EASWARI ENGINEERING COLLEGE, RAMAPURAM methods. 12. Name the different methods of setting out a...

III Semester Civil CE2204 SURVEYING-I by M.Dinagar AP / Civil

MAHALAKSHMI

ENGINEERING COLLEGE

TIRUCHIRAPALLI - 621213.

QUESTION BANK

DEPARTMENT: CIVIL SEMESTER: III

SUBJECT CODE / Name: CE 2204 / Surveying -I

Unit 5 – ENGINEERING SURVEYS

PART – A (2 marks)

1. What are the components of a single curve? (AUC Apr/May 2011)

Back Tangent, Forward Tangent, Point of Intersection, Point of Curve, Point of Tangency,

Intersection Angle, Deflection Angle, Deflection Angle to any Point, Tangent Distance, External

Distance, Length of the Curve, Long Chord, Mid Ordinate, Normal Chord.

2. What are the objectives of route surveys? (AUC Apr/May 2011)

Route survey is applied to the surveys required to establish the horizontal and vertical

alignments for transportation facilities. The transportation facilities may be highway, railway,

aqueducts, canals, water pipelines, oil and gas, cable ways, sewage disposal, power telephone

and transmission lines.

3. On what basis is a vertical curve designed? Name the preferable type of vertical curve.

(AUC Apr/May 2010)

Summit Curves

Sag or Valley Curves

4. Draw a neat sketch of a compound curve and mark the salient features of it.

(AUC Apr/May 2010)


5. What are transition curves? (AUC Nov/Dec 2011)

A transition or easement curve is a curve of a varying radius introduced between a straight

and a circular curve, or between branches of a compound curve or reverse curve.

6. Draw a neat sketch showing a simple circular curve and show essential notations.

(AUC Nov/Dec 2011)

7. Define point of curve. (AUC Nov/Dec 2010)

Point of curve is the beginning of the curve (T1) where the alignment changes from a

tangent to a curve.

8. What is mean by point of tangency? (AUC Nov/Dec 2010)

Point of tangency is the end of the curve (T2) where the alignment changes from a curve to

tangent.

9. What is tangent length in a simple curve? (AUC Nov/Dec 2009)

Tangent length is the distance between the beginning of the curve (T1) and point of

intersection (PI) of two tangents (also the distance from PI to PT).

10. What is mid-ordinate in a simple curve? (AUC Nov/Dec 2009)

Mid ordinate is the ordinate from the mid-point of the long chord to the mid-point of the curve.

It is also called the versine of the curve.

11. What are control stations in setting out works? State how they should be.

(AUC May/June 2012)

Primary control stations and

Secondary control stations.

Primary control stations may be the triangulation stations.

Secondary control stations are referred to these primary control stations. It may be found by

traversing methods.

12. Name the different methods of setting out a simple curve. (AUC May/June 2012)

i) Linear methods

Offsets from the long chord

Successive bisection of chord

Offsets from the tangents


Offsets from the chords produced

ii) Angular Methods

Tape and theodolite method

Two theodolite method

Tachometric method

Total station Method

13. What do you mean by temporary adjustment of theodolite? (AUC May/June 2013)

Temporary adjustments are those which are required to be undertaken at every new set

up of the instrument at each survey station before starting to make any observation.

Setting

Levelling and

Parallax removal

14. Write about well conditioned triangles. (AUC May/June 2013)

A well conditioned triangle is one in which no included angle is less than 30o or greater

than 120o. An equilateral triangle is the best well conditioned triangle.

15. What is meant by stopping sight distance? (AUC Nov/Dec 2012)

Stopping sight distance is defined as the distance needed for drivers to see an object on

the roadway ahead and bring their vehicles to safe stop before colliding with the object.

16. List out any four special instruments used in mine surveying. (AUC Nov/Dec 2012)

Theodolite tachometers,

Mining theodolite

Tachymeters with stereoscopic range finders

Angle gauges

PART – B (16 marks)

1. Explain the procedure for setting out a circular curve by Rankine’s method.

(AUC May/June 2013) (AUC Apr/May 2011)

RANKINE’S METHOD:

The method is known as Rankine’s method of tangential angle or the deflection angle

method. The method is accurate and is used in railways and highways. Let T1ab be a part of a

circular curve with T1, the initial tangent point. Thus, T1a is the first sub-chord which is normally

less than one chain length (Figure). From the property of a circle

C1 = 2δ1 R

δ1 = R

C

2

1 radian

= R

C

2

1

0180 degree


= R

C

2

1 180 60oo X minutes

δ1 = 1718.87 R

C1 minutes

Therefore to locate the point a with the help of a theodolite and tape, the instrument is set

at T1 and the line of sight is put at an angle of δ1 = Δ1 as computed above. Then with the help

of a tape and ranging rod, the tape is put along the line of sight and distance C1 is then

measured to locate point a along the line of sight.

