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ANALYSIS REPORT ON THE ACCIDENT OF #2 CHIMNEY COLLAPSE BALCO 4×300MW CPP PROJECT
Investigation Team of SEPCO Electrical Power Construction Corp November 20, 2009
Analysis Report On The Accident Of #2 Chimney Collapse
Contents
Chapter-1 General....................................................................................................4 1.
General Status of Chimney Construction ............................................................4
2.
Accident Description ...........................................................................................6
3.
Eyewitness Statement ..........................................................................................6
4.
Emergency Treatment After The Accident ..........................................................6
5.
Expert Consulting................................................................................................6
6.
Documents & Data ..............................................................................................7
Chapter-2 Chimney Design......................................................................................7 1.
Soil Investigation for Chimney ...........................................................................7
2.
Chimney Design ..................................................................................................7
3.
Chimney Design Recheck ...................................................................................8
Chapter-3 Material for Chimney Construction.....................................................9 1.
Construction Water ..............................................................................................9
2.
Coarse Sand & Stone Aggregate .........................................................................9
3.
Cement.................................................................................................................9
4.
Reinforcement .....................................................................................................9
5.
Concrete...............................................................................................................9
6.
Conclusion...........................................................................................................9
Chapter-4 Construction Facilities and Equipments............................................10 1.
Batching Plant ...................................................................................................10
2.
Slip Form System ..............................................................................................10
3.
Temporary Lightning Protection .......................................................................10
Chapter-5 Construction Management.................................................................. 11 1.
Experience of GDCL......................................................................................... 11
2.
Construction Management................................................................................. 11
3.
Construction Management System....................................................................12
4.
Conclusion.........................................................................................................12 Page 2 of 42
Analysis Report On The Accident Of #2 Chimney Collapse
Chapter-6 Post-incident Check & Test .................................................................13 1.
Check for Chimney Foundation and Pile ..........................................................13
2.
Evidence Obtaining and Inspection for Chimney Debris Rebar .......................15
3.
Evidence Obtaining and Inspection for Chimney Debris Concrete ..................15
Chapter-7 External Factors Analysis....................................................................15 1.
Local Weather Conditions (Wind and Rainfall) When Accident Occurred.......15
2.
Analysis of Thunder Stroke Factors ..................................................................15
3.
Man-made Factors .............................................................................................17
Chapter-8 Chimney Wreck distribution and Site Photos ...................................18 1.
Bird's View Of Chimney Area...........................................................................18
2.
Chimney Foundation Check ..............................................................................20
3.
ESP Area Broken Concrete At North Of Chimney Area ...................................22
4.
Concrete Pieces At Working Platform Area Which Is At North Side Of
Chimney ...................................................................................................................29 5.
Chimney Bottom Shell ......................................................................................33
6.
The Location Of Winch Machine ......................................................................33
7.
Wreck Distribution At The Bottom Of Chimney Shell .....................................33
8.
Concrete Piling Up At The Root Of Chimney...................................................35
9.
Slip Form And Operation Platform ...................................................................35
10.
Illumination of Chimney Ventilating Window Height...................................36
Chapter-9 Fracture Morphology Analysis of Chimney Collapse.......................37 1.
Chimney Debris Distribution Illustration..........................................................37
2.
Fracture Morphology Analysis & Speculation for Chimney Collapse..............37
Chapter-10 Analysis and Conclusion on the Accident ........................................39 Chapter-11 Appendices ..........................................................................................39
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Analysis Report On The Accident Of #2 Chimney Collapse
Analysis Report of the Accident Indian Bharat Aluminium Company Ltd awarded the EPC contract for its 4x300MW Captive Power Plant Project to Shandong Electric Power Construction Corp. For this project, every two units share one 275m double piped flue can chimney. As approved by the contract owner, the chimney work EPC contract was awarded to GDCL. BALCO appointed DCPL to be their engineering and construction supervision company. Site representative for project financing is BV. Till the accident, the RCC work for #1 chimney shell is completed. Flue can erection was preparing. RCC work for #2 chimney had reached 247.5m. Chapter-1 General 1.
