1. What is Coulomb Active Earth Pressure?

Coulomb's active earth pressure theory calculates the lateral earth pressure exerted by soil on a retaining wall when the wall moves away from the soil. It considers soil friction and wall friction in its calculations.

2. How Does the Calculator Work?

The calculator uses the Coulomb active earth pressure equation:

Where:

• \( P_a \) — Active earth pressure (kN/m)
• \( K_a \) — Coefficient of active earth pressure (unitless)
• \( \gamma \) — Unit weight of soil (kN/m³)
• \( H \) — Height of wall (m)

Explanation: The equation calculates the total lateral force per unit length of wall caused by soil pressure.

3. Importance of Earth Pressure Calculation

Details: Accurate earth pressure calculation is crucial for designing stable retaining walls that can withstand soil forces without failing.

4. Using the Calculator

Tips: Enter the coefficient of active earth pressure (Ka), unit weight of soil in kN/m³, and wall height in meters. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: How is Ka determined?
A: Ka depends on soil friction angle, wall friction angle, and backfill slope. It can be calculated using Coulomb's Ka formula or obtained from tables.

Q2: What are typical values for γ?
A: Typical values range from 16-20 kN/m³ for most soils, with clay soils at the higher end and sandy soils at the lower end.

Q3: What is the difference between active and passive pressure?
A: Active pressure occurs when wall moves away from soil (minimum pressure), passive when wall moves into soil (maximum resistance).

Q4: When is Coulomb's theory preferred over Rankine's?
A: Coulomb's theory is preferred when wall friction is significant (rough walls) or when backfill is sloping.

Q5: What are the limitations of this calculation?
A: It assumes homogeneous soil, plane failure surface, and doesn't account for water pressure, surcharge loads, or cohesion.