Wall & Soil Parameters

H — wall height (m)

φ' — effective friction angle (°)

γ_dry — soil unit weight, dry (kN/m³)

γ_sat — soil unit weight, saturated (kN/m³)

c' — effective cohesion (kPa)

δ — wall friction angle (°)

Surcharge & Water

q — uniform surcharge (kN/m²)

q_line — line load (kN/m)

Water table depth from surface (m, optional)

Water table measured from ground surface. Below the water table, submerged unit weight γ′ = γ_sat − 9.81 kN/m³.

Design Options

Design Approach 1 Set

Set 1 (γ_G=1.35, γ_Q=1.50, γ_φ=1.00) Set 2 (γ_G=1.00, γ_Q=1.30, γ_φ=1.25, γ_c=1.25)

DA1 Set 1 applies factors to actions only (γ_φ=1.00, γ_c=1.00). DA1 Set 2 applies factors to both actions and soil parameters (γ_φ=1.25, γ_c=1.25). Use the governing result.

Coulomb method is used when wall friction δ > 0°. For δ = 0° the two methods give the same result.

Earth Pressure Results

Earth Pressure Coefficients

Ka — Rankine active coefficient—

Ka — Coulomb active coefficient (δ ≠ 0)—

K0 — at-rest coefficient (Jaky)—

Kp — passive coefficient (Rankine)—

Active Thrust Components

P_a — active thrust (kN/m)—

z̄ — centroid of active thrust (m from base)—

P_q — line load contribution (kN/m)—

P_water — groundwater thrust (kN/m)—

Total Resultant

P_total — total active thrust (kN/m)—

σ_h,max — pressure at wall base (kPa)—

Design Values (EN 1997-1)

Partial factors used—

φ_design — design friction angle (°)—

c'_design — design cohesion (kPa)—

Pressure Diagram

Step-by-Step Breakdown

Export calculation report

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Frequently Asked Questions

What is the difference between Rankine and Coulomb earth pressure theory?

Rankine (1857) assumes a frictionless wall (δ=0) and gives Ka = tan²(45°−φ/2). Coulomb (1776) accounts for wall friction (δ>0) and backfill slope (β>0), producing a more general solution. For vertical walls with horizontal backfill and δ=0, both methods give identical results. Coulomb is preferred when wall roughness is significant.

When should I use the at-rest coefficient K0 instead of active Ka?

K0 applies when the wall is rigid and cannot move (retaining walls, basement walls, bridge abutments). Active Ka applies when the wall moves away from the soil (flexible walls, cantilever retaining walls). Use K0 for braced or propped structures where ground movements are restrained, per EN 1997-1 §9.3.2.

How does Design Approach 1 (DA1) affect earth pressure calculations?

EN 1997-1 §2.4.7 DA1 applies two combinations. Set 1 (A1+M1+R1): γ_G=1.35, γ_Q=1.50 on actions, γ_φ=1.00, γ_c=1.00 on soil — this governs when loads are unfavorable. Set 2 (A2+M2+R1): γ_G=1.00, γ_Q=1.30, γ_φ=1.25, γ_c=1.25 — this may govern for material-limited design. Both must be checked and the worse utilization retained.

How is water pressure combined with earth pressure?

Below the water table, the submerged unit weight γ′ = γ_sat − 9.81 kN/m³ reduces the effective soil pressure. The water pressure itself forms a triangular diagram with resultant P_water = ½·γ_w·h² at h/3 from the base of the submerged layer. Both are additive: total lateral thrust = P_soil + P_water.

What surcharge loads can be applied?

Uniform surcharge q (kN/m²) increases the active pressure uniformly over the wall height: ΔP = Ka·q·H. Line load q_line (kN/m) is treated as a uniform distribution over the full wall height: P_q = Ka·q_line·H applied at H/2. Point loads require integration of Boussinesq equations and are not in scope here.

How do I choose the wall friction angle δ for Coulomb calculations?

EN 1997-1 Table 9.1 gives indicative δ values: δ = 2/3·φ for rough concrete walls, δ = 1/2·φ for smooth concrete, δ = 1/3·φ for steel sheet pile walls. Never assume δ > φ — wall friction cannot exceed internal friction. For foundations on rock, δ may approach φ but is usually capped at φ/2.

Lateral Earth Pressure Calculator

Frequently Asked Questions