Lateral earth active pressure (Rankine theory for horizontal backfill)


Lateral earth pressure is the pressure that soil exerts in the horizontal direction. Rankine’s theory, is a stress field solution that predicts active and passive earth pressure. It assumes that the soil is cohesionless, the wall is frictionless, the soil-wall interface is vertical, the failure surface on which the soil moves is planar, and the resultant force is angled parallel to the backfill surface. The active state occurs when a retained soil mass is allowed to relax or deform laterally and outward (away from the soil mass) to the point of mobilizing its available full shear resistance (or engaged its shear strength) in trying to resist lateral deformation. When the backfill is not inclined to the horizontal the active lateral coefficient is depended on the angle of shearing resistance.

Related formulas


KaActive lateral earth pressure coefficient (dimensionless)
ϕAngle of shearing resistance (radians)