Novel Laboratory Pullout Device for Conventional and Helical Soil Nails

摘要

Soil nails are widely used to stabilize unstable slopes, vertical faces of excavation, and tunnels. Pullout capacity of soil nails is an important design parameter and is influenced by numerous parameters. Determination of accurate pullout capacity is essential to ensure the adequate internal stability of the stabilized structures. A novel laboratory pullout device has been developed to overcome the limitations of previously developed instruments as reported in the literature. This article presents the design details and new features of the fully instrumented laboratory pullout device. The device can be used to study the influence of various parameters such as installation process, installation angle, vertical surcharge pressure, and surface roughness on the pullout capacity of conventional (driven) and helical soil nails. A series of soil nail installation and pullout tests have been carried out to demonstrate the performance of the novel device. Typical test results are presented and discussed in detail. The test results indicate that the pullout behavior of soil nail is significantly influenced by the method of installation, surface roughness, and inclination angle besides the surcharge pressure. Further, the installation capacity may be correlated with the pullout capacity of driven soil nail. Moreover, the installation capacity is significantly influenced by the installation angle and configuration of helical soil nail.