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Construction Activity Report‐I (May‐2010) Submitted to: Dr. D. Sarkar

M.Tech, Construction and Project Management Department Faculty of Technology, CEPT University, Ahmedabad-9

Submitted By: Mitul S. Shah (CP1809)

Construction Activity‐Report‐I CP1809

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Construction Activity Report‐I Period: 5th May to 1st June Introduction: There were several civil construction activities going on at the 5x660 MW Thermal Power plant project at Mundra which consisted of the following:

Main Power House Building Chimney Construction and Internal Erections Cooling Towers Cooling Tower Main Control Buildings Mechanically accelerated Clarifiers Coal and Ash Silos Electrostatic Precipitator Erection Circulating Water Culvert Coal Conveyer Galleries Demineralization Plant Wastewater Treatment Plant Circulating Water Pump House

In addition there were various miscellaneous activities going on at the site which consisted of installation of pipelines and other buildings as required on the site. The work for the power plant components of the TPP were awarded to a main contractor i.e. SEPCOIII and they subcontracted the work to various other sub contractors as mentioned in the preliminary site report. Due to the vast nature of the activities which were going on at the site, two activities were concentrated upon during the first month, which are the main power house construction and the chimney construction. The details of the construction are as follows.


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Main Power House Construction Introduction The 4620MW Power plant consisted of 9 units which were divided into the following phases. Out of which the first and the second phase which consisted of a total of 4 units which produced 330 MW each and were subcritical were given as a direct contract to a particular Chinese contractor. But with the problems arising in the operation of the contract, Phase-III and Phase-IV which consisted of 5 units of 660 MW (Supercritical) were given as an EPC contract to a Chinese company SEPCOIII which specializes in power construction. They subcontracted the work to three major subcontractors who were

Gannon Dunkerley Ltd. [ Constructing Units 5, 7, 9 ] Simplex Infrastructure Ltd [ Constructing Units 6,8 ] Larsen and Toubro, ECC Division [ Fabrication and erection of ESP ]

4620MW Thermal Power

Plant, Adani Power, Mundra

Phase-I Phase-II Phase-III Phase-IV

Unit-7 Unit-8 Unit-9


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There was rapid civil construction work going on in the Unit-8 and Unit-9 and thus there was observation of the activities going on at both the sites. Typical Layout of the Main Power House Building

Legends showing various major components of a Main Power House (MPH) Legend No.

Description Legend No.

Description

1. Electrostatic Precipitators 6. High Power Turbines 2. Boiler House 7. Generator Area 3. Coal Bunkers (6 Nos) 8. Maintenance Access 4. Deaerator Area 9. Low Power Turbines (2 Nos) 5. Control Cabin Room 10. Conveyer Tower

1

2

4

3

6 8

7

5

9

10


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Status of the work when joined at the site: Unit-8: There are four stages of construction of a particular unit which is consisting of the raft foundation which is followed by the column construction and then there is the mid deck construction. After that there is a 3rd lift of the columns from the foundation which is followed by the final construction of the Turbine and Generator Deck slab. For the Unit-8, the staging works for the TG Deck slab were completed and the reinforcement was being fabricated along with the shuttering work for the TG Deck slab. A very important activity in the TG Deck Slab casting is the arrangement and leveling of the bolts for the turbines and generator. The bolts along with their sleeves were already roughly inserted in the slab, but the alignment, precise centre to centre distance and level were still not done. Unit:9 At Unit 9 the raft foundation works had been completed and the staging was being done for the construction of the columns above the foundation. All the steel erection work for the the Unit-9 was completed when we joined the site and the tower crane for the same was also erected. Reinforcement fabrication was going on for the columns as well.

Fig- Construction of TG Deck after Staging and Reinforcement Placed


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TG Deck Slab Construction

The Turbine and Generator Deck slab is the most important civil construction work in the main power house. The dimensions and the layout of the slab can be understood as follows:

Materials of Construction

Sr. No Material Grade Related IS Code

Remarks

1 Reinforcement CTD, Mild Steel

IS 1786, IS 432 Respectively

20mm, 25mm, 36mm, 16mm Reinf. used

2 Concrete M30, M35, M40

IS 456:2000 RMC Used

3 Shuttering Plates

1220x2440x12mm Plates Used

4 Staging Pipes and Clamps

Mild Steel 40mm NB Pipes Used, 6m length

5 MS Sleeves and Bolts

According to DongFang Turbine Measurements

For the Fixing of Turbines and Generator as by supplier.

