ROADS IN DESERT, SWAMPY & BLACK COTTON SOIL

1. Bhavya S. Patel, M.E.
Transportation Engineering
1
GUJARAT TECHNOLOGICAL UNIVERSITY
TATVA INSTITUTE OF TECHNOLOGICAL STUDIES
“ Roads in Desert, Swampy and Black Cotton Soil ”
Pavement Design, Construction & Evaluation (2721302)
Guided By: Presented By:
Dr. H. R. Varia Bhavya S. Patel (170900713008)
Prit B. Patel (170900713011)
Department of Civil Engineering
M.E. Transportation Engineering Semester 2
April 2018

2. Desert Areas:
Bhavya S. Patel, M.E. Transportation
Engineering2
 Deserts are those regions on Earth which are
categorized as having arid climates.
 Due to blowing of wind, sand dunes are formed in
deserts.
 Each dune type is the result of different wind
patterns, and the presence or lack of vegetation on
the ground.

3. Desert Areas:
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Engineering3
 Due to blowing of wind, sand dunes are formed in deserts.
 Types of Sand dunes:
1. Longitudinal sand Dunes:
o parallel to flow
o winds do not have much change in direction
2. Transverse sand Dunes:
o perpendicular to flow
o winds have a change in direction

4. Dunes:
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5. Road location in Desert area:
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 Not preferred where sand is loose and unstable.
 Align road where sand is covered by vegetation.
 Preference should be given to areas having
coarse sands.
 Avoid locating the road on the slopes of sand
ridges– instead locate them on the dunes or the
inter-dunel space.

6. Design:
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 Sections with partial cut and partial fill should be
avoided since they are difficult to maintain.
 The dunes were tackled by a excavation, and this
is crucial to excavation and building a rased
surface and foundations for the roads.

7. Bhavya S. Patel, M.E. Transportation
Engineering7
 Cuttings should be avoided as much as possible and
high embankments should be avoided in areas subjected
to strong winds.
 Low grade material should included for construction
because stones are rarely available in desert.
 Gravel can be used for base course and for surface
course in secondary roads.
 Sand-bitumen base courses are ideal for deserts
because they do not need stone aggregates and water.

8. Bhavya S. Patel, M.E. Transportation
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 Built-up spray grout and Dry bound macadam can be
used in deserts due to scarcity of water for water
bound macadam.
 This technique consists of two layer composite
construction of crushed coarse aggregate with
application of bituminous binder after each layer and
aggregate on the top of second layer.
 Sand bitumen mix consists of sand, bitumen and
filler.

9. Built up spray grout
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10. Maintenance:
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 Preventing wind erosion on the slopes of the
embankment.
 Clayey soils must be used as a thin cover to
foster the growth of vegetations.
 Locally available shrubs must be planted on
slopes.
 A thin spray of bituminous materials on slopes
where plants have grown, will faster the growth.

11. Roads in Swamp Soil:
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Engineering11
 Areas where there is stagnation of water and soil is
permanently saturated called swamps.
 Soil is extremely soft, highly compressible and has very
low strength.
 Some swamps fail under their own weight.
 The depth of this particular layer may vary from shallow
to deep. For construction of roads, shallow deposits can be
removed and deeper deposits strengthened by suitable
means.

12. Swamp SoilBhavya S. Patel, M.E. Transportation
Engineering12

13. Location Guidelines:
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 In most cases, it must be bypassed. If unavoidable, the
road must cross the swamp where its width is narrow and
its shallow.
 Proper soil surveys must be carried out to know the
exact characteristics and conditions.
 The depth of water and the type of water influencing the
area must be checked.

14. Design Approaches for Swamps:
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Compared with ordinary soil, for construction of roads in
swamps, special treatment and techniques are to be adopted
depending on the characteristics of the underlying soil.
They are:
 Partial or total removal of undesirable material.
 Stage construction and surcharge fill.
 Use of sand drains.
 Use of light weight material.

15. Partial or Total Removal of Swampy Soil:
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Engineering15
The undesirable material is excavated and
removed. Bog blasting is a method in which a layer
of sand is deposited over the undesirable soil and
the soil below is blasted. The blast disperses the
clay sideways and the resultant cavity is occupied
by the overburden sand.

16. Stage construction & Surcharge Fill:
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As consolidation takes long time, system of stage
construction is adopted so that embankment settlement
and further construction proceed side by side.
Alternatively, the embankment is constructed to an
elevation higher than the final requirement. The
surcharge so placed accelerates the settlement.

17. Use of Vertical sand drains:
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 Vertical sand drains consist of bore holes of 0.4 to 0.6 m diameter,
dug through the swamps and filled with sand. The depth of the
borehole can be 10m to 20m.
 The drains are spaced 2 m to 6 m centre to centre both
transversely and longitudinally. A sand blanket layer of 1 to 1.5 m is
placed on top of the vertical sand drains. The sand drains facilitate
quick removal of water from the soft strata as the embankment load
squeezes the water from the pores. The drainage of water helps in
the following ways: Quick settlement of the bank takes place and
shear strength of soil is increased.

18. Sand drains
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19. Use of light Weight Materials:
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 Settlement can be minimized by reducing the weight of
the embankment. For this, light materials such as cinder, fly
ash and saw dust can be used in embankment.
 Since the swampy soil is weak in strength, light weight
material must be used . Cinder is a good solution.
 Where the soil is extremely soft, it may be feasible to take
the road over trestles of reinforced cement concrete resting
on deep piles.

20. Black Cotton Soils:
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Engineering20
 As such Black cotton soil has very low bearing capacity
and high swelling and shrinkage characteristics. Due to its
peculiar characteristics, it forms a very poor foundation
material for road construction.
 Such soils exhibit changes when the water content
changes and thus the roads become wavy.
 As the soil absorbs moisture, the soil loses its supporting
power and the materials in the base sink into the sub
grade.

21. Black Cotton Soil
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22. Problems:
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 Having heavy-duty traffic of 4500 commercial vehicles per day and
msa 150 as generally found on our National Highways and taking CBR
value of 2%, total crust thickness of flexible pavement works out to 830
mm which is practically an impossible preposition.
 Assuming heavy traffic intensity of 4500 commercial vehicles per day
and msa 150, crust thickness of rigid pavement works out
approximately 300-320 mm, which is about one third of thickness
needed for flexible pavement. Therefore, it sounds reasonable to adopt
cement concrete pavement in Black cotton soil areas. This type of
pavement may save the engineers from day to day maintenance
problems also.

23. Solutions:
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 The most effective way of dealing with such soils
is to provide a suitable layer between the soil and
the stone layer. Minimum thickness – 10 cm.
 Material- gravel of low P.I. ,sand or soil stabilized
with lime.
 It is also found that soils can be improved by
compaction at water contents slightly above the
optimum.

24. Bhavya S. Patel, M.E. Transportation
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