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Optimization of Nail Inclination Angle in Soil Nail Walls Based on a Prevalent Limit Equilibrium Method


Although a variety of research works have been carried out to investigate the behavior of nailed slopes and nail walls, only a few studies are devoted to the optimum design of soil nail walls. In this study, the limit equilibrium-based approach presented in FHWA manual, which is the prevalent design method in conjunction with nonlinear programming, has been used. Based on this approach, the optimum nail inclination angle (η) leading to the maximum safety (FS) factor against overall failure was determined for typical soil nail walls. Effects of some primary contributing factors such as nail diameter, nail length, soil friction, slope angle, back slope angle, and layout of nails on the optimum design indices were investigated thoroughly and presented in dimensionless graphs. Results indicate that increase in the nail diameter gives rise to an increase in both FS and ηopt. In addition, increasing the length of nails up to 1.875H leads to the most significant improvement in slope stability. Furthermore, the increase in soil friction results in an improvement in FS and a limited rise in ηopt. Steeper nail walls are less stable and require higher ηopt, a linear function of slope orientation (α). A higher back slope angle was found to reduce FS. Furthermore, it was found that inserting the nails in the lower 1/3 part of the slope leads to the highest efficiency, and the nails have a minor influence on the stability of short walls or highly cohesive slopes.

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All required data have been presented in the manuscript.

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A custom code prepared by the authors was used in this study.


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Correspondence to Mohammad Reza Arvin.

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Arvin, M.R., Ghavami, E. & Motamedi Azari, M. Optimization of Nail Inclination Angle in Soil Nail Walls Based on a Prevalent Limit Equilibrium Method. Indian Geotech J (2021).

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  • Nail soil wall
  • Optimization
  • Limit equilibrium
  • Safety factor
  • Overall failure