Lateral Earth Pressure Wall Calculator
Retaining wall structural design: Calculate Rankine and Coulomb active (K_a), passive (K_p), and at-rest (K_0) earth pressures, total thrust, and overturning moment.
Wall Geometry & Soil Properties
Earth Pressure & Resultant Thrust
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Frequently Asked Questions
What is the fundamental difference between Rankine and Coulomb earth pressure theories?
Rankine's theory assumes the retaining wall is frictionless (wall friction δ = 0) and vertical, treating soil in a state of plastic equilibrium where slip surfaces are planes inclined at (45° + ϕ/2). Coulomb's wedge theory accounts for wall roughness/friction (δ > 0) and inclined backfill (β), analyzing the equilibrium of a sliding triangular soil wedge, which typically yields a slightly lower, more realistic active pressure Ka.
What is the "At-Rest" earth pressure condition (K0) and when must it be used?
The At-Rest condition exists when a wall does not yield or move at all (zero lateral strain). Active pressure (Ka) only develops after a wall rotates or translates outward by ~0.1% to 0.4% of its height. For unyielding structures like basement walls tied to rigid floor slabs, bridge abutments anchored to bedrock, or box culverts, engineers must design for the higher At-Rest pressure (K0 ≈ 1 - sin ϕ), never active pressure Ka.
How does poor drainage behind a retaining wall cause structural collapse?
Dry soil has a lateral pressure coefficient of ~0.3 (producing ~6 kN/m² pressure per meter depth). If weep holes clog and the backfill fills with water, water exerts full hydrostatic pressure (100% lateral coefficient, 9.81 kN/m² per meter depth) on top of the buoyant soil pressure. This hydrostatic head easily triples the total overturning moment, which is the leading cause of retaining wall blowouts during heavy rains.