6 Embedded Insert Plates

Mild Steel For Welding of Beams. 200x200x5mm Plates used

7 Structural Steel Beam Sections

ISMB 250 For the Foundation of Pulling Block

Manpower Employed at the Site

Sr. No. Type of Labour Quantity Remarks 1 Carpenters 58 For Shuttering 2 Semi Skilled

Labourers 40 For Various Works

3 Helpers 75 Assisting the Skilled Labour

4 Fabricators 40 Fabrication of Reinforcement

5 Welders 25 For Welding and Erection of Reinforcement


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6 Khalasi 20 For various works 7 Unskilled Labour 70 Other Misc Works Total 328 Equipment Used for Construction

Sr.No Equipment Manufacturer Model No. Capacity Remarks

1 Gantry Crane

SEPCO Fabricated

NA 80/20 Tons

2 Tower Crane

JINGLU-QTZ

TW-4563 10T

3 Crawler Based Lattice Boom Crane

KOBELCO CSK-2500 250 Tons

4 Telescopic Boom Crane

P&H R4ST-15 75 Tons

5 Air Compressor

6 Electric Operated Vibrators

3600 Vibrations/minute

2.5m Length, 6mm needle

7 Gas Cutters Ramco NA 8 Total

Station Leica, Germany

PON1243

9 Boom Placers

Sany SY5256THB 6 m3

10 Concrete Pumps

Putzmeister NA 45 cum/hr

11 Transit Mixers

Tata, Ashok Leyland

6m3

12 Bar Bending Machine

- For Reinforcement Bending

13 Bar Cutting Machine

- For Reinforcement Cutting

14 Batching Plant

Schwing Stetter

30 Cum/Hr


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Civil Works for the TG Deck Unit-8 were to be commenced on the date 10/03/10 and were to be completed by the date 28/3/10, but now the projected completion date has now gone behind to 28/4/10 which results in a delay of one month in the completion of the TG Deck. We have attempted to find out the reasons for the delays so that they can be corrected in the future execution of similar magnitude. Data Collection and Analysis Data collection was done from the records maintained by the client engineers and the major activities in the TG Deck Casting program are shown with their scheduled start and end dates along with the actual start and finish dates. Please note that we have assumed the date for casting as obtained from the site. Sr. No.

Activity Description

Sch.Dur Act.Dur Scheduled Start

Actual Start

Scheduled Finish

Actual Finish

1 Raft Foundation

42 45 20/10/09 26/10/09 1/12/09 9/12/09

2 Column 1st Lift

36 38 25/11/09 3/12/09 31/12/09 9/1/10

3 Column 2nd Lift

4 Mid Deck 41 46 22/12/09 29/12/09 1/2/10 12/2/10 5 Column 3rd

Lift 29 30 1/2/10 9/02/10 1/3/10 10/3/10

6 TG Deck 57 83 4/3/10 10/3/10 29/04/10 31/5/10 Table-1: Activity Planning for the MPH-Unit:8

Lag Analysis- Unit-8

050

100150200250300

MPH

Raft

Column L

ifts

Mid

Deck

Column 3

rd L

ift

TG Dec

k

Activity

Cu

m.

Du

rati

on

(D

ays)

Planned

Actual


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Lag Analysis As we can see that there is a total lag of 37 days in the completion of the MPH building up to the TG Deck Level. The Percentage Lags for each and every major activity for the MPH building can be shown as follows:

Activity % Lag Raft 7.14% Column Const. 5.55% Mid Deck 12.2% Column 3rd Lift 3.45% TG Deck 45.6% Total Project Lag 18%

Labour Productivity Analysis for TG Deck Productivity can be defined as, the total time (generally in terms of hours) required to complete unit work. We have attempted to find out the total productivity analysis for the TG Deck of Unit-8. The quantities of the materials to be worked upon are as follows: Description Qty. Nos. of

labourers Working hrs./day/labour

Productivity

Staging 25000 pipes 80 12

0.0384hrs/pipe

85000 clamps 0.0112hrs/clamp

Reinforcement 260 MT 84 12 3.87 hrs/mt

Shuttering 1025 sq.mt. 66 12 0.77 hrs/sq.mt

Concreting 1290

Table-2: Quantities and Productivity Calculation for the TG Deck Slab (Unit-8) Now the productivity calculated is as per the actual work done for the slab and the collected data has been used. Now the scheduled productivity and the actual productivity can be compared to find the productivity lag which would be very useful for planning in the future.

Productivity as Per Schedule and Actual

Item Scheduled Actual % Reduction in Productivity

Staging Pipes 0.0294 0.0384 23.2% Staging Clamps 0.0073 0.0112 34.11% Shuttering 0.462 0.77 40.76% Reinforcement 2.246 3.87 42.2%

Table-3: Productivity Actual and Scheduled


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Staging Productivity Analysis

00.0050.01

0.0150.02

0.0250.03

0.0350.04

0.045

Staging Pipes Staging Clamps

Activity

Pro

du

ctiv

ity

Scheduled

Actual

Productivity Analysis

00.5

11.5

22.5

33.5

44.5

Shuttering Reinforcement

Activity

Pro

du

ctiv

ity

Scheduled

Actual

Fig- Graphs showing the difference in the scheduled and actual productivities for TG Deck Slab-8 Activity Productivity Analysis for TG Deck Description Qty. Scheduled

Duration Actual Duration

Scheduled Productivity

Actual Productivity

Staging 25000 pipes

14 20

0.00056 0.0008

85000 clamps

0.00016 0.00023

Reinforcement 260 MT 20 31 0.076 0.12Shuttering 1025 sq.mt. 22 32 0.021 0.031Concreting 1290 1.5 1.5 0.0011 0.0011