General Status of Chimney Construction Natural foundation is adopted for the designing of #1 chimney, the external diameter of the foundation is 31M, the buried depth of the foundation is -14.235M, the bearing stratum consist of medium weathered bedrock. As Per Soil Investigation Report, Natural foundation cannot meet the design requirement, so cast-in-place pile is adopted for #2 chimney. Total number of the pile is 167 nos., and the diameter of each is 1M, the external diameter of pile foundation cap is 44M, the buried depth of the same is -6.235. The external diameter of #2 chimney shell at ground level is 25M and the thickness is 600mm. The external diameter of #2 chimney shell at EL271 is 14.2M and the thickness is 300mm. Contract duration of #1 chimney is 24.5 months; the same of #2 chimney is 25.5 months. Detailed progress of #2 chimney construction: ¾ For pile foundation construction: 2008.08.31~2008.11.13 ¾ For foundation construction: 2008.11.27~2009.01.07 ¾ For shell construction up to ground level: 2009.02.07~2009.02.09 The designed size of chimney shell is shown as in Chart-1 [EC-034-502-R0]
Chart-1 Chimney Shell Dimension
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Analysis Report On The Accident Of #2 Chimney Collapse
Height m
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Major Thickness diameter m m
271
14.200
0.3
265
14.200
0.3
245
14.200
0.3
225
14.200
0.35
205
14.200
0.35
185
14.200
0.35
165
15.368
0.35
145
16.535
0.35
125
17.703
0.35
105
18.870
0.35
85
20.038
0.40
65
21.205
0.40
55
21.789
0.50
45
22.373
0.50
25
23.541
0.50
16.775
24.021
0.56
12.15
24.291
0.60
7.525
24.561
0.60
0
25.000
0.60
-2.235
25.130
0.60
Analysis Report On The Accident Of #2 Chimney Collapse
2.
Accident Description On September 23rd 2009 after 3 o’clock p.m. local time, the weather at site area suddenly changed, the wind blew strongly accompanied with thundering and lightning, and then it started to rain heavily. A moment later about 4 o’clock p.m., the chimney (#2 chimney) in construction which has already reached the height of 274.5 meter collapsed during severe rainstorm and thundering.
3.
Eyewitness Statement Eyewitness statement of the incident site is in Appendix-1.
4.
Emergency Treatment After The Accident Our personnel reported the accident to the owner immediately after the accident happened. We tried to organize our subcontractors to rescue, but it had to be cancelled due to the attack launched by a few of labors at site. Local police and government officials hurried to the scene for rescue, sealed off the accident scene and took some special measures to protect Chinese staff. Then our H.O started the emergency plan at once, an accident treatment group was organized and deployed the concerned personnel to site emergently. At the same time, an accident analysis group was organized by our company, regarding the cause of the accident we consulted and discussed with well-known expert of China specializing in engineering, civil, mechanics and weather for several times. After the accident, the government took charge of organizing the rescue job, the accident treatment group from our side contacted with all concerned parties actively, follow up the condition of the accident and rescue progress on daily basis, try our best to collect all the true and valid information from various resources to develop the accident investigation job.
5.
Expert Consulting Regarding the causes of collapse, we consulted well-known expert of China specializing in engineering, civil, mechanics and weather, three times of expert meetings and several special meeting have been organized to discuss, and the experts were organized to site to develop on-site investigation, to analysis the causes in different aspects. The experts are as followings: NWEPDI: Xie Bao’an (Professorate Senior Engineer) ECEPDI: Cai Hongliang (Professorate Senior Engineer) SDEPCI: Zhang Lanchun (Professorate Senior Engineer), Zhang Bo (Senior Engineer)
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Analysis Report On The Accident Of #2 Chimney Collapse
CSEE: Ma Shen (Professorate Senior Engineer), Li Bingyi (Professorate Senior Engineer), Hou Jianguo (Professor), Zhou Liqiong (Professorate Senior Engineer), Jiang Yusheng (Senior Engineer) Institute of Mechanic, China Academy of Sciences: Zhou Jiahan (Researcher), Zhang Deliang (Researcher) China Institute of Water Resources and Hydropower Research: Zhang Yongzhe (Senior Engineer) Thunder and Lightning Protection Center of Shandong Province: Yu Zhenbo (Senior Engineer) Chinese Academy of Meteorological: Yang Weilin (Senior Engineer), Meng Qing (Senior Engineer), Dong Wansheng (Researcher), etc. 6.
