Subgrade The subgrade is the natural soil or prepared ground beneath the pavement structure. It forms the foundation that supports the subbase and the finished pavement above.
Before construction begins, the subgrade is shaped and compacted to provide uniform support across the project area. Weak or poorly compacted soil can contribute to settlement, cracking, and premature pavement failure. Contractors may improve unsuitable subgrade conditions before installing the pavement system.
Frequently Asked Questions About Subgrade
What is the subgrade?
The natural soil or prepared ground beneath the pavement structure, forming the foundation that supports the subbase and pavement above.
How is the subgrade prepared?
It is shaped and compacted to provide uniform support across the project area before base material is placed.
What happens with a weak subgrade?
Settlement, cracking, sunken flags and premature pavement failure, no matter how good the concrete above it is.
Can bad subgrade be fixed?
Yes. Unsuitable soil can be removed and replaced, stabilized, or bridged with additional base thickness, depending on conditions.