Pullout behavior of helical soil nails in cohesionless soil: a laboratory investigation

Abstract

The soil reinforcing method of incorporating helical soil nails is a technique involving the introduction of passive elements into the soil. The combined action of helical bearing and shaft skin friction from helical soil nails gives better reinforcement against failure of the composite soil mass. The current study is aimed to explore the laboratory pullout response of helical soil nails in cohesionless soil (river sand) under varying shaft cross-section (Circular & Square), shaft type (Hollow & Solid), transition in the position of the third helix, and overburden pressure to optimize the most suitable soil nail. In this study, pullout tests are conducted on the soil nails in the laboratory using the physical model setup. The pullout capacity of circular nails is higher than the corresponding square nail. Moreover, a solid shaft nail depicts a higher pullout load capacity than a hollow shaft soil nail. Maximum pullout load is achieved at third helix spacing of about 3.8 Dh and gives a 7.40% increase in pullout load as compared to the reference soil nail. SSCN1. Further, as the overburden pressure is increased, the pullout capacity also increases.