UNIT II.doc Railway Airport DOcks and Harbor Engineering

UNIT II – RAILWAY AND CONSTRUCTION MAINTENANCE
PART A
1.What are the types of signals based on the various categories(May/June 2015)
or What are the characteristic classification of signals? (May/June 2013)
i. Operating characteristics a) Audible signals b) Visual indication signals
ii. Functional characteristics a) Stop signals b) Warner signals c) Disc signals
d) Coloured signals
iii. Locational characteristics a) Outer signals (reception) b)
Home ignals d) Advanced Starter signals
c) Starter s
iv. Special characteristics a) Routing signals b)
Repeating signals d) Calling- on signals e) Indicators
2.State the principles of interlocking. (May /June 2011).
signals c) Co-acting
(a) When a train is properly set and locked to a particular line, it
shall be responsible to unlock or reverse points.
(b) It shall be impossible to admit trains from opposite or
converging directions in the same line, at the same time.
(c) When a signal is set for a particular line, it shall be impossible for
loose wagons from any yard to obstruct the line.
3.What is meant by track circuiting? (May /June 2011).
Trac
k
circuitin
g
is an electri
c
circui
t
formed
by
combining running
rails,
signals
an
d
cabin.
Its
prim
e
functio
n
is
to
specif
y
th
e
presence
of
an
y
train or vehicle
on
the
track. Various types of circuits used in Indian Railways are:
(i) D.C track circuit
(ii) A.C track circuit
(iii) Electric track circuit

4.What is cross-over? (May /June 2012).
When two adjacent parallel or diverging tracks, which may be straight or curved,
are
connected
by
two
set
s
of
turnouts,
with
or
witho
ut
a
straight
length
between
them,

the connecting line is known as cross-over.
.5. List the components of switch (Nov/Dec 2012)
A set of switches or points comprises of the following components:
(i) A pair of stock rails
(ii) A pair of tongue rail or switch rail.
(iii) A pair of heel blocks
(iv) Slide chairs
(v) Stretcher bars
(vi) A gauge tie plate.
6.Define interlocking (May /June 2013).
Interlockin
g
is defined
as
th
e
mechanic
al
relationships established between
variou
s
lever
s
operatin
g
th
e
signal
s
an
d
th
e
point
s
throug
h
mechanical or electrical
agencie
s
suc
h
tha
t
contrar
y
effect
s
ar
e
no
t
at
all
possibl
e
in the working of
the
signal
mechanism.
7.Distinguish between gravity yard and hump yard. (Nov/Dec 2013)
Sl no
Gravity yard Hump yard
1
Wagons move under gravity in
the marshalling yard
provided with suitable
gradient
The wagons are pushed
upon
the hump by the engine
and then allowed to
gravitate
2
Shunting operations are
carried out slowly assisted by
engine power.
Shunting operations are
carried out quickly
3
Uneconomical since power
is required to move the
wagons
Economical since no power
is required to move the
wagons
8. What are the various sources of moisture in a railway track? (May /June2014)

The various sources of moisture affecting a railway track are: a) Surface
water due to rain, dew or snow. b) Hydroscopic water or Held water. c) Seepage
water d) Moisture by capillary action in sub grade.
9. What is a buffer stop? (May /June2015)
The dead
end
of
a
sidin
g
or the
end
of any
track
of terminal station
is
no
t
kept
bar
e
bu
t
a
form
of stop
or
barrie
r
is provided
at
th
e
en
d
of
the
track,
to
preven
t
the

vehicles, from running off the track. This stop or barrier provided at the end, across
the track of a siding or at terminal station is known as “Buffer stop”.
10. Write the difference between ‘loop and siding’. (Nov/Dec 2012)
Loop: Loop lines are the ones provided near the station building to stop
slow- moving or passenger trains to stop and give way for express trains
to move on the mainline without any difficulty.
Siding: Sidings are provided at the marshalling yard. There are three types of
sidings
(i) Reception sidings – intended to receive incoming trains.
(ii) Sording sidings – for shunting operations
(iii) Departure sidings – similar to reception siding and is used
for departure