Activity Productivity Analysis-I

0

0.0002

0.0004

0.0006

0.0008

0.001

0.0012

Stagin

g

Concre

ting

Activity

Pro

du

ctiv

ity

ScheduledProductivity

Actual Productivity

Activity Productivity Analysis-II

00.020.040.060.080.1

0.120.14

Reinforce

men

t

Shutte

ring

Activity

Pro

du

ctiv

ity

ScheduledProductivity

Actual Productivity

Fig- Graphs showing the difference between the Actual and Scheduled Activity Productivity


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Reasons for the Lag in Schedule and Productivity There are various reasons because of which the MPH unit-8 civil works were delayed and the reasons can be stated as follows:

Improper Planning of Materials: There was a lack of planning on the part of the sub-contractor i.e. Simplex Infrastructure wherein the laborers were sitting idle for a lot of time due to the unavailability of materials. But the Simplex office stated that there was material available but it had to be deshuttered from a previous casting activity. This resulted in one gang de-shuttering the forms and one gang sitting idle which resulted in lag in schedule and productivity.

Unavailability of Materials: The Steel gangs were often sitting idle during the mid deck slab construction and TG Deck construction because the steel had not been provided to them for working by Simplex.

Unhygienic Labor Colony: There was a lack of cleanliness and other sanitation facilities in the labor colonies and hence there were frequent instances of many skilled, unskilled and semi-skilled labourers etc. remaining absent during critical times. This resulted in frequent delays and hence the lag occurred in completion.

Temperature: There was an inherent increase of about 10-13 degree Celsius in the temperature during the initial months of the construction activities for the MPH unit which was started in the winter season, but as the summer season approached, due to the high temperature and drastic variations in humidity there was a delay as well and loss of productivity.


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Construction Procedure Pre-Construction Activities: There are some pre-requisites which need to be fulfilled before the actual construction can commence on the site. The details for the same are as follows:

The Level of the third lift of the columns from the raft foundation level is to be checked if they have reached the required level as per the design.

All the columns are to be checked whether they are at the same level or not. Dowel bars from the third lift are extended enough for lapping for the final

casting or not.

After the following activities are completed, the actual construction activities of the TG Deck construction can start and the various activities of construction can be given as below:

Staging with Completion: First step of the TG Deck construction is to raise the staging which has been started from the Foundation Level, from the Mid Deck Level which is at a height of FL+7.2m to a height of FL+14.72m which is the height for the TG Deck top level. Normal Staging Material of 40mm NB Pipes and MS clamps are being used for the staging. The length of the pipes is 6m. The pipe lengths can be adjusted if required with the help of gas cutting. The clamp and pipe arrangement can be seen in the following image and staging material specifications and drawings can be given as follows. The staging pipes are clamped together horizontally and vertically to form a H-Frame as shown in the figure. These H-Frames are then provided with Cross Bracings clamped together to protect them from wind loads as well as to arrest the movement of the legs of the H-Frame. Vertical Pipes are placed at a distance of 675m C/C and the horizontal pipes are clamped together at the spacing of 1200mm C/C. Alternate Cross Bracings are provided and the frame is positioned. Similar procedure is followed and the staging is erected for 7m height. The total height of the staging is kept at 14.72m at the Beam Bottoms and 20m in the cutouts as shown in the plan of the TG Deck Slab.


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Beam Bottom and Insert Plate Fixing: After the staging works are completed, and the required level of the beam bottom has been achieved, beam bottom fixing and the insert plate fixing activities are commenced. Steps for the same can be given as follows:

Prop Heads are attached to the vertical staging pipes. ISMC100 Channel sections are then inserted into the prop heads as shown in

the figure bottom facing. Now horizontal wooden battens of 25x25x50 which can be called as waler

beams are then supported on the channel sections perpendicular to them as shown in the figure.

On the top of the waler beams the wooden shuttering plates of the dimensions 1220x2440x12mm are nailed together to the waler beams and the shuttering plates are as seen in the sketches for the formwork.

Care is taken at every point that the level is maintained and it is done either with the help of a bubble tube or in some cases with the help of a dumpy level. Centre-lines are also marked. When the entire bottom shuttering is completed, again the level is checked for being at FL+14.72m as indicated in the plans.

With that the activity of beam bottom shuttering is completed. After that the position of the bottom insert plates is checked and they are fixed

together. The dimensions of the plates vary and they range from 250x250x5mm to 500x500x5mm. They are provided by the Dong Fang Turbine Plant, China and are generally used for welding the beams which will support the hanging turbines and generator.

