Florida General Contractor Florida General Contractor Soils and Foundation Systems 1 — Questions and Answers
Question 1: Which material typically has the highest allowable bearing capacity for foundation design?
- Loose sand
- Soft clay
- Bedrock (Correct answer)
- Organic silt
Correct answer: Bedrock
Bedrock has the highest bearing capacity of any material, often exceeding 10,000 psf, making it the most suitable for heavy foundation loads.
Question 2: What is the standard unit used to express soil bearing capacity in the United States?
- Pounds per cubic foot (pcf)
- Pounds per square foot (psf) (Correct answer)
- Pounds per linear foot (plf)
- Kilopascals (kPa)
Correct answer: Pounds per square foot (psf)
Soil bearing capacity is expressed in pounds per square foot (psf) or tons per square foot (tsf) because it measures load distributed over an area.
Question 3: Why are Florida building footings NOT required to be placed at a minimum frost-protection depth?
- Florida code exempts residential buildings
- Florida's climate does not produce freezing ground temperatures (Correct answer)
- Footings in Florida must use special anti-frost concrete
- Florida relies on insulated slab edges instead
Correct answer: Florida's climate does not produce freezing ground temperatures
Florida has no frost line because ground temperatures do not drop low enough to freeze soil, so frost depth requirements that apply in northern states are not applicable.
Question 4: Which field test is most commonly used to verify the in-place density of compacted fill during construction?
- Atterberg limits test
- Grain size analysis
- Nuclear density gauge test (Correct answer)
- Standard penetration test (SPT)
Correct answer: Nuclear density gauge test
The nuclear density gauge test measures in-place moisture and density of compacted fill quickly and non-destructively, making it the standard QC tool on job sites.
Question 5: What is the primary reason geotechnical soil borings are performed before a construction project?
- To identify underground utilities
- To measure soil color and texture
- To determine soil layers, bearing capacity, and groundwater conditions for foundation design (Correct answer)
- To check for buried archaeological artifacts
Correct answer: To determine soil layers, bearing capacity, and groundwater conditions for foundation design
Soil borings provide engineers with data on soil stratification, bearing capacity, and groundwater depth, which are essential for designing an appropriate and safe foundation system.
Question 6: Which underlying geological condition is primarily responsible for sinkhole formation in Florida?
- Expansive clay layers
- Permafrost thaw
- Dissolution of limestone (karst) bedrock by groundwater (Correct answer)
- Liquefaction of saturated sand
Correct answer: Dissolution of limestone (karst) bedrock by groundwater
Florida sits on limestone karst bedrock that gradually dissolves when groundwater flows through it, forming voids that can collapse and create sinkholes at the surface.
Question 7: Which type of foundation is most commonly used for light residential construction on stable soil in Florida?
- Drilled caisson
- Mat (raft) foundation
- Spread (isolated) footing (Correct answer)
- Timber pile
Correct answer: Spread (isolated) footing
Spread footings are the most common residential foundation element because they are economical and effective for distributing column or wall loads on stable bearing soils.
Florida General Contractor Florida General Contractor Soils and Foundation Systems 1
Which material typically has the highest allowable bearing capacity for foundation design?