WHY DRAINAGE IS OF SO MUCH IMPORTANCE FOR PAVEMENT LONGEVITY & SAFETY?

Proper pavement drainage is a critical factor in pavement design. It involves managing water on and around roads to ensure safety and longevity. In this comprehensive guide, we’ll explore why pavement drainage is so important and how it impacts different types of pavements, including flexible and rigid surfaces.

The Importance of Pavement Drainage:

Pavement drainage is essential for several reasons:

Natural Terrain and Water Diversion:

When roads are built on natural landscapes, they often intercept natural waterways. To prevent water-related issues, it’s crucial to divert this water away from the road.

Rain and Snowfall:

Rain and snowfall can quickly cover road surfaces with water, posing safety risks. Efficient drainage systems are necessary to remove this water promptly.

Surface Drainage Elements:

Various drainage components, such as side ditches, lined drains, catch-drains, and cross-drainage structures, are integrated into the surface drainage system to manage water runoff effectively.

Seepage and Lower Layers:

Water from the road surface, medians, and shoulders can seep into lower pavement layers through permeable pavement, cracks, potholes, and joints. This seepage needs to be eliminated to ensure pavement durability.

Hydroplaning Hazards:

Excess water on a road surface can lead to hydroplaning, where vehicles lose traction due to a wedge of water forming beneath their tires. This is especially dangerous at high speeds.

Effects on Different Pavement Types:

Flexible Pavement:

Retaining stagnant water on bituminous pavement for extended periods is detrimental, causing premature deterioration.

It leads to bitumen stripping from aggregates, particularly in stones like granite, quartzite, and quartz susceptible to stripping.

When the bituminous mix is poorly compacted, has surface cracks or potholes, water infiltrates to lower layers, speeding up the stripping process.

This water tends to move down to the granular base and sub-base layers. If these layers cannot drain this water laterally, the pavement essentially rests on a waterbed, resulting in reduced aggregate-to-aggregate contact and ultimately premature pavement deterioration.

While bituminous pavement offers good skid resistance, it doesn’t facilitate swift surface water drainage due to surface tension and a pitted surface lacking continuity, unlike the textured surface of cement concrete pavement.

Concrete Pavement:

A properly compacted concrete pavement is typically impermeable to water and remains unaffected by standing water.

However, moisture can seep through joints, cracks, and shoulders.

This includes the longitudinal joints created with shoulders.

Full-depth cracks provide another pathway for water seepage.

In certain cases, seeped water is pushed to the surface through joints when there’s movement, carrying fine soil particles and creating hollow pockets beneath the pavement. This phenomenon, known as “mud pumping“.

This eventually leads to a loss of support in the pavement and the formation of corner cracks.

This moisture can also penetrate the lower granular layers, saturating and weakening them, ultimately causing premature pavement failure.

Concrete pavement surfaces are textured to enhance skid resistance and facilitate rapid surface drainage through minuscule texture channels.

Tine and brush textures are the two types of textures applied on concrete surface.

It has been observed that tine texture is more durable than brush texture. Brush texture tends to become bald faster.

Tine texture can be applied in both transverse and longitudinal direction, but a school of thought considers that tine texture in transverse direction is preferred to on account of its better capacity to drain surface water quickly vis-a-vis in longitudinal direction although noise pollution is said to be less in the latter case.

Granular/Earthen Surfaces:

Standing water on granular or earthen surfaces can saturate lower layers, leading to unusable, slushy conditions. Cross-slopes in earthen shoulders must be steeper to ensure efficient water flow.

Conclusion:

Proper pavement drainage is essential for road safety and longevity. It prevents hydroplaning, deterioration, and structural damage to different pavement types. Understanding the significance of pavement drainage is crucial for designing and maintaining safe and durable roads.