Transportation Engineering-II
Dr Rajat Rastogi
Department of Civil Engineering
Indian Institute of Technology - Roorkee
Lecture

- 8

Creep in Rails
Dear students,I welcome you back to the lecture seriesof transportationengineering2
coursematerial. So far we have discussedabout different aspectsof railway engineering
including the various gaugesin use, the history of the Indian railways and the various
stress, strains or bending moments in the different component of the tracks, the
permanentway and then nally we have also discussedabout the rails. Now todays
lectureis a basedon the creepin rails. This is one specificfeaturein rails which happens
becauseof certainaspects.We will be looking at all thoseaspectsin todays lecture.The
lecturehasbe alignedwith the creepin rails ,thatis, dening the creep,the effect of creep
in the rails, the theoriesof creep,the creepindicators,the methodsto reducecreep.
(Refer Slide Time: 01:30)

ua§1*ee;::r'5ss'=r
Raiis
m
of reaegzz

. re

So we start with the definition of creep. The creep can be dened as the longitudinal
movementof rails in a track. In the caseof the rails as we seendiscussedpreviouslyalso
they are being fastenedwith the sleepersusingdifferent fasteningsand thereforethey are
assumed to be static in nature, but there are certain reasons due to which these rails start

moving in certain directionand that movementin the longitudinaldirectionis termed as
creep.

(Refer Slide Time: 02:35)

Now this creep is location specific. We may not found a creep, that is the longitudinal
movement of the rails happening along whole of the length of the railway track. It is
mostly being found only at a certain specic location and that reason may be becauseof
certain things. We were looking at all those reasons, of course, during the course of the
lecture.

Another thing is that whatever is the magnitude of the creep at one point is not
necessarily is the same at the other point. Of course, there are number of factors which
are affecting, which are causing this phenomenon. Therefore, what we found is that the
total amount of creep which is happening at any location per unit time period will be
differing. So it means whatever longitudinal movements is happening at any of the
section of the rail may not be necessarily happening at the other section and at the saIne
time may not be happening with the same gravity or with the same amount as it is
happening in other section. Therefore, we have to curb this creep of the rail sections and
we have to look at different factors which may be causing all those creeps.
Now, how we are going to nd out whether there is creep in this rail section or there is
not any creep in this rail section. So there are certain indicators which we can look at.
The one thing is that there is a closing of joints in the direction of creep. What happensis
that if there is one rail section which is moving in the forward direction then the other rail
section which is not being affected becauseof the creep it will remain in its position.

(Refer Slide Time: 04:50)

Now both the rail sections have been jointed by a joint using fish plates and bolts. At that
location what we have found is that the first rail is trying to move in to that gap which is
being provided at this joint and that is how the closing of the joint will happen in the
direction of creep. Another aspect is that there may be an opening of joint at point from
where the creep starts;just it is another end of rail section which is moving. At one end of
rail section it is trying to close the joint at which it is being jointed with the other rail
section whereas when it is trying to move in one direction obviously on the other end of
that rail section it will try to open out. Therefore there are 2 things which happens
simultaneously; at one end it is closing the joint and at other end it is opening the joint.
Another indicator which has been observed is scrapping or scratching marks on the rail
anges or the webs due to spike head. Now what happensis as we have discussedthe rail
sections are being fastened to sleepers and the spike head is one of the fastener which
tries to x the rail section to the sleeper. Now if there is any movement in the rail section
the spike head tries to remain in its position and becauseit is awaiting with the ange or
the web of the rail section it will start putting the scrapping or the scratching mark on that
section because of the movement of the rail and if we found that there is any scratching
mark on the rail section or there is some material which has scrapped down because of
the relative movement of the 2 things that is the spike head which remains in its positions
and the rail section which is moving we can easily understand that there is some creep
happening in this section. So these are some of the ways by which we can easily identify
during the periodical maintenance checks that the creep has started in some of the
sections

of the rail

or the track.

Now what will happen becauseof these movements of the rails? There are certain things
which will be happening; one is that there will be an opening or jamming of the joints.
Now these are the 2 different aspectswhich will be happening and they belongs to the 2
reasonswhich we have just discussed.