PART B
1. How are stations classified? Explain the features of each station. (May/June
2014)
Stations and yards are the field control units of the railway communication
system.
They also provide waiting places and repairing places for the locomotives and wagons.
Classification of Railway stations:
Two categories: 1. Operational considerations
2. Functional considerations
Operational considerations:
As per Indian railways, (i) block stations or (ii) non-block stations
(i)
Block station: No traffic
is
dealt
,
bu
t
train
s
hav
e
to
get
permissio
n
to proceed
further. Further classified as A, B, C classes.
A – incoming train is received after clearing at least a distance of 400 m
beyond home signal
B –
permission
to
the
incomin
g
trai
n
is
given
befor
e
th
e
receiving
line
is made
a) A - Class Station

clear within the station section

b) B – Class station
C –stations where train do not stop
c) C – Class station
(ii)
Non-block station: classified
as
D-class or
flag
stations
.
Onl
y
traffic
is
dealt
and
no
arrangements
to
control the movement
of
train
.
Locate
d
betwee
n
two
block stations.
Functional classification:
(i) Halt stations
(ii) Flag stations
(iii) Wayside junctions
(iv) Junction stations
(v) Terminal stations
Halt
stations: simples
t
statio
n
wher
e
train
s
ca
n
sto
p
on a
railway
line
.
Provide
d
with
small waiting shed, name boards are provided at both end.

Flag
stations: provide
d
wit
h
station building
and
staff
.
Provide
d
wit
h
bookin
g
office,
benches, drinking water facility. Sometimes siding is also provided for stabling of
wagons booked for that station.
Flag station
Wayside station: called as crossing station. Provision is made to cross an up and a
down train or for over-taking the slow-moving trains by the fast-moving trains.
A wayside or crossing station on a single-line section
Junction
conditions
.
statio
ns:
is a meetin
g
point
of
thre
e or
more

line comin g from differe nt
a. Feasibility to interchange of traffic inbetween main and branch lines

b. Possibility to clean and repair vehicles which terminate at the junctions
Occur between a single branch line and a single or double main lines or between
double branch line and main tracks.
Junction station with single main line and single branch line
Terminal station: station at which a railway line or one of its branches ends or
terminates without further proceeding. Provided with facilities to reverse the
locomotive, examination pits, additional sidings, ticket office, restaurant etc.
Terminal station

2. What
is marshalling yard? Explain with a neat sketch, the working of a hump
type of marshalling yard. (Apr / May 2011)
Yard:
A yard
is
defined
as
a system
of
track
s
lai
d
withi
n
definit
e
limit
s
for various
purposes such as storing of vehicles, making up trains, despatch of vehicles, etc.
It attends to unscheduled movement of trains subjected to rules and regulations.
Types:
 Passenger yards
 Goods yards
 Marshalling yards
 Locomotive yards
Marshalling yards:
The main purpose of marshalling yard is to isolate goods wagons received from
variou
s
centre
s
in order
of
station at
which
they
are
to
be
sent.
It
works as
distribution centres and also the empty wagons are kept in marshalling yards.

Design aspects of marshalling yards:
 Shunting operations should not disturb the regular movement of trains.
 More number of wagons should be despatched rather than storing more
wagons.

 I
t shoul
d
be
feasible
fo
r
futur
e
expansion so as to
accommodate
more goods
traffic.
 To
th
e
maximu
m
exten
d
th
e
marshalling yards
should
be made parallel to the
running lines.
 All main stations should have the marshalling yard facility.
 Wagons are to be made to move in one direction only.
 Adequate repair facility for sick wagons.
 Enough lighting arrangements should be made to function at all times.
 The cost of construction and maintenance should be low.
Layouts of marshalling yards:
An ideal layout of marshalling yard consists of three types of sidings:
a) Reception sidings
b) Sorting sidings
c) Departure sidings
a) Reception sidings:
These sidings are used to receive incoming trains. These sidings are laid
in the
form
of
paralle
l
gri
d
wit
h
equa
l
length. Such
arrangement
enables
the goods trains to stand on these sidings till they are shunted out.
b) Sorting sidings:
These
siding
s
ar
e
intende
d
fo
r
shuntin
g
operation
s.
Each sidings is
allotte
d
to
specific
destination wagons.
The
sortin
g
siding
s
ar
e
generall
y
laid in
the
form of a
fan
or
balloo
n. The
number of sid
ings