Similarly,

δ2 = 1718.87 R

C 2 minutes

Since the theodolite remains at T1, b is sighted from T1 by measuring δ1+δ2=Δ2 from

the tangent line. The point b is located with the help of a tape and ranging rod. The tape with the

ranging rod is so adjusted that the tape measures ab = C2 and the ranging rod lies along the

line of sight T1b.

In practice, C1 is the first sub-chord and Cn the last sub-chord. C2 = C3 = ...Cn-1 are full chain

lengths. As a check the deflection angle n for the last point T2 is equal to Δ/2 where

Δ is the angle of intersection.


2. Distinguish between a compound curve and a reverse curve. (AUC Apr/May 2011)

COMPOUND CURVE:

Compound curves are used for those applications where design constraint like topography

or cost of land prevents the use of simple curve. They are generally used in the design of

interchange loops and ramps. Smooth driving characteristics require that the larger radius be more

than 1.3 times larger than the smaller one. Solutions to compound curve problems vary, as several

possibilities exist as to which of the data are known in any one given problem. All problems can be

solved by use of sine law or cosine law or by the omitted measurement traverse techniques.

Elements of a Compound Curve:

Figure shows a two centred compound curve T1T3T2, having two circular arcs T1T3 and T3T2

meeting at a common point T3 known as the point of compound curvature (PCC). T1 is the point of

commencement (PC) and T2 is the point of tangency (PT). The other elements such as tangent

lengths, length of the curve, etc. for the smaller and larger curves, will be designated by the

subscripts S and L, respectively.

Thus, RS, RL = the radii of the curves,

ΔS, ΔL= the deflection angles,

lS , lL= the length of the curves, and

tS, tL= the tangent lengths.

TS, TL = the tangent lengths on the sides of smaller and larger curves, respectively,

for the Compound curve.


Tangent Lengths for the Circular Curves


REVERSE CURVE:

Reverse curves are seldom used in highway or railway alignment. The instantaneous

change in direction occurring at the point of reverse curvature or point of reversed curve(PRC)

would cause discomfort and safety problems for all but the slowest speed. Additionally, since the

change in curvature is instantaneous, there is no room to provide super-elevation transition from

cross-slope right to cross-slope left. However, reverse curves can be used to advantage where the

instantaneous change in direction poses no threat to safety or comfort. Reverse curves are

unavoidable in hilly roads where a loop of a curve in a valley generally immediately followed by

another loop round the shoulder of the ridge. Cities where roads turn in different directions in

succession or when roads approach a flyover, the reverse curves are frequently used.

Elements of a Reverse Curve:

As with compound curves, reverse curves have six independent parameters (R1, T1, Δ1,

R2, Δ2,T2); the solution technique depends on which parameters are unknown. Figure shows a

reverse curve between two straights AT1 and T2B having a total deviation of Δ at I. Where as

O1 and O2 be the centres of the two circular curves of radii R1 and R2, respectively, and Δ1 and

Δ2 be the deflection angles or the central angles for the respective curves.

3. Discuss the various surveying to be carried out for an engineering project.

(AUC Nov/Dec 2011)

i) Reconnaissance

ii) Preliminary Survey

iii) Final Location Surveys

i) Reconnaissance:

Reconnaissance starts with a field inspection by walking, riding on ponies (in hills) or

driving in jeeps. All information of value, either in design, construction, maintenance or

operation of the facility should be collected, which may include, inter alia, the following:

Details of route vis-à-vis topography of the area – plain, rolling or hilly.

Requirements of cross-drainage works – type, number and length.

Gradients that are feasible, specifying the extent of deviations needed.


Curves and hair-pin bends etc.

Existing means of communication – mule tracks, jeep tracks, cart tracks etc.

Constraints on account of built-up areas, monuments and other structures.

Road length passing through different terrains, areas subjected to inundation and

flooding, areas of poor drainage conditions, unstable slopes etc.

Climatic conditions – temperature, rainfall, water table and its fluctuations etc.

Facilities/ Resources available e.g., availability of local labour, contractors etc.

Access points indicating possibility of induction of equipment.

Period required for construction.

Villages, hamlets and market centres connected.

Economic factors – population served, agricultural and economic potential of the area.

Crossing with railway lines and other existing roads.

Positions of ancient monuments, burial grounds, cremation grounds, religious structures,

hospitals and schools etc.

