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The flexible pavements has been modeled as a three layer structure and stresses
and strains at critical locations have been computed using the linear elastic
model.
To give proper consideration to the aspects of performance, the following three
types of pavement distress resulting from repeated (cyclic) application of
traffic loads are considered:
- vertical compressive strain at the top of the sub-grade which can cause
sub-grade deformation resulting in permanent deformation at the pavement
surface.
- horizontal tensile strain or stress at the bottom of the bituminous layer
which can cause fracture of the bituminous layer.
- pavement deformation within the bituminous layer.
While the permanent deformation within the bituminous layer can be controlled
by meeting the mix design requirements, thickness of granular and bituminous
layers are selected using the analytical design approach so that strains at the
critical points are within the allowable limits.
For calculating tensile strains at the bottom of the bituminous layer, the
stiffness of dense bituminous macadam (DBM) layer with 60/70 bitumen has been
used in the analysis.
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