1. What is Active Earth Pressure?

Active earth pressure is the lateral pressure exerted by soil on a retaining wall when the wall moves away from the soil. It represents the minimum lateral pressure that a soil mass will exert on a retaining structure.

2. How Does the Calculator Work?

The calculator uses the 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 retaining wall (m)

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

3. Importance of Active Earth Pressure Calculation

Details: Accurate calculation of active earth pressure is crucial for designing stable retaining walls and other earth-retaining structures to prevent failure.

4. Using the Calculator

Tips: Enter the coefficient of active earth pressure (Ka), unit weight of soil (γ), and wall height (H). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: How is Ka determined?
A: Ka depends on the soil's angle of internal friction (φ) and wall friction angle (δ). It can be calculated using Rankine or Coulomb theories.

Q2: What are typical values for γ?
A: Unit weight of soil typically ranges from 16-22 kN/m³ for most soils, with sand around 18-20 kN/m³ and clay around 16-20 kN/m³.

Q3: Does this equation account for surcharge loads?
A: No, this is the basic equation for soil self-weight only. Additional calculations are needed for surcharge or water pressure.

Q4: What's 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).

Q5: How does wall friction affect the results?
A: Wall friction reduces active earth pressure. The calculator uses Ka which should account for wall friction if applicable.