Ecology or environmental factors.

ii) Preliminary Survey:

Preliminary survey is a relatively large-scale investigation of the alternative(s) thrown up

as a result of the Reconnaissance survey. The survey consists in establishing a base-line

traverse. For hill roads, it may be necessary to cut a trace of 1.0-1.2m wide to enable the

traverse survey to be carried out. A theodolite or compass is used for traversing and levels are

taken along the traverse and across it. The distances are measured continuously along the

traverse line with a metallic tape. Bench marks should be established at intervals of 250 m to

500 m and the level should be connected to the GTS datum.

Physical features such as buildings, trees, burial grounds, monuments, railway lines,

canals, drainage channels etc should be located by means of offsets. The width to be covered

for such detailing should be about the land width proposed to be acquired. Information on

highest flood level, rainfall intensity, catchment areas of streams etc should be collected. The

survey enables the preparation of a map including the plan and longitudinal section. The scales

generally recommended are:

Built-up areas and hilly terrain: 1:1000 for horizontal scale and 1:100 for vertical scale Plain and rolling terrain:

1:2500 for horizontal scale and 1:250 for vertical scale

It is desirable to mark the contour intervals at an interval of 1 to 3m. The map should show all

the physical features surveyed.

At the end of the preliminary survey, it is useful to involve the local community in the

process of deciding on the alignment since several social issues are also involved. As such the

JE/AE must conduct a Transect walk along the alignment /trace together with the Panchayat

Pradhan / Ward Panchayat, local revenue and forest officials.

iii) Final Location Surveys:

After the preliminary survey and Transect Walk, the final alignment is to be determined.

The purpose of the final location survey is to fix the centre line of the selected alignment in the

field and to collect additional data for the preparation of the drawings. The centre line is translated

on the ground by continuous transverse survey and pegging the same. The points of transit (POT)

should be clearly marked on the ground by a nail in the existing pavement or a hub in concrete on


a new alignment.

Suitable references (at least two) should be marked permanently on the ground. The

horizontal intersection points (HIP) should be similarly marked on the ground and referenced. All

curve points viz beginning of transition (BS), beginning of circular curve (BC), end of circular curve

(EC) and end of transition (ES) should be marked and referenced. The centre line should be

staked at 50 m intervals in plain terrain and 20m intervals in hilly terrain. Bench marks should be

left permanently at 250 m intervals. The cross-sections taken during the preliminary survey should

be supplemented by additional cross-sections at the curve points. Generally, cross- sections

should be available at intervals of 50-100m in plain terrain, 50-75m in rolling and 20 m in hilly

terrain. Survey can be accomplished these days by a Total Station, with assistance from GPS

(Geographic Positioning System) which determines the location of survey points by satellite. But in

the absence of these instruments, an ordinary theodolite, levelling instrument and compass would

be acceptable.

4. Two straight lines having an intersection angle of 25o 12’ are to be connected by a circular

curve of radius 500 m. if the chainage of the intersection point is 1000 m. calculate the data

for setting out the curve by

i) Deflection distances method and

ii) Tangential angles method. Take the normal chord as 20 m. (AUC Nov/Dec 2011)

Solution:

i) Deflection distances method:

Angle of intersection is below 90O. So take Deflection angle, ∆ = 25O 12’

Degree of curve, D = R

1719 =

500

1719= 3O 26’ 16”

Tangent length, BT1 = R tan 2

= 500 x tan 2

'12250

= 111.76 m

Chainage at intersection point = 1000 m

Chainage at tangent point, T1 = 1000 – 111.76 = 888.24 m

Length of the curve = 0180

R =

0

0

180

'1225500XX= 219.91 m

Chainage at tangent point, T2 = T1 + length of curve

= 888.24 + 219.91 = 1108.15 m

Length of long chord, L = 2R sin 2

= 2 x 500 x sin 2

'12250

= 218.14 m

Half of long chord = 07.1092

14.218m

Mid ordinate, Oo = R -

2

2

2

LR = 500 -

2

2

2

14.218500 = 12.04 m


Ordinates at 20 m intervals are considered and calculated from

Ox = )(22

oORxR

O20 = 63.11)04.12500(20500 22m

O40 = 44.10)04.12500(40500 22m

O60 = 42.8)04.12500(60500 22m

O80 = 59.5)04.12500(80500 22m

O100 = 94.1)04.12500(100500 22m

O109.07 = 0)04.12500(07.109500 22

Ordinates for the right half are similar to those for the left half.

ii) Tangential angle method:

Angle of intersection is below 90O. So take Deflection angle, ∆ = 25O 12’


1719 =

500

1719= 3O 26’ 16”


= 500 x tan 2

'12250

= 111.76 m




R =

0

0

180

'1225500XX= 219.91 m


= 888.24 + 219.91 = 1108.15 m

Hence difference between two tangents = T2 - T1 = 1108.15 – 888.24 = 219.91 m

Length of initial sub-chord = 900 – 888.24 = 11.76 m

Number of full 20 m chord = 10

Chainage covered = 900 + (10 x 20) = 1100 m


Length of final sub chord = 1108.15 – 1100 = 8.15 m

Deflection angle of initial sub chord,

"25400500

76.111719 '0

1

X

Deflection angle for full chord of 20 m length,

"36531500

201719 '0

72

Xto

Deflection angle of final sub chord,

"1280500

15.81719 '0

8

X

Δn = "25400 '0+ (10 x "36531 '0

) + "1280 '0= 20O 4’ 26”

= 20O 4’ 26” = 20O

Hence the calculated deflection angles are correct.