Documents & Data According to the information which has been collected by us, we have analyzed various reasons and factors that may cause the chimney collapse and screened all the information that collect from various aspects. The reference information are as following: 1)
geology investigation report
2)
chimney technical specification (preliminary)
3)
chimney construction scheme, quality acceptance plan and inspection record
4)
all the drawings and design instructions related to chimney engineering
5)
construction material acceptance and test documents
6)
all the detailed information collected at site
Chapter-2 Chimney Design 1.
Soil Investigation for Chimney Soil Investigations Outline was provided by LNPDI. SDEPCI supervised SK doing site soil investigation. The soil investigation report was submitted by SK. The data of the report is true and reliable.
2.
Chimney Design Page 7 of 42
Analysis Report On The Accident Of #2 Chimney Collapse
Chimney design is complied by Tandon Consultant Company (New Delhi) which was approved by DCPL (Kolkata). GDCL supplied relevant drawing: Drilling Position Drawing (DCPL); Pile foundation cap design sheet (DCPL); Chimney pile design sheet (TCPL); Chimney shell design sheet (TCPL); Chimney 25m to 265m platform design (TCPL); #2 Chimney design drawing. There is only foundation difference between #1 and #2 chimneys. In principle the shell designs are almost the same. After the chimney accident, the chimney contractor GDCL contacted IIT (Delhi) to recheck the chimney design. Expert S.N. Sinha from IIT (Delhi) said in his report on October 23, 2009 that design of the chimney is safe and adequate. [enclosed Annex III of GDCL Technical Committee Report- Consultancy Report on Cause of Collapse of Chimney No.2]. 3.
Chimney Design Recheck ¾
Recheck by Indian Experts Invited by GDCL
Refer to above paragraph ¾
Recheck by Chinese Expert
Relevant experts from SDEPCI and Special Committee for Civil Construction for Electrical of Engineering Institute of China rechecked the chimney design according to relevant Chinese Standard. They also compared the chimney design with Chinese Standard. Standard and analysis software adopted: z
Chimney Design Standard (GB50051-2002)
z
Chimney design software (2009 version)
z
Architecture structure Loading Standard (GB-2001, 2006 version)
z
Technical Norms for Thermal Power Plant Civil Structure Design (DL5022-93)
Although there are some differences between Chinese and Indian Design on chimney concrete strength grade, shell thickness & dimension and reinforcing, full duct hole and strengthen measure for holes erection and slipping form technology, the result of inspection indicated that chimney design is adequate under normal design loading work condition.
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Analysis Report On The Accident Of #2 Chimney Collapse
Chapter-3 Material for Chimney Construction 1.
Construction Water Water for chimney construction is from industrial water system supplied by BALCO power plant. It is proved to be qualified after sample check and test by GDCL.
2.
Coarse Sand & Stone Aggregate Sand coarse and stone aggregate were purchased locally in India. Certificate of Origin is available. They did sample test for every batch of material. BV and our engineer supervised the process. The tests were qualified.
3.
Cement In chimney shell construction, GDCL only used #43 OPC cement. #43 cement was purchased from Ultra Tech and Ambuja Company by GDCL. They did sample test for every batch of material. BV and our engineer supervised the process. The tests were qualified.
4.
Reinforcement Chimney construction is adopted Fe500 reinforcement. We purchased reinforcement from SAIL, TISCO and ESSAR as per the EPC contract. Reinforcement was check after fabrication. Conformity certificate is available. After the accident, we did sample recheck on site reinforcement. We totally took 6 sets of 12mm and 16mm diameter reinforcement (3 were used and 3 were not). All are qualified [enclosed Mechanic Performance Test Report for Reinforcement used in Chimney shell].
5.
Concrete As per code, GDCL did cubic block every time before they did concreting, and then they did 7-day and 28-day strength test. BV and our engineer supervised the process. The tests were qualified.
6.
Conclusion After check the material quality certificate for chimney construction, site material sample test report and other materials, we confirmed that the material is satisfied the design and code requirements.
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Analysis Report On The Accident Of #2 Chimney Collapse
Chapter-4 Construction Facilities and Equipments 1.
