Survey & levelling

 

 

Preliminary work in road construction is surveying & leveling works. This consists of Traverse Survey, TBM Survey, and Centre Line Setting out, Centre Line marking, Cross Section Survey and Submittal of Drawings.

Traverse Survey

At the commencement of contract all the basic traverse points will be checked and if any are found to be missing or appear to have been disturbed, necessary arrangements should be made to re-establish the points and traverse survey is carried out after that.

Establishing TBMS

We did not use survey Department bench marks .The permanent concrete cube was selected to permanent bench mark. It height was assumed hundred meters. But this point is not sufficient for construction purposes. So reference to this point Temporary bench marks (TBM) should be established. TBMs are used to transfer reduce levels in road construction. Temporary bench marks should be established at the rate of four per km and also at or near all structures.

When establishing a TBM the following facts should be considered

• From one TBM it should be able to cover a long distance, when transforming reduces levels to the road.
• TBM must be a fixed one. It should not damage or disturbed during the construction period.
• It should easy to work with the established TBM. ( Easy to place the stuff on it etc. )
• So to be the TBM permanent concrete is marked point on it.

The pictorial view of the concrete TBM

 

Pictorial view of the TBM

TBM Travers

TBM traverse is done to establish the reduce levels of each and every TBM with reference to the Permanent bench marks established by us. Engineering level is used to establish TBMs.

Centre Line Marking

Centerline marking is the primary survey part in road construction. Centerline is useful while setting out for any road construction work. So it is very essential marking centre line first, before any construction work.

Equipment using for centre line marking

• Linen tape
• Road marking paint
• Nylon cord
• concrete nails

Safety equipment (e.g. Traffic cones, Bastinade boards etc.)

Centre Line Setting Out And Marking

Using total stations and approved coordinates of control points, the road centre line should be marked at every 10m interval on the road. With the aid of rope and road marking paint, the centre points marked in every 10m intervals of the road should be extended as a centre line and that established centerline should be maintained until the end of the project.

Chain age Marking

Chain age marking is done to describe the location of the road. Chain age should be marked on the road centre line in each 20m and 100m interval with meter and kilometer interval respectively.

Equipment used for chain age marking

• Linen tape
• Road marking paint
• Nylon cord
• Concrete nails

Safety equipment (e.g. Traffic cones, Barricade boards etc.)

Process of chain age marking

• Lay the nylon cord through the 20m interval centre points and draw the centerline using chalk.
• Write the chain ages using road paint.