highway drainage system ppt

1. BAJAJ INSTITUTE OF TECHNOLOGY,
WARDHA
HIGHWAY DRAINAGE SYSTEM
Presented by
1. Vaishnavi muraskar 41
2. Madhvi tilgam 53

2. CONTENTS
❏ Introduction
❏ What is highway drainage ??
❏ Requirements of highway drainage
❏ Importance of highway drainage
❏ Surface drainage
❏ Surface drainage methods
❏ Effect of road geometry on drainage
❏ Subsurface drainage system
❏ conclusion
➢ Inlets
➢ Storm sewers
➢ Open channel
➢ culverts

3. ❏ INTRODUCTION

4. WHAT IS HIGHWAY DRAINAGE ??
➢ Highway drainage is an essential part of
highway design and construction which
remove the surplus water with in
highway limits and dispose it.
➢ Roadway drainage is mainly due to
surface runoff from adjacent
area,precipitation of rain and moisture
rising by capillarity from ground water
table.

5. ❏ REQUIREMENTS OF
HIGHWAY
DRAINAGE
1. The surface water from the carriageway and
shoulder should be drained off effectively.
1. The surface water should not be allowed to enter
the roadway.
1. The side drain should have sufficient capacity
and longitudinal slope to discharge maximum
surface water collected in the region.
1. The flow of surface water along the slopes or
across the road should not be allowed to erode
them or form ruts.
1. The seeping water or seepage and other sources
of under ground water such as capillary rise
water etc., should be drained off at the earliest by
sub surface drainage system otherwise it will
reduce the bearing power of the sub-grade.

6. ❏ IMPORTANCE OF HIGHWAY DRAINAGE
● To prevent subgrade failure
● To prevent slope failure
● To prevent reduction in
strength of pavement material
● To prevent erosion of soil
● To prevent frost action
● To prevent decrease in volume
changes
● To prevent pavement edge

7. ❏ SURFACE DRAINAGE
● Under the surface drainage, water is
to be collected in longitudinal drains
and then disposed of at the nearest
stream, valley or water course.
● Surface water is removed from
surface of road by providing cross
slope to the road surface. The road
surface is also made impervious to
prevent the water entering the
subgrade.

8. ❏ SURFACE DRAINAGE METHODS
● For rural highways on embankments, runoff
from the roadway should be allowed to flow
evenly over the side slopes and then spread
over the adjacent terrain.
● This method, however, can sometimes
adversely impact surrounding land, such as
farms. In such instances the drainage should
be collected.
● for example, in longitudinal ditches and then
conveyed to a nearby watercourse. When a
highway is located in a cut, runoff may be
collected in shallow side ditches.

9. ➢ INLETS ● These are parts of a drainage system that
receive runoff at grade and permit the water to
flow downward into underground storm drains.
● Inlets should be capable of passing design
floods without clogging with debris.
● The entrance to inlets should be protected with
a grating set flush with the surface of gutters or
medians, so as not to be a hazard to vehicles.

10. ➢ STORM SEWERS
● The storm sewer is a system designed to
carry rainfall runoff and other drainage.
● These are underground pipes that
receive the runoff from a roadside inlet
for conveyance and discharge into a
body of water away from the road.

11. ➢ OPEN CHANNELS
● The ditches may be trapezoidal or V-shaped. The
trapezoidal ditch has greater capacity for a given
depth. Most roadway cross sections, however,
include some form of V shaped channel as part of
their cross-sectional geometry.
● In most instances, it is not economical to vary the
size of these channels. As a result, this type of
channel generally has capacity to spare, since a
normal depth must be maintained to drain the
pavement subbase courses.

12. ➢ CULVERTS
● A culvert is a closed structure for passage of
runoff from one open channel to another. One
example is a corrugated metal pipe under a
roadway.
● For small culverts, stock sizes of metal pipe
may be used. For larger flows, however, a
concrete box or multiple pipes may be
needed.
● If the culvert foundation is not susceptible to
erosion, a bridge may be constructed over the
waterway (bridge culvert).

13. ❏ EFFECT OF
ROAD
GEOMETRY
ON DRAINAGE
● Road surfacing materials are traditionally designed to be
effectively impermeable, and only a small amount of
rainwater should percolate into the pavement layers.
● It is important that any such water is able to drain through
underlying pavement layers and away from the formation.
● Rainfall which does not permeate the pavement surface
must be shed towards the edges of the pavement.
● Drainage is a basic consideration in the establishment of
road geometry and vertical alignments should ensure that:
a) outfall levels are achievable and
b) subgrade drainage can discharge.

14. SUB-SURFACE
DRAINAGE SYSTEM
● The change in moisture content of soil affects its
bearing capacity of soil.
● The increase in moisture content of soil reduces
its bearing capacity.
● Thus keeping this point in view, there should
not occur any change in moisture content of the
subgrade of the road.
● The change in moisture content of the subgrade
is due to fluctuations in the ground water table,
seepage flow, percolation of rain water and
capillary water.
● Thus the aim of the sub soil drainage is to
prevent changes in the moisture content of the
subgrade.

15. CONCLUSION
● Based on above study we can say that Highway drainage is process of
removing and controlling excess surface and sub-soil water with in the
right way.
● Highway drainage is an important part for design and construction of
highway.
● In surface drainage, surface water is intercepted and diverted to a natural
stream. If it is not done the surface water will cause erosion.
● In sub surface water drainage, sub surface water is interrupted and
disposed of to safe place.

16. Thank You