Surveys & alignment of Railway Engineering

RAILWAY SURVEYS
Reasons for laying a new
railway line
1. Strategic consideration:
Sometimes it becomes essential to join two
points by a railway line for strategic purposes so
that in case of emergency, the army can be
transferred from one point to the other.
2. Linking of trade centres:
Two trade centres may not be linked up by a
railway line. In such cases, a new railway line is
proposed between two such trade centres. 1

RAILWAY SURVEYS
3. Connecting port with the interior of the
country:
A port is sometimes not connected with the
interior of the country. In such cases, it
becomes essential to have a new railway line
joining the port and the trade centres of the
interior of the country.
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RAILWAY SURVEYS
4. Shortening existing route:
A route exists between two points. But if it is
possible to shorten the existing route, a new
railway line is to be laid.
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RAILWAY SURVEYS
5. Laying of a branch line:
It becomes necessary sometimes to lay a
branch line to an existing main line to
develop certain other cities on the proposed
branch line. The new branch line will serve as
feeder line for the existing main railway line.
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RAILWAY SURVEYS
6. Undeveloped area:
A new railway line is laid to develop an area
which may be rich in mineral resources or
other natural wealth like timber resources.
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Factors influencing the proposed route:
I. Cost:
Should be minimum
Is composed of:
{capital cost of the project + maintenance cost +
renewal expenditure + working expenses}
The route should be so selected as to bring the
sum of all these costs to a minimum.
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Factors influencing the proposed route:
II. Safety:
 The available passenger and goods traffic
should be transported safely,
 Route should be so laid as to have minimum
chances of train accidents
III.Speed:
 Route should be so selected as to have
reasonable speed of trains.
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RAILWAY SURVEYS
In order to have a proper and satisfactory new
route, various surveys are carried out:
1) Reconnaissance Survey
2) Preliminary Survey
3) Location Survey
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RAILWAY SURVEYS
1) Reconnaissance Survey:
 It is the first engineering survey.
 It is carried out in territory which has not been
previously surveyed for the purpose of laying a
new railway line.
 The main objects are as follows:
i. To obtain general knowledge of the whole territory,
and
ii. To obtain information regarding the salient features
of the territory.
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RAILWAY SURVEYS
Importance of reconnaissance survey:
• A number of possible alternative routes between
two points can be worked out.
• It is not a science but it is an art.
• Personal factors play an important role in the
reconnaissance survey.
• The successful conduct entirely depends on the
personal qualities of the engineer such as his
training and experience, his capacity of
observation and interpretation
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RAILWAY SURVEYS
Information gathered in reconnaissance survey:
A reconnaissance survey can broadly be divided
into two categories:
1. Traffic reconnaissance survey
2. Engineering reconnaissance survey
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RAILWAY SURVEYS
Traffic reconnaissance survey:
This consists of collection of the information
regarding the following:
a) The general character of the country and the
extent of cultivation;
b) Information regarding the local industries and
religious festivals;
c) The general condition as regards prosperity of
people in the locality and density of population
and its distribution;
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RAILWAY SURVEYS
d) The probable amount of traffic to be served by
new railway line;
e) The probable new traffic lines to be opened up
to join large centres of trade;
f) Nature and volume of exports and their
destination;
g) The amount of imports and centres of their
distribution;
h) Possibilities of development of industries as a
result of the new railway line;
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RAILWAY SURVEYS
i) Visiting all trade centres and consultation with
prominent citizens and local authorities
regarding the most suitable route for the
railway;
j) Standard of construction required for carrying
the probable traffic;
k) Study of the existing means of transport
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RAILWAY SURVEYS
Engineering reconnaissance survey:
This consists of collection of information
regarding the following:
a) Physical features of the country;
b) The surface formation of the ground;
c) Nature of soil and its classification;
d) Streams and rivers of the immediate
vicinity, especially those which are likely to cross
the proposed railway line;
e) Positions of hills and lakes; 15

RAILWAY SURVEYS
f) Samples of water from wells, rivers, etc. so as to
ascertain weather the water is suitable for use in
locomotive or not;
g) Availability of materials and labour for use
during construction.
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RAILWAY SURVEYS
Factors to be kept in view during
reconnaissance survey:
Following factors should be kept in view;
otherwise, the results are likely to be misguiding:
1) Area: A reconnaissance survey should be carried
out for the whole area of the country. It should
never be carried out for a line only.
2) Existing roads: The survey should not be guided
by the existing roads because the ground which
is favourable for construction of roads may not
be useful for the construction of a railway line.
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RAILWAY SURVEYS
3) Starting of route: The engineer should not reject
a particular route simply because it starts badly
i.e. with curvature or with sudden rise or fall, etc.
He must ascertain that the route continues badly
for a long distance.
4) Assumptions: The assumptions should be made
very carefully as sometimes they are likely to be
proved wrong, when tested by actual
observations.
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RAILWAY SURVEYS
5) Survey route:
6) Ocular illusions: Ocular illusions should be
prevented. Most common are:
 estimating wrong length of line or offset;
 Estimating wrong curvature;
 Overlaps of hills which may appear as a continuous
ridge from a distance.
7) Revenue: The probable revenue from the
proposed railway line may be worked out.
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RAILWAY SURVEYS
2) Preliminary Survey:
Object of preliminary survey:
 To conduct the survey work along the alternative
routes found out by reconnaissance survey and;
 to determine with greater accuracy the cost of
the railway line along these alternative routes.
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RAILWAY SURVEYS
Importance of preliminary survey:
a. It decides the final route and recommends
only one particular route in preference to
other alternative routes;
b. Thus, should be carried out with great
precision as on it depends the alignment of
the final route.
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RAILWAY SURVEYS
3. Location Survey:
Object of location survey:
 To carry out the detailed survey along the route
which has been found and fixed as the most
economical route from the data of the
preliminary survey.
 It establishes the centre-line of the actual track
to be laid.
 As soon as the location survey is completed, the
construction work is started.
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RAILWAY SURVEYS
Work of location survey: It is carried out in two
stages:
1. Paper location
2. Field location
1. Paper location:
 The final route selected is put up on paper and
details such as gradient, curves, contours, etc.
are worked out;
 All the working drawings are prepared, even of
minor structures such as signal cabins.
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RAILWAY SURVEYS
 After the paper location is over, the field work is started
and the centre-line of the track is fixed.
2. Field location:
 The field location transfers paper location on the
ground;
 It gives all the requirements of the construction
engineer such as bench-
marks, levels, measurements, etc.;
 The centre-line pegs are driven at every 300 metres
along the centre-line of the track;
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RAILWAY SURVEYS
Every change of direction, the beginning and end
of the curve and also the intersecting points are
clearly marked;
In addition to the fixing up of the centre-line of
the track, the centre-lines of bridges, culverts,
tunnels, station buildings, signal cabins, etc.
should also be fixed.
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Surveys & alignment of Railway Engineering

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Surveys & alignment of Railway Engineering