ACKNOWLEDGEMENT

This Report is the outcome of laborious and fruitful Survey carried by the Group 3 in Survey Camp 2070 from Baishak 6 to 18th organized by the Department of Civil Engineering, Thapathali Engineering College, Thapathali, Kathmandu. The purpose of this fieldwork was to make the each Student independent to carry out the work in real problem. We think, the purpose is fruitful and which make us to produce the report of the fieldwork in time.We are sincerely indebted to Department of Civil Engineering, Thapathali Campus, for providing opportunity to consolidate our theoretical and practical knowledge in engineering surveying. We would like to express our sincere gratitude to Camp coordinator and sub coordinator Er.Bharat dhakal & Er. Toran Prasad Bhatta for their helpful suggestions and instructions, during the fieldwork, with out which it was very difficult to do the work in the field and to produce the report. We are equally indebted to our respected teachers cum instructors , Er.,Er.,Er,Mr. ,Mrs.Durga Adhikari for their valuable instructions; friendly behavior and guiding any time during the field work and also providing prompt comments and rectification necessary before finalization of the report. We cannot proceed further without thanking to Mr Prakash Pudashainee(account/ logistics),storekeeper Raju Bhandari and others for providing the instrument on needy.

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PREFACE

This Report on Survey Camp is the brief Description of the works that were done in the Campsite during the Period of 12 days. The Materials in this report are the outcomes of the unbelievable works of each and every member of Group 3, who gave their valuable time and knowledge for this report. This report is compilation of great efforts from the group members.

The main objective of this Survey Camp is to provide an opportunity to consolidate and update the practical knowledge in engineering Surveying in the actual field condition and habituate to work in different environment with different people. In this Survey Camp, We are supposed to survey a given plot in all its aspect and work on road and bridge alignment with proper cross-section and profile and its topography fulfilling all technical requirements.

This Report includes the entire description of the practical carried out during the Survey Camp. This report includes the Topographic Map of the area which we surveyed. It also includes the profile and cross-sections at different points of the Road Alignment and Bridge Site Survey. Also, this report includes the determination of various orientations and curve fitting problems. This Report helps us in our further Engineering Practice. The number of problems and calculations done in this report helps us to deal with the similar problems in our further Engineering practice.

Every effort has been taken to ensure the accuracy in this report. However some errors might have occurred. We will be very much grateful to the viewers who go through this report for bringing such errors in our notice. Furthermore we would be very thankful for the examiners or viewers for their suggestions in improving this report.

Survey Camp 2070 IOE Thapathali

GROUP: 3

ABSTRACT

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Arjan Wagle 53/BCE/2067Bhola Nath Silwal 61/BCE/2067Manoj Adhikari 69/BCE/2067Prajjwal Neupane 77/BCE/2067Salina Maharjan 85/BCE/2067Subash Adhikari 93/BCE/2067

Surveying is the science and art of determining the relative positions of above, on, or beneath the surface of earth, and is the most important part of Civil Engineering. The results of surveys are used to map the earth, prepare navigational charts, establish property boundaries, develop data of land used and natural resource information etc. Further survey maintains highways, railroads, buildings, bridges, tunnels, canals, dams and many more. Thus, the objective of survey camp was to make us gain the experience in this field by performing topographic survey in a large area, learning to propose road alignment and select suitable site for bridge axis.The report reflects the methodology, observations, and calculations made by the students in the Camp with the corresponding drawings. The large portion of the course covered with elements of topographic surveying, and then those of road alignment and bridge site survey follow it.

The main objective of the Survey Camp organized for us is to take an opportunity to consolidate and update our practical and theoretical knowledge in engineering surveying in the actual field condition.. In this survey camp we have to prepare a topographic map of the given area, road and bridge site survey fulfilling all technical requirements. In this regard, we are required to carry out the necessary field works in our sub-group so that we will get ample opportunity to the decision on planning and execution of field works for the preparation of topographic map and detail road and bridge site survey. This survey camp helps us to build in our confidence to conduct engineering survey on required accuracy. The summary of the conduction of whole report is presented as follows:

Project Title : Survey Camp 2070Location : TU Kirtipur, Kathmandu.Duration : 6th Baishak to 17th 2070 (12 days)Working Time: 07:00am to 05:00 pmSurveyed by : Group No. 03 (Group captian :Bhola Nath Silwal)

2067(III-I) Batch Civil Engineering Working Schedule for Group 03

S. N. Day Survey Field Work1. 6th Baishak Reconnaissance for topography survey2. 7th topography survey (major traverse)3. 8th topography survey (Minor Traverse)4. 9th topography survey(detailing) and Rl transfer Diff

leveling5. 10th topography survey(Detailing)6. 11th Bridge site and axis Selection surveying7. 12rd Bridge site surveying8. 13th Bridge site surveying9. 14th Road survey

10. 15th Road survey

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11. 16th Road survey12. 17th Presentation And viva

SALIENT FEATURES OF THE PROJECT.

Name of the project: Detail survey, Design and Complete report of SURVEY CAMP-2068

Description of the project: Location

i. Region : T.U. Kirtipur (metropolitan city)ii. Zone : Bagmati

iii. District: Kathmandu

Sites:i. For topographic survey of the area - Kirtipur (within the premises of Tribhuwan

University) ii. Bridge site and road alignment within the same area.

Geographical Features: i. Terrain: Hilly

ii. Climate: Mild Temperature iii. Geology: Project area follows the geomorphic form of higher Himalayan of Mid-

Eastern Nepal of Kathmandu district.

Description of work:

Traversing: i. No of Major Traverse Stations:20 (including CP1 & CP2)

ii. No of Minor Traverse Stations:13

Detailing: i. Plot No: I

ii. Area: Central library, gandi bhawan, and up to Back face of Environment

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Department

Road Alignment: i. Starting point of the road: Bridge

ii. Length of the road 716.76 M

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iii. Crosssection: 10m left and 10m right on Both side from center line

.

Bridge Site Survey:i. Bridge span: 46.617M

ii. Surveyed area for Topography: 150m up stream and 50m downstream.iii. Cross-section up to 150m on upstream and 50m on downstream.

Acronym

R.L. = Reduced Level

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BM = Bench Mark

TBM = Temporary Bench Mark

FS = Fore Sight

BS = Back Sight

RECCE = Reconnaissance

I.P. = Intersection Point

INTRODUCTION

1.1 Background1.1.1 Surveying

Surveying is an art and science of determining the relative position of point on above or beneath the surface of the earth by means of angular and linear measurements. The application of surveying requires skills as well as knowledge of mathematics, physics, to some extent, astronomy.

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The knowledge of surveying is advantageous to many phase of engineering. The earliest surveys were made in connection with the land surveying. Surveying is the most essential subject matter before and during all engineering works like civil engineering works such as designing and construction of highways, water supply systems, irrigation projects, buildings etc. Land area surveys are made to determine the relative horizontal and vertical position of topographic features and to establish reference mark to guide construction.

In surveying, all measurement of lengths is horizontal, or else is subsequently reduce to horizontal distance. The object of survey is to prepare plan or map so that it may represent the area on a horizontal plane. A plan or map is horizontal projection of an area and show only horizontal distance of the points. Vertical distances between the points are shown on map by contour lines and are usually represented by means of vertical sections drawn separately.

The main objectives of surveying courses allocated for civil engineering students is to promote them the basic knowledge of different surveying techniques relevant to civil engineering works in their professional practice. The completion of all surveying courses including two weeks survey camp work organized by the Department of Civil Engineering, Thapathali Engineering College,Thapathali,Kathmandu will give better enhancement to students to use all surveying technique covered in lecture classes.

This is a detail report of the works, which were performed by group no. 3, have six members, during the camp period. It briefly explains the working procedures and technique used by this group during that camp period. In addition, it also contain observations, calculations, methods of adjustment of error, main problem faced during work and their solution, results of all calculations and their assessments with some comments is presented in a concise form.