36mm-# TMT Bar Tie Rods @ 700mm C/C

12mm thick Ply Shuttering Plates

Wooden Walers (15x5mm) W/Jacks

Wooden Battens (50x100) Nailed @ 300mm C/C

Prop Heads and ISMC 75 Channel Sections @ 675mm C/C

40mm NB MS Pipes (IS: 1239) @ 1200mm C/C Vertically


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Fig- Staging and Shuttering arrangement for Beams

Fig- Arrangement of Formwork and Staging for the TG Deck Slab

Reinforcement Work Completion: Reinforcement work for the beams and the columns which form the decks slab are then fabricated and erected on the top of the bottom shuttering plates. As shown in the structural drawings, the main reinforcement for the beams consists of 36mm# reinforcement which are tied together with the help of 20mm# bars. 40mm cover is used before the reinforcement in placed into position. The reinforcement cages are either fabricated on the deck or on the ground and then are transported to the deck with the help of a crawler crane or a tower crane according to the suitability. The reinforcement are then tied together to complete the erection with the help of 2mm binding wires. Reinforcement is then checked if it is according to the structural plans provided. This steel checking is done by all parties involved in the construction which are Adani Power Limited, SEPCO III and Simplex Infrastructure. After that the shuttering and bolt-sleeve fixing activity is commenced.

Fig- Horizontal and Vertical Reinforcement Arrangement for the TG Deck Slab


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Fig- Typical Reinforcement Arrangement for the TG Deck Beams and Slab

Fig: Section 1-1 of the Reinforcement Cage for the TG Deck Slab


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Side Insert Plate Fixing: After the reinforcement work is almost completed or is nearing completion, the side insert plate fixing is commenced either besides the reinforcement activity or after its fabrication. Side Insert Plates are generally of 5mm thickness and are welded to the reinforcement cage with the help of 4-10mm# reinforcement bars with a weld length of 35mm on the plate. The side insert plates are used for welding the beam sections which will support the turbines and generator which are hanging. Additionally the bolts according to the arrangement provided by M/S Dongfang turbines which are used which vary from the bore sizes of 56mm to 89mm, which are used to fix the turbines and generator are to be inserted into the reinforcement cage. The bolts and sleeves are provided by the turbine supplier and are made available at site. Their initial position is fixed and stayed with the help of random channel sections with holes in them as shown in the figure. This is a high precision activity and the bolts should be aligned and leveled with an allowance of +1-2mm error only. Thus continuous leveling and alignment with the help of level instruments and total station goes on with the succeeding activities. Shuttering: After the rough alignment and level of the bolts has been completed along with the reinforcement work, the shuttering work commences. Shuttering works can be divided into two parts:

Inside Shuttering: Shuttering enclosing the Cutouts Outside Shuttering: Shuttering enclosing the entire slab.

Total Shuttering Quantity as mentioned above is 1350 Sq. Ft and the shuttering material used is the Bonded Plywood which is having the size of 1220x2440x12mm which was specially manufactured for this project. Shuttering Procedure can be started by first nailing the shuttering plates with each other to form the chain of shuttering which is of the size of a particular section. Waler beams and props are then nailed to the shuttering boards. This may be already done or is done on site. Now this shuttering is then first nailed to the sides and the bottom, and immediately stayed with the help of jacks which are made of the same staging 40mm NB Pipes attacked with the prop heads. Tie Rods are considered to be most important component of the shuttering and they are inserted after boring a hole through the shuttering plates at approximately 750mm C/C and at every 500mm C/C vertically. Tie rods are made out of 36mm# reinforcement. Additionally sometimes the two back to back angle sections welded together may be used as props which will act as tie rods and as props for the side shuttering. The line and level of the shuttering is checked and then final jacking is done to completely fix the shuttering. Any space in the tie rod holes is filled with gunny bag wastes, so that the cement slurry does not leak from the particular place during concreting. This is the shuttering procedure for the TG Deck Slab.


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Checking of Bolts, Reinforcement and Shuttering: After the shuttering is fixed, then the final checking of the bolts, reinforcement and shuttering is commenced. Firstly the

reinforcement needs to be checked, whether the column and beam reinforcement is according to the structural plans provided by the contractor. If not, the additional reinforcement required is then welded to the cage. Along with the checking of the reinforcement, the bolts are then checked for level and alignment along with their centre to centre distance which are provided by the contractor after receiving the details from the turbine and generator supplier. It was seen that a lot of time is taken up during this activity to achieve the required accuracy in work. Dumpy level and total station with the regularly calibrated measure tape is being used

for the particular activity. After checking is completed by Clients Mechanical division and the contractor’s mechanical division, permission is given to the subcontractor to commence casting of the TG Slab.