(Refer Slide Time: 09:35)

As the rail is moving it is trying to open out the joint at one end whereas it is trying to
close the joint at the other end. Therefore, this is one of the effects which of the creep,
that is, it will be opening the joint or it will be jamming the joint means it will just try to
abort the 2 rail sections with each other and therefore the joints will not be there or there
will be a problem associated with the movement of the rails with respect to the some
other

stresses.

Another thing is that there can be a kink formation at the rail joints. Now if the another
rail to which the previous rail is trying to come and closing the joint is not moving then
what will happen is there will be a sort of a kink which will get created at the joint of the
2 rail sections and this kink is a point of uncomfortablity. When the train moves, when
the wheel moves at this location there will be a sort of a jerk being induced and because
of this jerk there will be discomfort which will happen to the passengersin the wagons or
the compartments. So the kink formation is, of course, not required thing in any of the
rail section. We have to remove whatever the kinks are there by a certain smooth joining
conditions.

Then another aspect is that becausethe rail is being fastened or xed to the sleepers and
if the rail tries to move out in one direction then it will create a problem to the sleepers
also. In that caseif the creep is quite heavy then the sleeperswill start coIr1ingout of their
location or position and they will be shifting relatively along with the rail sections and if
this is happening then this is going to create a problem to the gauge. It will also create a
problem to the alignment. So both have the conditions of quite a difficult conditions,
they are going to create an effect in terms of total operations of the train and the safety of
the movement

of the trains

from

that

section.

So we have

to look

into

consideration

this

one. If there is heavy creep and if there is such type of movement happening of all the
components then that needs to be rectified.

Another aspect is that there can be buckling of the track. Now when there is a buckling of
the track means it is trying to buckle out in one direction because it has got jammed in
one location and still there is a creep keep on going and there is no place where the rail
can move out then obviously it will start buckling in the outward direction. Now when it
is trying to buckle in the outward direction it is going to create an effect on the gauge and
the alignment again and this type of a condition is more hazardous in terms of that it may
cause the derailment of the trains. So therefore, if a very heavy sort of a creep is
happening in any of the section and it is going to jam the joints and nally coming
towards the buckling stage it is going to be a worst sort of a condition on the track.
Another aspect related to these creep is that that point and crossings or switches or
interlocking which gets distorted. Now points, crossing, switches or interlocking, these
are the aspectswhich are used for the turning of the train from one track to another track.
Now if there is a movement of the rail then obviously whatever points or crossing are
being provided or the locations of the switches being provided or there is an interlocking
aspects of these points and crossings with signals then everything get distorted and if
everything is getting distorted in that sensethen there is going to be hazardous condition
in terms

of the movement

of the train

from

one track

to another

track

or the movement

of

the train on the same track with the signals operating on that. So this is another safety
hazard in terms of the movement of the creep and its effect.
Further there are some more things which will happen. Now the fish plates and bolts
which are used at the joints where the 2 rail sections have been jointed together and if
there is the movement of the rail section with respect to the another rail section which is
jointed then obviously there will be smashing of the sh plates and the bolts.
(Refer Slide Time: 12:55)

E3
5."

Because what will happen is that when the fish plates and the bolts will try to remain in
their position because of no movement in the rail section but in the another rail section
because

there

is a movement

it will

tries

to create

stresses

and when

this

stresses

become

much heavier this induced stresseswill start smashing the sh plates or the bolts there
may be cracking which will start from the point of hole at which the bolt have been
placed and finally it may propagate towards the outer sides and this type of thing
happening then sh plates will come out of their position and there will be no joint
remain

the section.

Then the next aspect is the removal or the replacement and the maintenance becomes
difficult.

Now whatever materials need to be maintained; now at this location where the 2

rail sections are averting each other. We have different types of things which can be
removed. It may be either rail sections, it may be the fastenings which have been used or
it may be the sleeperswhich have been provided at the bottom. If there is any removal or
replacement requirement at that location or if a periodical maintenance has to be carried
out then all of these things become difcult becausethere is no gap being placed between
the 2 rail sections or there has been a distortion in the position of different components.
In all these conditions we found that the maintenance cannot be performed as such. Then
there is forging of ballast. Forging of ballast means that becausethere is some movement
of the rail along with some movement of the sleepers because the heavy creep is being
induced, the ballast will start coming out and it will get start accumulating at one place
and when that sort of a condition is happening that is what is the forging of ballast will be
there. Then bending of bars is another effect of the creeps. Whatever bars have been
provided which have been used to connect at certain locations some of the things they
will start bending out because of the movement of the rail sections in the longitudinal
direction.

