Base heave

Definition

Base heave refers to the upward movement of soil beneath a foundation, typically occurring due to changes in moisture content or pressure. This phenomenon can significantly affect the stability and integrity of various types of foundations, leading to structural issues if not properly addressed during the design and construction phases.

5 Must Know Facts For Your Next Test

1. Base heave is primarily caused by increased water content in clay soils, leading to swelling and upward movement.
2. It is crucial to assess soil conditions during the site investigation phase to predict potential base heave issues before foundation design.
3. Proper drainage systems can be implemented to manage water flow around foundations, minimizing the risk of base heave.
4. Different types of foundations, such as deep foundations, may be used to mitigate the effects of base heave in problematic soils.
5. Engineers may incorporate techniques like soil stabilization or the use of flexible materials in foundation design to accommodate potential base heave.

Review Questions

• What are the main causes of base heave and how can they affect different types of foundations?
  • Base heave is mainly caused by increased moisture content in clay soils, leading to swelling that pushes foundations upward. This can create significant structural problems for shallow foundations as they may not be able to withstand the upward forces. In contrast, deep foundations may have a better chance of resisting these forces, but if not designed appropriately, they too can experience issues such as cracking or tilting due to uneven pressures.
• Discuss how proper site investigation and drainage solutions can reduce the risks associated with base heave.
  • Thorough site investigation helps engineers identify soil types and moisture levels that could lead to base heave. By understanding these conditions, effective drainage solutions can be designed to redirect water away from foundations. This reduces the likelihood of moisture-induced swelling in the surrounding soil, ultimately protecting the integrity of the structure. Implementing a combination of proper grading and drainage systems is key to managing these risks.
• Evaluate different foundation design strategies that can be used to address base heave issues in construction projects.
  • To address base heave issues effectively, engineers can employ various foundation design strategies such as using deep foundations that extend below the influence of moisture changes. Additionally, incorporating flexible materials or adaptive designs allows for some movement without causing structural damage. Soil stabilization techniques, like using lime or cement, can also be implemented to increase the soil's load-bearing capacity and reduce susceptibility to heaving. By evaluating site conditions and choosing an appropriate strategy, engineers can greatly enhance foundation performance under potential base heave conditions.

Related terms

Hydrostatic Pressure:

The pressure exerted by a fluid at equilibrium due to the force of gravity, which can influence soil behavior and contribute to base heave.

Settlement:

The downward movement of the ground or foundation due to loading, which can be contrasted with base heave as both are crucial in understanding foundation performance.

Soil Compaction: The process of increasing the density of soil by reducing air gaps, which can help mitigate the effects of base heave by improving soil stability.