Grameen Sampark Final April 0... - pmgsy

India mostly consist of granular pavements with thin
bituminous surfacing, in which rutting is considered as
the only mode of failure. This is attributed to the vertical
compressive strain at the top of subgrade layer.
Several highway organizations have developed their
own failure condition and performance criterion for
design of low-volume roads. In this study, the criteria
developed by AASTHO, AustRoads, Asphalt Institute
TRRL, etc. have been discussed.
Performance and Failure Criteria for
Pavement Design
In mechanistic design methods, the limiting values of
stresses and/or strains at which a given degree of distress
will occur are commonly known as the performance
criteria. The rationality of the design procedure can be
judged from the way the corresponding performance
criteria have been developed. Performance criterion is
generally developed considering a failure condition,
which may be any structural or functional failure or
both. Fatigue cracking of bituminous surfacing and
permanent deformation (rutting) along wheel paths,
mainly due to repeated application of traffic loads, have
been identified as the two major modes of structural
failures that need to be addressed in the structural
design of pavements. Some performance criteria also
use roughness as the mode of failure in terms of present
serviceability index (PSI) [1]. The low-volume rural
Pradhan Mantri Gram Sadak Yojana
roads in India mostly consist of granular pavements with
thin bituminous surfacing, in which rutting is
considered as the only mode of failure, which occurs
due to vertical compressive strain at the top of subgrade.
In this paper, the rutting criteria adopted by different
highway organizations for design of low-volume road
pavements have been presented with the objective of
comparing these criteria with that adopted for design of
Indian roads.
Selection of Critical Performance Parameters
Horizontal tensile strain at the bottom fibre of
bituminous bound layer and vertical compressive strain
on top of subgrade have traditionally been taken to be
causative for the two major modes of failures
considered, i.e., fatigue cracking and rutting. Excessive
strains applied repeatedly have been considered to be
the major factors for the development of the two modes
of failures. Figure 1 shows a typical layered flexibile
pavement system subjected to a dual wheel loading
applied at the surface.
Deformation or rutting provides the principal indication
of deterioration in granular pavements with thin
bituminous surfacing. It develops chiefly in the wheel
tracks,and increases with time or more precisely with
the cumulative application of commercial traffic.
Bituminous Surfacing
Granular Base
Granular Sub-base
Subgrade
Figure 1: Critical mechanistic parameters
ε z
ε E t 1,µ 1
E, 2 µ 2
E, 3 µ 3
E, 4 µ 4
Grameen Sampark 17