Now looking at this creep there are different theories which have been postulated by
different researchers.They found in all there are three major theories. The first theory is
termed as the wave theory.
(Refer Slide Time: 13:30)

Another theory is termed as percussion theory and the next theory is termed as drag
theory. These are the three major theories along with some associatedfeatures or regions
which have been provided or given by the experienced persons or researcherswho have
worked with the creep. We will be looking at all these theories and along with those
associated

features

in the continuation

of these

this

lecture.

(Refer Slide Time: 15:00)

Starting with the rst theory, the wave theory. The wave theory says that there are certain
moving wheels and these loads set a wave motion in the rails. Now whatever wheels are
moving on the rail section obviously they are putting the load, they are transferring loads
from the top to the rail section. Now when this load is being transferred to the rail section
it says that some sort of a wave motion will get induced because of this loading coming
from the top. Now what happens is a vertical reverse curve is formed ahead of wheels in
the rails. At the point of location application of the load the rails will get depressedor
deformed or deected in the downward direction. When this are getting deected or
deformed in the downward direction, that is, deection is there then what will happen is a
vertical reverse curve will get formed. So if we take this rail section in a continuous form,
it will be acting as a vertical reverse curve. We were looking at this aspect in the
diagrammatic form also and then as the wheel moves this reverse curve will be moving
which is there in the front of the moving load, it will be carried forward.
Now when this reverse curve is being carried forward it will cause the creep of the rail
because the rail will start trying to move in the forward direction and this is what the
wave theory says. Now in this diagram what we are seeing is that this is the rail section
and this rail section is being jointed with another rail section at this point with the help of
the sh plates and the sh bolts, that is, these bolts which have been provided here and at
the bottom the sleepershave been provided.

(Refer Slide Time: 15:24)

Now when there is number of wheels which are moving in this particular direction then
what is going to be the effect of these wheels it is to be seen. Now what we see is that,
now this is a condition which is happening because of a single wheel. Now this single
wheel is being placed here and whatever load is being transferred this load is transferred
at this position.
(Refer Slide Time: 15:55)

This is the normal rail level at this point. The dotted line is showing the normal level of
the rail at which this wheel was placed. Now because of the loading condition there is
this much deection being caused in the rail section. So the rail section has boned down
like this at point A that is the point of application of the loading. Now when this has gone
down in this form what is going to happen is a reverse curve gets formed like this.

This is a reverse curve; it is having a reverse curvature on this side as well as on this side.
This curvature is having a point of center on this direction whereas this curvature is
having a point of center in this direction, that is why this is a reverse curve condition. So
we have a reverse curve here and in this reverse curve just before this wheel section, that
is, at this location and just as well as in the front of this wheel at this location what we are
nding is that the this rail section is going above the normal level of the rail. Now when
this rail section is going above the normal level of the rail then this is what is the amount
of lift which will be there with respect to the normal rail section whereas this is the
amount of depression which will be there at this location becauseof the loading condition
due to this wheel. So the distance between this point and this one is termed as the pitch
whereas this is the total overall depth is taken from this point to this point so that will be
the depth of total by which this rail section is going to be deected and we have to look at
this wave depth as well as we have to look at the pitch section. So any uni loaded position
of the rail is there then this is the condition. That the same thing will be happening with
the rest of the wheels which are placed on the rail section. So it means at number of
locations the sametype of phenomena will be happening.
Now as soon as this wheel starts moving in the forward direction what will happen is that
this sort of a reverse curve condition will start moving in the forward direction
longitudinally and due to this movement of this section which is being shown here in this
curve form, the creep will be induced. Now if there are numbers of rails which are
moving in this direction and all of those wheels are going to create the same kind of
effect then obviously the total amount of movement will be induced because of all the
wheels on that rail section is going to be the total amount of creep which will be induced
in this section. So this is how the wave is formed in the caseof wave theory.
Now in the case of the wave theory, what we have seenis that the wave action is going to
be affected by the 2 type of parameters.
(Refer Slide Time: 20:00)