depends on
the number
of
destinations.
c) Departure sidings:
These
ar
e
simila
r
to
reception
sidings.
If
th
e
mainline
is
no
t
bus
y
their
sidings
ma
y
be omitted.
The
number
of
siding
s
bot
h
fo
r
reception and
departure depend on the intensity of traffic on the main line, time
required to marshall and number of goods trains to be marshalled at
the same time.
Types of marshalling yards:
 Flat yards

 Gravitation yards
 Hump yards
Hump yards:
Hump
or summit
s
or man-
made
hill
s
ar
e
provide
d
an
d
th
e
wagon
s
are
pushe
d
upt
o
thi
s
point
by
th
e
engine.
Then
th
e
wagon
s
ar
e
allowed
to
gravitate
dow
n
th
e
slope.
The
moder
n
trend
is
to
adopt
thi
s
typ
e
of marshalling yards as
shunting operations are carried out more quickly than gravity or flat yards.
They
ar
e
foun
d
to
be
mor
e
economical because
no
powe
r
is required to
mov
e
th
e
wagons.
A
risin
g
gradie
nt
of 1
in
15
0
or 1 in 175
is
provided at the
pushing end for a length of about 183 metres. Then the hump is kept level
and it is followed by falling gradients of 1 in 150 and 1 in 300 an then level.
(Ref Fig)
Hump yard
Functions: The stopping of individual wagons or group of wagons in hump
yards is carried out as follows:
(i) Men run along the wagons and apply the wagon brakes at the desired
point of stoppage.

(ii) Retarders may be employed to stop the moving wagons. These are blocks or
bars
whic
h
ar
e
fixe
d
on
either
side of the
rails.
Th
e
retarder
s
ar
e
operated
automatically
to it.
pres
s
agains
t
th
e
sides
of
wheels
of
movin
g
wagon
s
to stop
(iii) Skids ma
y
be placed
on
th
e
rails
to
prevent
further
moveme
nt
of wagon by
friction developed on skid.
The action of hump yards is little uncertain because the rate of movement of
wagons depends on the following factors:

 Climatic conditions
 Different types of axle-boxes
 Weight of the wagons
3. Describe the following:
(i)
(ii)
Necessity of track maintenance
Essentials of good track maintenance
(6)
(5)
(iii) Advantages of proper track maintenance (5)(May/June 2014)
(i)




Necessity of track maintenance:
There are mainly two reasons for maintain track in proper order:
New track:
The newly laid track will settle down slowly, so special gangs are to be
employed to bring the embankment to the proper formation level.
Generally 4 men are employed per kilometre length of this track for this
purpose.
Constant use:
The railway tracks are being constantly used by trains, therefore it requires
some treatment to remain in the working condition.
It is achieved by maintenance gangs all along the railway track, which keeps the
track in good condition.
 Fo
r
thi
s
typ
e
of
maintenance
th
e
trac
k
is divided
into
suitabl
e
sections
,
each
having a length of about 6 km for main line and 8 km for branch line section
and
one
gang
is
attached
to
thi
s
section.
The
numbe
r
of
men
require
d
depends on
the volume of traffic, nature of soil and strength of permanent way.

