Soil nail walls are a cost-effective earth retention system, but the design process described in the FHWA Soil Nail Reference Manual is dense, empirical, and rarely practiced outside of specialized geotechnical firms. When a community centre project required a permanent anchor wall review, I built the design capability from the ground up - no prior expertise or official calculations existed within the firm.

My Role

Lead / sole developer of the design methodology. I took on the technical challenge under tight deadline and budget constraints, studied the reference manual in depth, and delivered a complete reusable design framework.

What I Did

Decomposed the FHWA empirical design process:

  • Studied the Soil Nail Reference Manual cover to cover and identified the critical design parameters, failure modes, and checks required for a compliant design
  • Broke down the iterative empirical process into a structured decision flowchart that an engineer can follow step by step
  • Identified which parameters are project-specific inputs versus standard assumptions, and which checks gate the design progression

Created comprehensive design workflows:

  • Full design flowchart covering nail length, spacing, diameter, inclination, and corrosion protection selection
  • Separate workflows for internal stability (nail pullout, nail tensile, facing flexure, facing punching shear) and external stability (global, sliding, bearing, overturning)
  • Clear documentation of the empirical relationships and lookup tables used at each step

Developed Mathcad calculation sheets:

  • Parametric Mathcad worksheets that accept project-specific soil properties, wall geometry, and loading conditions
  • Automated the iterative design checks - nail spacing and length are iterated until all internal and external stability checks pass
  • Calculation sheets produce design-ready output with factors of safety for each failure mode

Impact

  • Reduces soil nail anchor design from a dense, time-intensive empirical process to minutes per design iteration
  • Enables the firm to bid on future soil nail projects at significantly reduced cost - the structural discipline chair described the capability as enabling bids “for pennies on the dollar”
  • Established a new structural design capability where none previously existed
  • Reusable framework - the flowcharts and calculation sheets work for any future soil nail project, not just the original application