One is the pitch of the wave another one is the depth of the wave. Now if we can control
this pitch of the wave and we can control the depth of the wave, that is, the total amount
of deection which is being created in the positive and negative direction as well as the
amount by which it has moved in the forward direction that is the pitch, then obviously
the whole of the creep can be controlled. So that is why these 2 factors are going to be the
sort of a controlling factor for the creep in the wave theory. Now this pitch and depth is
going to depend on certain factors. Now those factors are track modulus, track stiffness
and track stability. Now what does it mean is, now if we are looking at this depth or if we
are looking at the pitch, just assume a condition where we have the sleepers being
provided very closely to each other below the rail section.
Now if this type of condition is happening obviously this depth of the wave can be
controlled becausewhatever is the load which is coming from the top is not unsupported
and it will be directly transferred to the sleeper. Now as soon as it is directly transferred
to the sleeper then there will not be any deformation or deection being created at that
location. So that is how the total depth of the wave will be controlled and if there is no
depth of the wave it is eliminated or being minimized then in that casethis pitch will also
get minimized or eliminated. It means we have to look at certain conditions by which the
track modulus can be increased. the track modulus as we have discussedpreviously when
we discussed about the stressesand resistances in the permanent way sections and its
components. We have observed that this is one parameter which tries to define the
strength of the track. So, it means that when we are trying to find out or while you are
trying to discuss the strength of the track and if there are certain ways by which the
strength of the track or the track modulus can be increased then obviously we can reduce
or we can control the pitch or the depth of the wheel.
Another aspect is the track stiffness. The track stiffness is another thing like it denes in
terms

of the resistance

towards

the deformations

or the resistance

toward

the deections.

That is what can be used here in terms of when we are talking about the depth of the
wave or if we are talking about the pitch of the wave. So if the track is stiff enough if we
are using the rail sections which are more heavier if we are using the rail sections which
have much of strength at the same time we are using the supporting systems like sleepers
or the ballast cushions which have been provided of the material which are having much
more stiffness as compared to the normal condition then in that case the total stiffness of
the track will increase. Unless this total stiffness of the track is increasing then it will not
allow or it will resist any deformation in that section because of the loads which are
coming from the top. Therefore in that case there will not be any depth of the wave or
there will not be any pitch and both the things will get controlled.
The last aspect which is going to create an effect is the track stability. The track stability
is related towards the safety point of the operation of the trains or the wagons on the
track. Now in this case if the track is stable enough, if all the things which have been
provided remain in their position, they are not losing out their location. Then in that case
there all chances that we can reduce or we can control further the pitch and depth. So it
means if these are the three things. If we can control these three things then we provide
the components in such a way that they enhance all these three properties, that is,

modulus, stiffness and stability. Then we can for some point of time or for a certain
amount we can reduce the creep or we can reduce the total amount of gap for pitch of the
wave which is being induced. Now in this case so control of wave action is going to
happen by the certain things in field like we can use angular and heavy ballast.
(Refer Slide Time: 23:51)

This is from the supporting condition as we have discussed that we have to increase that
track stability or we have to increase the track modulus. So what we can do is we can use
heavy ballast which is more angular in shape. Angular is required becauseas soon as the
ballast is angular or the stones are angular they will start tting in with each other and if
they are starting fitting in with each other then they will try to transfer the load through
their point of contact from one stone aggregate to another stone aggregate. If this is the
thing which is happening then the load will get transferred to a much wider area. So this
is why the angular stone for ballast is required.
Another thing is the lesser sleeper spacing. Just before only I have discussed that if we
provide the number of sleeperswhich have been placed very closed to each other then in
that casethere will not be any possibility of a deformation getting induced becauseof the
load in the rail section. So this is what we are talking here, if we have a lesser sleeper
spacing or in other words if we increase the sleeper density, that is, the number of
sleepers being provided per rail length. Then also we can control the amount of wave
action but obviously there is certain amount of spacing which needs to be provided
whatever is the condition and in that senseit is not possible to have the sleepersprovided
aborting each other.
The next thing is the bigger rail section. Now this point also we have discussed just
before when we have tried to discuss the track modulus or stiffness. If we have a bigger
rail section then obviously it is going to be much heavier and much stiffer and if it is
going to be much stiffer and heavier then the deformation induced because of the loads
will

be lower.

So that is how

it will

control

the wave

action.