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1.1.2 Primary Division of SurveyAs to whether the surveyor must regard the earth surface as curved or may regard it is as plane depends upon the character and magnitude of the survey, and upon the precision required. Primarily, surveying can be divided into plane and geodetic.

In plane surveying, mean surface of the earth is considered as a plane and spheroidal shape is neglected, all triangle formed are considered as plane triangles, level line is considered as straight and plumb line are considered parallel. It is reasonable for the area involving less than 250 sq. km. since length of an arc 12 km. long lying on the earth surface is only 1 cm greater than the subs tended chord. And the difference between the sum of angles in a plane triangle and sum of those in spherical triangle is only 1 second for a triangle at the earth surface having area of 195 sq. km.In geodetic surveying, the shape of the earth is taken into account. All line are curved line, all triangle are spherical triangle so it involves spherical trigonometry. The object of geodetic survey is to determine the precise position on the surface of the earth, of a system of widely distant point which forms the control station to which survey of less precision may be referred.

Keeping in view the above fact in our survey camp we conduct plane surveying since the area to be surveyed is small and precision required is within the limit as that obtained by plane surveying.

1.1.3 Classification of SurveySurvey may be classified on the different heading depending upon the uses or purpose of resulting map.

Based on Nature of Field Survey Land survey: it includes topographical, cadastral and city survey. Hydrographic survey Astronomical survey

Based on object of survey Engineering survey Military survey

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Mine survey Geological survey Archaeological survey

Based on instrument used Chain survey Theodolite survey Traverse survey Triangulation survey Tachometric survey Plane table survey Photogrammetric survey Aerial survey

In our survey camp, the type of survey that we performed is engineering survey which includes the preparation of topographic map, in which both horizontal and vertical controls are necessary. As per instrument used we perform theodolite traverse survey for fixing control points, tachometric survey for detailing and triangulation survey for establishing control points in bridge site survey.

1.1.4 Principle of SurveyingThe fundamental principles of plane surveying are:

Working from whole to part: it is very essential to establish first a system of control points with higher precision. Minor control points can then be established by less precise method and details can then be located using minor control points by running minor traverse. This principle is applied to prevent the accumulation of error and to control and localize minor error.

Location of point by measurement from two points of reference: the relative position of points to be surveyed should be located by measurement from at least two (preferably three) points of reference, the position of which have already been fixed.

Consistency of work: The survey work should performed by keeping consistency in method, instrument, observer etc. to get desired level of accuracy.

Independent check: Every measurement taken in the field must be checked by some independent field observation so that the mistake is not passed unnoticely.

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Accuracy required: Proper method and proper instrument should be used depending upon amount of accuracy required. Accuracy of angular and linear values should be compatible.

In our survey camp, survey work is performed by considering the above fundamental principle of surveying.

1.2 Accuracy and Errors:1.2.1 General: Precision is the degree of perfection used in the instrument, the methods and the observations. Accuracy is the degree of perfection obtained which depend on precise instrument to simplify the work, save time & provide economy, on precise method to reduce the effect of all type of error, and good planning to save time & reduce the possibility of errors. The important function of surveyor is to secure measurements which are correct within a certain limit of error prescribed by nature and purpose of particular survey. A discrepancy is the difference between two measured values of the same quantity, it is not an error.

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1.2.2 Source of errors:Error may arise from three sources.

Instrumental error: are those arising due to imperfection or faulty adjustment of the instrument with which measurement is being taken. E.g., a tape too short.

Personal error: Are those arising due to want of perfection of human sight in observing and of touch in manipulating instrument. E.g., error in taking level reading.

Natural error: Error due to variation in natural phenomenon such as temperature, refraction, magnetic declination etc.

1.2.3 Kind of errorError may be classified as:

Mistake: are errors arising from inattention, inexperience, carelessness and confusion in the mind of observer. If undetected, it produces a serious effect. Hence, every measurement to be recorded in the field must be checked by independent check.

Systematic error: Are error that under the same condition will always be of same size and sign, a correction can be determined and applied, these make the result too great or too small accordingly treated as positive or negative error.

Accidental error: Are those which remain after mistake and systematic error have been eliminated and caused by a combination of reason beyond the ability of observer to control. They tend sometimes in one direction and sometimes in other. Accidental error represented the limit of precision in the determination of value.

1.2.4 Permissible error:It is the maximum allowable limit that a measurement may vary from the true value or from a value previously adopted is correct. Its magnitude in any given case depends upon the scale, purpose of the survey, the instrument available, class of the work etc. The limit of error cannot be given once for all. The best surveyor is not he, who is extremely accurate in all his work, but he who does it just accurately enough for the purpose without waste of time & money.

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Objectives Of Survey Camp

The main objective of the camp is to provide a basic knowledge of practical implementation of different survey work, which must be encountered in future. It enhances the practical knowledge thereby implementing different work and in other side it involves self-assured feeling everlastingly. It guides to tread on the path ending with success.The main objectives of the survey camp are as follows:

To become familiar with the problems that may arise during the field works.

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To became familiar with proper handling of instrument and their functions. To become familiar with the spirit and importance of teamwork, as

surveying is not a single person work. To complete the given project in scheduled time and thus knows the value of

time. To collect required data in the field in systematic ways. To compute and manipulate the observed data in the required accuracy and

present it in diagrammatic and tabular form in order to understand by others.

To tackle the mistake and incomplete data from the field during the office work.

To make capable for the preparation of final report.

PROJECT AREA

Tribhuvan University was selected as the project area of Survey Camp-

2070. University lies in the north-west corner of the Kathmandu valley. The

typical features related to the site are as follows:

1.4.1 Location And Accesability

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Kirtipur is about 6km North West of Kathmandu. The area allocated to us for

survey is about 50 sq. km .Of land with dense human settlement. The detail of

the area is:

Country: Nepal

Region: Central Development Region

Zone: Bagmati

District: Kathmandu

Location: Tribhuvan University, Kirtipur.

The major part of our survey camp work was done in the compound of

Tribhuvan University (T.U), founded in 1959, Nepal’s first university,

situated in Kirtipur, five kilometers away from Kathmandu.

With the rapid development of Katmandu and proximity of the capital to

Kirtipur, the town has come under increasing pressure for modern

development. It is a farming town. During the 1960’s, the paddy fields to the

north east of the town were chosen as the site for Tribhuvan University, and

were compulsorily purchased from their owners. With the university, came a

new-pitched road and bus transport to the edge of the town. Naya Bazaar,

which developed without any planning two decades ago to the south east of

the town, at the foot of the hill is now the main commercial center. It is of

course unrealistic to stop the development of new areas around Kirtipur but if

the growth of Naya Bazaar is not supervised, it may develop to a large

unplanned township without appropriate infrastructures. With the

development of Naya Bazaar and because of the students commuting to T.U

transportation facility in and around Kirtipur is quite developed. There are

regular buses running to and from Kirtipur. Thus, our project area was quite

suitable and easily accessible.

1.4.2 Topography and Geology

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Kirtipur has gently steep topography. It is said that the city is standing on a

huge hard rock. Especially the low land below the town is found to be good

for the agricultural product. The area contains ground features ranging from

step slopes to almost flat grounds. These features were shown by contours.

The area also shows a variation in the elevation.

The latitude and longitude of Nepal is as following:

Latitude 2622N to 3027NLongitude 804E to 8812EThe latitude and longitude of Kirtipur is as follow:

Latitude 2953'06”N

Longitude 8455'00’E

1.4.3 Climate and Vegetation:

The climate of Kirtipur is temperate. The city is situated at the height of more

than 5000 ft. above the sea level. Hence summer is warm with the maximum

and minimum temperature 28C and 16C. Winter is cold with maximum and

minimum temperature of 17C and 0C. However, in winter days are sunny

and a bit warm.

