Caisson foundation

Definition

A caisson foundation is a type of deep foundation that consists of a large, hollow structure, typically made of reinforced concrete, which is sunk into the ground to support heavy loads from structures above. This foundation type is particularly useful in situations where soil conditions are poor or when there is a need to reach bedrock or stable strata beneath the surface. Caissons can be open at the bottom or closed and are often used in bridge construction and waterfront structures.

5 Must Know Facts For Your Next Test

1. Caisson foundations are particularly effective in underwater construction, such as piers and docks, because they can be constructed in dry conditions and then sunk into place.
2. There are different types of caissons, including open caissons, which allow water and soil to enter during construction, and pneumatic caissons, which use air pressure to keep water out.
3. The size and depth of a caisson foundation depend on the load it needs to support and the soil conditions at the site.
4. Caissons are often used in urban areas where vibration from pile driving would disturb nearby structures.
5. The construction process for caisson foundations typically involves excavation and placement techniques that minimize soil disturbance and ensure structural integrity.

Review Questions

• How does a caisson foundation differ from traditional shallow foundations, and in what scenarios would a caisson be preferred?
  • Caisson foundations differ from traditional shallow foundations primarily in their depth and load transfer mechanism. While shallow foundations distribute loads to near-surface soils, caissons penetrate deeper into stable strata or bedrock, making them ideal for heavy structures in poor soil conditions or near water bodies. Scenarios where caissons would be preferred include bridge piers or offshore platforms where stability and load-bearing capacity are crucial.
• Discuss the construction techniques involved in building caisson foundations and the challenges that may arise during this process.
  • Building caisson foundations involves several techniques, such as excavation of the caisson shaft on land or using underwater methods for marine constructions. Challenges include ensuring proper alignment and stability during sinking, managing water intrusion for open caissons, and dealing with varying soil types that can affect the placement. Additionally, workers must monitor for potential hazards like collapsing soil or unexpected groundwater levels during construction.
• Evaluate the importance of understanding soil conditions when designing a caisson foundation and how this knowledge impacts overall structural safety.
  • Understanding soil conditions is crucial when designing a caisson foundation because it directly influences both load-bearing capacity and stability. Knowledge of soil properties allows engineers to determine appropriate caisson size, depth, and type based on how the soil will interact with the structure. This evaluation impacts overall structural safety by preventing failures due to inadequate support from unstable soils or excessive loads that exceed the caisson's design specifications.

Related terms

piling: Piling refers to the process of driving long, slender columns into the ground to provide support for structures, often used in similar situations as caissons.

deep foundation: A deep foundation transfers structural loads to deeper, more stable soil or rock layers, providing support when surface soils are not adequate.

load-bearing capacity: Load-bearing capacity is the maximum load a foundation can support without risking failure, an essential consideration when designing caisson foundations.