Other data required to set out the curve are

i) Apex distance = R m34.12)12

'1225(sec500)1

2(sec

0

ii) Versed sine of the curve = R m04.12)2

'1225cos1(500)

2cos1(

0

Deflection angle details:

Point Chainage Chord length

Deflection angle for

chord

Total deflection

angle

Angle to be set

Remarks

T1 888.24 Starting

point of the curve

F1 900 11.76 "25400 '0 "25400 '0

"20400 '0

Least count of verniers = 20”

F2 920 20 "36531 '0 "01342 '0

"00342 '0

F3 940 20 "36531 '0 "37274 '0

"40274 '0

F4 960 20 "36531 '0 "13216 '0

"20216 '0

F5 980 20 "36531 '0 "49148 '0

"40148 '0

F6 1000 20 "36531 '0 "250810 '0

"200810 '0

F7 1020 20 "36531 '0 "010212 '0

"000212 '0

F8 1040 20 "36531 '0 "375513 '0

"405513 '0

F9 1060 20 "36531 '0 "134915 '0

"204915 '0

F10 1080 20 "36531 '0 "494217 '0

"404217 '0

F11 1100 20 "36531 '0 "253619 '0

"203619 '0

T2 1108.15 8.15 "1280 '0 "260420 '0

020 Finishing

point of the curve


5. Two straight AB and BC intersect at a chainage of 4242 m and the angle of intersection is

140o. It is required to set out a 5o simple circular curve to connect the straights. Calculate all

the data necessary to set out the curve by the method of offsets from the chord

produced with an interval of 30 m. (AUC Apr/May 2010)

Solution:

Angle of intersection = 140o

Deflection angle, ∆ = 180o – 140o = 40o

Radius of curve, R = D

1719 =

5

1719= 343.8 m


= 343.8 x tan 2

400

= 125.13 m




R =

0

0

180

408.343 XX= 240.02 m


= 4116.87 + 240.02 = 4356.89 m

Length of long chord, L = 2R sin 2

= 2 x 343.8 x sin 2

400

= 235.17 m

Half of long chord = 58.1172

17.235m

Mid ordinate, Oo = R -

2

2

2

LR = 343.8 -

2

2

2

17.2358.343 = 20.73 m

Ordinates at 30 m intervals are considered and calculated from

Ox = )(22

oORxR

O30 = 42.19)73.208.343(308.343 22m


O60 = 45.15)73.208.343(608.343 22m

O90 = 74.8)73.208.343(908.343 22m

O117.58 = 0)73.208.343(58.1178.343 22

Ordinates for the right half are similar to those for the left half.

6. Explain the methods of transferring reduced levels from surface to underground in a tunnel

setting out work. (AUC Apr/May 2010)

i) Setting out central line of tunnel

ii) Setting out inside tunnels

iii) Transferring of alignment through shafts

i) Setting out central line of tunnel:

The centre-line of tunnels are fixed on the surface along with shaft locations.

Generally the surface control points of the tunnels are not visible from each other. However, by the

method of reciprocal ranging points on the summit can be established which can be joined to get

the central line. The measurements should be made accurately. Linear measurements are made

using invar substance bars with an accuracy of 1 in 10000. Angular measurements are made using

1 second theodolite with an accuracy 0f 15 N where N is the number of angles. In case of

tunnels in hilly regions it is neither feasible to align the tunnel ends by direct ranging or reciprocal

ranging. In such cases precise triangulation has to be used.

The figure shows a scheme of triangulation network with QR as base line for a tunnel

project. Here all the angles are measured accurately by one second theodolite. Usual corrections

for length, temperature, terrain, sag and reduction of levels with respect to sea level are all

followed in arriving at the values of the coordinates. The traverse is adjusted for angles and

coordinates. The proposed tunnel axis is shown in figure as HR.

ii) Setting out Inside Tunnels:

After the coordinates of portals and shafts are finalized, setting out is started. Centre line of

tunnel is done as shown in figure from various portals and shafts.

