Optimization of geometric parameters of soil nailing using response surface methodology

Optimization of parameters of soil nailing is an important task in reinforcement soil problems. This paper focuses on the effect of nail geometric parameters on soil nailed wall analysis and identifies which factors that most affect their stability and cost using response surface methodology (RSM). RSM has been chosen to achieve an optimum combination of the soil nailing wall design. The influence of three factors has been considered; it included nail length, its inclination, and vertical spacing between nails. After a finite element analysis to model and perform the soil nailing simulations, a Box–Behnken design was applied, based on a set of experiments using various combinations. For this purpose, 15 runs were conducted to analyze tested parameters and to determine their interactions. The analysis of variance (ANOVA) and contour lines plots were investigated, and therefore, the most important parameters affecting the safety factor and the cost were identified. From the goodness-of-fit analyses of the model and the illustrative example, the proposed regression model provides a reasonably good estimate of the overall safety factor for soil nail walls and their cost. The results obtained from this study showed that RSM is an efficient and effective tool to identify the optimal combination, and it emerges that the safety factor and cost are most influenced by nail length and vertical spacing.