Fig- Arrangement of Sleeves and Bolts and their connection with Reinforcement


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Casting: After all the checks have been completed and the protocol has been signed by the client, contractor and the subcontractors, the casting activity of the TG Deck Slab is commenced. M40 grade of concrete is used in the casting which is of Ready Mixed Concrete type and is produced by a Macons Batching plant of 60 cum/hr capacity operated by Simplex Infrastructure. Mix Design for the same can be given as follows:

Proportions 1 M3 Mix 0.5 M3 Mix

Cement 460.00 230.00

Water 193.20 96.60

Sand 743.93 371.97

10 mm Aggregates 400.35 200.18

20 mm Aggregates 600.53 300.27

Admixture ( Sikament 600 HP/2 APL )

4.60 2.30

The total amount of concreting that needs to be done is 1290m3 and has to be completed as soon as possible and hence no joints should be allowed to form as it is a very important structure. Hence the entire concreting is done at a single go in 36 hrs. The concreting is done by using One Concrete Pump with the capacity of 45 m3/hr and Two Boom Placers which are having a capacity of 100m3/hr if no operation and movement of boom is involved. The frontal sides were to be concreted with the help of the boom placers whereas the inner sides with the help of the concrete pump. Concrete Pipe used was of 100mm diameter. A rubber hose pipe was to be attached for maneuvering the flow of concrete.

Fig- Concrete Pump and Boom Placers in Operation


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Precautions and other Procedures followed during Casting:

The temperature of the concrete had to be maintained at 23 degree Celsius because of the mass concreting and if not then micro-cracks could develop during the casting itself. This was achieved by adding ice into the water which was used for producing concrete.

The Boom placer operator had to be positioned at the slab rather than at Ground level and this was achieved with the help of a remote control which the operators of the Boom placers had. It is for the efficient movement of the boom during concreting and quick co-ordination.

No particular area of the concreting was allowed to be filled in layers larger than 300mm at a time. The layers were not allowed to become dry and new concrete was immediately placed above it as soon as the signs of dryness occurred.

Vibrators were immersed in the concrete at full depths of 3m as the vibrator needle had a depth of 2.5m and the vibrator was kept immersed in the concrete for about 7-8 seconds. The vibrators were immersed only in the centre and where concrete stack had formed and not at the edges because then it can harm the shuttering and affect the tie rods as well.

Any concrete on the reinforcement top was cleaned with the help of Khurpi or Vibrators.

If by any chance there was a dry area formed in the concrete then it was treated with Nito-bond compound from Fosroc mixed with cement slurry and then the new concrete was poured above it.

Level bolts known as Topping Bolts were also welded to the reinforcement to maintain the level of the concreting of the slab.

Additionally all the equipment foundation bolts were covered by gunny and plastic bags so that concrete does not enter the sleeves of the bolts.

Constant checking was done so as to avoid any failure of shuttering or tie rods.

Fig- Level Bolt for Concrete (Welded) Fig- Boom Placer in Operation


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Pour Card

Pour Records TG DECK SLAB Unit No. 8

Date Time BP1/ Macons BP2/

SEPCO Total

Cumulative Pour

Cum.Hours Average

31-May-10

17:00 25.00 20.00 45.00 45.00 1.00 45.00

18:00 15.00 18.50 33.50 78.50 2.00 39.25

19:00 10.00 20.00 30.00 108.50 3.00 36.17

20:00 15.00 20.00 35.00 143.50 4.00 35.88

21:00 20.00 30.00 50.00 193.50 5.00 38.70

22:00 20.00 45.00 65.00 258.50 6.00 43.08

23:00 15.00 29.80 44.80 303.30 7.00 43.33 01-Jun-10 0:00 15.00 16.80 31.80 335.10 8.00 41.89

1:00 10.00 24.50 34.50 369.60 9.00 41.07

2:00 20.00 30.00 50.00 419.60 10.00 41.96

3:00 30.00 40.00 70.00 489.60 11.00 44.51

4:00 30.00 30.00 60.00 549.60 12.00 45.80

5:00 20.00 12.50 32.50 582.10 13.00 44.78

6:00 15.00 12.50 27.50 609.60 14.00 43.54

7:00 20.00 32.50 52.50 662.10 15.00 44.14

8:00 10.00 15.75 25.75 687.85 16.00 42.99

9:00 10.00 20.00 30.00 717.85 17.00 42.23

10:00 20.00 25.00 45.00 762.85 18.00 42.38

11:00 15.00 25.00 40.00 802.85 19.00 42.26

12:00 17.50 35.00 52.50 855.35 20.00 42.77

13:00 23.00 30.00 53.00 908.35 21.00 43.25

14:00 10.00 35.00 45.00 953.35 22.00 43.33

15:00 20.00 20.00 40.00 993.35 23.00 43.19

16:00 15.00 47.00 62.00 1055.35 24.00 43.97

17:00 20.00 25.00 45.00 1100.35 25.00 44.01

18:00 15.00 40.00 55.00 1155.35 26.00 44.44

19:00 10.00 45.00 55.00 1210.35 27.00 44.83

20:00 20.00 15.00 35.00 1245.35 28.00 44.48

21:00 10.00 15.00 25.00 1270.35 29.00 43.81

22:00 5.00 20.00 25.00 1295.35 30.00 43.18

23:00 5.00 10.00 15.00 1310.35 31.00 42.27 Table: Pour Card Details for the TG Deck Slab Unit-


