PileCalc
FHWA-IF-99-025 (O'Neill & Reese 1999) · Horvath & Kenney (1979)

Drilled shafts to FHWA-IF-99-025 — axial and lateral, one tool.

α-method clay, depth-dependent β sand, Horvath & Kenney rock sockets, belled-base uplift and exclusion zones — with the lateral p-y run of the same shaft one tab away.

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The drilled-shaft module implements the FHWA O'Neill & Reese (1999) procedures: α side resistance in cohesive soil with top and bottom exclusion zones, depth-dependent β in cohesionless soil, rock-socket side resistance, and clay/sand/rock tip bearing.

Belled (underreamed) bases are handled for both bearing and uplift, and because the lateral p-y solver lives in the same product, the same shaft's lateral response — including the Reese (1997) weak-rock p-y model for sockets — doesn't need a second license.

The FHWA canon

α and β methods, exclusion zones, rock sockets and tip bearing per FHWA-IF-99-025.

Belled bases

Underream geometry for end bearing and breakout-style uplift.

Lateral in the same tool

p-y analysis of the same shaft — weak-rock sockets included — without buying a second program.

Every value visible

Unit resistances, exclusion zones and intermediate factors shown segment by segment.

Validated against published benchmarks

Every figure below is produced by the engine on the cited published problem — closed-form solutions, design-manual tables, or independent codes — and reproduced by the test suite on every release.

FHWA-IF-99-025 (O'Neill & Reese, 1999) α / β method

QuantityPileCalcReferenceAgreement
β depth function at the published cap depth (z ≈ 4.94 ft → 1.2)FHWA-IF-99-025 β = 1.5 − 0.135√z1.1991.20 (cap)within 0.1%
Clay tip pressure Nc*·Sᵤ (cᵤ 2000 psf, Nc* = 9)FHWA-IF-99-025 end bearing17,990 psf18,000 psfwithin 0.1%
Clay side resistance, α = 0.55 with FHWA exclusion zonesFHWA-IF-99-025 α-method (5 ft top / 1D base excluded)331,750 lb331,752 lbexact
See the full per-tool validation report

The numbers, published

PileCalc's engine is checked term-by-term against the reference codes. A representative sample of the benchmarks — every intermediate value is visible in the app so you can reproduce them yourself.

Free-head pile (EI 1.43×10⁶, D 1 m, L 24.4 m)Liang et al. (2014) exact solution / RSPile
Max moment
792.2 kN·m
792.1 kN·m (exact)
within 0.1%
Fixed-head pile (EI 1.43×10⁶, D 1 m, L 24.4 m)Liang et al. (2014) exact solution / RSPile
Head moment
−581.1 kN·m
−581.0 kN·m (exact)
within 0.1%
Cantilever pile (EI 320, D 0.1 m, L 5.25 m)Liang et al. (2014) exact solution / RSPile
Head deflection
8.75 mm
8.750 mm (exact)
within 0.1%
Cantilever pile (EI 320, D 0.1 m, L 5.25 m)Liang et al. (2014) exact solution / RSPile
Max moment
2.335 kN·m
2.334 kN·m (exact)
within 0.1%
Circular pile, API sand (D 0.5 m, L 10 m, H 100 kN)RSPile verification manual
Deflection & moment profile
RSPile 2018 problems #1/#2/#8/#15
chart-reading tolerance
within 1–3%
Steel pile, multi-layer slope stabilization (17 m)RSPile / TZPile / LPile
Lateral resistance
607 kN
582 kN
within ~4%
Read how we validate — and why against two independent codes

Drilled shafts: common questions

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