Roads must be carefully designed and constructed in desert, swamp, and black cotton soil areas due to challenging soil conditions. In deserts, roads should avoid loose sand and be located where sand is stabilized by vegetation. Different types of sand dunes form from changing wind patterns. In swamps, soft and compressible soil requires removing undesirable material, using sand drains or lightweight fill to accelerate consolidation. Black cotton soil is prone to swelling and shrinking, requiring a stabilized soil layer between the road base and subgrade. Rigid pavements are better suited than flexible pavements for high traffic volumes on black cotton soil.

1. Roads in Desert, Swamp &
Black cotton Soil

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

4. Dunes:

5. Road location in desert area:
• 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-dunal space.

6. Design:
• 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 road

7. • 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. • 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. MAINTENANCE
• Preventing wind erosion on the slopes of the embankment.
• Clayey soils must be used as a thin cover to foster the growth of
vegetation.
• Locally available shrubs must be planted on slopes.
• A thin spray of bituminous materials on slopes where plants have
grown, will faster the growth.

10. Roads in swamp soil:
• Areas where there is stagnation of water and soil is permanently
saturated are 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.

11. LOCATION GUIDELINES:
• 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.

12. Design Approaches for Swamps:
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

13. Partial or total removal of swampy soil:
• 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.

14. Stage construction and surcharge fill:
• 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.

15. Use of vertical sand drains:
• 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.

16. Use of lightweight materials:
• 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.

17. BLACK COTTON SOILS:
• 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 subgrade.

18. Problems:
• 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.

19. SOLUTION:
• 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 stabilised with lime.
• It is also found that soils can be improved by compaction at water
contents slightly above the optimum

20. References:
• http://courses.missouristate.edu/EMantei/creative/glg110/deserts-
wind.html
• https://www.quora.com/How-are-the-roads-in-deserts-constructed
• http://www.brighthubengineering.com/building-construction-
design/84480-how-are-roads-built-over-swamps/
• http://www.nbmcw.com/roads-pavements/307-practical-problems-
of-highway-construction-in-black-cotton-soil-area.html