The average rainfall in Kirtipur area is 90 inches in summer and very little

rain in winter. Our survey camp was held on Falgun and Chaitra month. At

that time the temperature out there was moderate and we had no problem in

work regarding weather. Vegetation of Kirtipur: The vegetation in Kirtipur is lush and ranges

from huge trees with thick trunk and deep-seated root to weeds. Plenty of

paddy fields were found out there. Similarly, most of the parts of the

university were covered with green grasses.

1.5 Others:

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Kirtipur is a very old and historic city. It was a small kingdom. In 1821 B.S,

king Prithvi Narayan Shah conquered this little city in the course of unifying

Nepal. The people here are very religious. There are famous enshrines like

Bagh Bhairav, Bhagwati, and quite a few Buddhist Monasteries. Lots of

festival and cultural traditions are observed over there every year but we were

not lucky enough to see any of such processions.

Kirtipur municipality is the main administrative authority of this area, and is very close to Kathmandu. Therefore, the education level of people is in increasing trend. All modern facilities are available. The main occupation is agriculture and some percentage is engaged in other business like transport, tourism and trade. It is very well connected with Kathmandu by good metallic road. As an effect, the life-style is changing, standard of living is rising and per capita income is also increasing. Many new commercial and modern styled buildings are rising on the eastern slopes of the mound. Tribhuwan University, the oldest and biggest University of Nepal lies in its vicinity

TOPOGRAPHICAL SURVEY

Topographical surveying is the process of determining the positions of natural

and artificial features of the locality by means of conventional signs up on a

topographical map. Topographic surveys are three-dimensional; they provide

the techniques of plane surveying and other special techniques to establish

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both horizontal and vertical control. Topographic is simply the graphical

representation of positions of the earth’s surface

Hence the fieldwork in a topographical surveying consists of three parts.

It establishes both horizontal and vertical control.

It locates the contours.

It locates the details such as rivers, streams, lakes, roads, houses and trees

etc.

2.1 Objectives:

The main Objective is to prepare the topographic map of the given area with

horizontal control and vertical control with required accuracy. By topographic

survey we can determine the position of both on plan and elevation, of any

features of a locality for the purpose of delineating them by means of

conventional sign and symbol upon the topographic map.

Brief description of the area:

The area, where surveying was performed, is situated at TU Kirtipur,

Kathmandu. The major traverse was run throughout the campus area, which

cover the half area of the campus. Our objective was to prepare a topographic

map of the given small area, which is a part of the campus area. So, we were

assigned to prepare the topographic map of the area including Central

Library, Gandi Bhawan and forest at Back face of Environment

Department that includes the entire natural and man-made features that may

come in the general survey work.

2.2 Norms (Technical specifications):

Conduct reconnaissance survey of the given area. Form a close traverse

(major and minor) around the perimeter of the area by making traverse

station. In the selection of the traverse station maintain the ratio of

maximum traverse leg to minimum traverse leg less than 2:1 for major

and less than 3:1 for minor.

Measure the traverse legs in the forward and reverse directions by means

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of a tape calibrated against the standard length provided in the field, note

that discrepancy between forward and backward measurements should be

better than 1:2000.

Measure traverse angle on two sets of reading by theodolite. Note that

difference between the mean angles of two sets reading should be within

the square root of no of station times least count of the instrument.

Determine the R.L. of traverse stations by fly leveling from the given

B.M. Perform two-peg test before the start of fly leveling. Note that

collimation error should be less than 1:10000. Maintain equal foresight

and back sight distances to eliminate collimation error. Take R.L. of

T.B.M 2 is 1322.580. The Permissible error for fly leveling is (±25√k)

mm.

Balance the traverse. The permissible angular error for the sum of interior

angles of the traverse should be less than ±√n x 1 minutes for Major

Traverse and ±√n x 1.5 minutes for Minor Traverse (n = no of traverse

station). For major and minor traverse the relative closing error should be

less than 1: 2000 and 1: 1000 respectively.

Plot the traverse stations by coordinate method in appropriate scale, i.e.

1:1000 for major traverse and 1:500 for minor traverses.

Carry out the detail survey of the given area by tachometric method with

reference to the major and minor traverse stations, which have been

already plotted. Use conventional symbols for plotting.

2.3 Equipment:

The equipment used in the survey during the preparation of topographic map

are as follows:

1. Theodolite.

2. Staffs.

3. Ranging rods

4. Tapes

5. Leveling instruments

6. Nails, Pegs

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7. Compass

8. Marker pen

2.4 Methodology:

The methodology of surveying is based on the principle of surveying. They

are as follows:

1. Working from whole to part

2. Independent check

3. Consistency of work

4. Accuracy Required

The different methodologies were used in surveying to solve the problems

arise in the field. These methodologies are as follows:

2.4.1 Reconnaissance (recci)

Reconnaissance (recci) means the exploration or scouting of an area. In

survey, it involves walking around the survey area and roughly planning the

number of stations and the position of the traverse stations. Recci is primarily

done to get an overall idea of the site. This helps to make the necessary

observations regarding the total area, type of land, topography, vegetation,

climate, geology and indivisibility conditions that help in detailed planning.

The following points have to be taken into consideration for fixing traverse

stations:

The adjacent stations should be clearly intervisible

The whole area should include the least number of stations possible.

The traverse station should maintain the ratio of maximum traverse leg to

minimum traverse leg less than 1:2 for Major Traverse and 1:3 for

Minor Traverse.

The steep slopes and badly broken ground should be avoided as far as

possible, which may cause inaccuracy in tapping.

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The stations should provide minimum level surface required for setting up

the instrument.

The traverse line of sight should not be near the ground level to avoid the

refraction.

Taking the above given points into consideration, the traverse stations were

fixed. Then two way taping was done for each traverse leg. Thus, permanent

fixing of the control points completes recci.

2.4.2 Traversing:

Traversing is a type of surveying in which a number of connected survey lines

form the framework. It is also a method of control surveying. The survey

consists of the measurement of

Angles between successive lines or bearings of each line

The length of each line

There are two types of traverse. They are as follows:

(i) Closed traverse:

If the figure formed by the lines closes at a station i.e. if they form a

polygon or it starts and finishes at the points of known co-ordinates

then the traverse is called closed traverse.

(ii)Open traverse:

If a traverse starts and finishes at points other than the starting point or

point of unknown co-ordinates, then the traverse is called open

traverse.

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(a) Closed

(a) Loop Traverse (b) Closed Traverse (c) Open Traverse

Fig: Types of Traverses

(a) Theodolite traversing

Theodolite traversing is defined as the course taken when measuring a

connected series of straight lines, each line joining two points on the

ground. These points are called traverse station. The straight line between

two consecutive traverse stations is called a traverse leg. The angle at any

station between two consecutive traverse legs is known as traverse angle.

The directions and the lengths of the survey lines are measured with the

help of an angle-measuring instrument such as Theodolite and a tape. If

the co-ordinates of the first station and the bearing of the first line are

known, the co-ordinates of all successive points can be computed as

follows:

XB = XA + Lcosθ

YB = YA + Lsinθ

Where, L=Length of traverse leg

(b) Measurement of Traverse Length:After completion of recci survey, taping of the major traverse was

performed with the help of tapes. The distances between the adjacent

control points were measured accurately as far as possible for the

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accuracy of the whole traverse. To attain the accuracy required i.e. 1:2000

ratio, a two way taping was done independently so that the length from

each measurement was found within specified range.

To measure the horizontal distances accurately on the slopping ground,

the short length was measured at a time so that the tape could be pulled

horizontally without sagging. For this ranging was done accurately to

divide the length into shorter length. Finally, all the lengths were added

to obtain the whole length, which is also, called stepping method. For

accuracy, traverse legs may be checked by electronic distance measuring

instrument (EDM).

Major Traverse

The skeleton of lines joining those control points, which covers the whole

entire area, is called Major Traverse. Work on Major traverse must be precise.

