ENGINEERING SURVEY FOR ALIGNMENT

DIFFERENT TYPES OF SURVEY FOR HIGHWAY , ALIGNMENT, LOCATION : 

1. MAP STUDY. 

2. RECCONNASSANCE SURVEY. 

3. PRELIMINARY SURVRY. 

4. LOCATION SURVEY. 

5. ENGINEERING SURVEY FOR HIGHWAY. 

6. TOPOGRAPHIC SURVEY. 

1. Map study

• In the beginning, various data in the forms of maps, aerial photographs, charts or graphs, etc. are collected. Topographical maps are done by the survey of India are available with 15 m to 30 m contour interval.

• Maps show the various topographical features like river, hills, and valleys.

• With the proper map study at the office, it is possible to obtain the basic details to fix the alignment of roads.

• Possible alignment can be fixed based on the following details available on the map :

i) Alignment passing through valleys, lakes, and ponds.

ii) Location of bridges for crossing rivers.

iii) Availability of a mountain passing a mountain range.

iv ) Joining of two stations at different elevation by taking a suitable ruling gradient.

v) Determination of length of the roadway using contour interval and ruling gradient.

 2. Reconnaissance survey

Definition

A field survey party examines the general character of a fairly broad stretch of land between the terminal stations in the field, along the proposed alternative alignments marked on the map is known as reconnaissance survey.

• In this survey, simple survey instruments like a prismatic compass, Abney level, tangent clinometer, barometer, etc. may be used to collect additional details rapidly.

OBJECTS

• To collect the details of obstruction along the route which are not available in the map. For example, Valleys, ponds, lakes, marshy land, ridge, hills, permanent structure, etc.

• To collect geological features of the field. For example, Soil type along the route from the field identification tests and the observation required for foundation work of bridges and construction of road pavements.

• To collect information regarding the availability of local construction material, water, and labor.

• To determine the approximate values of a gradient, length of gradients and radius of curves of alternate alignments.

• To locate the obligatory points along the alternative routes.

• To determine an approximate estimate of the total cost of construction of the road along each route.

• To determine two or three best possible routes.

 3. preliminary survey

Definition

The art of finding the details of alternative alignments found suitable during the reconnaissance survey is known as preliminary survey.

• In a preliminary survey, the survey instruments to be used are chain type, prismatic compass, leveling instrument, plane table theodolite.

OBJECTS

1] To survey along the various alignments found after the reconnaissance and to collect all necessary physical information and details of topography, drainage, and soil.

2] To compare the different proposals in view of the requirements of good road alignment.

3] To estimate the cost of constructing the road including bridges and other construction aspects along each alternative alignment of the road.

4] To finalize the best alignment from construction, maintenance, and traffic operation point of view.

 4. Location Survey

Definition

The detailed examination of the field along the alignment finally recommended during the preliminary survey is called Location survey.

• In this survey instruments used are theodolite, level, plane table, tape, etc.

OBJECTS

(i) The alignment finalized at the design office after the preliminary survey is to be first located on the field by establishing the centerline.

(ii) The detailed survey should be carried out for collecting the information necessary for the preparation of plans and construction details for the highway project.

(iii) To determine the cost of the total road project.

 5. Engineering Surveys for Highway

Engineering Surveys;

(I) TRAFFIC SURVEY

(II) SOIL AND MATERIAL SURVEY 

(III) DRAINAGE SURVEY

When the selection of final alignment or final centerline is done with the help of a planning survey, the next part is to perform an engineering survey.

Engineering surveys consists of three surveys to be carried out as follows.

6. Topographic surveys

• Topographic surveys consist of determining the horizontal and vertical locations of objects on the surface of the earth.

• Topographic surveys show the nature of the ground or profile of ground which is the most essential part for proper road alignment.

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