Subgrade

The subgrade provides support to the subbase level and acts as an integral load-bearing layer.

Failure of the subgrade can cause depressions and rutting of the upper base and surface courses.

These in turn can lead to water pooling in deformations and cause vehicle aquaplaning among other issues.

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

This is to ensure their ability to absorb the loads being transferred down from the upper layers, increasing the life and wear of the surface courses.

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