So two-set of reading should be taken for Major Traverse. For convenience,

the readings are taken by setting the theodolite at 00’0” for one set and

9000’00” for the second.

In the Kirtipur Survey Camp, two traverses - major and minor had to be

established. The major traverse had 20 control stations including two given

control points. The control stations were named as 3M1, 3M2 and so on along

with CP1 and CP2 (the two given control points) .The leg ratio of maximum

traverse leg to minimum traverse leg was maintained within 1:2. The

discrepancy in length between the forward measurements and the backward

measurements of all the traverse legs was within 1:1000. Two sets of

theodolite readings were taken for measuring the horizontal traverse angles.

The difference between the mean angles of two sets of readings was within a

minute for all the angles.

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Minor Traverse

It is not sufficient to detail the area by enclosing with the help of major

traverse. Minor traverse is that one which runs through the area to make

detailing easy. Minor Traverse covers only small area. Less precise work than

that of major traverse is acceptable so that single set reading is sufficient. The

minor traverse had 13 control stations and enclosed the Gandhi Bhawan as the

major details. The control stations were named as 3m1, 3m2 and so on along

with the 1 control stations common for both the major and the minor traverses.

The leg ratio of maximum traverse leg to minimum traverse leg was

maintained within 1:3. The discrepancy in length between the forward

measurements and the backward measurements of all the traverse legs was

within 1:1000.

Measurement of Horizontal and Vertical

a) Two set of horizontal angle was measured at each station and one set of

vertical angle. And it was done in the following way-:

i) One the face left temporary adjustment was done.

ii) After setting zero to the first station the second station was sighted by

unclamping the upper screw.

iii) For better accuracy and exact bisection horizontal angle was measured at

the bottom of the arrow.

iv) And on the same setting or same face vertical angle at both the station

was taken.

v) Now again changing the face the horizontal angle was taken and vertical

angle too.

vi) Now setting the reading to ninety at the first station again one set of

horizontal angle was taken but the vertical angle is enough, taken earlier.

vii) Before shifting the instrument to the next station the height of instrument

was taken.

viii) Similarly the instrument was shifted to other station and in each station

one set of vertical angle and two set of horizontal angle and height of

instrument was measured.

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ix) For comparison of the tape distance and the Tachometric distance the

stadia reading (top, mid, bottom) was taken at each station and for the

calculation of the reduce level of each station we need to read mid

reading which can be compared with the level transferred using auto

level.

2.4.3 TOTAL STATION:

Introduction:

A total station is an optical instrument used a lot in modern surveying and

archaeology and, in a minor way, as well as by police, crime scene

investigators, private accident reconstructionist and insurance companies to

take measurements of scenes. It is a combination of an electronic theodolite

(transit), an electronic distance meter (EDM) and software running on an

external computer known as a data collector.

With a total station one may determine angles and distances from the

instrument to points to be surveyed. With the aid of trigonometry and

triangulation, the angles and distances may be used to calculate the

coordinates of actual positions (X, Y, and Z or northing, easting and

elevation) of surveyed points, or the position of the instrument from known

points, in absolute terms.

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Some total stations also have a GPS interface which combines these

two technologies to make use of the advantages of both (GPS - line of sight

not required between measured points; Traditional Total Station - high

precision measurement especially in the vertical axis compared with GPS) and

reduce the consequences of each technology's disadvantages (GPS - poor

accuracy in the vertical axis and lower accuracy without long occupation

periods; Total Station - requires line of sight observations and must be set up

over a known point or within line of sight of 2 or more known points).

Most modern total station instruments measure angles by means of electro-

optical scanning of extremely precise digital bar-codes etched on rotating

glass cylinders or discs within the instrument. The best quality total stations

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T/2

TotalStation

Target

are capable of measuring angles down to 0.5 arc-second. Inexpensive

"construction grade" total stations can generally measure angles to 5 or 10

arc-seconds.

Measurement of distance is accomplished with a modulated microwave or

infrared carrier signal, generated by a small solid-state emitter within the

instrument's optical path, and bounced off of the object to be measured. The

modulation pattern in the returning signal is read and interpreted by the

onboard computer in the total station. The distance is determined by emitting

and receiving multiple frequencies, and determining the integer number of

wavelengths to the target for each frequency. Most total stations use a

purpose-built glass Porro prism as the reflector for the EDM signal, and can

measure distances out to a few kilometers, but some instruments are

"reflector less", and can measure distances to any object that is reasonably

light in color, out to a few hundred meters. The typical Total Station EDM can

measure distances accurate to about 3 millimeters or 1/100th of a foot.

Some modern total stations are 'robotic' allowing the operator to control the

instrument from a distance via remote control. This eliminates the need for an

assistant staff member to hold the reflector prism over the point to be

measured. The operator holds the reflector him/herself and controls the total

station instrument from the observed point.

Figure: Working Principle of Total Station

The basic principle of Total Station is that the distance between any two

points can be known once the time light takes to travel the distance and back

and the velocity of light is known. Then the following relation, which is

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D = (T/2)*Vel. Of Light

D

already programmed in the memory of the instrument along with other

correction factors, calculates the required horizontal distance and is

displayed on the LCD screen.

Balancing the traverse:

There are different methods of adjusting a traverse such as Bow ditch’s

method, Transit method, Graphical method, and Axis method. Among them

during the survey camp, Bow ditch’s method was used to adjust the traverse.

The basis of this method is on the assumptions that the errors in linear

measurements are proportional to L and that the errors in angular

measurements are inversely proportional to L, where L is the length of a line.

The Bow ditch’s rule is mostly used to balance a traverse where linear and

angular measurements are of equal precision. The total error in latitude and in

the departure is distributed in proportion to the lengths of the sides.

2.4.4 COMPUTATION OF THE CO-ORDINATES

According to the accuracy aimed and the nature of the

ground, the lengths of traverse legs are measured directly

on the ground either by chaining or taping. The

traverse angles are measured with a theodolite by setting

up the instrument at each station in turn and the vertical

angle at each station measured will help to find the

tachometric distance and reduce level of that point. And the bearing of the any

one of the traverse leg measured and the entire traverse angle measured, the

bearing of all the legs can be calculated by:

Bearing of a line = (bearing of previous line +included angle) (180) or

(540)

If is the bearing of line (c.p,A say), and l be the length of the line and

provided that co-ordinate of the control point(c.p) is known then the co-

ordinate of the point ‘A’ can be calculated as follow-:

X-coordinate of A=x-coordinate of control point (c.p) +l*sinY-coordinate of A=y-coordinate of control point (c.p) +l*cos

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R.L or z-coordinate of A=R.L of point (c.p) +H.I H*Tan-Height of signal.

Where, H.I=Height of instrument

H=horizontal distance

Balancing the consecutive coordinate:

The process of adjusting consecutive co-ordinates of each line by applying correction to them in such a way that each algebraic sum of the latitude and departure of a close circuit is equal to zero i.e. the sum of the northing should be exactly equal to the sum of the southing and sum of the easting should be exactly equal to the sum of the westing.

The closing error however is distributed through out the whole traverse

stations such that its effect is not apparent on the plotted location of the

station. And the error can be distributed among the stations if the closing error

is within the permissible limit, which is given by-:

Precision = √ (ΔX2+ΔY2) /P = e/P

This should be greater than 1:2000

Closing Error

If a closed traverse is plotted according to the field measurements, the end of

the traverse will not coincide exactly with the starting point. Such and error is

known as closing error.

Mathematically, Closing error (e) = √ {(L) 2 + (D) 2}

Direction, tan θ = D/L

The sign of L and D will thus define the quadrant in which the closing error

lies.