Back sighting on the pillar, aligned and constructed as far as practicable on the extended

centre line such as pillar C and then by transiting. Reference points are constructed on the roof of

tunnels or slightly below the invert for every 300 m.

iii) Transferring of alignment through shafts:

Transfer of alignment is done through shafts by adopting any one of the following methods:

i) By hanging two or more plumb lines down the shaft.

ii) By lighting directly from edge of shaft where shaft diameter to depth ratio is high.

Co-planning is done by hanging two or more plumb lines down the shaft and determining

the bearing of the plumb planes so formed which are connected to the surface. The plumb lines

should be well apart as for as possible. The plumb lines are of special type. The line shall be of

fine steel wire and carrying a symmetrical weight of 35 kg or more. The wire should be well

stretched to keep it tight. In order to keep the wires vertical, the bob should be contained in a

canister with a hood. This arrangement will shield the bob and will reduce oscillations set up by air

currents or by water dropping down the shafts. The canister can be filled with water or oil to reduce

the vibrations. The bearing of the plumb plane underground is assumed same as at the surface.

This forms the starting direction for the underground survey work.


The following procedure is adopted for transferring the centerline from top.

A theodolite is set up on top of the hill at a suitable position to maintain the centre line of the

shaft.

The RLs of both the ends of the shaft are determined by a level. Knowing the bottom RLs of

the ends the depth of the shaft is found.

Excavation of the shaft is started and verticality is maintained with the help of the plumb-bob

which is suspended from wires from top through pulleys.

The excavation is continued until the required bottom level is reached. The depth of the shaft

is measured by measuring the length of suspended wire.

The centre line inside the tunnel is maintained by a precise theodolite. This type of

theodolites are provided with an artificial illumination system to enable work at night and in

the darkness of the tunnel.

It should be properly taken care to see that the centre line is maintained from both ends and

one transferred from top coincide.

7. List out the linear methods of setting out a circular arc. Explain any one method.

(AUC Apr/May 2010)

Linear methods of setting out a circular arc:




Offsets from the chords produced i) Offsets from the long chord:

The method is suitable for setting out circular curves of small radius, such as those at road

intersections in a city or in boundary walls. In Figure 5, the offset Oxa to the point a on the curve is

the perpendicular distance of point a from the long chord T1T2, at a distance xa from D along the

long chord. Considering the origin at D, Oxa is the y-coordinate of point a.


The long chord is divided into equal parts of suitable length. The offset Oxa corresponding to

the distances xa from D are calculated for different points on the long chord. These offsets are

measured perpendicular to the long chord with the help of an optical square and points are

located. Joining these points will produce the desired curve. The points on the right side of CD are

set out by symmetry.


8. Two tangents intersect at chainage 1250 m and the angle of intersection is 150o. Calculate

all data necessary for setting out a curve of radius 250 m by the deflection angle method.

The peg intervals may be taken as 20 m. prepare a setting out table when the least count of

the vernier is 20”. Calculate the data for the field checking.

(AUC May/June 2012) (AUC Nov/Dec 2012)

Angle of intersection = 150o

Deflection angle, ∆ = 180o – 150o = 30o


1719 =

250

1719= 6O 52’


= 250 x tan 2

300

= 66.98 m




R =

0

0

180

30250XX= 130.89 m


= 1183.02 + 130.89 = 1313.91 m

Hence difference between two tangents = T2 - T1 = 1313.91 – 1183.02 = 130.89 m

Length of initial sub-chord = 1190 – 1183.02 = 6.98 m

Number of full 20 m chord = 6

Chainage covered = 1190 + (6 x 20) = 1310 m

Length of final sub chord = 1313.91 – 1310 = 3.91 m

Deflection angle of initial sub chord,

"59470250

98.61719 '0

1

X

Deflection angle for full chord of 20 m length,

"12482250

201719 '0

72

Xto

Deflection angle of final sub chord,

"53260250

91.31719 '0

8

X

Δn = "59470 '0+ (6 x "12482 '0

) + "53260 '0= 18O 04’ 04”

= 18O 04’ 04”= 18O

Hence the calculated deflection angles are correct.

Other data required to set out the curve are

i) Apex distance = R m82.8)12

30(sec250)1

2(sec

0

ii) Versed sine of the curve = R m52.8)2

30cos1(250)

2cos1(

0


Deflection angle details:

Point Chainage Chord length

Deflection angle for

chord

Total deflection

angle

Angle to be set

Remarks

T1 1183.02

Starting point of the curve

F1 1190 6.98 0O 47’ 59” 0O 47’ 59” 0O 48’ 00” Least count of verniers = 20”

F2 1210 20 2O 48’ 12” 3O 36’ 11” 3O 36’ 20”

F3 1230 20 2O 48’ 12” 6O 24’ 23” 6O 24’ 20”

F4 1250 20 2O 48’ 12” 9O 12’ 35” 9O 12’ 40”

F5 1270 20 2O 48’ 12” 12O 00’ 47” 12O 00’ 40”

F6 1290 20 2O 48’ 12” 14O 48’ 59” 14O 49’ 00”

F7 1310 20 2O 48’ 12” 17O 37’ 11” 17O 37’ 20”

T2 1313.91 3.91 0O 26’ 53” 18O 04’ 04” 18O 00’ 00” Finishing point of the curve

9. Explain the setting out of a simple curve by two theodolite method. (AUC Nov/Dec 2009)

Two theodolite method:

This method is employed for setting out a curve by making angular measurements.