(ii) Essentials of good track maintenance:
The following are the characteristics of a well maintenance track
i. Curvature of gauge subjected to limitations.
ii. Rails at same level with appropriate super elevation at curves.
iii. Alignment free from kinks and other irregularities
iv. Gradients as per standards, prescribed.

v. Track
wit
h
th
e
property
of
resilience
to
regai
n
it
s
origin
al
position after
deformation.
vi. vi
.
Trac
k
wit
h
latera
l
strength
to
withstan
d
sid
e
thrus
t
an
d
centrifug
al
an
d
lateral
forces and to maintain the alignment intact.
vii. vii
.
Upkee
p
an
d
maintenanc
e
of
radius
of curvature, super elevation,
points
and
crossings.
viii. Perfect drainage system.
ix. Precaution against creep.
x. Various components of the railway track such as formation, ballast, sleepers
and rails fullfill the essential requirements of maintenance.
(iii) Advantages of Proper track maintenance:
It consists of one gangmate or ganger, one keyman and nine to ten workers for B.G
and
about four to five workers. Each
gang
work
s
in a length of
about
90 meters a day. The
duties of gangmate, keyman and P.W.I are:
i. The
gange
r
is
the
head
of
th
e
gan
g
an
d
he is personall
y
responsible for the
upkeep of track in his section.
ii. The ganger must keep his section in good running condition at all times.
iii. He is responsible for maintaining the track in his section in correct alignment
and level.
iv. The ganger has to arrange for tools and other equipments required by his gang.
v. The

points
and cro
ssi
ngs
shoul
d
be
periodically
checke
d
an
d
examined
by
the
ganger.
vi. vi
.
In case
of
emergenc
y,
th
e
gange
r
shoul
d
stop
or
slo
w
down a
running
train by
the use of temporary signals.
vii. In case of accident, the ganger should look after the broken fittings of the
rolling stock and track components.
4.(i) List the conventional and modern methods of maintenance of railway track.
What are the different types of equipment used?

4.(ii)
What are the advantages of welded rails? Describe any one method of
welding the rails. (May/June 2012)
(i) Track maintenance:
The
maintenance
of
trac
k
irrespective
of
ol
d
or new
is
to be done periodically.
Since the track may be damaged due to weathering effect like rain, sun and sand, track
maintenance is necessary.
Conventional methods of track maintenance:
The
convention
al
metho
d
of maintaining
of
track
s
by manual
labour
has been
traditional
ly
accepted
.
Th
e
calenda
r
syste
m
of
maintenance
ha
s
bee
n
followed by
Indian railways. As per this system a time table has been charted out which outlines
the
trac
k
maintenanc
e
wor
k
to
be
performe
d
by
gangs
in
the
course
of
the
year.
The
following operations are carried out:
 Through packing
 Systematic overhauling
 Packing up slacks
i. Through packing:
Due to
th
e
movement
of
train
s
ove
r
th
e
trac
k
frequentl
y
th
e
ballas
t
under
the
sleeper
s
become
loose.
Th
e
ballas
t
unde
r
th
e
sleeper
s
should be
regularly packed so as to keep the track in good running condition.
ii. Systematic overhauling:
In order
to
ens ure
the best possible

standard of
track co
ndit ions, tracks
should be overhauled (renewing) periodically.
iii. Picking up Slacks:
Slacks are those points in the track where the running of trains is
faulty or substandard. Depending on the season working sessions are
decided. In rainy season only slacks are picked up and no through
packing is done. In every working session, a certain number of days
in each week are allotted for picking up of slacks.
Modern methods are track maintenance:
 Track Machines (TMs)