Batching Plant The batching plant is manufactured by Schwing-Stetter (German company located in India). It is a plant of 60 cum/hr capacity. This batching plant has computerized operation. Engineers both from our company and BV check it every month. It operates well.
2.
Slip Form System Slip form system for chimney shell construction is designed by Interform, a Sweden company and fabricated by GDCL. Before and during use of the slip form BV and our Engineers did specific inspection on its safety and quality. It is qualified. Photo-1 Slip form system and working platform (09,09,2009)
3.
Temporary Lightning Protection Page 10 of 42
Analysis Report On The Accident Of #2 Chimney Collapse
The arrangement of the protection during construction is shown in 20091027 GDCL Technical Committee Report Annex V - Detail of Earthing During Construction of Chimney. The temporary lightning protection was designed and provided as per Para-E-2.6.1 of IS 4998 (Part-I) 1975[enclosed 20091027 GDCL Technical Committee Report Annex IV]. During construction we tested the earthing resistance of the lightning protection, it meets the requirement.
Chapter-5 Construction Management 1.
Experience of GDCL GDCL is one of the few construction companies in India specializing in construction of tall chimneys since 1980s. It is understood that the chimney which collapsed in the accident was the 6th 275m high chimney being completed by GDCL after already completing 5 nos. chimneys of the same height. At BALCO project a chimney of the same height design had already been completed by GDCL and standing intact after the accident.
2.
Construction Management We arranged two civil engineers to supervise chimney working progress control, quality management, work scheme inspection and safety management etc. Piling Foundation Construction: Before foundation constructing start, we reviewed the construction plan submitted by GDCL and also submitted the same to BALCO and DCPL for approval. Before piling construction, our engineers supervised piling test done by GDCL and also complied loading test for the tested pile according to the drawing and relevant standard. During piling, engineers from BALCO, DCPL and SEPCO supervised and checked the same. After piling, we did loading test and UT test on a sample pile. The tests were qualified. Piling Foundation Cap Construction: In the process of piling foundation cap construction, our engineers implemented supervision nearby the same. There was no abnormality occurred during construction. Shell Construction: Our engineers reviewed and examined the shell slip form construction scheme submitted by GDCL and submitted to DCPL and BALCO for review and approval. In the process of shell construction, our engineers together with DCPL
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Analysis Report On The Accident Of #2 Chimney Collapse
& BALCO engineers implemented one nos. acceptance every two days for the rebar, radius, verticality and appearance quality of the shell. There was no abnormality occurred during construction and the whole construction process was under controllable & controlled conditions. Construction progress schedule of the chimney shell is shown as in Chart-2. the curve of construction progress record is smooth and reasonable, not over-speed progress occurred during chimney construction. Chart-2 shell construction schedule records (#2) 250
200
150
100
50
09-9-21
09-9-7
09-9-14
09-8-31
09-8-24
09-8-17
09-8-3
09-8-10
09-7-27
09-7-20
09-7-6
09-7-13
09-6-29
09-6-22
09-6-8
09-6-15
09-6-1
09-5-25
09-5-18
09-5-4
09-5-11
09-4-27
09-4-20
09-4-6
09-4-13
09-3-30
09-3-23
09-3-9
09-3-16
09-3-2
09-2-23
09-2-9
3.
09-2-16
0
Construction Management System We established construction management system. GDCL also made relevant management systems as per our requirement, for example, layout plan, construction scheme, employee training and etc. GDCL and our management arrangement for chimney construction is efficient and in order.
4.
Conclusion To sum up, in the various construction stages for pile foundation, foundation and the shell of the chimney, the management of SEPCO, DCPL and BALCO was all in good condition, there were no unusual conditions in the process of the construction and the construction quality was under controlled conditions all the time.
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Analysis Report On The Accident Of #2 Chimney Collapse
Chapter-6 Post-incident Check & Test Our personnel did a serial of check and survey on the form of chimney at site after the collapse, including chimney foundation and pile check, sample test for RCC debris of the chimney and reinforcement and distribution status of the chimney debris. 1.