Further point is thus increasing the stiffness of track. Now this increasing the stiffness of
track means we have to use certain measuresby which like in the case of very good type
of fastenings which are which can take the loads of a very large amount. If you use those
one and we provide and just connect the rail sections with the sleepersby using those one
probably the stiffness of the track can be increased. So these are the some of the ways by
which we can control the wave action in the wave theory.
Now we look at another theory that is percussion theory. The percussion theory states
that the creep is due to impact of wheels at the rail end ahead at joints. Now this theory
also is talking in terms of joints, what it says is that there are 2 rail sections which have
beenjointed together using sh plates and the sh bolts.
(Refer Slide Time: 27:52)

At this location as soon as any wheel comes it will strike on the rail section which is
placed in the forward direction. So if it is going to strike at the rail end of the rail which is
provided in the forward direction then that rail will move in the forward direction because
of a horizontal component of the thrust and this is the reason due to which the creep will
get induced in the rail section. So at the rail joint the wheel load pressesthe trailing rail
down thus causing an impact of wheel with the forward rail. So this is the reason which
will be causing the creep in the rail section. So at the strike, the force in the direction of
the movement pushes the forward rail ahead thus causing creep. So as soon as there is
this strike, strike means as soon as there is a force which is coming at the end of the rail
section

in

the

forward

direction

and

then

we

resolve

this

force

in

the

horizontal

component and in the vertical component then the horizontal component will induce the
creep whereas the vertical component will depressthat rail end section in the downward
direction and this is what we have seen in the previous lecture where we have talked
about the hogged rails.

Further in the case of the percussion theory that this resultant of the vertical load and the
forward force causes battering of the rail end of the forward rail and that is what is the
hogging of the rail is.

(Refer Slide Time: 28:32)

Now in this diagram we are looking at the same aspect. In this casethis is one rail section
which is being jointed along this rail section using the fish plates and the bolts. This is a
wheel

which

has come

to this

location.

(Refer Slide Time: 28:46)

Now

as soon

as the wheel

circumference

of this

wheel

touches

the end of this

rail

end it

will be putting an impact in terms of this force R at this point so at the point of this

contact of the wheel and the rail section in the forward direction there will be an impact
force which will be acting in this inclined direction like this. Now if we take the 2
components of this one becausethis rail section is moving in this direction. So we will be
having a component P which will be in the longitudinal direction, that is, the movement
of the wheel and we have one another component Q which will be working in the
downward direction like this one. Then in this casethis component P will try to move this
rail section in the forward direction. So this trailing rail section will try to remain at the
same location whereas this rail section will start moving in this direction. So, if this is the
case which is happening then obviously this joint will start getting open out becausethis
will remain at this location, this is moving forward. So this is what is termed as opening
of the joint.
Now when this opening of joint will be created this sh bolts they will try to resist the
movement of this rail section in the forward direction. Now when this fish bolts they are
trying to resist this movement or these 2 sh bolts they are trying to resist the movement
of this rail section in this direction obviously there is a concentration of stressesat these
locations, that is locations of these sh bolts or holes and if they become excessive then
they may cause tearing of the sh plate at this location in this direction. So there can be
some tearing in this one and that is how it will get smashed out. This is what we have
discussedpreviously in the caseof the effect of the creep.
(Refer Slide Time: 31:04)

ti?

So in the case of the percussion theory, what we found is that the creep is going to
increase due to certain reason becausewe are talking about the joint at which the striking
of the wheel is happening. So what are those factors which can create an effect at this
joint will be taken into consideration. Now these factors are; there can be the weak and
loose fish bolts where the fish bolts are not properly fitted or there has been some
loosenessbeing left in that one. Then obviously they will allow the movement of the rail
section. Another thing is that the fish plates if they are old enough and they have started
to worn out, then in that case also they will not be having sufficient strength so as to keep

the rail sections in place. So this may be another reason due to which the creep can
happen in the rail sections.
Then the next aspect is the loose packing the load. the ballast cushion which is being
provided at bottom if that is not being compacted sufciently and it is being placed in a
loose

condition

then

it will

reduce

the total

stiffness

of the track.

So in that

case also

the

creep will increase. Further there will be a wide joint expansion gap. In that case also
what happens is that in this case if the 2 rails have been jointed together but the gap
provided between the rail sections is quite wide then the wheel which is coming at the top
of the rail section which will have sufficient resistance at which it is going to strike on the
forward rail section. So if the gap is more, this type of effect will also be more whereas if
the gap is lesser then it is more or less of a continuous sort of a surface being provided
and therefore in that case the striking behavior of the wheel on the rail section will not be
there.

