BFC 31802 Chapter 6

BFC 3042 HIGHWAY ENGINEERING

Lecturer: Mr. Basil David Daniel

Chapter 6

Highway Drainage

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BFC 3042 HIGHWAY ENGINEERING

Lecturer: Mr. Basil David Daniel

HIGHWAY DRAINAGE Highway Drainage is a process which • 

diverts and removes water from the pavement surface

• 

controls and directs sub-surface w water ater into p proper roper channels

in order to protect the road from damage.  A well maintained drainage system system • 

enhances safety to mo motorists torists by removing water away from the road and pavement surface •  prevents highwa highway y surface water water from flooding neighbouring properties • 

reduces the risk of water damage to the highwa highway y

Poor drainage can cause water spraying on the windshield, thus reducing visibility, and reduces the grip between the tyre and the road which can lead to skidding. sk idding. Sources of water on highways: (1) Surface Run-off – eg. from rain, snow and sleet (2) Subsurface Run-off – eg. from streams and ground water

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BFC 3042 HIGHWAY ENGINEERING

Lecturer: Mr. Basil David Daniel

HIGHWAY DRAINAGE

 Also called aquaplaning. Occurs when a layer of water builds between the rubber tires of the vehicle and the road surface. surface. This leads to the loss of traction and thus preventing the vehicle from responding to steering, braking or accelerating. It becomes, in effect, an unpowered and unsteered sled.

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BFC 3042 HIGHWAY ENGINEERING

Lecturer: Mr. Basil David Daniel

HIGHWAY DRAINAGE EFFECTS OF MOISTURE ON: HIGHWAY SURFACE  SURFACE  Stagnant pools of water on the road can: - slow down traffic - cause accidents due to skidding and low visibility HIGHWAY STRUCTURE STRUCTURE   Surface run-offs and subsoil moisture can reduce the strength of the construction materials: - High moisture content in the subgrade will reduce the stability of the soil, leading to to pavement failure. - Prolonged contact w with ith water can cause stripping of aggregates from the bituminous pavement, leading to the formation of potholes which slows down traffic and causea damages to vehicles. SOIL   SOIL Excess moisture content in the underlying soil can increase the weight of the soil and increase stress conditions. These are the two main reasons for failure of slopes and embankment foundations.  foundations. 

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BFC 3042 HIGHWAY ENGINEERING

Lecturer: Mr. Basil David Daniel

HIGHWAY DRAINAGE Flexible Pavements are prone to waves and corrugations due

Rigid Pavements are prone

to poor drainage:

to failures caused by mud-pumping:

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