Check for Chimney Foundation and Pile After the accident happened, the government’s investigation team sent persons to dig out the whole foundation and to clear & clean the surface; besides, dig out the three piles in the bottom at the southern side of the foundation, and our engineers & experts executed inspection and observation at site for many times and observed: the pile body was in good condition and there’s no fracture; no crack on the surface of the foundation, no uneven subsidence and no deviation for the foundation.(see pile foundation pix 1-3) Photo-2 Pile Picture 1 (26, 10, 2009)
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Analysis Report On The Accident Of #2 Chimney Collapse
Photo-3 Pile Picture 2 (26, 10, 2009)
Photo-4 Pile Picture 3 (26, 10, 2009)
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Analysis Report On The Accident Of #2 Chimney Collapse
2.
Evidence Obtaining and Inspection for Chimney Debris Rebar After the accident occurred, we implemented sampling reinspection for the site rebar and got totally six groups (three groups have never been used and three groups have been used) of 12mm and 16mm diameter rebar, and the testing results were all qualified. [Testing reports for shell rebar dynamics performance]
3.
Evidence Obtaining and Inspection for Chimney Debris Concrete 我方委托当地有资质的实验室（加尔各答）进行混凝土钻芯取样试验。根 据试验结果，所有取样合格。 We consigned local qualified lab (Kolkata) to implement concrete core sampling testing. As per the testing results, all the samples were qualified.
Chapter-7 External Factors Analysis 1.
Local Weather Conditions (Wind and Rainfall) When Accident Occurred We inquire meteorological information that day from Korba local meteorological station after the accident occurred, yet due to equipment failure, the meteorological station did not preserve weather information on September 23rd. According to witnessed testimony, when the accident occurred that day, there was furious storm with strong thunder and lightning at construction site: “at that time “fierce wind” at site, difficult for persons to advance and even the office doors could not be closed”, “the wind was too strong, although #2 turbine hall roof had already been enclosed there’s no place to shelter from wind & rain”, “fierce wind, lightning flashes and thunder rumbles and rainstorm pouring”, “accompanied strong lightning from the sky to the ground and the situation was quite shocking”, “the strong wind made the windows sound heavily and I had never experienced so strong wind”. Generally speaking, wind velocity of gust is 50% or even stronger than average wind velocity. The stronger the average wind velocity is, the rougher the ground surface is, and the wind velocity of gust is more percentage than average wind velocity.
2.
Analysis of Thunder Stroke Factors ¾
Data Analysis on thunder & lightning records
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Analysis Report On The Accident Of #2 Chimney Collapse
Indian IPLN Company provided thunder & lightning records information [20091021 Lightning Report IPLN] on the date of September 23rd Sheet-1 provided thunder & lightning records sheet
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Analysis Report On The Accident Of #2 Chimney Collapse
Chart -3 lightning records showed on Google Map
Through review and examination for the lightning record, we thought: the lightning report provided by IPLN Company showed that there were nine times of thunder strokes within 6km around #2 chimney when the accident occurred, and the occurring time of the lightning record conformed to the collapse time of chimney; although there was slight difference between the coordinate of measured thunder stroke and the coordinate of #2 chimney (22°23′50″ north latitude and 82°44′23″ east longitude), in view of the working principle and inherent error of lightning locator, it could be confirmed that chimney collapsed accident conformed to thunder stroke record information. ¾
Witness Statement
B.C.Chatterjee (GDCL site staff) reported that before the collapse they saw a lightning entered the hollow of the top of chimney. [20091027 GDCL Technical Committee Report Annex 1 - Eyewitness Report on Chimney Mishap at Korba]. 3.
Man-made Factors At present there is no evidence that the collapse was caused by man-made damage.
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Analysis Report On The Accident Of #2 Chimney Collapse
Chapter-8 Chimney Wreck distribution and Site Photos From 3rd Nov.2009 to 14th Nov.2009, several field surveys for the cleared chimney site have been conducted by our investigation team, and detail surveys and investigations have been done for the cleared chimney foundation, the remaining concrete at the bottom of chimney shell, shell reinforcement, the broken concrete scattering distribution when the chimney collapsed and the distribution of surrounding buildings/ structures. Details are as follows: 1.
