This is about highway drainage.

2. 
 Highway drainage - the process of removing and
controlling excess surface and subsurface water
within the roadway or right of way.
 Types:
1.surface drainage(removal & diversion of
surface water from the roadway & adjoining land )
2.subsurface drainage(diversion or removal of
excess soil-water from subgrade)
Highway Drainage

3. 
 Excess moisture in soil subgrade causes lowering of
its stability
 If any improper drainage system, flow of surface
water across the road & shoulder and along slopes
should cause erosion
 If stagnant of water, it causes diseases
 loss of money, human life
Effects of drainage

4. 
 The side drain should have sufficient capacity and
longitudinal slope to carry away all the surface water
collected from the roadway
 Lowering of moisture content of soil
 The pavement should be higher than water table
 To control the capillary rise
Maintenances of highway drainage

5. 
 Cross slope or camber
 The road side drains
 Cross drains
Components of surface drainage system

6.  Water from the pavement surface & shoulders is first
drained off within the help of cross slope or camber
 Rate of slope depends on :
Type of the pavement surface
Amount of rainfall in a region
 Recommended range of camber :
For earth road : 1 in 25 or 4%
For bituminous road : 1 in 60 or 1.7%
For earth shoulders: 4 to 5%
Cross slope or camber

7. 
Cross slope or Camber

8. 
 The road side drains of highways are generally open or
unlined or kutcha drains of trapezoidal shape
 If provided to parallel to road alignment – longitudinal
drains
 On plain terrain with embankment –provided on both
sides of toe of embankment
 On sloping terrain( cross slope<4%)-provided on one
side only.
Road side drains

9. 
Road Side Drains

10.  The water flowing along the road side drains are
collected by suitable cross drains through cross drainage
structures(CD structure)
 It is collected from natural valleys & streams and
disposal off to the natural water course
 Different types of culverts(CD structure) : slab, box &
pipe culvert
 If the width of river or stream > 6m – CD provided is
called minor bridge
 If the width of river or stream > 60m- CD provided is
called major bridge
Cross drains

11. 
Cross drains

12. 
 to keep the variation of moisture in subgrade soil to
a minimum
 Components:
Lowering of Water Tables
Control of Seepage Flow
Control of Capillary Rise
Sub-surface Drainage

13. 
 The highest level of water table should be fair below
the level of subgrade, in order that the subgrade &
pavement layers are not subjected to excessive
moisture.
 From practical considerations- water table > 1.0 to
1.2m below the subgrade
 water table at ground level -1.2 to 1.5m above the
ground level
Lowering of water table

14. 
 If the soil is relatively permeable, it may be possible
to lower the high water table by construction of
longitudinal drainage system with drain pipe and
filter sand
 If the soil is relatively less permeable, the water
table can controlled by construction of longitudinal
drainage system with transverse drains( at particular
interval)

15. 
 When the general ground & impervious strata
below are sloping ,seepage flow exist
 If depth of seepage zone < 0.6 to 0.9m longitudinal
pipe drain may be constructed to intercept the flow
Control of seepage flow

16. 
Control of seepage flow

17. 
 If water due to capillary rise is less, it is possible to
solve problem by arresting capillary rise instead of
lowering of water table
 Two methods of control
Granular capillary cut off
Impermeable capillary cut off
Control of capillary rise

18. 
 A layer of granular material provided between
subgrade & highest level of subsurface
Granular capillary cut off

19. 
 An impermeable membrane or bituminous layer
inserted in place of granular materials
Impermeable capillary cut off

20. 