Page 62 - Lecture Notes DCC3113

The Flexible Pavement Works

Figure 4-4: The Flexible Pavement Work

The functions of flexible pavement’s layer:

Table 4-2: The functions of flexible pavement’s layer

Layer Function

Subgrade
i. Subgrade is a layer of natural soil or filled soil, ready to receive
the pavement material over it.
ii. Subgrade is the lowest layer below the road formation level.
iii. It acts as foundation underneath the pavement structural layer.
iv. Must possess enough soil bearing capacity.

Sub-base Sub-base is one course that is constructed with quality materials. This is
the lowest layer of pavement that is constructed onto the sub-grade. The
functions of sub-grade:
i. Support the road base and spreads the force to the sub-grade.
ii. Prepares the drainage using rough materials.
iii. Prepares a cover at any layer that is constructed.
iv. Bears the pressure from heavy vehicles so the sub-grade will not
crack.
v. Prevent the sub-grade from traffic flow.
Road base
Base or road base is the main course to absorb force from surface
directly and spread the force to the thickest layer. This layer is normally
made from broken stones which may be bounded or unbounded. It is
used to help spread traffic load on large area of sub-grade so that the
stress intensity remains within the capabilities of the sub-grade. Thus
undue deformation caused by the consolidation of the sub-grade is
prevented.

Surface layer
i. The wearing course is the top most layers in a pavement.
ii. Provides smooth and dense ridding surface.
iii. Takes up wear and tear due to traffic.
iv. Provides water tight surface against filtration of surface water.
v. Provides hard surface which can withstand the pressure exerted
by tyres of vehicles.

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