What is the Importance of Highway Drainage?
- It arrests the moisture variation in the subsurface layers thus preventing the reduction in bearing capacity of subgrade soil.
- It prevents the erosion of side slopes.
- It prevents the failure of formation slope caused by the poor drainage system.
- It prevents the stripping of bitumen from aggregates in flexible pavements.
- It prevents the mud pumping in rigid pavements.
- It prevents the skidding of vehicles caused by a reduction in friction coefficient.
- It prevents the frost action caused by the accumulation of water.
What are the Requirements of a Good Highway Drainage System?
- The surface water on the carriageway and shoulder should be drained off effectively as soon as possible.
- The surface water from the adjoining land should be prevented from entering into the roadway.
- The groundwater table should be maintained well below the bottom surface of the subgrade soil.
- The capillary rise & seepage water should be controlled effectively.
- The longitudinal drains & cross drains should have sufficient capacity to carry the collected water.
- The longitudinal drains & cross drains should have sufficient bed slope for gravity flow.
- The flow of water across the road surface & in the drains should not cause erosion.
- Complex & costly cross drainage structures should be avoided as much as possible.