Another aspect is the heavy axle loads which are moving at a faster speed. Now if the
axle loads are quite lower or the speedsare quite low in both the conditions the impact
which is going to be created at the rail end will be quite less but if the loads are heavier
and at the same time these loads are moving at a much faster speedthen total amount of
impact energy which is going to be transferred with the point of contact of the wheel with
the forward rail section which will be much heavier and if becauseof this large amount of
energy which is going to be transferred at this point of the contact, the horizontal
component will also become large and in that sensethe total amount of creep induced in
the rail

section

will

also be more.

Now another theory related to creep is drag theory. The drag theory says that it relates to
the motion of a locomotive and the motion of the wagons. What it tries to say is that the
driving wheel of the locomotive causesbackward thrust and it tries to push the rail of the
track

backward.

(Refer Slide Time: 35: 17)

on of a i=nmamin$i.*m

Here what we are trying to assume is a condition that the total drive in force is being
provided to the locomotives and the wagons have been attest to it will just follow the
movement which is being caused or induced by the locomotive. In this case the tractive
effort will be coIr1ingthrough the driving wheels of the locomotive and this tractive effort
acts in the backward direction. Now as we have seen in the case of the percussion theory
where the impact force is acting in the forward direction, it is a reverse of that one where
the tractive force will be acting in the backward direction. When we take this tractive
force which is acting in the backward direction coming in inclined position it will be
having again 2 components of which one component will be in the opposite direction to
the longitudinal movement of the wheels and due to this reason this thrust will try to push
the rails

in the backward

direction.

Another condition is the wagons which have been provided at the back of the locomotive.
Now these wagons tries to remain in its position because of the Newtons law and
therefore they will try to resist by providing a force which is acting in the forward
direction and in this case when we again resolve this force in 2 components there will be
one component which will be acting in the longitudinal direction, in the direction of the
movement of the wheels. So therefore we have 2 forces; one is the force due to tractive

force which is acting in the backward direction and another is the force due to wagons
which are opposing the motion due to inertial effect which tries to push the rail in the
forward direction or in direction of travel. Now whatever is the force which is larger will
create or induce the creep in that direction. So if the force which is caused due to tractive
effort is more then it is going to create the creep in the backward direction whereas if the
force due to wagons is more then it is going to create a creep in the forward direction.
Now in this case what is going to happen is that this is more than the effect of the driving
wheels becausethat is the combined effect of the wagons or force which is being induced
by those wagons.
(Refer Slide Time: 36:28)

Now there are some more reasons which have been stated which cause the creep in the
rail sections. The one of the reason is the starting, accelerating, slowing or stopping of the
wheels.

(Refer Slide Time: 36:40)

These are the 4 things which can happen during the operation of the any of the rolling
stock. Now when the rolling stock is starting as we have seen it tries to cause certain
movement

in the

forward

as well

as the backward

direction.

The

same

is the

condition

with the accelerating one because it is trying to accelerate from a speed v1 to V2.
Therefore, again it will be pushing the track in the backward direction as well as the
driving wheels are concerned and the rest of the wheels again will try to move in the
forward direction the rail section. Similarly, when we are from a movement if we are
going to stop and there is a sudden application of the brake or if we are going to slow
down then also there is an application of the brake. Then this application of the brake
coming through driving wheels will be in the forward direction which will be having a
component in the forward direction and it will try to induce the creep in the forward
direction. So it means starting or accelerating causes the backward thrust where the
slowing or de acceleration causespush in the rails in the forward direction.
The another aspect is thermal expansion or contraction of rails. As we have seen that the
rails are laid at a certain temperature and if the surrounding temperature is lower than that
one or it is more than that one, in both the cases there will be relative movement of the

rail section and that is what is known as the thermal movement of the rails, may be
expansion or may be contraction. So it is going to be affected by the range of the
temperature which can be there and it is also going to be affected by the surrounding
conditions that is whether there is position any placement or shadesetcetera or it may be
also effect have its effect in terms of the location at which that section is being provided.
So these will also create a movement and this movement will be in the any of the
direction may be in the forward direction or the backward direction.

