This document discusses road construction challenges in desert, swampy, and black cotton soil areas. In deserts, roads must avoid loose sand and be located where sand is stabilized by vegetation. In swamps, roads often must bypass or use lightweight fill and deep foundations. Black cotton soils lose strength with moisture changes, requiring a stabilized layer between the soil and pavement to prevent sinking. Rigid pavements are recommended over flexible pavements for heavy traffic volumes on black cotton soils due to reduced maintenance needs.

1. ROADS IN DIFFICULT AREAS
(DESERTS,SWAMPY SOILS AND BLACK
COTTON SOILS)
BY: AASTHA R. MEHTA
GUIDED BY: PROF. M.P. JAIN

2. 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

3. Longitudinal Transverse

4. PRINCIPLES OF ROAD LOCATION IN DUNE AREAS
• Avoid sections 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.

5. GUIDELINES FOR DESIGN
• Sections with partial cut and partial fill should be avoided since they
are difficult to maintain.
• Cuttings should be avoided as much as possible and high
embankments should be avoided in areas subjected to strong winds.
• Stones are rare in the desert regions so specifications involving locally
available materials (though of low grade) must be included. Gravel
and dhandla can be used for base course and for surface course in
secondary roads.

6. Contd.
• Sand-bitumen base courses* are ideal for deserts because they do
not need stone aggregates and water.
• Built-up spray grout# and Dry bound macadam^ can be used in
deserts due to scarcity of water for water bound macadam.
*Sand bitumen mix consists of sand, binder(bitumen) and filler.
#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.
^Dry bound macadam refers to roadbase material in which unbound
stones are compacted in a dry state .

7. 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.

8. SWAMPY AREAS:
• Areas where there is stagnation of water and soil is permanently
saturated are called “swamps” or “bogs”.
• Soil is extremely soft, highly compressible and has very low strength.
• Some swamps fail under their own weight.
• Example- Rann of Kachchh in Gujarat.

9. 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.

10. EMBANKMENT DESIGN
BOG BLASTING VERTICAL SAND DRAIN

11. Contd..
• 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.

12. BLACK COTTON SOILS:
• 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.

13. TYPE OF SURFACE
• 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.

14. 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.

15. REFERENCES
• www.john-knapton.com/roads.htm
• Google images
• Wikipedia
• http://nbmcw.com/articles/roads-pavements/307-practical-
problems-of-highway-construction-in-black-cotton-soil-area.html
• Kadiyali L.R.- Principles and practices of highway engg.