Retaining Wall Load Calculator computes Rankine active earth pressure on vertical retaining walls. It estimates lateral earth pressure and loads based on soil density, wall height, and surcharge conditions, and provides Ka, total force, and resultant height with optional surcharge.
About parameters. Wall height H (m/ft), soil unit weight γ (kN/m³ or lb/ft³), friction angle φ (degrees), and uniform surcharge q (kPa or psf). The model assumes level backfill and no wall friction (Rankine).
About Ka and pressure distribution. Rankine active coefficient: Ka = tan²(45° − φ/2). The earth pressure increases linearly with depth; surcharge adds a uniform component.
Calculation. The calculator applies Rankine’s earth pressure theory to estimate lateral soil loads on retaining walls. It combines triangular pressure from soil weight and rectangular pressure from surcharge to find the total active force and its point of application.
Total active force per unit wall length:
Pa = ½ Ka γ H² + Ka q H.
Resultant location from base combines triangular (at H/3) and rectangular (at H/2) components.
- Example 1: H = 4 m, γ = 18, φ = 30°, q = 5 ⇒ Ka ≈ 0.333. Pa ≈ ½(0.333)(18)(16) + 0.333 × 5 × 4 ≈ 47.9 kN/m. Resultant ≈ 1.47 m above base.
- Example 2: Increase φ to 35° ⇒ Ka ≈ 0.271 → lower force.
- Example 3: Set q = 0 (no surcharge) to see purely triangular distribution: Pa = ½ Ka γ H² acting at H/3.
Corresponding tools.
Explore Slope Stability, estimate Excavation Cost, and convert units via ft ⇄ m and ac ⇄ ft².