One more aspect is the unbalanced trafc. Now what happens is that on all the tracks if
we connecting a city A with a city B and city A is the point of production of certain
commodities and city B is the point of consumption of those commodities then there will
be a ow of these commodities from city A to city B.
(Refer Slide Time: 39:00)

In that case the train or the freight which will be moved through rolling stock which will
be much

heavier

in the

direction

of movement

from

A to B whereas

in the

case of the

movement from B to A if there is no such commodity which needs to be transferred back
then it will be coming as empty load. It means that it is going to be an unbalanced trafc
condition in the 2 directions. So if there is an creep which is being induced in one
direction of travel there is no traffic which can just nullify that creep while moving from
the opposite direction and due to this reason the creep will keep on increasing in that one
direction. What is being observed is that this unbalanced trafc causesthe creep because
of further the ill design of the track and it is being observed to be more on the 2 specic
aspects of the track that is where the curves are being provided or where there the
gradients are being provided. More or less steeper are the gradients, it means more force
is to be applied in the forward direction so as to move the train on these gradients or if the
train is coming down grade then more applications of brakes will be there and due to both
of the reasonsthere will be the creep in the rail.
Further, as we have seen in the case of the percussion theory the poor maintenance of
track also causesthe creep. Here we are talking about the type of the rail sections whether
the rail sections are old, or whether they are new, or whether the rail sections are light, or
whether they are heavy. On the basis of these combinations whether the heavy sections
have been used or the lower sections have been used they are going to create its effect.
All of these factors basically like the fastenings, the joints, the ballast cushion or the
formation all of these factors are going to create an effect on the stability and stiffness of

the track. So therefore in this case if the track is not being maintained properly then
obviously it is going to create an effect and it will be in terms of creep.
The next point comes is that how we can measure the creep? The measurement of the
creep as being shown in this diagram what we found is that this is sleeper on which the
rail sections have been placed and there is one post which is provided at this location and
there is another post which is provided at this location.
(Refer Slide Time: 41 :40)

This 2 are being jointed together by using a string. So this is known as the creep
indicator. So what is happening, now we can see in the plan here these are the 2 rail
sections being provided and these are the sleepers under these 2 rail sections are resting.
Here this is the rail post and this is the string which is passing like this and these are
being passed at the bottom of the rail section. Now as soon as there is a creep at any
point, now at this point where this string is being placed a mark is made on the rail
section here. Now if there is any creep in this rail section, or in this rail section, if there is
a creep in this rail section in this direction then what will happen is that this mark will
start moving along this scale in this direction and there will be certain distance by which
this mark has moved from the string. So whatever is this distance which is being moved
with respect to this string is the creep in the rail section and this creep is to be measured
in terms of per month, that is, how much amount of creep is being induced per month and
then this is how it keeps on going.

(Refer Slide Time: 44:34)

So how we can prevent the creep? Now there are different ways by which it can be done.
One thing is that pulling back the rails. In the case of pulling back the rails what we are
going to do is that first of all we have to remove the sh plates and the sh bolts. Once
we have removed this fish plates and fish bolts then we use some of the equipments
which are the crow bar and hooks. Using these crow bar and hooks what we do is that
this hooks is placed in the hole which is being created for the sh bolt and then using the
crow bars we try to pull the rail section back. Now the rail section which we have seen it
is having a very very heavy load as we have seen that it is generally of 13 meter length
and for 1 meter length the weight of the rail section varies from 50 to 60 kg. Then it
means the total amount of weight of a rail section is very high.
So looking at that aspect if we have to manually use the hooks and the crow bars and try
to pull back the rail section then this is going to be very slow and tedious process. It is a
very difcult situation where we require a large amount of manpower and also we require
large amount of energy to do that. So therefore, it is practicable only for those conditions
where there is a small length in which the creep has been induced but if it is being
induced in a much larger section then it is not possible to pull back whole of this section
by using crow bars and hooks.
Another way of preventing the creep is the use of steel sleepers. In the case of steel
sleepersit is being found that the steel sleepersthey are the best in preventing the creep.
The reason is that there can be jointed in such a way to the rail section that they try to
keep the movement in tact at that location itself.

