California Supplemental (CSE) Practice Exam

Which type of foundation should be considered for soils that are expansive or have a high water table?

1. Typical footings

2. Piles and grade beams

3. Shallow foundations

4. Concrete slabs

The correct answer is: Piles and grade beams

When dealing with expansive soils or conditions where there is a high water table, the use of piles and grade beams is the most suitable choice. Expansive soils can undergo significant volume changes due to moisture fluctuations, leading to potential structural damage if conventional foundations like typical footings or shallow foundations are employed. Piles are deep foundations that are driven or drilled into the ground to reach stable soil or bedrock, bypassing problematic soil layers entirely. This method provides the necessary stability and load-bearing capacity, mitigating the effects of soil movement. Grade beams act as a structural support element that connects the tops of piles or other foundations, distributing loads evenly and providing further stability. In contrast, typical footings, shallow foundations, or concrete slabs may not adequately handle the challenges posed by expansive soils or high water tables, as they are more susceptible to movement and moisture-related issues. Therefore, employing piles and grade beams offers a reliable solution for such foundation challenges, ensuring the integrity of the structure over time.