projection gbt tower

INDIA

GBT Site Survey & Construction Procedure.

Now, we will discuss about GBT Site Survey & Construction Procedure

Survey ToolsSurvey tools are same for RTT & GBT sites;

White Paper, Scale (30cm), Pencil, etc,. to draw the rough layout Measuring tape – Steel tape or Cloth tape

Compass

Tower Details like

Height

Weight

Base Width

No of Legs (3 legged tower OR 4 legged tower)

Shelter Details like External dimensions, No of pedestals, c/c distance of pedestals, Shelter Weight

DG Bed Size, DG Weight

Earth pit size, No. of pits & c/c distances (INDIA)

SITE SURVEY – GBT

SURVEY PROCEDURE / CHECKS

(INDIA)

SITE SURVEY – GBT

Before going to the survey, we should know the following dimensions:

Tower Base Width & Excavation Width,

Shelter Size

DG Size

With the above details we can find out whether the given size of the site is suitable or not to arrange the all above equipments.

(INDIA)

SITE SURVEY – GBT

Tower Excavation Width

If foundation drawing is available, excavation width can be know from that drawing

If foundation drawing is NOT available: take excavation width = 2 x Tower Base width

40 m

Tower

3.2

6.4 = 2 x 3.2

This is only for survey purpose; during execution we have to follow as per foundation drawing only.

Excavation Line

4.01.2 3.53.3

ELECTROTEK(INDIA)ELECTROTEK(INDIA)

1. Write Site Name, Tower Ht., Site Address at the top of the page.

Kota – 40m, Near Petrol Pump, Main Road, Nellore Dt.

3. Indicate the NORTH direction.

2. Draw the boundary line with dimensions.

15m

20m

N

4. Mark the adjacent roads, surrounding structures and its distances.

Street road

Green

Field

Green

Field

5. Mark the site level w.r.t. the road level

6. Mark the proposed area of tower, DG & Shelter

12. Write your name, Employee ID No., Date & Sign

P Rajesh

401501

03.03.06

Rajesh

P

9. Mark the proposed Earth Pits

11. Mark the nearest Elec. Pole / Transformer to the site

PREPARATION OF LAYOUT AT SITE

PROCEDURE / CHECKS

13. Take the Owner sign and customer site engineer sign

Electric Pole

Make sure that, 0o Should be placed upward of your

page

14. This Rough layout should be sent to Design department to prepare CAD Layout

Main Road

15m

20m

40 m

Tower

3.21.51.5

Shelter

2.5x3.2

DG

2 x 1.5

1.5

2.5

1.5

1.5

Security

Room

3 x 3

+ 0.5 m w.r.t. the road level

EP

0.5 x 0.5

EP

0.5 x 0.5

EP

0.5 x 0.5

EP

0.5 x 0.57. Mark all dimensions w.r.t. the boundary as shown

8. Mark the cable tray rooting

10. Mark the Security room and gate GATE

Owner Customer

4.01.2 3.53.3To design the foundation, we require soil parameters like SBC, Density, Angle of repose etc.,

Kota – 40m, Near Petrol Pump, Main Road, Nellore Dt.

15m

20m

NStreet road

Green

Field

Green

Field

P Rajesh

401501

03.03.06

Rajesh

P

SOIL TEST

Electric Pole

Main Road

15m

20m

1.51.5

Shelter

2.5x3.2

DG

2 x 1.5

1.5

2.5

1.5

1.5

Security

Room

3 x 3


GATE

Owner Customer

Soil sample to be collected within the proposed area of the tower

Soil sample collected areas

Soil report should be sent to design department to design the foundation

The following are the different types of foundations depends upon the soil conditions

Isolated Foundation

Raft Foundation

Pile Foundation

Rock-Anchor Foundation

ELECTROTEK(INDIA)

CONSTRUCTION PROCEDURE (Raft Foundation)

Site Cleaning

Marking

Excavation

Levelling of excavated pit

Laying of PCC

Bar-bending

Shuttering

Raft Concreting

1st lift column concreting

Tie beam concreting

Template Fixing

Final concreting

Backfilling with proper compaction

INDIA)

4.01.2 3.53.3Carry the CAD layout and foundation drawing

NStreet road

Green

Field

Green

Field

Marking

Main Road

1.51.5


At site

Mark the distances from the boundary Mark the Excavation line with the help of Foundation Drawing

Ex.: 6 m is the width of the excavation

6

6

Check the diagonal distances

= 8.485 m62 + 62

Excavation with JCB is recommended

Excavation

In case of lose soil, proper shoring should be provided to prevent soil collapse.

ELECTROTEK(INDIA)

Supports to prevent the soil collapse In case of seepage, de-watering

should be done

Seepage of water

Motor for de-watering

Excavation with JCB is recommended

Excavation

Proper levelling should be done to maintain uniform foundation depth

Levelling

Check the depth of foundation at all corners as per drawing

In case of lose soil, proper shoring should be provided to prevent soil collapse.

