The limit equilibrium method LEM is widely used for static and pseudo-static soil nailing designs. Soil nailed wall stability is usually evaluated based on a global factor of safety FS_G under a predefined failure mechanism. When appropriate failure surfaces are adopted, FS_G should reduce with the soil nailed wall inclination β for different nail geometries (length L, inclination α and diameter D), soil-nail strength r_s, soil cohesion c’ and angle of friction ϕ’. However, nail spacing S can change this trend since FS_G increases with β under certain combinations of β and S. In this study the nail spacing effect has been evaluated using LEM assuming a bilinear failure surface with two rigid blocks and the Morgenstern-Price method where the failure surface is neither linear nor circular. However, it was found that FS_G increases with β for S < 2.00 m, which can lead to potentially unsafe designs. Alternatively, the finite element method FEM was chosen including the strength reduction factor SRF methodology which is equivalent to FS_G under failure conditions. It was found that results from FEM represent a significant improvement respect to those from LEM because curves in a FS_G-β-S plot follow a logical trend as with the other parameters (L, α, D, r_s, c’ and ϕ’). Finally, it is recommended to choose FEM instead of LEM in soil nailing designs. In case of using LEM, results should be carefully assessed, in particular for steep walls and close nail spacing.

极限平衡法LEM广泛用于静态和拟静态土钉设计。通常根据预定义的破坏机制下的整体安全系数FS _G评估土钉墙的稳定性。当采用适当的破坏面时，对于不同的钉子几何形状（长度L，倾角α和直径D），土钉强度r _s，土的内聚力c '和摩擦角ϕ' ，FS _G应随着土钉壁的倾角β的减小而减小。 。但是，钉间距S可以改变这种趋势，因为在某些β和S组合下，FS _G随着β的增加而增加。在这项研究中，使用LEM假设具有两个刚性块的双线性破坏面，以及破坏面既不是线性也不是圆形的Morgenstern-Price方法，则使用LEM评估了钉距效应。但是，发现对于S <2.00 m，FS _G随β的增加而增加，这可能导致潜在的不安全设计。或者，选择有限元方法FEM，其中包括强度折减系数SRF方法，该方法等效于失效条件下的FS _G。发现FEM的结果与LEM的结果相比有显着改善，因为FS _G- β- S曲线与其他参数（L，α，D，r _s，c '和ϕ'）。最后，在土钉设计中，建议选择FEM代替LEM。如果使用LEM，应仔细评估结果，尤其是对于陡峭的墙壁和狭窄的钉子间距。