Therefore, the instrument required is only a theodolite. The method is quite accurate. It is specially

preferred when the ground is rough, and accurate chaining is not possible. Since, in this method

each point is fixed independently the error in setting out is not carried forward.

The method is based on the property of a circle that the angle between the tangent and the

chord is equal to the angle which that chord subtends in the opposite segment. Thus, for the

chords in Figure 12.


IT1a T1T2 a 1

IT1b T1T2 b

The method requires setting up two theodolites, one at T1 and the other at T2. The

theodolite at T1 should read zero for the point I and the theodolite at T2 should read zero for the

point T1. Set the first deflection angle δ1 on both theodolites. Thus, their telescopes are in the

direction T1a and T2a, respectively. Now the attendant is asked to move with a ranging rod in the

line of sight of one of the theodolites. The observer of the other theodolite finds the point where the

ranging rod is intersected by the vertical hair of his theodolite. This point is the required location on

the curve. The second point is located by setting the second deflection angle δ2 on the two

theodolites and the location of the point on curve is determined by the procedure given above. The

process is continued for locating the other points on the curve till all the points are located on the

ground.

10. Describe the different surveys to be carried out for the highway projects.

(AUC Nov/Dec 2012) (AUC May/June 2012)

i) Reconnaissance

ii) Preliminary Survey

iii) Location Survey

i) Reconnaissance:

During the reconnaissance survey the following factors have to be taken into consideration.

Obstructions along the route.

Gradients and length of curves.

Cross drainage works.

Soil type along the route.

Sources of construction materials and

Type of terrain.

ii) Preliminary Survey:

The preliminary survey in a highway project is done with the main objectives

Various alternate arrangements

Estimate the quantity of earth work materials and other construction aspects

Compare different proposals.

The following surveys are constructed

Primary transverse

Topographical surveys

Levelling work

Hydrological data

Soil surveys.

iii) Location Survey:

The final alignment decided after the preliminary survey is to be first located on the field by

establishing the centre line. Next the detailed survey should be carried out.

The detailed survey involves:

Fixing temporary bench marks along the route for every 300 m.

The cross sectional details are taken for 30 m on either side of the central line.

All details of cross drainage works are taken.


Topographical details are taken.

Detailed soil survey is carried out.

11. Explain the concepts of route survey for highways, railways and waterways.

(AUC May/June 2013)

Route surveys are performed with two objects:

To determine the best general route between the terminals and

To fix the alignment grades and other details along the selected route.

The route survey has to be done by

i) Reconnaissance survey

ii) Preliminary surveys

iii) Location survey

iv) Construction survey.

i) Reconnaissance survey:

Reconnaissance survey of a route survey comprises of a rapid and thorough examination

of a strip of an area between the terminal points. During the survey several possible routes worth

trying under detailed survey are explored. The reconnaissance work of a route survey should be

given to a very experienced group of engineers so as to save time and unnecessary expenses.

During the first step of reconnaissance is to collect all details from the topographic maps available

from survey of India. If data available is inadequate, a photogrammetric survey between the

proposed points may be done to get the adequate data.

Following informations have to be collected during reconnaissance for a route surveying:

Based on the topography and other data, the terrain of the route between the two points

may be classified as level, rolling or mountainous.

The natural gradient has to be noted to fit in the required alignment of proposed project.

Cross drainages, high water elevations, flood conditions, bank conditions, width of stream,

etc, so as to plan proper cross drainage works such as culverts, bridges, etc.

Information about other route crossings such as highways, railroads, pipelines, etc, have to

be noted down.

Geological and soil conditions to have a stable foundation for bridges, better subgrade for

road and railways, etc.

Availability of construction materials their quality and quantity all along the route.

Availability of labour along the route for the construction work.

Value of land along the alternate routes tobe acquired.

ii) Preliminary survey:

It is a detailed survey which is taken along the decided location of the route. During the

preliminary survey an accurate topographic map of the strip of the area along the selected route

are done so as to get a fairly close estimate of the project.

