API: axial capacity & settlement

Computes single-pile axial capacity and settlement: side friction and end bearing by the NAVFAC DM-7.02 static method, elastic + Vesić settlement, and the full load–settlement curve so capacity can also be read off at a settlement limit. Compression, uplift, and downdrag are all reported. The method and every input are explained in Axial capacity & settlement; the same analysis runs interactively at the axial tool.

Endpoint

The request takes a pile (uniform or sectioned, with elasticModulus and unitWeight; displacement: true for driven displacement piles) and a soil profile of layers typed cohesive / cohesionless / rock. Each layer must carry the strength parameter its type uses — cohesion (or qu) for cohesive, phi for cohesionless, qu plus an explicit rockJointCondition for rock. Jointed rock also requires rqd from 20 through 100 and is rejected at the pile tip until a compatible base method is released. Factors of safety, transfer discretization, method, and an unfactored serviceLoad are explicit. If a water table is present,waterUnitWeight is required; there are no hidden water or numerical defaults.

Authentication, rate limits, and the error envelope are shared by every endpoint — see the API overview. Requests are unit-agnostic: any self-consistent unit system works, and results come back in the same units. The examples below use SI (m, kN, kPa, kN/m³).

Request fields

This table is generated from the same schema that validates the request, so it cannot drift. Where a field appears once per variant row, it belongs to that variant only.

Response fields

Code examples

A complete, runnable request. Replace YOUR_API_KEY (or set PILECALC_API_KEY in your environment).

curl https://api.pilecalc.com/v1/axial \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "unitSystem": "si",
  "method": "navfac-dm7-reese-oneill",
  "pile": {
    "kind": "uniform",
    "length": 18,
    "diameter": 0.61,
    "elasticModulus": 30000000,
    "unitWeight": 24,
    "displacement": true
  },
  "soil": {
    "layers": [
      {
        "type": "cohesive",
        "top": 0,
        "bottom": 6,
        "gamma": 17.5,
        "cohesion": 45
      },
      {
        "type": "cohesionless",
        "top": 6,
        "bottom": 13,
        "gamma": 19,
        "phi": 34
      },
      {
        "type": "rock",
        "top": 13,
        "bottom": 18,
        "gamma": 22,
        "qu": 4500,
        "rockJointCondition": "massive-intact"
      }
    ],
    "waterTableDepth": 3,
    "waterUnitWeight": 9.81
  },
  "serviceLoad": 1000,
  "segments": 240,
  "penetrationRatioSide": 20,
  "penetrationRatioTip": 20,
  "kDown": 1,
  "kUp": 1,
  "fsTip": 3,
  "fsSide": 2,
  "fsWeight": 1.5,
  "fsUplift": 3,
  "allowableSettlement": 0.012,
  "loadSettlementPoints": 160,
  "maxTipSettlement": 0.08,
  "convergenceTolerance": 0.05
}'

The GET variant returns capacity.allowableDown,service.settlement,method.id as a plain-text CSV line — made for Excel's WEBSERVICE() and Sheets' IMPORTDATA() (see Use PileCalc in Excel). Omit fields to get the full JSON response.

Interpreting results

• allowableDown is the design number for compression; allowableUplift for tension. The segments array shows where the side resistance comes from, layer by layer.
• service.settlement is the serviceability result at the exact serviceLoad you supply. settlement.total is the Vesić estimate at fully mobilized resistance, and loadSettlement is the plotted transfer curve.
• Downdrag (capacity.downdrag) is reported separately — subtract it from capacity per your code's load-combination rules rather than assuming the API did.