PAVEMENT

PAVEMENT

PAVEMENT

Road Pavement

A pavement is smooth surface or matalled structure built to carry the traffic load under climate conditions.

Why Needed?               A pavement structure is provided for

• The natural earth surface cannot support the modern heavy wheel loads.
• The natural earth surface cannot provide an adequate smooth wearing surface.

Therefore a constructed pavement distributes the wheel load sufficiently and provides a necessary smooth wearing surface.

ROAD PAVEMENT               Road pavements are generally classified into two types:

• Flexible Pavement     The pavement which have very low flexural strength and are flexible in their structural behavior under the wheel loads are called flexible pavement.

Flexible Pavement

• Rigid Pavement     Rigid pavements are those which process considerable flexural strength in their structure behavior.

Rigid Pavement

Compression between Rigid & Flexible Pavement

Points	Flexible	Rigid
Design precession	Less	More
Life	Less	More
Initial cost	Less	High
Maintenance	High	Less
Stage construction	Feasible	Not feasible
Penetration of water	Less impervious	More impervious
Sub grade	Required strong strata	Do not heavily depend on it
Opening of traffic soon after construction	Soon after	3-4 days after construction
Night visibility	Less	More
Tractive  resistance	More	Less
Glazing effect	More	Less

Design of Flexible Pavement               The following are the four universal recognized factors which must be considered in the design of flexible pavement.

1)     The characteristics of natural soil
2)     The volume and character of traffic that will use the highway
3)     Design speed for vehicle
4)     The climate conditions

Method of Design of Flexible Pavement               Following of two methods for the design of flexible pavement.

• GI MethodGI of a soil is a number which reflects the characteristics of oil. The value of GI varies from 0-20. The sub base thickness is directly proportional to the group index of the soil, thus higher the group index of the soil the larger is the thickness of sub base. The thickness of the base and surface course varies with the volume of daily traffic.

• CBR MethodCBR of a soil or material which varies from 0-100% give an idea about the quality of a material compared to that of an excellent base material for which the CBR is assumed to be 100%. There are many version of CBR method for flexible pavement design. Due importance has been given by certain agencies to account for differences in annual rain fall, position of ground water table, frost action, sub surface drainage condition and traffic.