CSLB C-27 Landscaping ContractorHardscape and FeaturesMedium
A landscape contractor is constructing a segmented retaining wall (SRW) using concrete blocks. To ensure the wall's long-term stability against lateral soil pressure and prevent bulging or overturning, what is the primary function of geogrid reinforcement in walls taller than 3-4 feet?
- ATo prevent weeds from growing through the wall joints.
- BTo extend the 'gravity mass' of the wall into the soil.
- CTo provide a decorative finish to the wall face.
- DTo increase the permeability of the backfill material.
Show answer & explanationAnswer & explanation
Correct answer: B. To extend the 'gravity mass' of the wall into the soil.
Geogrid reinforcement works by extending the effective 'gravity mass' of the retaining wall into the backfill soil. The geogrid layers interlock with the soil, creating a reinforced soil mass that acts as a larger, heavier gravity structure, thereby significantly increasing the wall's resistance to lateral forces and preventing overturning or bulging.
Why the other options are wrong
- A. While some fabrics might deter weeds, geogrid's primary purpose is structural reinforcement, not weed control.
- C. Geogrid is a structural component and has no decorative function.
- D. Geogrid itself does not increase the permeability of the backfill; proper aggregate selection does that.
Geogrid in SRW
A polymer mesh material used as horizontal reinforcement layers within the backfill of segmented retaining walls.
- Extends the wall's effective mass into the soil.
- Increases resistance to lateral earth pressure.
- Crucial for stability of taller SRWs.
Memory trick: Geogrid makes the wall's 'muscle' reach DEEPER into the earth, like roots holding a tree.