The relative error of closure = Error of Closure / Perimeter of the traverse

= e / p

= 1 / (p / e)

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The error (e) in a closed traverse due to bearing may be determined by

comparing the two bearings of the last line as observed at the first and last

stations of traverse. If the closed traverse, has N number of sides then,

Correction for the first line = e/N

Correction for the second line = 2e/N

And similarly, correction for the last line = Ne/N = e

In a closed traverse, by geometry, the sum of the interior angles should be (2n-

4) x 90˚ where n is the number of traverse sides. If the angles are measured

with the same degree of precision, the error in the sum of the angles may be

distributed equally among each angle of the traverse.

2.5.5 Detailing:

Detailing means locating and plotting relief in a topographic map. Detailing

can be done by either plane table surveying or tachometric surveying. Plane

tabling needs less office work than tachometric survey. Nevertheless, during

our camp, we used the tachometric method

Tachometry

Tachometry is a branch of angular surveying in which the horizontal and

vertical distances of points are obtained by optical means. Though it only has

accuracy about 1/300 to 1/500, it is faster and convenient than the

measurements by tape or chain. It is very suitable for steep or broken ground,

deep ravines, and stretches of water or swamp where taping is impossible and

unreliable.

The objective of the tachometric survey is to prepare of contour maps or plans

with both horizontal and vertical controls. For the survey of high accuracy, it

provides a check on the distances measured by tape.

The formula for the horizontal distance is

H = 100*S*Cos2

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The formula for the vertical distance is

V = 100 *S*(Sin2)/2

Where, S = staff intercept; = Vertical Angle

If the angle used is zenithal angle then

H=100*S*Cos2V = 100*S*(Sin2)/2

Where, =zenithal angle.

2.4.6 Leveling:

Leveling is a branch of surveying the object of which is:

(i) To find the elevation of given points with respect to given or assumed

datum.

(ii) To establish points at a given elevation or at different elevations with

respect to a given or assumed datum.

The first operation is required to enable the works to be designed while the

second operation is required in the setting out of all kinds of engineering

works. Leveling deals with measurements in a vertical plane.

To provide vertical controls in topographic map, the elevations of the relevant

points must be known so that complete topography of the area can be

explored.

Two types of leveling were performed at the site, namely direct leveling

(spirit leveling) and indirect leveling (trigonometric leveling).

1. Direct leveling:

It is the branch of leveling in which the vertical distances with respect to a

horizontal line (perpendicular to the direction of gravity) may be used to

determine the relative difference in elevation between two adjacent points. A

level provides horizontal line of sight, i.e. a line tangential to a level surface at

the point where the instrument stands. The difference in elevation between

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two points is the vertical distance between two level lines. With a level set up

at any place, the difference in elevation between any two points within proper

lengths of sight is given by the difference between the rod readings taken on

these points. By a succession of instrument stations and related readings, the

difference in elevation between widely separated points is thus obtained.

Following are some special methods of direct (spirit) leveling:

a. Differential leveling:

It is the method of direct leveling the object of which is solely to

determine the difference in elevation of two points regardless of the

horizontal positions of the points with respect of each other. This type of

leveling is also known as fly leveling.

b. Profile leveling:

It is the method of direct leveling the object of which is to determine the

elevations of points at measured intervals along a given line in order to

obtain a profile of the surface along that line.

c. Cross-sectioning:

Cross-sectioning or cross leveling is the process of taking levels on each

side of main line at right angles to that line, in order to determine a

vertical cross-section of the surface of the ground, or of underlying strata,

or of both.

d. Reciprocal leveling:

It is the method of leveling in which the difference in elevation between

two points is accurately determined by two sets of reciprocal

observations when it is not possible to set up the level between the two

points.

2. Indirect leveling:

Indirect method or trigonometric leveling is the process of leveling in which

the elevations of points are computed from the vertical angles and horizontal

distances measured in the field, just as the length of any side in any triangle

can be computed from proper trigonometric relations.

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Two Peg Test

Before starting the fly leveling, two peg test was carried out to check the

accuracy of the level used. The collimation error was found to be 1: 10000

which satisfied the permissible error limit (1:10,000).

Temporary adjustments of Level:

The temporary adjustment for a level consists of the following:

1. Setting up the level: The operation of setting up includes fixing the

instrument on the stand and leveling the instrument approximately.

2. Leveling up: Accurate leveling is done with the help of foot screws and

with reference to the plate levels. The purpose of leveling is to make the

vertical axis truly vertical and horizontal line of sight truly horizontal.

3. Removal of parallax: Parallax is a condition when the image formed by

the objective is not in the plane of the cross hairs. Parallax is eliminated

by focusing the eyepiece for distinct vision of the cross hairs and by

focusing the objective to bring the image of the object in the plane of

cross hairs.

Permanent adjustments of Level:

To check for the permanent adjustments of level two-peg test method should

be performed. Two staffs were placed at A and B of known length (about 60

m). First the instrument was setup on the line near B and both staff readings

(Top, Middle, and Bottom) were taken. Then, the instrument was setup at the

middle C on the line and again both staff readings on A and B was taken.

Then computation was done in order to check whether the adjustment was

within the required accuracy or not. No permanent adjustment was required

since the error was within the permissible value.

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Booking and reducing levels:

There are two methods of booking and reducing the elevation of points from

the observed staff reading

Height of the Instrument method

Arithmetic Check: ∑BS – ∑F.S. = Last R.L. – First R.L.

Rise and Fall method

Arithmetic Check: ∑ BS – ∑ F.S. = ∑ Rise – ∑fall = Last R.L. –

First R.L.

Fly Leveling:

The RL of Given TBM1 point was found by transferring the level from

Known BM located at Lab School by the process of fly leveling. In this

method auto level was used and the level was transferred directly by taking

BS and FS at every Turning Point.

Level transfer to the major and minor traverse stations:

The R. L of the temporary benchmark was then transferred to the control

stations of the major and minor traverse. The closing error was found to be

within the permissible limits. The misclosure was adjusted in each leg of the

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leveling path by using the following formula:

Permissible error = ±25k mm.

Where k is perimeter in Km

Actual Error (e) = ∑BS – ∑F.S. = Last R.L. – First R.L.

Correction ith leg=-(e x (L1 + L2 +…. + Li)/P

Where L1, L2, Li Length of 1st, 2nd,….. ith leg.

P is perimeter

Relative Precision= 1/(p/e)

2.4.7 Contouring:

A contour is an imaginary line, which passes through the points of equal

elevation. It is a line in which the surface of ground is intersected by a level

surface. Every fifth contour lines must be made darken. While drawing the

contour lines, the characteristics of the contours should be approached.

The characteristics are as follows:

Two contours of different elevations do not cross each other except in the

case of an overhanging cliff.

Contours of different elevations do not unite to form one contour except

in the case of a vertical cliff.

Contours drawn closer depict a steep slope and if drawn apart, represent a

gentle slope.

Contours equally spaced depict a uniform slope. When contours are

parallel, equidistant and straight, these represent an inclined plane

surface.

Contour at any point is perpendicular to the line of the steepest slope at

the point.

A contour line must close itself but need not be necessarily within the

limits of the map itself.

A set ring contours with higher values inside depict a hill whereas a set of

ring contours with lower values inside depict a pond or a depression

without an outlet.

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When contours cross a ridge or V-shaped valley, they form sharp V-

shapes across them. Contours represent a ridge line, if the concavity of

higher value contour lies towards the next lower value contour and on the

other hand these represent a valley if the concavity of the lower value

contour, lies toward the higher value contours.

The same contour must appear on both the sides of a ridge or a valley.

Contours do not have sharp turnings.

Taking the reading at the change point on the ground does the indirect method

of locating contours. The interpolation method is used to draw the contour

lines. Interpolation of contours is done by estimation, by arithmetic

calculations or by graphical method. The eye estimation method is extremely

rough and is used for small-scale work only. Generally, arithmetic calculation

method of interpolation is used to draw the contour lines and is performed as

follows:

X= (H/V) * Y

Where,

X= Horizontal distance of the point to be located.

