CSLB C-27 Landscaping ContractorHardscape and FeaturesMedium
A landscape contractor is planning to install an interlocking concrete paver driveway. The local soil report indicates a clay-rich subgrade with poor drainage characteristics. What is the most appropriate action to ensure long-term stability and prevent frost heave?
- AIncrease the thickness of the paver bedding sand layer to absorb excess moisture.
- BApply a liquid soil stabilizer to the clay subgrade before laying the base material.
- CExcavate the clay, replace it with a well-draining granular material, then compact.
- DInstall a geotextile fabric directly on the clay subgrade and then the paver base.
Show answer & explanationAnswer & explanation
Correct answer: C. Excavate the clay, replace it with a well-draining granular material, then compact.
Clay-rich soils with poor drainage are highly susceptible to frost heave, which can severely damage paver installations. Replacing the problematic soil with a well-ddraining granular material provides a stable, non-frost-susceptible base, essential for the longevity of a driveway.
Why the other options are wrong
- A. Increasing bedding sand thickness will not compensate for poor subgrade drainage and can lead to instability.
- B. Liquid soil stabilizers may improve some soil properties but are generally not a substitute for proper subgrade preparation in frost-susceptible areas.
- D. Geotextile fabric can separate layers but does not fundamentally change the drainage or frost susceptibility of a clay subgrade.
Subgrade Preparation for Pavers
Proper subgrade preparation involves ensuring a stable, well-draining, and compacted base for paver installations, especially crucial in areas with problematic soils or frost heave potential.
- Poorly draining soils (e.g., clay) are susceptible to frost heave.
- Frost heave causes uneven lifting and damage to paver surfaces.
- Replacing problematic subgrade with granular fill is a common solution.
Memory trick: Pave your way, but first, ensure the ground won't play!