Retaining wall type. Gravity walls resist overturning by self-weight; cantilever walls use a reinforced stem and base slab. Cantilever is more economical for heights above 10 ft.

Height of retained soil above the top of the base slab, in feet. Typical range: 4-30 ft. Heights above 20 ft may require counterfort or anchored designs.

Total width of the wall footing (base slab) in feet. Rule of thumb: 0.5-0.7 times the wall height for cantilever walls. Must be wide enough for overturning and bearing stability.

Length of the toe (front projection of base beyond the stem face) in feet. Typical: 1/3 of base width for cantilever walls. Helps distribute bearing pressure. If omitted, defaults to 0.0 ft (no toe projection).

Thickness of the wall stem in feet. Required for cantilever walls. Typical minimum: 8-12 inches (0.67-1.0 ft). Increases with wall height for structural adequacy. Only required when wall_type is cantilever.

USCS soil classification (e.g., 'SW', 'CL', 'SM'). Used to look up friction angle, unit weight, and earth pressure coefficients from reference tables. Recommended: enables automatic soil property lookup from reference tables.

Internal friction angle of the retained soil in degrees. Typical: 28-36 for sands, 0-20 for clays. Used to compute Rankine active/passive earth pressure coefficients. If omitted, looked up from soil_type via reference table.

Total unit weight of the retained soil in pounds per cubic foot. Typical: 100-130 pcf. Sandy soils ~110-125 pcf; clayey soils ~100-120 pcf. If omitted, looked up from soil_type via reference table.

Uniform surcharge pressure on the retained soil surface in psf. Common values: 100 psf for light traffic, 250 psf for highway loading (AASHTO HL-93 equivalent). If omitted, defaults to 0.0 psf (no surcharge).

Depth from the ground surface to the water table in feet. If above the base, hydrostatic and buoyancy effects are included. Omit if no groundwater is present.

Unit weight of the wall concrete in pcf. Normal-weight concrete: 145-155 pcf. Lightweight concrete: 90-120 pcf. If omitted, defaults to 150.0 pcf.

Thickness of the base slab in feet. If omitted, defaults to 10% of wall height (minimum 1.0 ft). Typical range: 1-3 ft for walls up to 20 ft.

Depth of soil embedment in front of the wall toe in feet. Provides passive resistance against sliding. Typical: 2-4 ft below grade. Often ignored conservatively. If omitted, defaults to 0.0 ft (no passive resistance).