Chapter 2 - Review Questions

Question 1

1. What is the nature of the most common type of foundation failure? What are its causes?

Answer 1

Excess differential settlement caused by variations in soil types, building loads, or structural systems among different parts of the building.

Question 2

2. Explain the differences among sand, silt, and clay, both in their physical characteristics and their behavior in relation to building foundations.

Answer 2

Silt and clay are fine-grained soils while sand is coarse-grained. Coarse-grained soils are generally the most stable materials for supporting foundations. Clay soils are particularly difficult to build on due to consolidation.

Question 3

7. Under what conditions would you use a watertight barrier instead of well points when digging below the water table?

Answer 3

If lowering the water table will affect neighboring buildings, watertight barriers should be used instead.

Question 4

10. If shallow foundations are substantially less costly than deep foundations, why do we use deep foundations?

Answer 4

Deep foundations are used when the frost line is deep or when the soils directly below the substructure are weak or unstable.

Question 5

13. Explain the difference between waterproofing and dampproofing. When is one or the other an appropriate choice for protecting a foundation from moisture?

Answer 5

Dampproofing is moisture-resistant and is used where groundwater conditions are mild. Waterproofing does not allow the passage of any water through the foundation and is resistant to hydrostatic pressure.