Pile capacity from CPT

The axial capacity of a single pile directly from a cone penetration test (CPT) sounding, by the method the engineer chooses: LCPC (Bustamante and Gianeselli 1982) as UFS 3-220-20 (DM7.2, 2026) 6-5.4.4 gives it, or Eslami and Fellenius (1997) as FHWA GEC 12 (FHWA-NHI-16-009, 2016) 7.2.1.3.6 gives it. The other method is reported beside it for comparison.

Inputs of the CPT pile #

• Pile: round or square, width or diameter b, toe depth L (in the sounding's depths), and the depth above which no side resistance counts (pre-drilled, scoured or downdrag zone).
• LCPC: the pile group of UFS 3-220-20 6-5.4.4 (I-A drilled shafts, CFA and gravity-grouted micropiles; I-B drilled shafts with permanent casing; II-A driven or jacked concrete; II-B driven or jacked steel), and careful construction (the bracketed fp values of Table 6-22, only with careful execution: the engineer's judgment).
• Eslami and Fellenius: the cone area ratio a and the toe influence zone (8b above to 4b below the toe for a pile driven through weak soil into denser soil, 2b above to 4b below for a pile into weaker soil).
• CPT sounding: one row per reading: depth, qc, fs (recorded only), u2, and the soil type from the engineer's classification of the sounding (it sets Cs and the LCPC category).
• Loads: axial per load type (compression positive), the resistance factor φ (LRFD; GEC 12 suggests the factor of the field verification method) or the factor of safety (ASD).

Auto-design varies the toe depth in 1-ft steps within the sounding. See Auto-design.

Checks performed #

The side resistance is integrated between the readings (trapezoids, cut at the toe and at the top of the counted zone). The drawings show the pile beside the cone resistance and the unit side resistance along the depth.

Limitations #

• The soil type of each reading is the engineer's entry; the soil behaviour type is not derived from the CPT.
• UFS 3-220-20 Table 6-22 prints its group columns compactly; the column assignment used here (I-A, I-B, II-A, II-B) follows Bustamante and Gianeselli's table as recalled (to confirm against the original).
• GEC 12 states qE without subtracting the effective overburden; this follows GEC 12 as printed.
• No group effects, downdrag, setup or relaxation, structural capacity or driveability.

Verification examples #

Verification status: 9 values compared in 5 examples (0 published, 5 hand calculations from the cited equations): 9 within tolerance, 0 recorded deviations. No published example: every value is a hand calculation. That checks the program against this reading of the code, not the reading itself. Code basis: the provisions it uses were read in the target edition.

No published worked example of either method is on disk. Uniform soundings make each value a hand calculation from the published equations and tables (backend/tests/test_verify_cpt_pile.py):