is of practical importance in the design and performance of a soil nail system. The most commonly adopted method of measuring this interface shear strength is by soil nail pullout testing. This study introduces a novel soil nail system in the form of a screw nail and compares its performance with a conventional grouted soil nail. Both types of soil nails are tested in a controlled laboratory setting using residual soil in a large purpose-made pullout box. The development of the screw nail and the laboratory testing procedures are briefly discussed first, followed by presentation and discussion of the results of the interface shear behaviour measured from pullout tests. It is shown that the screw nail offers many advantages in terms of pullout load–displacement behaviour and the interface shear mechanism than that of the conventional grouted soil nail.