Bird's View Of Chimney Area There are lots of auxiliary and temporary constructions/ structures surrounding the chimney, the detailed distribution is shown as in the general layout sketch of chimney and surrounding constructions/ structures; bird's view pictures of chimney area are shown in Photo-5 ~ Photo-7. Photo-5 bird's view of chimney area (from north to south)
烟囱北侧
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Analysis Report On The Accident Of #2 Chimney Collapse
Photo-6 Bird’s View of working platform for Water Wall of boiler (North to chimney area)
North to Chimney
Photo-7 Bird’s View of working platform for water wall and ESP hopper (N by E area of Chimney)
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Analysis Report On The Accident Of #2 Chimney Collapse
2.
Chimney Foundation Check Chimney foundation surface is cleaned. There are several deep pits with water in them at outer side of foundation which were used for checking the quality of pouring pile under the foundation. Showed in Photo-8 and Photo-2 ~ Photo-4. From the foundation surface, we did not find any apparent cracks or damages, except for some scratches by excavator. Foundation concrete quality is good as seen at site. See Photo-9 and Photo-10. Photo-8 Deep pit at south side of chimney foundation
South of Chimney
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Photo-9 Integrality status at the top of chimney foundation
Photo-10 Scratches at the top of chimney foundation
3.
ESP Area Broken Concrete At North Of Chimney Area After the collapse of the chimney, the broken concretes are mainly dropped at chimney north by east - each platforms of ESP, hopper and working platform for water wall area which is at north by east side of chimney. The sizes of broken concretes are not the same: the ones which are at #3 ESP area are bigger, the ones which are at working platform for water wall are smaller, and some are even like powder; the down sides of two hoppers of #3 ESP from south are blocked by big broken concretes; although the 4 hoppers from north are not blocked, there are many small concrete pieces on the ground under the hoppers; besides, many stairs and steel grids at each platform of #3 ESP were broken by concrete pieces. See Photo-11 ~ Photo-20.
Analysis Report On The Accident Of #2 Chimney Collapse
Photo-11 blocking status A of broken concrete (the west hopper on south side of #3 ESP)
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Analysis Report On The Accident Of #2 Chimney Collapse
Photo-12 blocking status B of broken concrete (the lower part of east hopper on south side of #3 ESP)
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Analysis Report On The Accident Of #2 Chimney Collapse
Photo-13 scattering status A of broken concrete (EL 9.1m platform of #3 ESP area )
Photo-14 scattering status B of broken concrete (EL9.1m platform of #3 ESP area)
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Analysis Report On The Accident Of #2 Chimney Collapse
Photo-15 scattering status C of broken concrete (EL9.1m platform of #3 ESP area)
Photo-16 scattering status D of broken concrete (EL2.5m platform of #3 ESP area)
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Analysis Report On The Accident Of #2 Chimney Collapse
Photo-17 scattering status E of broken concrete (EL2.5m platform of #3 ESP area)
5.3kg
12.8kg 34.5m away from the center of the chimney slid form component
Photo-18 scattering status F of broken concrete (EL9.1m platform of #3 ESP area)
12.3kg 35m away from the center of the chimney
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Analysis Report On The Accident Of #2 Chimney Collapse
Photo-19 scattering status G of broken concrete (EL9.1m platform of #3 ESP area)
20.9kg 36.4m away from the center of the chimney
Photo-20 scattering status H of broken concrete (EL9.1m platform of #3 ESP area)
5.9kg 24.9kg 37.5m away from the center of the chimney
4.2kg
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Analysis Report On The Accident Of #2 Chimney Collapse
4.
Concrete Pieces At Working Platform Area Which Is At North Side Of Chimney Concrete pieces at working platform for water wall of boiler at north side of chimney are very dense. The pieces are very small, and they are mainly like powders. See Photo-21 ~ Photo-26; There are a bit of concrete pieces at boiler operation platform area which is far from chimney. See Photo-27.
Photo-21 scattering status A of broken concrete on the water wall of boiler (at north side of chimney)
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Analysis Report On The Accident Of #2 Chimney Collapse
Photo-22 scattering status B of broken concrete on the water wall of boiler (at north side of chimney)
Photo-23 scattering status C of broken concrete on the water wall of boiler (at north side of chimney)
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Photo-24 scattering status D of broken concrete on the water wall of boiler (at north side of chimney)
Photo-25 scattering status E of broken concrete on the water wall of boiler (at north side of chimney)
Photo-26 scattering status F of broken concrete on the water wall of boiler (at north side of chimney)
Photo-27 scattering status of broken concrete on the operation level of boiler(at north side of chimney)
Analysis Report On The Accident Of #2 Chimney Collapse
5.