H = Horizontal distance between two guide points

V = Vertical distance between the two guide points

Y = Vertical distance between lower elevation point and the point to be

located.

2.4.8 Computation and plotting

For the calculations as well as plotting, we applied the coordinate method

(latitude and departure method). In this method, two terms latitude and

departure are used for calculation. Latitude of a survey line may be defined as

its coordinate lengths measured parallel to an assumed meridian direction. The

latitude (L) of a line is positive when measured towards north, and termed

Northing and it is negative when measured towards south, and termed

Southing. The departure (D) of a line is positive when measured towards east,

and termed Easting and it is negative when measured towards south, and

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termed Westing. The latitude and departures of each control station can be

calculated using the relation:

Latitude = L CosDeparture = L SinWhere, L=distance of the traverse legs

=Reduced bearing

If a closed traverse is plotted according to the field measurements, the end of

the traverse will not coincide exactly with the starting point. Such and error is

known as closing error.

Mathematically,

Closing error (e) = √ {(L) 2 + (D) 2}

The relative error of closure = e / p

The error (e) in a closed traverse due to bearing may be determined by

comparing the two bearings of the last line as observed at the first and last

stations of traverse. If the closed traverse, has N number of sides then,

Correction for the first line = e/N

Correction for the second line = 2e/N

And similarly, correction for the last line = Ne/N = e

In a closed traverse, by geometry, the sum of the interior angles should be

equal to (2n-4) x 90˚ where n is the number of traverse sides. If the angles are

measured with the same degree of precision, the error in the sum of the angles

may be distributed equally among each angle of the traverse.

Mathematically,

a) Correction in departure of a side of traverse

= - (Total departure misclosure / traverse perimeter) x length of that side

b) Correction in latitude of a side of traverse

= - (Total latitude misclosure / traverse perimeter) x length of that side

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In the case of length, the difference in values obtained by forward and

backward taping is called discrepancy. In addition, the reciprocal of the

discrepancy divided by the mean of the two measurements is called precision.

Both the discrepancy and the precision for each traverse leg should be within

the given limits.

Plotting of Major and Minor traverse:

After computing the co-ordinate of each of the control points, they were

plotted in A1 size grid paper. Both major and minor traverses were plotted to

1:1000 scales. The plotted traverse was made at the center of the sheet with the

help of least co-ordinates and highest co-ordinates. Minor Traverse was plotted in

similar way to scale 1:500 over which later detailing by tachometry was done.

2.5 Comments and conclusions:

The site for survey camping was the campus area of TU, Kirtipur. The pattern

was very suitable because all the facilities for engineering work were

available with the good environment of doing work except due to the rainfall

at a day for few hours.

The fooding facilities were not up to the task and not hygienic and fresh. The

briefing to be done as scheduled was not done as both the teachers and the students

were tired of their days work and could not concentrate on the briefing. In the field,

even though the teachers helped us a lot, we felt that their visiting is not sufficient.

We hope that above mentioned problems will be solved and the up coming camps

will run smoothly without any problems.

Some other problems during the field works were during fly leveling during

transferring the R.L. from given benchmark to the T.B.M. due to the disturbance

by traffics.

Conclusion:

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The given Topography survey camp work was finished satisfactorily within

the given span of time. The subject survey needs practice as much as possible.

For surveying, theory can only taken as the introduction but if there is

practice, there will be much gain of knowledge about the techniques of

surveying. Thus, this camp helps us by practicing the survey work to gain the

much essential knowledge as far as possible. It is better to say that it provides

us a confidence to perform survey and apply the techniques at any type of

problem facing during the actual work in the future career.

All the groups prepared their topographic map of the given area of the TU

campus areas in the same scale. The whole area was divided in such a way

that area allocated for one group contains some part of the area allocated for

another group. One traverse leg is also common to all groups and hence the

combination of all groups' effort will provide a perfect and complete

topographic map of TU after combining it.

BRIDGE SITE SURVEY

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3.1 Objectives:The adequate functioning of a road depends to a large extent on the effectiveness of the cross drainage like bridges etc. The main objective of the bridge site survey is to give the students the preliminary knowledge on selection and planning of possible bridge site and axis for the future construction of the bridge. The purpose of the bridge site survey was not only to prepare plan and layout of the bridge site but also from the engineering point of view, the purpose is to collect the preliminary data about the site such as normal water flow level, high flood level, geological features of the ground for planning and designing of the bridge from the details taken during the surveying. Moreover bridge construction is an important aspect in the development of transportation network. Surveying is required for topographical mapping, knowledge of longitudinal sections of the river and cross sections at both the upstream and downstream side of the river for the construction of a bridge.

3.2 Brief Description of the Area

Bridge site survey was conducted over a small rain spring on the T.U facility.

The spring collects water etc coming from the departments and flows through

a ravine formed by two hill slopes. Our site was between the physics and

chemistry departments and the coronation garden. The site was mossy and

swampy. No huge boulders are to be found near the site. It was damp and

hilly.

3.3 Hydrology, Geology and Soil Condition

Trees surrounded the site. There are no rocks. The ground was damp and

swampy. The soil was soft and clayey. It was brown in color. The hill slopes

on both sides are not very steep and are thus geologically stable. There is not

much water to be found on the bridge site. The only water is collected from

rain and other sources.

3.4 Technical Specification (Norms):

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A bridge site topographical survey was carried out and the alignment of the bridge axis was fixed by triangulation. Two base lines were measured by tape with two way linear measurement. Along with these we are also supposed to take L-section and X-section of the river downstream and upstream. A topographic map was prepared by tachometric surveying and longitudinal and cross-sectional profile of the area was drawn. The scales for plotting are as follows:Scale of topographic map =1:500Scale of L-Section: Horizontal scale =1:1000 Vertical scale = 1:100Scale of Cross-section Horizontal scale = 1:200 Vertical scale =1:200

3.5Equipment:The equipment used in the survey during the preparation of topographic map, are as follows:

Theodolite Ranging rods Leveling instruments Abney level Marker Arrow Staffs Compass Tapes Pegs Tripod

3.6 Methodology:The various methods performed during the bridge site survey were triangulation, leveling, tachometry, cross section, L-section etc. The brief descriptions of these methodologies were given below:

3.6.1 Recce:

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The bridge site was observed and the overview of the placement of axis was made.3.6.2 Site Selection:

The selection of bridge site is an art and requires considerable investigations. There are various factors for the selection of bridge site such as geological condition, socio-economical and ecological aspect etc. Therefore, the sites was chosen such that it should be at well-defined and stable banks and not affect the ecological balance of the flora and fauna of the site area. The site should be on a straight reach of the stream. The site which is sufficiently away from the confluences of large tributaries, which offers a square crossing & more advantageous foundation conditions, which is sufficiently away from landslides & subsidences should be preferred. The bridge axis should be so located that it should be fairly perpendicular to the flow direction and at the same time, the river width should be narrow from the economical point of view and the free board should be at least 5m. The starting point of bridge axis should not in any way lie or touch the curve of the road. A site which blends with the topography and landscape will be aesthetically pleasing.

Keeping in minds the above factors, the bridge site was selected. For the purpose of the shortest span, the stations were set perpendicular to the river flow direction. The riverbanks were not eroded and were suitable for bridge construction. The chance of change of direction of river on the selected axis line was nominal.

3.6.3 Fixing of control points and triangulationFor the topographic survey of the bridge site, triangulation was done. First the bridge axis was set and horizontal control stations were fixed on either side for detailing. Distances between stations on the same sides of river i.e. base line were measured with tape precisely. Then the interconnecting triangles were formed and horizontal angles (two set) were measured with theodolite. While doing so, first of all the entire polygon having six sides is considered, then two adjacent quadrilaterals are considered, finally eight triangles are considered. For each case, they are adjusted to satisfy the geometrical condition since the closing angular error is within the permissible limit. While applying the correction, only unaffected angles are taken into account. The bridge axis length or span was calculated by solving the triangles using the sine rule. From the measured bearing of the line, the

42

bearing of all traverse legs are computed, the coordinates of each legs is calculated, and the closing error which is found to be within the permissible limit is adjusted using the Bowditch’s method. Thus the horizontal control was set out.

