Construction Supervisor License Practice Exam

A commercial building with an 8' high, 10" thick plain concrete foundation wall has a maximum unbalanced backfill height of how many feet?

1. 4

2. 8

3. 7

4. 5

The correct answer is: 7

To determine the maximum unbalanced backfill height for a commercial building with an 8-foot high, 10-inch thick plain concrete foundation wall, it's important to understand the structural limitations and the principles of soil pressure on retaining walls. The maximum unbalanced backfill height is typically based on the height of the concrete wall and the potential for soil pressure behind the wall. An 8-foot high wall, when considering soil pressure due to backfill, usually allows for a theoretical maximum of about half its height to maintain stability. Therefore, if the wall is 8 feet high, the maximum unbalanced backfill height should ideally be around 4 feet. However, since the wall is also supporting the weight of the backfill, it is essential to account for material characteristics and the wall’s structural integrity. Taking into account the thickness of the wall and the common practices in civil engineering, the maximum unbalanced backfill height is more conservatively limited—generally leading to approximately 7 feet. This considers additional factors such as wall material, compaction of the backfill, and drainage which can contribute to the effective loads on the foundation. Given these concepts, while the answer of 7 feet seems most reasonable due to engineering practices, the educational aspect may