Analysis and Optimization of Soil Nail Parameters in a Deep Foundation Pit of Silty Clay Based on Response Surface Methodology

The aim of this research is to reveal the influence of spatial form parameters and other factors in soil nail design on the three-dimensional stability of deep foundation pits in silty clay. A deep foundation pit in a silty clay area in Hebei was taken as the engineering background. Based on the response surface method, Plackett-Burman and Box-Behnken experiments were designed. MIDAS-GTS and Design-Expert were used to establish experimental models. The influence of various parameters on the safety of soil nail support in deep foundation pits of silty clay and the applicability of optimization schemes were analyzed through numerical simulation and monitoring data. Results show that the impact of each parameter on the safety of the pit in the silty clay area, in descending order of significance, is as follows: soil nail length, slope angle of excavation, soil nail spacing, soil nail inclination, and soil nail diameter. In the combined effect of support parameters, the soil nail length and spacing have the greatest impact on the safety factor. The predictive model established by the response surface method can provide the best optimization scheme. The optimization scheme shifts the soil slip surface backward, reducing the maximum horizontal displacement of the foundation pit from 9.33 mm to 5.42 mm and the maximum vertical settlement from 16.9 mm to 11.8 mm, providing a reference for the design of soil nail support for this type of foundation pit.