For vertical control, the level was transferred from the TBM (located at right bank) to the control points and was transferred to the stations on the next bank by reciprocal leveling. For the same bank direct level transfer method was used.

Triangulation was performed for the determination of the approximate span of the bridge axis. The triangulation stations can be taken as the control points for detailing. Two points on either bank of the river were fixed as control points and one of the sides of the triangle was taken as the bridge axis. Then two triangles from each bank were fixed.

The base line was measured accurately by two ways linear measurement as well as tachometry and interior angles were measured by taking two sets of HCR reading by theodolite. The accurate span of bridge was computed by applying sine rule. To minimize the plotting error as far as possible well-conditioned triangles were constructed i.e. the angles greater than 30 degree, less then 120 degree and nearer to 60 degree. The best triangle is equilateral triangle.

3.6.4 Topographic surveyThe topographic survey of bridge site was done with the help of theodolite. The important details, which were not included in the cross-section data, were taken. Trigonometric leveling may be performed to find out the RL of the inaccessible points, but this situation was not arrived in the given bridge site. All the detailing points were noted for the topographic view of the bridge site.

3.6.5 Longitudinal Section The L-Section of the river is required to give an idea about the bed slope, nature of the riverbed, and the variation in the elevations of the different points along the length of the river. Keeping the instrument at the control (traverse) stations on the river banks, the staff readings were taken at different points along the center line of the river up to a 80 meters upstream and 80 m downstream. The R.Ls of the traverse stations being known previously; the levels of the different points on the

43

river were calculated. Then the L-Section of the riverbed was plotted on a graph paper on scale 1:100 for vertical and 1:1000 for horizontal.

3.5.6 Cross-SectionFor the cross-section of the river, the staff readings were taken at an interval of 20m. This was done up to 80m downstream and 80m upstream. While taking the reading the staff was erected on the bed of river.

At every 20m chain age the readings were taken for cross sectioning. The spot heights were taken where the change in slope was noticed or remarkable points were noticed such as normal depth level flood depth level, riverbank, etc. Theodolite was used for this purpose.

3.5.7 Leveling: Transferring R.L. from B.M. to control points:

The R.L of benchmark TBM= 1628.325m(located at right bank) was given and was transferred to the triangulation stations by fly leveling along the turning points by taking the back sight reading to the bench mark which should be within the given accuracy.

Reciprocal Leveling:When it is required to carry leveling across a river, ravine or any obstacle requiring a long sight between two points so situated that no place for the level can be found from which the lengths of foresight & back sight will be even approximately equal, reciprocal leveling must be used to obtain accuracy and to eliminate the error in instrument adjustment, combined effect of earth’s curvature & the refraction of the atmosphere, and Variations in the average refraction.Reciprocal leveling was carried out to transfer the R.L. from TBM to A.

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True difference in elevation between A and B = H = ha- (hb-e)Also the true difference in elevation = H = (ha '- e)-hb'Taking the average of the two differences we get the difference in elevation between A and B.

3.5.8 Computation and Plotting:The following tachometric formulas were used for the calculation of the horizontal distance and R.L. of different points:

Horizontal distance of any point from the traverse station, D = 100 x S x cos2θ

Where, S = Staff intercept = Top - Bottom stadia reading θ = Vertical Angle

And R.L. of a point = R.L. of station + H.I + D x Tan θ - axial hair reading

The topographic map, the longitudinal section and the cross section were plotted on the respective scales after the completion of calculations. By forming

45

the grid lines of 10cm x 10cm, control stations were plotted accurately. Then all ground details as well as contours were plotted with reference to the control stations by the method of angle and distances.The observation and calculation sheet are included in ANNEX-AThe topographic map, L-section of river bed and cross section are included in ANNEX-B

3.6 Comments and ConclusionThe bridge axis was set keeping in mind all the requisites that the proper site for the bridge has to be. The result of the computations of the triangulation gave the axis span of 46.617M

During the selection of the site all the considerations like geological, socio-economical and topographical considerations were made and the best site was selected. The site was steep on both the banks and very little water flowed in there. The site was deep and there was presence of trees along with bushes.

The bridge site survey was conducted to give broad knowledge about importance of reciprocal leveling, necessities of triangulation concept for fixing bridge span & to give wide concept about bridge site.

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ROAD ALIGNMENT SURVEY

4.1 Introduction

Road is an important infrastructure for development. It occupies a pivotal position in the growth of developing countries. The various civilizations of the world that are known for their excellence and attainments have left traces of their art of road construction. Roads can be constructed to penetrate the interior of any region and to connect remote villages. The advantage becomes particularly evident when planning the communications system in hilly regions & sparsely populated areas. Road transport offers quick & assured deliveries, a flexible service free from fixed schedules, door to door service, permits simpler packing, has a high employment potential etc.The safe, efficient and economic operation of a highway is governed to a large extent by the care with which the geometric design has been worked out. Geometric design includes the design elements of horizontal & vertical alignment, sight distance, X-section components, lateral & vertical clearances, control of access, etc.

The general guide-lines in selecting the alignment & locating route are: Should handle the traffic most efficiently & serve inhabited localities. Should have minimum Gradients & curvature, necessary for terrain. Should involve least impact on the environment. Should be located along the edge of properties.

In case of hill road, Should attain change in elevation by adopting ruling gradient in most of

length. Should avoid unstable hill features & areas prone to land slides. Should avoid steep terrain. Should avoid hair-pin bends. Should align preferably on the side of hill exposed to sun during winter. Should avoid deep cuttings & costly tunnels. Should develop alignment to suit obligatory points like passes, saddles,

valleys, crossing points of major rivers.

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In short, road should be short, easy, safe and economic as far as possible.

Roads are specially prepared ways between different places for the use of vehicles, people & animals. In countries like Nepal, where there are less chances of airways & almost negligible chances of waterway, roads form a major part of the transportation system. Therefore, it would not be an exaggeration in saying that the roads have an almost importance. 4.2 Brief description of the project area:Road alignment includes the works to run a road between two far distance points along the route. This specific job is essential for an engineer combating with the mountainous topography of Nepal. 4.2.1 Brief Description of the Project Area

Road alignment is an important aspect in the development of the

transportation network of the country. Road alignment is important part of the

survey. Road alignment and bridge site survey goes side by side to run a road

between two terminals and to carry a survey for the bridge construction along

the route. This specific job is essential for an engineer combating with the

mountainous topography of Nepal.

4.2.2 Hydrology and Geology

The road had to go along a Dry route that was much undulated. The place

some was damp. There were no large boulders or rocks of any kind along

the proposed site.

4.2.3 Soil

When the soil surface is inclined, there is a component of gravity that tends to

move the soil downward. If along the potential slip surface in the soil the

stress produced by gravity exceeds the shear strength of the soil along the

potential failure surface, the slope will become unstable. Obviously, the shear

strength of soil is largely depends upon the type of soil. Cohesive soil has

more shear strength than others do. The hard and dense soil is best for slopes.

We found soft clayey soil that was very damp. Other kinds of soils were not

found along our proposed route.

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4.3 Norms (Technical Specifications)

Recci alignment selection was carried out of the road corridor considering

permissible gradient, obligatory points, bridge site and geometry of tentative

horizontal and vertical curves.

The road setting horizontal curve, cross sectional detail in 15m interval and

longitudinal profile were prepared.

The topographic map (scale 1:1000) of road corridor was prepared. Geometric

curves, road formation width, right of way, crossings and other details were

shown in the map.