They are performed by three parties under the general supervision of the location engineer:

a) Transit party, b) level party and c) topography or cross section party.

a) Transit party:

It consisting of four to seven persons conducts open traversing. During the traverse the

azimuths of the first and the last line of traverse are taken. The party also records topographical

details, property lines, drainage structures, pipe lines, roads and railways, etc.


b) Level party:

It consisting of three persons undertakes two important jobs

Establishes bench marks along the selected route at regular and convenient places.

Conducts a longitudinal section of the traverse lines.

c) Topography:

It consisting of three to four persons conducts a detailed topographic survey. Also cross

sections details at every 30 m intervals perpendiculars to traverse line on either side of it are taken.

iii) Location survey:

Transferring of paper location to the ground under the field condition is called the location

survey. The main purpose of location survey is to make minor improvements on the line keeping in

view the terrain reality and to fix the final grades. The final alignment and location made in the

ground is called the field location.

After this profile levels are run over the centre line, bench marks are established. All

relevant surveys keeping the central line are performed so as to identify cross drainage works,

cross sections to compute earth work, horizontal and vertical curve locations etc are done.

iv) Construction survey:

The purpose of construction survey is to re-establish points, line and grades on the ground

at the time of construction.

Remarking the central line based on the plan and reestablishing certain points on the

central line.

Checking RLs of bench marks and running centre line levels over the retraced line.

Computing RLs to find the elevations of all stations, at points where cross sections are to

be taken for earth work volume computations.

Setting up slope stakes and grade stakes.

Setting stakes for the complete layout of culverts and bridges.

Setting out horizontal and vertical curves.

Making minor adjustments with respect to drainage structure, lines or grades, etc.

To submit a program report.

To submit the final estimate.

12. Explain some mine survey instruments. (AUC May/June 2013)

The mine transit is usually of a smaller size than the ordinary instrument. Special provisions

are made for steep or vertical sights. Due to very steep sights the horizontal circle of the ordinary

transit will obstruct the pointings of the telescope of an ordinary transit. To overcome this difficulty

an auxiliary telescope is attached either at one end of the horizontal axis or above the main

telescope and at a distance more than one half of the diameter of the horizontal plate. The two

mountings are arranged in such a way that the auxiliary telescope is interchangeable between the

top and side positions. In each position a counterpoise is attached to keep the telescopes in

balance. In either position, the line of sight of the auxiliary telescope is parallel to that of the main

telescope. For steep sights upward, a prismatic eye piece is attached to the main telescope. The

instrument is generally mounted on an extension leg tripod. For ease in reading the vertical angles

by the transitman, the vertical circle is sometimes graduated on the edge instead of the side. The

centre point of the transit is definitely marked on the top of the telescope.

In places where a tripod cannot be used, suspension type mine transit is employed. The

instrument is supported on a bracket being screwed horizontally into adjacent mine timbers. The


horizontal circles along with its verniers are on the top of the telescope and the vertical circle and

hence the use of auxiliary telescope is obtained. The horizontal circle is 9cm in diameter, the

vertical circle 7cm in diameter and the whole instrument weighs only 5.5 lb. if required, the

instrument can also be supported on tripod and for this purpose of the vertical circle and the

telescope are provided with sensitive reversion spirit levels.

13. Write short notes on sight distances and Shafts. (AUC Apr/May 2011)

Sight Distance:

The minimum sight distance available on a highway should be sufficient length to stop a

vehicle without collision. The absolute minimum sight distance is therefore equal to the stopping

sight distance, which is also sometimes called as non-passing sight distance.

The sight distance available on a road to a driver at any instance depends on

i) Features of the road ahead

ii) Height of the driver’s eye above the road surface

iii) Height of the object above the road surface.

Design speed Stopping sight distance

30 mph (48 km/hr) 200 ft (61m)

40 mph (64 km/hr) 275 ft (84m)

50 mph (80 km/hr) 350 ft (107m)

60 mph (96 km/hr) 475 ft (145m)

70 mph (113 km/hr) 600 ft (184m)

The expressions for sight distance (S) on vertical curves will now be derived for two cases:

i) when the sight distance S is entirely on the curve (S < L) and

ii) when the sight distance overlaps the curve and extends on to the tangent (S > L)

let h1 = height of drivers eye above the roadway.

h2 = height of object or hazard on the travelled road.

Case 1: S < L:

L = ftggS

1460

)( 21

2

L = metresggS

297

)( 21

2

Case 2: S > L:

S = 2

2

1

11002

1

g

h

g

hL

Where,

XAhh

hg

21

1

1

XAhh

hg

21

2

2


S = A

hhL

2

21 )(100

2

1

L = 2S A

hh 2

21 )(200

Shafts:

Shafts are vertical holes excavated thought the soil or rock or other materials for different

purposes. Shafts are also drives for installation of drilled piers. Shafts are also made for transfer of

centre line inside tunnel by suspending plumb bobs.