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Chimney Construction The Chimney System will discharge combustion gases to the atmosphere. One common chimney with 2 brick flues (insulated outside the flue) will be provided and will consist of the following major components:- a) Shell： The shell will physically enclose and protect each flue from forces induced by wind as well as provide support to access components of the chimney. The chimney shell will be of reinforced concrete. The shell will be of 275 metres. b) Flues： The flue dedicated to each unit, will convey combustion gases to the atmosphere and protect the shell and equipment in the annulus from high temperatures and corrosive gases. The flues will be made of refractory brick. The flues will be insulated to achieve desired working temperatures around internal platforms. The inside of the steel flue will be provided with corrosion resistant lining/coating, SS metal cladding as per requirement. c) Aviation Obstruction Lighting ; The aviation obstruction lighting will warn aircraft of the chimney obstruction to air navigation during daylight, twilight, and night hours. The aviation obstruction lighting will be flashing high intensity lights during daytime with reduced intensity for twilight and night time operation. Intensity step changing will be controlled by a photoelectric light detector. The lighting will conform to the standards of the Civil Aviation Department of the Government of India. The supplier will furnish the detail design and technical data sheet of the Aviation lighting system and along with the electrical cabling for the approval of client. d) Lightning Arrestor; Lightning protection system complete with air terminal rods, circumferential conductor, down conductors duly earthed or connected to the general grounding system for the plant will be provided. e) Platforms and Access; Internal Platforms: Adequately sized access platforms will be provided for access and space for service and maintenance of equipment (insulation, lining, etc) installed in the Chimney System. Platforms will have a minimum width of 1 meter. External Platforms will be provided at various levels as per operation & maintenance

requirements. Access to the external platform will be from the internal staircase/lift. f) Stack Elevator; One elevator of adequate capacity & size for landing on platforms of the chimney to be provided.


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General Description of Chimney-4: Height of Chimney : 275 m Type of chimney : RCC, triple flue Slip form method is used for Shell construction. Outer bottom diameter : 30 m Outer top diameter : 21.2 m Shell thickness at top : 400 mm Shell thickness at bottom : 800 mm No. of flue openings : 3 Size of flue opening : 6.5 m (width) x 12.5 m (height) Level of flue duct opening : Bottom level- CD (+) 19.750 m Top level – CD (+) 32.250 m Cover to concrete : 50 mm Erection opening : 7.5 m (width) x 7 m (height) at G.L. Level of erection opening : Bottom level- CD (+) 10.00 m Top level – CD (+) 16.30 m EPC contract is given to Simplex infrastructures by SEPCO III. Reinforcement is provided by SEPCO III & design, execution, concrete, labour, slip form

is of Simplex infrastructures.

Fig- Fully Chimney Shell casted at a height of 275m (+GL)


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Slipform Main Components: The Form:

The form consists of height 1.2 m of 8mm thick mild steel plate. Both the sides of the form are supported and held together by yokes.

Yokes:

Yokes represent an inflexible steel construction, which consist of vertical legs & horizontal beams.

They are placed at distance of about 1.2 to 2.4m along periphery. The walings of the form & the hanging scaffold frames & steel brackets are bolted

to the yoke leg. Yokes give the following functions: To support the walers & the form. To transmit the lifting forces from the jacks to the walers. To support the working platforms & hanging scaffolds.

Jack holder:

A jack holder acts as lifter of the head beam (Yoke beam). The jack is enclosed in these two jack holders which are resting on the yoke

system. It also has a base plate. When the jack moves up on the jack rod, it lifts the jack holder which in turn lifts

the yoke beam. Yoke beams which are interconnected with the yoke legs lift the yoke leg.

Jack rods:

The hydraulic Slipform jacks are designed to climb up plain steel rods with solid or tubular circular section.

The outside dia. of these jack rods is nominally fixed for the various types of jacks.

In normal Slipform casting the jack rods are placed inside the slide-cast concrete & thus carry a compressive load.

At their lower end they rest on the foundation and are then successively extended by the addition of further lengths during distance covered by the Slipform structure.

Total nos. of hydraulic jacks – 64 2 nos. of jacks are fit on the lower yoke beam where main truss comes on spider

beam & in surrounding two spider beams. 1 no. of jack is fit in the rest of the yoke assembly of Slipform. Length of jack rod varies from 3m (at the yoke legs) to 2m (at the main truss

support). The nominal external dia. is 32mm & internal dia. is 16mm. 6.2 MT capacity of each jack rod.


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Hydraulic pump:

Hydraulic pumps are provided to circulate required quantity of hydraulic oil at desired pressure for energizing jacks to lift the assembly and facilitate its uniform lifting.

The pump bottom is submerged in the oil tank. When the pump is running, oil is sucked directly form the oil tank up through the

pump & pressed out to the automatic return valve & the gauge and from there into the oil piping to the hydraulic jacks.

Hydraulic oil 68 is used in pump. Operation Capacity-64 Jacks. Pressure on the Pump-80 T/m².

Fig- Yoke Leg and Yoke Beam Assembly Fig- Yoke Legs Positioning

Fig- Various Components and total erection of Slip Form System


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Slipform Operation:

Slipform construction is an extrusion process in which the form of 1 to 1.8m high & is constantly being raised.