 Measured shovel packing (MSP)
 Directed Track maintenance (DTM)
i. Track Machines:
below
:
Differe
nt
types
of
trac
k
machine
s
ar
e
use
d
in
Indian
railway
s
are discussed
Plassermati
c aligning.
tampin
g
machine
s
hav
e
th
e
functions
of
tampin
g,
levellin
g
and
Plasser Ballas
t
cleanin
g
machin
e
is
used
to
excavate,
clean and
put
th
e
screen
ballast back in the track and remove unwanted material.
Switc
h
relayin
g
machine
s
ar
e
use
d
whic
h
ca
n
remove
and
instal
l
parts or
complete assemblies of points and crossings.
Track Relaying Trains are capable of relaying the entire track automatically
with very less use of labour.
ii. Measured Shovel packing:
It comprises
of
takin
g
accurat
e
measurements
of
trac
k
defects such as
unevenness and voids in ballast.
iii. Directed Track Maintenance:
It is
a method
of
maintainin
g
trac
k
base
d
on the directions that
are
give
n
for
maintenance every day rather than routine maintenance.
Different types of equipments used in maintenance:
TOOLS REQUIRED DURING MAINTENANCE
S.No Name of the tool Use
1 Beater cum pickaxe To pack ballast under sleeper
2
Rail guage
To verify the distance between inner
faces of rails i.e. gauge
3 Cant board To verify cant
4 Spanner To tighten or loose fish-bolts

5 Powrah To handle the ballast
6 Jim crow To bend the rails
7 Auger To drill holes for the spikes
8 Chisel To cut rails, bolts, etc.
9 Lifting jacks To lift the track
10 Rail tongs To lift the rails.
11 Ballast screens To screen the ballast
12 Sleeper tangs To lift sleepers

(ii) Advantages of welded rails:
a) It increases the life of rails due to decrease in wear of ends.
b) It results in decrease in maintenance cost to the extent of about 25%.
c) It results in comfort of passengers due to smooth working of the track.
d) The creep is considerably reduced.
e) For track circuited and electrified tracks, the welding of rails shows better
results.
f) They are helpful for large bridges as rails of length equal to each span give
better performance and reduce the effect of impact.
g) It decreases construction cost due to less number of rail joints.
h) The fast and heavy traffic may be permitted on track with long welded rails.
i)The
rai
l
coache
s
an
d
wagon
s
wit
h
reduce
d
weight
s
can
be
used
on
the welded
track.
j)The
pullin
g
effort
is
reduce
d
due
to
elimination
of
th
e
los
s
of
strain
energ
y
and
impact energy at rail joints, hence it reduces fuel consumption.
k) The use of long welded rails affords more lateral, longitudinal and vertical
stability to the track.
Methods of welding:
 Electric arc welding
 Oxy-acetylene welding
 Chemical welding
 Flash-butt welding
Oxy-acetylene welding:
In
this
process
,
intens
e
hea
t
is produced
by
means
of
oxy-acetylene flame. Site

welding can be done, since it can be easily carried from one place to another. The
cost of welding is high and this can be adopted for cutting of steel.
It is als
o
known
as
ga
s
pressur
e
weldin
g
proces
s
and
it
is
used
widel
y
due to
variou
s
techno-
economic
considerations.
In
thi
s
process
,
th
e
rai
l
ends are heated by
ga
s
mixtur
e.
Th
e
temperatur
e
doe
s
no
t
reach
the
fusion temperature of
the
rai
l
ends
either
at
th
e
beginnin
g
or
at
th
e
end of the welding process. The welding temperature

render
s easy plasti
c
flo
w
wher
e
upo
n
th
e
applicatio
n
of
pressure
causes the welding
surface to come into close contact and be joined with smooth upsetting.
It is
mainl
y
performe
d
mechanicall
y
as a result
of
which, the weld strength is
uniform and its reliability is high. In India, it was successfully used for rail welding
on the Konkan Railway for its entire 760 km. The gas pressure welding plants can
be either as a portable plant or as a movable plant.
6.Name the various methods of tunneling in hard and soft rocks. Describe one in
each case. (R 2013)
Tunneling may be basically divided into two main groups.
(a) Tunneling in hard rocks
(b) Tunneling in soft rocks
Tunneling in Hard Rocks
 Full face method
 Heading and bench method
 Drift method
 Pilot tunnel method
Full face method
The full face method is normally selected for small tunnels whose dimensions
do not exceed 3 m. In this method, the full face or the entire facade of the tunnel is
tackled
at
the
sam
e
time
.
Vertica
l
column
s
ar
e
erecte
d
at
the
face
of
th
e
tunnel and a large
number of drills mounted or fixed on these columns at a suitable height as shown in
Fig.

