Evaluation of soil nailing design methods using 3D finite element analysis and an instrumented vertical excavation

This study evaluates soil nailing design methods using a 3D finite element model (FEM) and data from an instrumented vertical excavation. Eight methods were analysed: four based on Rankine’s and Coulomb’s Lateral Earth Pressure Methods (LEPM and Modified Coulomb’s), three regional methods from the 1980 s (German, Davis, and French), and a Limit Equilibrium Method (LEM) using software. The methods were compared in terms of (i) critical slip surface; (ii) Factor of Safety (FoS); (iii) nail tensile loads; and (iv) location of maximum load in the nails. The FEM model was calibrated using field monitoring data and served as a benchmark. Results showed that the LEM software and French method best matched the FEM model regarding slip surface shape and FoS, with differences under 5%. For tensile loads and their distribution along the depth, one LEPM method aligned best with FEM results. The remaining LEPM approaches, along with Modified Coulomb’s, Davis, and German methods, showed only limited agreement with the FEM results.