(Refer Slide Time: 45:26)

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Now if we increase the number of sleepersthen also the creep can be reduced. So that is
another way as we have discussed previously too that we can reduce the creep. Further,
there are some specific devices. If we use those specic devices then also we can reduce
the creep. These devices are anchors or anti-creepers. Anchors or anti-creepers means by
the word itself we can understand this anchor has come from the marine transportation
where the ships have been using the anchor so as to remain in standstill condition in the
water by throwing the anchors in the water.
(Refer Slide Time: 47:05)

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Now these anchors will go down to the bottom of that location where the ship is standing
and it will just hit bottom of the sea and it will struck there. So that was the phenomenon
which was used in the case of anchors. Now the same type of anchors is used in the case

of the rails but in a different form. They are also termed as anti-creepers becausethey are
trying to resist the creep in the rails. Now these anchors generally they are provided as 4
anchors per rail length. If the creep is 7.5 centimeters to 15 centimeter per month whereas
if the creep is from twenty 2.5 centimeters to 25 centimeters per month then 6 anchors
per rail are used and they are used at the level crossings, they are used in the yards and
they are used at places of heavy brake application.
Now all these locations which have been listed here they are the locations where we will
find that there are most of the movements or the creeps will are going to be induced. As
we have seen one of the reasons of the creeper is the starting of the train, or its breaking
effort, or slowing down effort, or the accelerating effort. Now all of these things happen
very near to the rail level crossings or in the yards or there are certain locations like the
platform area of this station where the heavy brake applications will be there. So, on all
these locations we have to provide anchors and these anchors have to be provided on the
basis of total amount of the creep being induced but they are not used on bridges.
Now this is the diagram which is trying to show how the anchors can be placed. There are
different ways of doing this. This is the direction of movement; one way is that we are
providing the anchor at this location and this location then this alternate sleeper is being
left.

(Refer Slide Time: 48:08)

Then further the alternate sleepers on all the sides of the sleepers the anchors have been
placed, that is, one anchor has been placed here, another has been placed here. The same
way it is being placed from outer side and if it is more of the creep is there then obviously
they have to be placed in this form and then there is another anchor which is placed at
this location. Now, another way of doing the same type of thing is that we have tankers
being placed on both the all the locations becausethere are chances of the creep getting
induced in both the direction

of the movement.

Therefore,

the anchors have been

provided on this direction as well as in other direction and again these anchors are

provided on all the alternate sleepers.They are not being provided continuously. Further
in the case of the anchors, these anchors need to be fastened to the foot of the rail.
(Refer Slide Time: 49:30)

M

wit

If they are not being anchored to the foot of the rail then they will not be transferring the
load. If they are not transferring the load then they will not be in a position to resist the
movement of the rail sections. Therefore, this is one of the important things which needs
to be taken care off while providing the anchors or the anti-creepers. Now there are 3
different ways by which this can be done; one is by the wedging action, another is by
clamping and the third is by spring grip. In the case of wedging action what is being done
is that if the anchor is something like this one then at one location the wedge is being
inserted and when this wedge is inserted it will provide the connectivity between the
anchor with respect to the foot of the rail section and this is the way by which the loads
will be transferred from one point to the another point.
In the case of the clamping what we do is the clamps are provided at the foot of rail
section and so that this rail section is being kept in location and the third one is the spring
grip condition. The spring grip condition is a type of an anchor in which using the
springing action of the anchor the grip is maintained. We are not using any wedge in this
case and because of this spring gap which is provided, becausethis anchor moves from
one side to the other side of the rail section and by using the spring action it will be
transferring the load. Now the next thing is that there are certain important points which
needsto be remembered while making the rail and controlling that one.

s(Refer Slide Time: 51:40)

One

is that

it should

be able to resist

the movement

of the rails

whatever

anchors

we are

trying to provide we should be able to resist that one we should not move forward along
with the rail section. Then they should butt against the sleepers,as I have told that if they
are not butting against the sleepers and they are not touching the rail sections then the
load will not be transferred and therefore the resistance will not be improved and then
they should be xed to the good sound sleepers, that means the sleepers have to be
checked what type of category of sleepershave been provided and they shall not be used
on bridges.
So students this is all about the creep. What we have discussedtoday is the definition of
the creep, the effects of the creep, certain theories which are tried to dene the creep, the
measurement of the creep and the prevention of creep. So we stop at this point and I say
goodbye to you. Thank you.