What is the at-rest earth pressure coefficient K0?

K0 is the ratio of horizontal to vertical effective stress when there is zero lateral strain in the soil mass. It applies to walls, buried structures, or any scenario where no horizontal movement occurs.

What is Jaky's formula?

Jaky (1944) proposed K0 = 1 − sin(φ) for normally consolidated cohesionless soils. It is the most widely used estimate and gives K0 ≈ 0.5 for a typical friction angle of 30°.

When should I use the Mayne & Kulhawy method?

Use Mayne & Kulhawy (1982) when the soil is overconsolidated (OCR > 1). Overconsolidation significantly increases K0 because the soil 'remembers' a higher past stress. The formula is K0 = (1 − sin φ) · OCR^sin(φ).

The overconsolidation ratio (OCR) is the ratio of the past maximum effective vertical stress (preconsolidation pressure) to the current effective vertical stress. OCR = 1 means normally consolidated; OCR > 1 means overconsolidated.

How does at-rest pressure differ from active pressure?

At-rest pressure (K0) is larger than active pressure (Ka). Active pressure develops only after the wall moves away from the soil, reducing stress. At-rest applies when the wall cannot move (e.g., basement walls propped at the top).

Does this tool handle cohesive soils?

The K0 formulas used here are friction-angle-based and most accurate for granular soils. For clays, K0 can also be estimated as K0 ≈ 0.95 − sin φ (for NC clays) or via correlations with plasticity index, but those methods are not included in this tool.

At-Rest Earth Pressure Calculator

Name: At-Rest Earth Pressure Calculator
Availability: InStock
Author: Nham Vu

Compute K0 using Jaky's formula or the Mayne & Kulhawy OCR correction, then get the lateral pressure diagram and resultant horizontal force on a retaining wall.

Soil & Wall Parameters

K0 Method

K0 = 1 − sin(φ) — normally consolidated soils.

Units:

Internal Friction Angle φ (degrees)

Typical range: 28° – 42° for granular soils.

Soil Unit Weight γ (kN/m³)

Typical: 17–21 kN/m³ (108–133 pcf).

Wall Height H (m)

Surcharge Load q (kN/m²) (optional)

Uniform load on the backfill surface (e.g. traffic, slabs).

—

dimensionless

Resultant Force / width

—

kN/m

Pressure Diagram

Lateral pressure (kPa)

Depth	Soil Press.	Surcharge Press.	Total Press.

Force Breakdown (per unit width)

Triangular soil force (P_soil = ½·K0·γ·H²) —

Rectangular surcharge force (P_q = K0·q·H) —

Total resultant P_h —

Soil component acts at — from base (H/3).

Surcharge component acts at — from base (H/2).

Combined resultant acts at — from base.

Enter soil parameters and click Calculate.

K0 and the at-rest pressure diagram will appear here.

Summary