At-rest earth pressure

Definition

At-rest earth pressure is the lateral pressure exerted by soil on a retaining structure when the soil is in a state of rest, meaning there is no movement or change in volume. This condition occurs when the soil is not allowed to expand or contract laterally, which contrasts with the active state where the soil exerts less pressure due to movement, and the passive state where it exerts more pressure due to compaction. Understanding at-rest earth pressure is essential for designing retaining walls and other structures that interact with soil.

5 Must Know Facts For Your Next Test

1. At-rest earth pressure is typically greater than active earth pressure and less than passive earth pressure.
2. The coefficient of at-rest earth pressure (K₀) can be calculated using various empirical relationships, often dependent on the type of soil and its properties.
3. At-rest conditions are commonly encountered in situations like vertically sided excavations or walls that do not yield or move.
4. This type of pressure is crucial for stability calculations in geotechnical engineering, particularly for structures like basement walls and retaining structures.
5. Understanding at-rest earth pressure helps engineers predict potential failures or movements of soil adjacent to structures.

Review Questions

• How does at-rest earth pressure differ from active and passive earth pressures in terms of soil movement?
  • At-rest earth pressure occurs when the soil remains static, meaning there is no lateral movement or change in volume. In contrast, active earth pressure arises when the soil can move away from a wall, resulting in decreased lateral stress on that wall. On the other hand, passive earth pressure occurs when soil is pushed against a wall, increasing the lateral stress. These differences are crucial for understanding how soil behaves under various conditions and how this impacts structural design.
• Discuss the significance of the coefficient of earth pressure at rest (K₀) and how it is influenced by soil properties.
  • The coefficient of earth pressure at rest (K₀) is vital for determining the lateral forces acting on retaining structures under static conditions. It reflects the relationship between vertical and horizontal stresses within the soil and is influenced by factors such as soil type, density, and prior loading conditions. For instance, granular soils typically have different K₀ values compared to cohesive soils due to their distinct behavior under stress. Accurate determination of K₀ helps engineers design safe and efficient structures.
• Evaluate the implications of ignoring at-rest earth pressure in the design of retaining walls and other geotechnical structures.
  • Ignoring at-rest earth pressure in design can lead to significant structural failures or inefficiencies. If engineers underestimate this lateral force, it may result in inadequate support for walls, leading to potential failures like buckling or overturning. Conversely, overestimating it could lead to unnecessarily robust designs that inflate costs without providing real safety benefits. Therefore, accurately accounting for at-rest earth pressure is crucial for optimizing structural integrity while ensuring safety and cost-effectiveness.

Related terms

Active earth pressure: The lateral pressure exerted by soil on a structure when the soil is allowed to move or deform, leading to reduced pressure on the structure.

Passive earth pressure: The lateral pressure exerted by soil on a structure when the soil is pushed against it, resulting in increased pressure due to compaction.

Coefficient of earth pressure at rest (K₀): A ratio that defines the relationship between vertical stress and horizontal stress in a soil mass at rest, typically influenced by soil properties and stress history.