Numerical investigation of gravity-grouted soil-nail pullout capacity in sand

Soil nailing reinforces soil slopes and retaining walls by installing reinforcing elements into the soil, which rely on bonding strength with surrounding soil to transfer axial forces. This study focuses on the pullout capacity evaluation of grouted soil-nailing, which is conventionally determined through costly and time-intensive site-specific field pullout tests or simplified design methods, Federal Highway Administration (FHWA), and Effective Stress Method (ESM). However, these methods neglect important soil nail configuration parameters governing the pullout capacity. To address this limitation, we present a parametric study on a validated Finite-Element model using PLAXIS 3D to comprehensively investigate the pullout characteristics of grouted soil nailing. The study considers various factors such as sand relative densities, lengths, diameters, and inclination angles of the soil nails. The results reveal that the pullout capacity is significantly influenced by the sand relative density, diameter, and the length of the nailing, while the angle of inclination has only a marginal effect. The comparison with FHWA and ESM methods shows significant scatter, attributed to their lack of consideration for these governing parameters in determining pullout capacity. These findings provide valuable insights into the design and optimization of grouted soil nailing pullout capacity for geotechnical applications.