Subgrade

Layers in the construction of a mortarless pavement: A.) Subgrade B.) Subbase C.) Base course D.) Paver base E.) Pavers F.) Fine-grained sand

Section through railway track and foundation showing the sub-grade

In transport engineering, subgrade is the native material underneath a constructed road, pavement or railway track (US: railroad track). It is also called formation level.

The term can also refer to imported material that has been used to build an embankment.

Construction

Subgrades are commonly compacted before the construction of a road, pavement or railway track

See also

• Subsoil
• Track bed