A series
of holes measuring 10
mm
to 40
mm
in
diameter
with about 1200
mm
centre-
to-centre distance are then drilled into the rock, preferably in two rows. These holes
are
charge
d
wit
h
explosive
s
an
d
ignite
d.
Nex
t
th
e
muck
is
remove
d
befor
e
repeatin
g
the
process of drilling holes.

Vertical columns
Sliding drill
Sliding drill
Full face method
Advantages
(a) Since an entire section of the tunnel is tackled at one time, the method is
completed expeditiously.
(b) Mucking tracks, which are tracks used for collecting muck, can be laid on the
tunnel floor and extended as the work progresses.
(c)(c) Wit
h
th
e
development
of
th
e
‘jumb
o’
or
drill
carriage,
this
metho
d
can
be
used for
larger tunnels too.
Disadvantages
(a) The method requires heavy mechanical equipment.
(b) It is not very suitable for unstable rocks.
(c) It can normally be adopted for small tunnels only.
Tunneling in Soft Ground or Soft Rock
Tunneling in soft ground
or
soft
rock
is a specialized job. It does
not
involv
e
the use of
explosives and the requisite excavation work is done using hard tools such as pickaxes
an
d
shovels.
In
recen
t
times
,
compresse
d
ai
r
ha
s
also been used for
this
purpose.
Durin
g
excavation
,
th
e
rai
l
require
s
support
at
th
e
sidewall
s
an
d
th
e
roof
s
depending

upon the type of soil. The support could be provided in the form of timber or steel
plates
or
other
simila
r
material.
The
variou
s
operation
s
involve
d
in
soft
roc
k
tunnelin
g
are as
follows:
(a) Excavation or mining
(b) Removal of excavated material
(c) Scaffolding and shuttering
(d) Lining of tunnel surface

Forepol
e
Support
Wooden
pole
Sheet
The nature of the ground is the most important factor in deciding the method to be
used for tunneling.
The important methods of tunnelling in soft rock are:
 Forepoling method
 Linear plate method
 Needle beam method
 American method
 English method
 Austrian method
 Belgian method
FOREPOLING METHOD
Forepolin
g
is an ol
d
metho
d
of tunnelling
through
sof
t
ground.
In
thi
s
method, a
frame
is
prepared
in
th
e
shape
of
th
e
letter
A,
placed near
the
face of the
tunnel,
and
covere
d
wit
h
suitable
planks.
Poles ar
e
the
n
inserte
d
at
the
top
of
the frame up to a
viable depth.
The
excavatio
n
is
carried
ou
t
belo
w
these poles, which are supported by
vertical posts.
The
excavatio
n
is
carried
ou
t
on
the
side
s
an
d
th
e
excavated portion is
suitabl
y
supported
by
timbe
r.
Th
e
entir
e
section
of
th
e
tunnel
is
covered
thus.
The
process is repeated as the work progresses.

Cross-sectional view
Forepoling method
Forepoling
is
a
slow
an
d
tediou
s
proces
s
an
d
require
s
skille
d
manpower and
strict supervision. The method has to be meticulously repeated in sequence and
there is no short cut for the same.

7.Explain about Track Drainage, and how Surface and Sub surface Water Can be
removed From Railway track. Give all in Details. (AUC NOV/DEC 2011)
Definition
Drainage of a track, Station Yards and platforms are the three places
Where Drainage arrangements are needed. Track Drainage Comprises of
Interception, Collection and disposal of from the track. This is done by adopting
proper Surface and Subsurface Drainage System.
Types of track Drainage
Surface Drainage
Surfac
e
Wate
r
du
e
to rain
or
Snow
or
Flo
w
Fro
m
Adjacen
t
areas have to be
Disposed
of
Throug
h
Surfac
e
Drainage
.
Surfac
e
Drainag
e
ha
s
to
be
attended to in
three locations. Drainage in mid- Section Between railway Stations.
1.Drainage in mid-section
2.Drainage in Station Yards
3.Drainage at Station
Platforms
1.Drainage in mid-section
A
typical
arrangement
of
cros
s
Section
of
a mid-
section.
Side Drain
s
may be
unlined or lined. At a level Crossing
all
water should flow to the
side
Drains. In cutting
catch water Drains Have Been Provided Wherever Necessary. All Extra Ballast on the
Side Should be Recovered Which Encourage Growth of the vegetation.