Fresh concrete is placed into the pumps. The concreting of chimney is to carried out in layers. The form panels are filled

with fresh concrete layers of 300-400mm. Freeboard i.e. the distance between the form top level & layer of fresh concrete

top level is 150-200mm. When the concrete reaches to that level, reinforcement is to carried out. That

means r/f also carried out simultaneously while concreting. After two to three hours, the concrete reaches the initial set & loses its plasticity

and starts supporting the newly fresh concrete above that. The rate of movement of the forms is controlled & matches the initial setting of

concrete so that the forms leave the concrete after it is strong enough to retain its shape while supporting its own weight.

The forms move upward by mean of jacks climbing on smooth steel rods embedded in the hardened concrete & anchored at the concrete foundation base.

These jacks may be hydraulic, electric or pneumatic & operate at speeds up to 600 mm/hr.

Yokes are frame that are used to support the lateral loads & transfer the vertical loads to the jack rods.

Laboures continually vibrate the concrete so as to prevent any honeycombing. A top working platform is attached to the slip form assembly and slides up with it

to provide a place form where laboures can place concrete. A middle working platform is attached to the inner form from where laboures can

vibrate the concrete & fabricate steel reinforcement. A lower working platform is suspended from the outer form (in both the sides of

shell (inner-outer)) to allow workers to apply a curing compound & to repair any honeycombing that may occur.

Radius Screw Operation

As the diameter of chimney shell decreases, the radius of the slip form assembly has to be reduced as per the requirement at that elevation.

The numbers of rotation are as per the requirement, till the inner face of the inner yoke leg reads as per marking on spider beams.

The pitch of the radius screw is 2 mm/revolution. Every 12 Hour record is maintained and is compared with the required radius.

Wall Thickness Reduction

The wall thickness screws are also operated continuously to reduce the thickness of shell at the height of chimney increases.


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There is one wall thickness screw between the channels of upper yoke beam on the inner yoke leg & another wall thickness screw on the lower yoke beam of the outer yoke leg.

The pitch of wall thickness screw is 2mm/revolution. These wall thickness screws are operated as per the slip form program from which

number of revolution can be calculated as per the reduction in the Chimney shell at that level. How to Know the Working Height of Chimney?

To know the working height of chimney, the jack rods of some yoke legs have marking of paint at interval of 50 cm in height.

From those marking of paint we can have idea about the working height of chimney.

Spindles for Periphery Reduction For the periphery reduction of chimney during its construction, spindles are

connected to the console assembly. The form panels being free from one end the slide over each other as per the

reduction in periphery. This sliding is controlled by the rotation of spindles which are rotated by console

assembly mechanism. It has a piston for its operation which is controlled by hydraulic pump connected

by the high pressure hose pipe. A circuit connection is made to all the pistons of all the yoke legs.

The pitch of the spindle is 5 mm/ revolution. The amount of slipping of the form panels depends upon the reduction in the chimney shell periphery slip form programme. Turn buckles are located in to the console assembly of the yoke legs which are used to rotate the spindle for periphery reduction as thee chimney height increases. (for turn buckle arrangement see attached diagram 9)

The turn buckles are piston operated which operates the console assembly. The amount of slipping of the form panels depends upon the rotation of spindles

which are rotated by the turn buckles & the amount of rotation & there by sliding operation of the pistons which is carried out as per slipform programme. Chimney Concreting Procedure:

Concrete will fill up in the bucket of 0.6 m³ capacity from Transit mixer through chute.

Lifting of that bucket to the working level. Dump the concrete from the bucket to hopper. Fill the trolley with concrete form hopper. Dump the concrete from trolley to M.S.Funnel. Concrete will pass through 200 mm dia. PVC pipe attached with M.S.Funnel.


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Precautions while Concreting of Chimney

Concrete layer thickness shall not exceed 250mm during each pour. Sliding of Slipform panels shall not excee 25mm per lift Sliding of slipform panels shall after be 3 to 4 hours subsequent to completion

of placement of earliest layer The lifting frequency of form panels shall be restricted to 10 minutes Freeboar in slipform panels shall be maintained minimum 250mm while top

layer is poured Care shall be exercise that concrete manufactured is consume within 2 hours

and 30 minutes; this includes the time consumed towards the manufacture of concrete, transportation of concrete an final placement into the forms.

At two discrete locations diametrically opposite to each other, tilt an or twist an or complex phenomenon involving tilt and twist shall be checked at 6 hour intervals during the course of the pour. This verticality check shall be exercised with Self-Leveling Auto Shut-off Laser Instrument. The locations at ground where the instruments are proposed to be placed shall be protected from spilled off concrete from atop, e.g. by covering with plastic sheet or empty cement bag.

Site record indicating Tilts/Twists and both shall be maintained for hour to hour monitoring of verticality.

The preventive maintenance of Slipform structure shall be planned will in advance (minimum of two occasions during the course of pour). The period of such maintenance shall not exceed 12 hours.

