CSLB C-27 Landscaping ContractorSite Preparation and DrainageHard
A C-27 contractor is preparing a subgrade for a new gravel pathway that will experience moderate foot traffic. To ensure proper stability and prevent settling, what is the minimum recommended compaction percentage for the subgrade in this application?
- A90% Modified Proctor
- B95% Modified Proctor
- C100% Modified Proctor
- D85% Modified Proctor
Show answer & explanationAnswer & explanation
Correct answer: B. 95% Modified Proctor
For subgrades supporting hardscape elements like gravel pathways, a minimum compaction of 95% Modified Proctor is typically required. This ensures adequate bearing capacity, minimizes settlement, and provides a stable base for the pathway, especially in areas with moderate traffic.
Why the other options are wrong
- A. 90% Modified Proctor might be acceptable for some landscape areas but is often insufficient for hardscape with moderate traffic.
- C. 100% Modified Proctor is ideal but can be difficult and costly to achieve uniformly across a large area for a gravel pathway subgrade, and 95% is generally sufficient.
- D. 85% Modified Proctor is generally too low for hardscape subgrades and would likely lead to excessive settlement and instability.
Subgrade Compaction (Hardscape)
Subgrades for hardscape elements like patios, walkways, and driveways typically require a minimum compaction of 95% Modified Proctor to ensure stability and prevent settlement.
- Modified Proctor is a standard test for soil compaction density.
- High compaction increases bearing capacity.
- Reduces future settlement and movement of hardscape.
- Achieved through proper moisture content and mechanical compaction.
Memory trick: Ninety-five is the 'prime' for a stable subgrade's climb!