Chimney Bottom Shell Photo-33 shows that after the collapse, there was a new pile of earth at the north side of the chimney. According to the relevant position between this new pile of earth and buildings around chimney in the picture, we can conclude that the new pile of earth is backfilling earth of chimney foundation raised by the falling of the root of chimney shell. The new pile was pushed 5 meters to north side of the chimney shell.
6.
The Location Of Winch Machine The arrangement of #2 chimney and winch machine is similar to the same of #1 chimney. The winch machine area was destroyed due to the collapse of #2 chimney, and the survey for the scene was not available. Take the location of #1 chimney and winch machine for reference. The details are as showed in Photo-28. Photo-28 Relative location between #1 chimney and winch machine shed
Winch machine shed
7.
Wreck Distribution At The Bottom Of Chimney Shell From the photos taken after the accident, there are laminated concreted shells at the bottom of chimney which fell down to the south side. It is presumed that the circled shell was damaged by extrusion, while the inner sides were covered each Page 33 of 42
Analysis Report On The Accident Of #2 Chimney Collapse
other. See Photo-28 and Photo-29. Photo-29 Overlap condition A of the bottom section of chimney shell after collapse
Photo-30 Overlap condition B of the bottom section of chimney shell after collapse
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Analysis Report On The Accident Of #2 Chimney Collapse
8.
Concrete Piling Up At The Root Of Chimney Broken concrete and pulverized concrete piled up at the root of chimney shell, it was analyzed that the same may be caused by the piling of the concrete pieces which was resulted by the inside recessing damage of the middle part and root part of chimney shell. The details are as indicated in Photo-30 & Photo-31. Photo-31 Concrete debris at the bottom of chimney (northeast direction)
Upper part of chimney shell (the thickness of shell is thin) Bottom part of the chimney shell
The inner side of the chimney shell is filled with plenty of broken concrete
Photo-32 Concrete debris at the bottom of chimney (southwest direction)
the inner side of the chimney shell is filled with plenty of broken concrete
9.
Slip Form And Operation Platform It is presumed according to photos taken on site, all wrecks of slip form system and operation platforms fell at the south side of the chimney, and they fell down first. Some of the slip form system and operation platform fell down at 20m to 30m of south-east side of the chimney. Page 35 of 42
Analysis Report On The Accident Of #2 Chimney Collapse
Photo-33 Illustration of Construction Platform and Slip form device crash
Wrecks of slip form system and operation platforms fell at the south side of the chimney, and they fell down first
10. Illumination of Chimney Ventilating Window Height Chart-4 Illumination of #2 Chimney Ventilating Window Height
EL 223m (2009.09.08)
EL 186m
EL 146m
EL 106m
EL 66m
EL 26m
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Chapter-9 Fracture Morphology Analysis of Chimney Collapse 1.
Chimney Debris Distribution Illustration According to eyewitness statement, the photos taken by project personnel and collected through the media, the scene of the accident is re-created as in following picture: Chart-5 Illustration of chimney debris distribution
The length of chimney debris through vertical axis is 75 meters. 2.
Fracture Morphology Analysis & Speculation for Chimney Collapse We analyzed and speculated through survey data from the chimney collapse at site and various existing photos & data after chimney collapsed and witnessed testimony, and there were the following morphologies for chimney collapse breaking: Morphology I: Breaking from Chimney Upper Portion ¾
The chimney shell suffered from thunder stroke in the strong wind in a sudden way, and the chimney shell also bore many strong effects of complex impacts, consequently the part at the tens meters of the top of concrete shell broke off with destructiveness towards southern side; the
Analysis Report On The Accident Of #2 Chimney Collapse
slip form platform fell on the ground in the southern side of the chimney and the concrete debris of shell cracking scattered in #3 ESP in the direction of north by east. ¾
Under the joint impacts of chimney top section’s breaking fracture pull, pressure, torsion and strong wind, the concrete shell in the middle section suffered from partial destabilization, inside concave and inflexion, and broken concrete fell and filled inside the shell in the chimney bottom.