After fixed the centre line on the surface the setting out of underground line can be done

by transferring surface line down the shafts wherever they are vertical. A theodolite is then set over

one of these points on the surface and the line of sight is directed towards the other point. A

theodolite is then transferred underground and set exactly in line with the two suspended wires.

The line joining these wires and hence the line of sight of that theodolite gives the direction of the

centre line of the tunnel underground. The line is then set with the instrument on nails driven into

convenient byates of timber from which plumb bobs or lamps may be suspended. The exact center

line is marked bt steel punch or a file mark. The plumb wires are fine wire stretched tight by

attaching weight at their lower ends. The wires must be so suspended that they do not touch the

sides of the shaft. to avoid this, there should be some arrangement for removing them and again

placing them if required. The arrangement with the help of which the wire can be lifted up or

lowered down.

14. List out the linear methods of setting out a circular arc.

Linear methods of setting out a circular arc:




Offsets from the chords produced

Successive bisection of chord:

The method being approximate is suitable for small curves. It involves the location of points

on the curve by bisecting the chords and erecting perpendiculars at the midpoint of the chords.

In Figure 6, T1T2 is the long chord and D is its midpoint. C is the point of intersection of the

perpendicular line at D, with the curve. DC is the mid-ordinate, which is equal to

At D, a perpendicular offset equal to M is erected and the position C is located. Now

consider the chords T1C and T2C, locate their midpoints d1 and d2 respectively. Erect two

perpendiculars at d1 and d2 and measure the offsets equal to d1c1 and d2c2, respectively. The

offsets d1c1 and d2c2 are computed from the following formula:

Now, by the successive bisection of these chords, more points can be located in a similar manner.


After locating T1 and T2, the midpoint D of T1T2 is obtained, by measuring T1T2. The

perpendicular offset DC is set out at D with an optical square and point C is located. Measure T1C,

and T2C, and locate their midpoints d1 and d2. The perpendicular offsets d1c1 and d2c2 are set

out at d1 and d2, and the points c1 and c2 are established on the curve. The process is continued

till sufficient numbers of points on the curve are fixed.

Offsets from the Tangents:

This method is used when the deflection angle and the radius of curvature both are

comparatively small. In this method, the curve is set out by measuring offsets from the tangent.

The offsets from the tangent can be either perpendicular or radial to the tangent.

a) Perpendicular Offsets Method:

Let the point a be on the curve and the perpendicular offset from the tangent T1 to it at P be

Oxa . Let the distance of P from T1 be xa . Draw a line Qa perpendicular to T1O, intersecting OT1

at Q.


Before setting out a curve, a table of offsets for different values of x (e.g., 10 m, 20 m, 30 m,

etc.) is made. Then from T1 the distances x1 , x2 , x3 etc., are measured along the tangent and

the corresponding offsets are measured on the perpendiculars to the tangent with the help of an

optical square. Since the offsets of points equidistant from T1 and T2, are equal, the same table is

used for offsets from both the tangents.

b) Radial Offsets Method:

Let the radial offset to the point a on the curve be Oxa from the point P at a distance of xa

from T1.


A table of offsets for different values of x is made. Then from T1 the distances x1 , x2 , x3

etc., are measured along the tangent and the corresponding radial offsets are measured such that

point a etc. on the curve lie on the line joining the point and the centre of the curve. It should be

noted that if the curve is set out by the approximate expression, the points on the curve will lie on a

parabola and not on the arc of a circle. However, if the versed sine of the curve is less than

one-eight of its chord, the curve approximates very closely to a circle.

c) Offsets from the Chord Produced:

The method has the advantage that not all the land between the tangents points T1 and T2

need be accessible. However to have reasonable accuracy the length of the chord chosen should

not exceed R/20. The method has a drawback that error in locating is carried forward to other

points. This method is based on the premise that for small chords, the chord length is small and

approximately equal to the arc length.

For setting out the curve, it is divided into a number of chords normally 20 to 30 m in length.

For the continuous chainage required along the curve, the two sub-chords are taken, one at the

beginning and the other at the end of the curve. The first sub-chord length is such that a full

number of chainage is obtained on the curve near T1 and the second sub-chord length near T2.

From the property of a circle, if the angle ∟FT1a = δ1 (Figure 9)


The first chord C1 is called the sub-chord. The length of the sub-chord is so adjusted that

the chord length when added to the chainage of T1 makes the chainage of point a as full chain.

Subsequent chord lengths C2, C3, C4 ... are full chains. T1a is then produced to b’ such that ab’=C2,

full chain.

The second offset O2 = C2 (δ1 +δ 2)

O2 = R

C

2

2

2

where Cn-1 is a full chain and C n is the last sub-chord which is normally less than one chain length.

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