A Study on Soil Nailing as a Deep Excavation Support in Railway Track
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Date
2019-10
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Addis Ababa University
Abstract
Soil nailing is one of the in-situ soil reinforcement and deep excavation support that has been used worldwide, with the main components as nail and facing. This study covers both conventional and state-of-the-art numerical analysis. It mainly focuses on the numerical analysis using PLAXIS 2D due to the drawback of deformation prediction in the conventional limit equilibrium method. The soil properties and initial wall parameters are taken from measurements on sites, were appropriately modeled and used in the finite element based software, PLAXIS 2D for the simulation. The global factor of safety as computed using limit equilibrium was greater than that of the finite element method. The effect of mesh density on the factor of safety and wall deflection was explained. Modeling of soil nail using a plate and geogrid elements were illustrated and from the analysis result, bending stiffness showed no effect on the global factor of safety at the end of the construction stage. However, it showed a significant effect on the other construction stages. A parametric study was conducted to investigate how the lateral displacement and the global factor of safety are influenced by varying the length, inclination, and spacing of the nails. When the nail length increases the lateral displacement decreases and the factor of safety increases. It was observed that when the nail inclination increases the global factor of safety increases however, for higher length to wall height ratio the global factor of safety decreases after 150 inclination. Based on the analysis result, the nail inclination angle between 100 and 150 is recommended as the optimal use of the nail.
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Keywords
Soil Nail Wall, Lateral Deflection, Global Factor of Safety, PLAXIS 2D