¾
chimney bottom section suffered from the joint effects of pull, pressure and torsion from the middle section’s, and the concrete shell in the bottom flue opening and holes remaining position of the opening was pressed and damaged, then collapsed towards south by east with the collapsed debris remained about 75m.
Morphology II: Breaking from Chimney Top Portion ¾
Various complex impacts caused damage of partial concrete on the top of the chimney;
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Under the integrated impact of thunderstorm, strong settling airflow, gust front and transverse wind shear, affected by elastic effects of chimney shell, the chimney fractured and inclined at the location of tens of meters in height from the top.
¾
Eccentricity resulted from Inclined shell caused chimney suffering pressure and the chimney shell destabilized, then the concrete in the bottom of the shell suffered gravity impact breakage from top concrete shell and construction machineries and continuously damaged and collapsed, and the chimney root received the impact and extrusion breakage from the concrete on high, all of these finally caused chain collapse.
Photo-34 fresh earth deposits after concrete shell collapsed (in the chimney northern side)
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Analysis Report On The Accident Of #2 Chimney Collapse
Chapter-10 Analysis and Conclusion on the Accident In conclusion of the above analysis, #2 chimney designs for BALCO project satisfied the related standard and requirements, construction facilities and materials satisfied the requirements of designs and specifications, construction technology was reasonable and construction management was in order. To sum up the site weather conditions, debris distribution after chimney collapse, concrete debris distribution conditions and witnessed testimony that day, and after our analysis of all aspects we think that, under the complex impacts of strong thunder and lightning and strong wind, some section of #2 chimney shell upper portion or top of chimney firstly suffered from damage, causing top section damaged fracture, and the bottom shell suffered integrated effects of torsion, pull, pressure and impact and continuously collapsed and damaged.
Considering the relevant information collected up to date is not so sufficient or accurate to support to locate exactly the specific position of broken-down of the chimney, we think that the upper portion of chimney is the most possible position which broke down firstly, yet at this time we do not exclude that there are any other possibilities of broken-down mode. We shall try all our efforts to obtain updated information and execute analysis continuously. If there’s further result, we will complement the investigation report in a timely manner.
Chapter-11 Appendices Appendix-1 20091107 Summary of witnessed testimony regarding weather condition Appendix-2 Thunder Stroke Phenomenon and Damage Appendix-3 20091027 GDCL Technical Committee Report
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Analysis Report On The Accident Of #2 Chimney Collapse
Appendix-1 20091107 Summary of witnessed testimony regarding weather condition
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Analysis Report On The Accident Of #2 Chimney Collapse
Appendix-2 Thunder Stroke Phenomenon and Damage
Various physical phenomenon and damage due to thunder stroke discharging are as follows: Electricity Effects: When thunder stroke discharging, there can be produced ten thousand volts impulse voltage; Heat Effects: when several dozens to several thousands Amps of strong thunder and lightning current passed conductor, it can be changed to a lot of thermal energy in extremely short time. Taking medium thunder as example: instant power P of thunder main discharging is extremely large, take I=50kA, arc road drop E=”6kV”/m, thundercloud is calculated by 1000m height, main discharging power P=”UI”=50x6x1000=300,000MW, it is even higher than any power plant’s power all over the world at present. This shows that thunder discharging instant power is extremely high, i.e. the destructive power is extremely high. Mechanical Effects: due to thunder’s heat effects, the air in the thunder passageway expanded when heated, and meanwhile make water content and other matter resolve into gas and spread around by supersonic velocity, therefore, there’s strong mechanical pressure inside the objects stroke by lightning, causing the stroked objects suffering from severe damage or causing explosion. Affected by thunder’s mechanical effects, cold air surrounding thunder passageway is strongly compressed to form “shock wave”. As for the place where “shock wave” arrives, air density, pressure and temperature would suddenly increase. After “shock wave” air pressure in this area declines until lower than atmospheric pressure. This kind of “shock wave” spread in the air, and can make the buildings nearby suffering from damage, and the effects of shock wave are like explosives explode which have the same damage for the buildings nearby. Other Effects: There are such effects as electromagnetic induction and thunder incoming wave, etc. of other effects for thunder.
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Analysis Report On The Accident Of #2 Chimney Collapse
Appendix-3 20091027 GDCL Technical Committee Report
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