Pile section designation as listed in the pile capacity reference table (e.g., 'HP14x73', 'PP12.75x0.375'). Determines perimeter, cross-section area, and structural capacity.

Embedded length of the pile below ground surface in feet. Typical driven piles: 20-100 ft. Longer piles develop more shaft friction but may hit refusal on hard strata.

Dominant soil type along the pile shaft. 'sand' uses beta (effective stress) method, 'clay' uses alpha (total stress) method, 'mixed' splits the pile into upper clay and lower sand zones.

Effective friction angle of the soil in degrees. Required for sand or mixed soil types. Typical: 28-36 for sands, 30-40 for gravels. Used for shaft friction and end bearing via Meyerhof. Only required when soil_type is sand or mixed.

Undrained shear strength (su) of clay in psf. Required for clay or mixed soil types. Typical: 250-2000 psf for soft to stiff clay. Used in the alpha method for shaft resistance. Only required when soil_type is clay or mixed.

Total (bulk) unit weight of the soil in pcf. Used to compute effective vertical stress along the pile. Typical: 100-130 pcf. Saturated soils use total weight; buoyant weight is computed internally below the water table. If omitted, defaults to 120.0 pcf.

Depth from ground surface to the groundwater table in feet. Reduces effective stress below this depth, decreasing both shaft friction and end bearing in granular soils. If omitted, defaults to no groundwater effect.

Factored axial compressive load applied to the pile in kips. Used to compute demand-to-capacity ratio against both geotechnical allowable and structural capacity. Typical: 50-200 kips for building columns, 200-1000 kips for bridge piers.

Factor of safety on ultimate pile capacity. Typical: 2.0-3.0 per IBC/ASCE 7. Use 2.5 for normal conditions, 3.0 where load test data is unavailable. If omitted, defaults to 2.5.

Steel grade for structural capacity check. A36 (Fy=36 ksi) for older designs; A572 Gr. 50 (Fy=50 ksi) is current standard for H-piles per ASTM A572. If omitted, defaults to A572.