2.Drainage in Station Yards
Open Surface Drains-Shaped Drains, Longitudinal Drains and Open
Drainage are Provided to Free Station Yard From Water.

A typical surface drainage system with open Drains for a Station Yard
.Every Station Yard is Provided with a network of Cross and Longitudinal Drains.
In Station Yard the vulnerable points are water columns and carriage watering
points with washing Hydrants.
3.Drainage at Station Platforms
For Drainage of Station Platforms the following Points Should be Taken
into account 1.Slopes away From the track
2. Discharge on non-Track Side
3. Discharge not towards Ruin-through lines
In
general
al
l
end
of
platform
s
should
be
slope
d
awa
y
Fro
m
the
Track.
al
l
other
Discharge
s
For
m
te
a
Stalls, Toilets
,
Water taps.
If
ther
e
is need be covered
longitudinal Drains Should Be Provided
In case of island platforms, all Drains Should discharge on the less important side of
the track
2.Sub-Surface Drainage
Sub-surface water is due to the capillary water. Other sources are seepage from
adjacen
t
area
s
percolation of rain
water.
Th
e
su
b
grad
e
an
d
the
formation
are
immediately affected by the Sub-Surface irrigation.

1. Provision of an inverted fillers
2. Sand piling
3. Laying of Geotextiles
4. Other Methods
1. Provision of an inverted fillers
An inverted fillers blanked of adequate thickness is provided between the ballast

and the week formation. The Blanket is of non-Cohesive material with enough bearing
capacity to sustain the load.
The inverte
d
filler
s
Blanke
t
is a ver
y
effectiv
e
method
of
improvin
g
th
e
bearing
capacity.
It
serve
s
as a porou
s
mediu
m
to drain
to
drai
n
o
ff
th
e
Surface
Water
and
Serves as a barriers for the upward movement of fine Grained particles
2. Sand piling
Sand
filling
is an effectiv
e
techniqu
e
. A series of 30cm diameter vertical holes
are drilled inside and outside the rail to a depth of 2-3m. the holes are filling with clean
san
d
an
d
th
e
surface
is
resurfaced.
The
are
a
covere
d
by
the
Sand pile
s
Should be
Abou
t
20% of the formation
area.
Sand pile
s
provid
e
a
mechanical
suppor
t
and the
Drainage of the Sub grade improves.
Furthe
r
by
the
arrangement
of
th
e
Subsoi
l
rise
s
through
the
sand
column
And
get evaporated.

3. Laying of Geotextiles
Geotextiles are made of polymers which are Extensively as a new Technique in
improving the Soil Properties and Drainage.
On Indian railways Geotextiles are Extensively used. Geotextiles are having the
uniqu
e
property
to
allo
w
wate
r
to
pass
through
but
not the
soil
fines.
They
no
t
only
Work as separate and filters But also as reinforcement bed.
Geotextile
s
ar
e
eithe
r
lai
d
directl
y
belo
w
th
e
ballas
t
or sandwich between a
50mm layer of sand on top and a 25mm layer so sand below so that the ballast
directly does not rest on Geotextiles .and thereby preventing tear and puncture of
textiles .
4. Other Methods
Al
l
othe
r
methods
Which
ar
e
use
d
to
for
Soil Stabilizatio
n
may be
used
to
arrest
Sub-

Soil water. Cement Grouting , Chemical Grouting

UNIT II.doc Railway Airport DOcks and Harbor Engineering

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UNIT II.doc Railway Airport DOcks and Harbor Engineering