In case of seepage, de-watering should be done

PCC (Plain Cement Concrete)

Grade of Concrete

Proportion

Ballast (cum)

Sand (cum)

Cement (cum)

M10

1:3:6 0.9 0.45 0.15 4.5 bags

1:4:8 0.92 0.46 0.115 3.45 bags

1:5:10 0.95 0.475 0.095 2.85 bags

Volumes per Cu M

Generally used mix

PCC – Thickness should be as per drawing

Bar bending – Shuttering – Concreting

PCC

After laying the PCC, mark the column positions to place the column reinforcement.

Check the c/c distances and diagonal distances

Bar bending – Shuttering – Concreting Bottom reinforcement in two way direction

Cover Blocks b/w the PCC and bottom reinf.

Bar bending – Shuttering – Concreting Column reinf.

Place the column reif. exactly on marked portion of PCC

Side view


Place the column reif. exactly on marked portion of PCC

Side view

Tie the ‘L’ bends of the column reinf. to the bottom steel


Column Stirrups

Set

Stirrups at the top of the column reifn.

Stirrups at the bottom of the column reifn.

First arrange the stirrups at top and bottom of the column reinf.


Arrangement of chairs to support the top reif.

Chairs


Stirrups

Top reinf. of the raft


If chairs are not provided properly at regular intervals, top rainf. may sag as shown

Raft Shuttering


Now it is ready for Raft Concreting


Checks before Raft Concreting

Check the size of the raft reinf. and spacing as per drawing or not

Check the size of the column reinf. and no. of bars as per drawing or not

Check the c/c dist. and diagonal dist. of column reinf. As per drawing or not

Check the raft width and depth as per drawing or not

Check for shuttering gaps

Mixing of concrete should be machine mix

Grade of concrete should be M20 (as per drawing) as discussed in RTT

While concreting, vibrators should be used for compacting the concrete


Aggregate should be immersed in the concrete as shown to develop the bond for column concrete

Picture at siteAfter Raft Concrete


Side shuttering can be removed after 24hr. from the concreting

Arrange the column shuttering for first lift concreting

Curing should be done properly for the minimum period of 7 days


Before first lift concreting:

Again check the c/c distance and diagonal distance of the column shuttering

Check the column sizes as per the drawing or not

Aggregate should be immersed in the concrete as shown to develop the bond for 2nd lift column concrete

Shuttering can be removed 12hr. after concreting


After Concreting


Tie beam & 2nd lift column

2nd lift column shuttering

Tie beam shuttering


Tie beam reinforcement

Tie Beam C.S.

Position of T B Bars

Bar Bending


Arrange the tie beam reinf. Tie beam reinf.

Check the alignment of the columns by pulling the thread from one end to other

All corners should be in a straight line


Template fixing

Recall the procedure which we have discussed in RTT site

Template & Foundation bolts fixing

Measures before fixing the template on foundation

Fix the template on ground

Check the c/c distance at all sides as per drawing

(In this example c/c distance is 2.1 m )

Check the diagonal distance in both ways


Template fixing

Procedure for water level checking

Alignment & Fixing of Anchor Bolts

Isometric View

Side View

Top View


Template fixing



Template fixing


In the same way check at all corners as shown


Template fixing

Top level should be same for all fn. bolts


Now it is ready for final concreting

Checks before Final Concreting

Check all dimensions are per drawing or not. i.e. Tie beam size, column size and tie beam distance from the top of the column etc.,

Check the tie beam reinf. Size and no. of bar at top and bottom as per drawing or not

Tie Beam C.S.

Check all foundation bolt thread portion is covered to protect while concreting

All the threaded portion of the fn. Bolts should be applied by Greece and covered with polythene cover


Now it is ready for final concreting

After Concreting


Site shuttering can be removed after 24hr. (except tie beam bottom shuttering)

Tie beam bottom shuttering can be removed after 5 to 7 days

Template can be removed after 12 hr. from the concreting period

Curing should be done min. of 14 days

Back filling

Back filling should be done with proper compaction up to the above ground level to allow settlement in future

Excavation in Hard Rock

If we found hard rock for small depth, it has to be removed to reach the complete foundation depth



If we found hard rock nearer to the below ground level, we have to go for the Anchor Foundation

Level the rock surface

Drilling

Anchorage

Anchoring Rod

Chemical Grouting



If we found hard rock nearer to the below ground level, we have to go for the Anchor Foundation

Level the rock surface

Drilling

Anchorage

Raft and Columns

Pile Foundation

If the bearing capacity is low in the given area, piles are required

Boring

Pile Foundation

If the bearing capacity is low in the given area, piles are required

Boring

Reinforcement & Piling

Pile Concreting should be of M25 mix (1:1:2)

Pile Cap & Column

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