SettingsSettings for this calculationUS
The grout-to-soil bond strength, from FHWA GEC-7 tables or site-specific pullout testing.
Varies substantially by soil type and installation method (e.g. rotary drilled vs. driven casing).
The diameter of the drilled hole for the nail and grout.
Typically 3-8 in (75-200mm) for soil nails.
The length of the nail bonded (grouted) beyond the potential failure surface.
Only the length beyond the failure plane contributes to pullout resistance.
The nail's design tensile load.
From the overall wall stability analysis.
Pull-out safety factor
3.56 (target ≥2.0)
The design load on this nail is below the most the grout-to-ground bond would carry at a pullout safety factor of 2.0 shown with it — FHWA's minimum for soil nailing gives it. Site-specific pullout testing can establish a bond strength the assumed value does not. Being under the allowable pressure is not the whole ground question: settlement, groundwater and the footings alongside are all untouched here.
- Pullout capacity
- 63.97 kips
They open the calculator with your figures already in it
Soil Nail Pull-Out Safety Factor Calculator: 3.56 (target ≥2.0) — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
Show calculation logicHide calculation logic
How this was calculated
Formula source(s)
- FHWA GEC No. 7 soil nail wall design: pullout capacity = nominal bond strength x pi x drill hole diameter x bonded length; a minimum pullout safety factor of 2.0 is standard practice
Inputs used
- Nominal Bond Strength (qs)
- 2088.54 psf
- Drill Hole Diameter
- 6 in
- Bonded Length
- 19.5 ft
- Design (Working) Load
- 17.98 kip
Intermediate steps
- Pullout capacity
- 63.97 kips
Confidence note: The design load on this nail is below the most the grout-to-ground bond would carry at a pullout safety factor of 2.0 shown with it — FHWA's minimum for soil nailing gives it. Site-specific pullout testing can establish a bond strength the assumed value does not. Being under the allowable pressure is not the whole ground question: settlement, groundwater and the footings alongside are all untouched here.
What this calculation does not cover
- This checks the grout-to-ground bond and nothing else. The nail bar's own tensile capacity, the grout-to-steel bond, and the head plate and facing connection are separate checks — a nail can pass this one and still fail by yielding the bar or punching through the shotcrete face.
- It is a check on one nail, not a wall design. Global and sliding stability, bearing at the toe, facing reinforcement and the analysis that produced the design load per nail all sit outside it, and the design load you type in is taken as given rather than tested.
- Only the bonded length beyond the potential failure surface earns capacity, and the calculation cannot locate that surface for you. Enter the whole nail length instead of the portion past the failure plane and the answer is overstated in direct proportion.
- Bond strength is treated as one uniform value along the whole bonded length. Soil layering, change with depth, drilling method, groundwater and grout pressure all move it, and a tabulated figure remains an assumption until verification and proof pull-out tests on site confirm what the ground actually delivers.
- Static, short-term conditions only, and the 2.0 target is the common static minimum. Seismic loading, construction surcharge, creep in fine-grained soils and corrosion over a permanent wall's life are not in the arithmetic, and a project specification or a load-and-resistance-factor design can demand a different margin. This does not replace a geotechnical engineer's design.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-06 · in the site-wide review of 2026-09-06 · v1.0.1
Regulatory standards & verification citations1
- FHWA GEC No. 7 soil nail wall design: pullout capacity = nominal bond strength x pi x drill hole diameter x bonded length; a minimum pullout safety factor of 2.0 is standard practice
Cite this page
Your workspace
Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.