Active Pressure

Definition

Active pressure refers to the lateral force exerted by retained earth against a structure, such as a retaining wall. This pressure is a result of the earth's weight and any additional loads applied to it.

Purpose

Active pressure is a critical consideration in the design and construction of retaining walls and other structures that hold back soil. Understanding active pressure ensures that these structures are stable and safe, preventing potential failures or collapses. Engineers use calculations of active pressure to determine the appropriate thickness, materials, and reinforcement needed for retaining walls to withstand the forces exerted by the retained earth.

Examples of Use

1. Retaining Wall Design: When designing a retaining wall for a garden or road embankment, engineers calculate the active pressure exerted by the soil to ensure the wall can resist these forces without tipping over or sliding.
2. Slope Stabilization: In hillside construction projects, active pressure calculations help in designing measures to stabilize slopes and prevent landslides.
3. Basement Walls: For buildings with basements, the walls must be designed to withstand the active pressure from the surrounding soil to prevent structural damage and water infiltration.
4. Bridge Abutments: Engineers calculate the active pressure exerted on bridge abutments to ensure they can support the lateral loads from the soil and traffic above.

Related Terms

1. Passive Pressure: The resistance provided by the soil against a structure moving towards it, opposite of active pressure.
2. Bearing Capacity: The capacity of soil to support the loads applied to the ground.
3. Earth Pressure at Rest: The lateral pressure exerted by soil when it is not allowed to move or deform.
4. Soil Mechanics: The study of soil properties and behavior under various conditions of load and pressure.
5. Lateral Earth Pressure: General term for pressure exerted by soil in a horizontal direction against a structure.

Notes

• Active pressure depends on factors such as soil type, moisture content, and the height of the retained earth.
• The angle of internal friction and cohesion of the soil also play a significant role in determining active pressure.
• Calculations typically use theories such as Rankine's or Coulomb's earth pressure theories to estimate active pressure values.
• Proper drainage behind retaining walls is crucial to reduce hydrostatic pressure, which can increase active pressure and lead to wall failure.