Why roads need drainage beneath their surface

Slide 1

The pavement depends on its foundation

A road surface transfers wheel loads into layers beneath it. Water trapped in those layers can reduce support and accelerate damage.

Slide 2

Water needs a continuous escape route

A permeable drainage layer is useful only if water can reach a working outlet. Local depressions or blocked exits can leave a nominally drained road saturated.

Slide 3

Keep the soil out of the drain

Filters or suitable separating layers can let water pass while limiting movement of fine soil. Without separation, migrating particles can clog drainage paths.

Slide 4

Traffic can worsen a wet weakness

Repeated wheel loads act on the entire pavement system. Weak, wet support can encourage deformation and movement of material beneath the surface.

Slide 5

Drainage needs maintenance access

Outlets and collection paths can become obstructed after construction. Inspectable, maintainable details help preserve the drainage system over its service life.

Sources

• Geotechnical Aspects of Pavements: Construction and Inspection

  Federal Highway Administration