The jack rod retrieval extraction period shall not exceed 4 hours hence all the requisite arrangements and activities be pre-organized and made well in advance.

Requisite PPE shall be enforced and made mandatory for all working platforms atop the slipform and below the chimney during the course of work.

Recommendations enumerated at Points 1,2,3 and 4 shall vary as per climatic conditions which would include temperature and humidity mainly.


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Productivity Analysis of Chimney-4 Civil work for chimney 4 were commenced on the date 11/10/08 and were to be completed by the date 07/09/10, but due to various delay in construction the schedule on date had gone behind to 2/5/11 which resulted due to a delay of 8 months in the final completion of chimney work. We have attempted to find out the reasons for the delays so that they can be corrected in the future execution of similar magnitude. Data Collection and Analysis: Data collection was done from the records maintained by the contractor and owner engineer. The schedule and actual starting and completion of major activity are listed in table below. No.

Item Schedule start

Schedule Finish

Actual start

Actual Finish

1 Drawings for excavation received and approved by employer

11/10/2008

18/10/2008

15/10/2008

12/11/2008

2 Drawing for raft of chimney received and approved by employer

20/10/2008

18/11/2008

17/11/2008

11/1/2009

3 Drawing for shell of chimney received and approved by employer

14/1/2009

11/2/2009

20/1/2009

16/2/2009

4 All other construction drawings received and approved by employer

4/4/2009 2/5/2009

6/4/2009 18/5/2009

5 Excavation and PCC 10/11/2008

18/2/2009

24/11/2008

30/1/2008

6 Foundation 23/2/2009

2/5/2009

5/2/2009 26/8/2009

7 RCC shell up to 25 m 4/5/2009 14/8/2009

12/9/2009

17/11/2009

8 RCC shell up to 100 m

17/8/2009

23/8/2009

7/12/2009

5/2/2010


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24/8/2009

15/9/2009

11/2/2010

8/4/2010


16/9/2009

14/10/2009

16/4/2010

14/6/2010

11 Dismantling of Slipform construction equipment

16/10/2009

14/11/2009

17/6/2010

2/7/2010

12 Fabrication of first steel flue and all necessary steel structures

16/11/2009

7/1/2009

21/7/2010

30/8/2010

13 Erection of first steel flues, insulation, elevator etc

9/1/2010 18/1/2009

6/9/2010 19/9/2010

14

Fabrication of second steel flue and balance steel work

19/1/2010

2/4/2010

20/9/2010

27/11/2010

15 Erection of second flues, insulation, elevator erection

5/4/2010 25/6/2010

10/12/2010

31/1/2011

16 Fabrication of third flue and balance steel work

25/3/2010

22/5/2010

4/11/2010

3/1/2011

17 Erection of third flues, insulation, elevator erection

28/6/2010

2/9/2010

16/2/2011

28/4/2011

18 All other work 7/9/2010 17/11/2010

2/5/2011

Labour Availability at Site: There were 6 gang of labour available at site, which was working 24 hours at site in two shifts. Average no of worker in each gang is mention in table below. No. PARTICULARS SHIFT No. of heads 1 Reinforcement gang Day 30

Night 30 2 Slipform gang Day 25

Night 25 3 Concreting gang Day 25

Night 25 4 Finishing gang

Day 15 Night 15

5 Curing gang Day 5


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Night 5 6 Khalasi Day 7

Night 7 Monthly Concreting Report of Chimney: Monthly reports are available from feb-09 to April-10. Table contains monthly concreting and monthly labour report for chimney. From the table we can say that with increase in height, production rate is decreasing..

Month Cmt/month labours/month

Productivity (Hrs/cmt.)

Feb-09 5454 3106 13.66776678

Mar-09 1817 3000 39.62575674

Apr-09 38 100 63.15789474

May-09 0 0 0

Jun-09 0 0 0

Jul-09 887.5 2206 59.65521127

Aug.09 482 1962 97.69294606

Sept.09 1287 3105 57.9020979

Oct. 09 1188.5 3213 64.88178376

Nov.09 1829.5 3300 43.29051653

Dec.09 1756.75 3845 52.52881742

Jan-10 1443 4761 79.18503119

Feb-10 1344 3781 67.51785714

Mar-10 1185.5 3619 73.26528891

Apr-10 309 1071 83.18446602


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The chart represents monthly fluctuation in productivity.

Reasons for the lag in schedule and Productivity: Major delay occurred due to unavailability of slipform assembly for more than 2

months. Reinforcement was behind schedule. There was Labour shortage in summer. A laser instrument which was used for height and alignment measurement of

chimney was not working properly. There was a lack of cleanliness and other sanitation facilities in the labor colonies

and hence there were frequent instances of many skilled, unskilled and semi-skilled labourers etc. remaining absent during critical times. This resulted in frequent delays and hence the lag occurred in completion.

Recommendations: Proper equipment management should have been done for important equipments

so that, they would have been available as and when required. For proper availability of labour during summer some innovative steps should

have been implemented, such as increase in wages, & other facilities to maintain productivity of work.