While performing the road alignment survey, the following norms were

strictly followed:

The road had to be designed starting at the side of Bridge and ending

Near tower 3

If the external deflection angle at the I.P. of the road is less than 3°,

curves need not be fitted.

Simple horizontal curves had to be laid out where the road changed its

direction, determining and pegging three points on the curve - the

beginning of the curve, the middle point of the curve and the end of the

curve along the centerline of the road.

The radius of the curve had to be chosen such that it was convenient and

safe i.e. not less than 12 m radius.

The gradient of the road had to be maintained below 12%.

Cross sections had to be taken at 15 m intervals and at the beginning,

middle and end of the curve, along the centerline of the road -

observations being taken for at least 10 m on either side of the

centerline. If undulations are there then section at that place should be

taken.

Plan of the road had to be prepared on a scale of 1:1000

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L-Section of the road had to be plotted on a scale of 1:1000 horizontally

and 1:100 vertically.

The cross section of the road had to be plotted on a scale of 1:100 (both

vertical and horizontal).

The amount of cutting and filling required for the road construction had

to be determined from the L-Section and the cross sections. However, the

volume of cutting had to be roughly equal to the volume of filling.

4.4 Equipment

The equipment used in the survey of road alignment were as follows:

Theodolite

Staffs

Ranging rods

Tapes

Leveling instruments

Compass

Abney level

Pegs

Marker

4.5 Design parameters

The design standards are adopted according to Nepal road standard. The design parameters are as follows:S.N Design Parameters Adopted Values1 Type of Road Single lane Black topped2 Minimum radius in horizontal curve (m) 153 Maximum gradient (%) 124 Minimum gradient (%) 15 Side slope of cutting 1:16 Side slope of embankment 1:1.5

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4.6 Methodology:4.6.1 Reconnaissance:

First of all reconnaissance were done by walking through the purposed road alignment, where the actual alignment of road has to be run. After this pegging was done on the proper position for instrument station for traversing ensuring that the preceding and succeeding pegs were visible and simultaneously pegs were marked.

4.6.2 Horizontal alignment:Horizontal alignment is done for fixing the road direction in horizontal plane.The interior angles were observed using 10" Theodolite at each IP and then deflection angles were calculated. The distance between two traverse stations was measured in the desired precision by tape.

Deflection angle = (360 or 180) - observed angleIf +ve, the survey line deflects right (clockwise) with the prolongation of preceding line and deflects left if –ve (anti-clockwise). The radius was assumed according to the deflection angle. Then the tangent length, BC, M.C EC, along with their chainage were found by using following formulae,

Tangent length (T L) = R * tan (/2)Length of curve (L.C) = π* R * /180Apex distance = R * 1/ (Cos (/2)-1)Chain age of BC = Chain age of IP – TLChain age of MC = Chain age of BC +LC/2Chain age of EC = Chain age of MC + LC/2

The BC and EC points were located along the line by measuring the tangent length from the apex and the points were marked distinctly. The radius was chosen such that the tangent does not overlap. The apex was fixed at the length of apex distance from IP along the line bisecting the interior angle.

4.6.3 Topographic survey

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Topographic survey of road corridor was done by taking the deflection angle at each point where two straight roads meet. The chainage of intersection point, tangent point and middle points were also taken by linear measurements and applying formula. The staff readings of each of these points were also taken. The staff points were chosen at every change of slope, important feature, existing electrical pole etc.

4.6.4 Vertical AlignmentVertical profile of the Road alignment is known by the vertical alignment. In the L-section of the Road alignment, vertical alignment was fixed with maximum gradient of 12 %. According to Nepal Road Standard, the minimum gradient of road is about 1% so as to facilitate the flow of drainage to specified direction. However the maximum of 12% was taken wherever not possible.

4.6.5 Leveling:The method of fly leveling was applied in transferring the level from the given T. B.M. to all the I.Ps. The R.L. of beginnings, mid points and ends of the curves as well as to the points along the center line of the road where the cross sections were taken, are taken by tachometry.

4.6.6 Longitudinal section:For the longitudinal section of the road the staff reading was taken at the interval of every 20m along the centerline of the road. Besides, these staff readings at beginning of the curve, ending of the curve and apex were also taken. The RL of each point were calculated. The profile was plotted on the graph at the horizontal scale of 1:1000 and vertical scale of 1:100.

4.6.7 Cross – section:Cross section was run at right angles to the longitudinal profile at 20 m interval on either side up to 10m distances wherever possible. For this, staffs reading of respective points were taken using theodolite.

The cross section was plotted on graph paper using following scale.Horizontal scale =1:100Vertical scale =1:100

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4.7 Comments and Conclusions:Survey of the road alignment was done to make most economical, comfortable, safe and durable. Extra care is taken to avoid any soil erosion and any other ecological damage. Vertical and horizontal curves are set according to Road Design Standards for comfort and other factors.

While setting the road alignment, it should be kept in mind that the minimum IP points should be taken as far as possible and deflection angles should be minimum as far as possible. The task was challengeable and tough due to the high altitude along the route.

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CURVES

5.1 IntroductionCurves are generally used on highways and railways where it is necessary to change the direction of motion. A curve may be circular, parabola or spiral and is always tangential to two straight directions. Circular curves may be simple, compound, & reverse.

5.2 Simple Circular CurvesA simple circular curve is the curve, which consists of a single arc of a circle. It is tangential to both the straight lines. The elements of simple circular curves are tangent length, external distance, length of curve, length of long chord, mid ordinate. The notations used are back tangent, forward tangent, point of intersection, point of curve, point of tangency, external deflection angle, normal chord, sub chord etc. The sharpness of the curve is either designated by its radius or by its degree of curvature. Setting out of curves can be done by two methods depending upon the instrument used.

i) Linear method:In this method, only a chain or a tape is used. Linear methods are used when a high degree of accuracy is not required and the curve is short.

ii) Angular method: In this method, an instrument like Theodolite is used with or without chain or tape. Before a curve is set out, it is essential to locate the tangents, point of intersection, point of curves and point of tangent.The linear methods for setting out simple circular curves are:

By ordinate from long chord. By successive bisection of arcs. By offsets from tangents. By offsets from chord produced.

The linear methods for setting out simple circular curves are: The Rankine’s method

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The two theodolite method The tachometric method

5.3 Vertical Curves A vertical curve is used to join two intersecting grade lines of railways, highways or other routes to smooth out the chainage in vertical motion .The vertical curve contributes to the safety, increase sight distance , give comfort in driving and have a good appearance.

A grade, which is expressed as percentage or 1 vertical in N horizontal, is said to be upgrade or + ve grade when elevation along it increases, while it is termed as downgrade or -ve grade when the elevation decreases along the direction of motion.

The vertical curves may be of following types: Summit curve: It is formed when an upgrade followed by a down

grade, an upgrade followed by another upgrade, a down grade followed by another down grade.

Valley curve: It is formed when a down grade followed by an upgrade, an upgrade followed by another upgrade, a down grade followed by another down grade.

In vertical curve all distance along the curve are measured horizontally and all offsets from the tangent to the curve are measured vertically. The methods for setting out vertical curve are:

The tangent correction method Elevation by chord gradient method Co-ordinate method

The length of vertical method must be long enough to provide at least minimum required sight distance throughout the vertical curve.

5.4 Transition Curves Transition curve is a curve of varying radius introduced between a straight line and a circular curve. While the vehicle moves on the straight line of infinite radius to

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the curve of finite radius, the passenger feels uncomfortable and even the vehicle may overturn. This is due to the causes of the centrifugal force couple with the inertia of the vehicle .To avoid these effects , a curve of changing radius must be introduced between the straight and the circular curve, which is known as the transition curve.

The main functions of the transition curve are as follows: To accomplish gradually the transition curve from the tangent to the

circular curve, so that the curvature increased gradually from zero to a specific value.

To provide a medium for the gradual introduction or change of required super elevation

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