Presenter: Kayla Hanson, P.E., NPCA
Thursday, April 8, 2021
Noon – 1:00 p.m. Eastern
The word “buoyancy” is associated with flotation, so it may bring to mind balloons, boats or fishing bobbers. However, buoyancy applies to more than just objects that float in air or water; it also applies to objects surrounded by soil. In the right conditions, buoyant forces can be significant enough to lift a buried structure out of the ground. Therefore, understanding the forces that act on buried structures, how to calculate buoyant forces and how to counteract buoyant forces is critical for proper design and installation of these structures. During this presentation, we will first explore the concepts of weight, volume and density, and learn how density relates to an object’s buoyancy. Then we will discuss the main forces that act on underground structures and learn how to determine whether those forces will cause the structure to float. Next, we will demonstrate the calculation of buoyant forces on a typical buried precast concrete tank under different conditions, and finally we will discuss countermeasures that can be taken to prevent flotation. This is essential information for those who design, manufacture, install, regulate, and inspect underground structures.
At the conclusion of this course, you will be able to:
- Define density and buoyancy and explain how they are related.
- List the main forces that act on an underground structure.
- Describe how to calculate buoyant forces.
- Determine if an underground structure requires ballast to prevent flotation.