Page 1 of 4
European Journal of Business &
Social Sciences
Available at https://ejbss.org/
ISSN: 2235-767X
Volume 07 Issue 05
May 2019
Available online:https://ejbss.org/ P a g e | 850
Reinforced Flexible Pavement Design Over Clayey Sub-Grades
G. SEKAR
DEPARTMENT OF CIVIL ENGINEERING
PRIST (Deemed to be University), THANJAVUR.
ABSTRACT
Expansive soils are one of the most problematic materials that are widely encountered in
significant land areas in several parts of the world; like Africa, Australia, India, United States
and Canada. The South Tamilnadu region in India have majority of top soil as black cotton
soil. The black cotton soil has characteristics of shrinking on drying and heaving on wetting.
This soil being expansive creates several types of damages to pavement structures, and in
some cases the pavement may even become unserviceable. The normal climate condition of
study area shows short wet and long dry period which aggravate the problem of swelling and
shrinkage.
INTRODUCTION
Frost, Fleming and Rogers (2004) [2]
outline the primary roles that a subgrade
or pavement foundation must play in
pavement design. The volume change at
subgrade creates variety of failure in
flexible pavement like cracking, rutting,
potholes etc. Expansive soils are one of
the most problematic materials that are
widely encountered in significant Land
areas in several parts of the world e.g.
parts of Africa, Australia, India, United
States and Canada. In these countries
expansive soil is having great impact on
the construction and maintenance costs of
highways.
The South West region of India is
covered by top soil as black cotton soil.
Fig. 1 map of soil deposits in Tamilnadu
State shows that the majority of South
Tamilnadu area having black cottons soil
as top layer.
Roads are vital to link our
communities and sustain the economy
and quality of life in society. Roads
constructed over the expansive soil
observed with high maintenance
Page 2 of 4
European Journal of Business &
Social Sciences
Available at https://ejbss.org/
ISSN: 2235-767X
Volume 07 Issue 05
May 2019
Available online:https://ejbss.org/ P a g e | 851
expenditure in spite of high capital
cost. As per Austroads (2002) [1]
construction and maintenance works on
pavements in Australia and New
Zealand cost three billion per year, or
approximately half of the total annual
road expenditure. These are because
many roads in this region are failing
prematurely due to the expansion of
reactive soils underneath the roadway,
causing safety issues and increases
road maintenance costs.
To understand the phenomenon of
expansion of swelling soil and to provide
economical solution along with feasible
application utilising various strength of
Geotextiles study started at the madurai
campus, South Tamilnadu region of India.
Geotextile is provided below the
pavement components to act against the
heaving of the swelling soil at the same
time it helps as drainage layer also. Field
study is undertaken to observe the effect
of geotextile in flexible pavement
performance and 2 specific boundary
conditions are created for observations.
Observations summarized shows about 50
% reductions in shrinkage effect for paved
road reinforced with geotextile compared
to road without geotextile.
IMPROVEMENTS DUE TO
GEOTEXTILES
In the past few decades, many researchers
have attemptted to quantify the
improvements of using geotextiles in
pavements. Two tests were most
commonly used to quantify the
improvements in geosynthetically- stabilized pavement: (i) Falling Weight
Deflometer (FWD), and (ii) surface
rutting of the pavement. The FWD is a
nondestructive testing device used to
measure the structural capacity of the
pavement.
Through surface-deflection measurements
at different distances from the loading
point of the pavement, one can
backcalculate the resilient moduli and the
thicknesses of the different layers of the
tested pavement surface. If the presence
of geosynthetics affects (directly or
indirectly) the pavement layer moduli,
that can be detected. The failure criterion
of rutting according to recommendations
Page 3 of 4
European Journal of Business &
Social Sciences
Available at https://ejbss.org/
ISSN: 2235-767X
Volume 07 Issue 05
May 2019
Available online:https://ejbss.org/ P a g e | 852
by the Asphalt Institute pavement design
method is 12.7 mm (0.5 in); however, for
low volume roads, 0.8 in (20mm)
Laboratory and Field Studies
Le (1982), in his Ph.D. thesis, describes
the use of various geotextile fabrics in the
construction of streets in New Orleans.
The fabrics were placed between the
subgrade and the base, between the base
and the hot-mix asphalt (HMA) layer or
between the HMA layers and overlays.
All the applications pertained to soft clay
subgrades. Strain gages within the
subgrade, moisture sensors and falling
weight deflectometer (FWD)
measurements were used to monitor the
performance of constructed roadways.
FWD results from his studies showed an
increase in pavement stiffness in sections
where geotextiles were placed as a
separator. His conclusion was that the
inclusion of fabric provided an increase in
pavement strength by improving load
distribution and acting as a separating
membrane. No analytical modeling was
performed to predict the observed
behavior.
CONCLUSIONS
The introduction of geotextile
fabric in sector of walls on both
sides shows 40% reduction in
shrinkage of fill & subgrade.
Wall on right & free surface on left,
Chainage 54 – 90 m. The
performance in December 2011
shows 43 mm average reduction of
settlement of surface in fabric
reinforced zone. (Reduction of
about 60 % with reference to no
reinforcement zone)
In middle sector with wall on right
& free water access to left typical
ingress of water can be seen to
centre of road by December 2011.
The left end shows ultimate heave
where as right end shows
settlement with little movement at
centre in zone. In reinforced sector
of this road overall performance
shows settlement (- heave, +
settlement) of 37 to 19 mm.
In general, trend shows shrinkage
effect leading to settlement
indicates drastic reduction of 50 %
