Estimating System Stiffness of Soil Nailing Wall for Deep Excavation in Clay

The major concern for underground construction, such as deep excavation in urban areas, is the lateral retaining wall displacement. Therefore, it is necessary to choose the appropriate retaining structure in reducing the displacement affected by deep excavation. The system stiffness for braced excavation has been well characterized; however, there is a lack of studies of soil nailing walls, especially to determine the system stiffness of the wall to reduce lateral wall deformation. The objective of this article is to develop design charts that can be used for predicting the lateral wall displacement for soil nailing walls. Two-dimensional finite element analysis (2D FEM) with the Soil Hardening model is used to analyze all of the cases. A series of parametric studies are performed with some important factors, such as: the (1) soil nailing length, inclination, and horizontal spacing; (2) location of the groundwater level; (3) excavation depth and thickness of the clay layer; and (4) undrained shear strength of the soil. Furthermore, the charts are validated through a well-documented case study, which is located in Jakarta. A comprehensive 2D FEM of the case study is simulated. The results show that the maximum lateral deformation of the secant pile obtained from the design charts, FEM model, and field measurement is 48.0 mm, 47.5 mm, and 45.9 mm, respectively. Hence, the proposed charts are suitable for predicting wall deflection with acceptable error.