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Unexpected Tunnel Collaps
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UNEXPECTED EVENTS ONTUNNEL CONSTRUCTIONS
CLOSE COOPERATION OF THE CLIENT-ENGINEER-CONTRACTORS
IN PREVENTIVE ACTIONS TO PRECLUDE UNEXPECTED EVENTS ON
THE BUDAPEST M4 LINEPROJECT
Author: László Frigyik MSc. Dipl. Engineer Technical DirectorTechnical assistant: Hannes Ertl
Engineer Consultant: Tamás Bozsó
EUROMETRO Project Management Consultant Ltd. 1143 Budapest, Zászlós u. 18
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Budapestis the Pearl of the Danube
Budapest has one of the best publictransport system amongs thecapitals in the European Union
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Europe’s first Metro line is: the Millennial Underground Railway in Budapest
in the past and today
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Brief presentation of the Budapest Metro 4 Line project- 7.34 km length in the 1st phase- 10 stations from Kelenföld Railway st. to Eastern Railway s t.- 4 further stations from Keleti to Bosnyák tér in the 2nd ph ase
ProjeProje cct t OrganizationOrganization , , RelationsRelations
CONTRACTUAL PRICECONTRACTUAL PRICE : 1: 1.300 M.300 M EEurur oo / / EXPECTED COMPLETIONEXPECTED COMPLETION: 2013. j: 2013. j úúnius 6nius 6 . . 29. October 2010. CzTA Prague
BKV(DBR METRO Project)
2 3 4 5 6 7 8 9 10 11
Construction worksRollingStockSiemens M4 Konzorcium
Systems
Depot
Budapest Municipality
Owner
Trackworks
National Telecom Auth NHH
ICA
National Traffic Authority NKH
Client
Advisers
1
Other Authoritires, eg.: Firebrigade
Engineer: Eurometro
…
Further contractseg: Monitoring
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Typical geological longitudinal section of Stage 1 of the Budapest Metro 4 Line
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Standard cross section of a diaphragm wall station
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Unexpected events may take place anywhere
• Preparatory measures need to be taken to prevent unexpected (undesirable) events
• The majority of such events, however, are due to foreseeable reasons
• Preparatory measures can be taken, at least the unfavourableimpacts of a possible occurrence can be minimized
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The most frequent reasons ofunexpected events are :
• defects in design,
• irregularities in the applied method,
• human errors,
• negligence,
• disregard of method or safety requirements
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Tragic events in recent years in major Metro Projects
• Sao Paulo (Brazil) - 12.01.2007. -New metro 4 line in the platform tunnel of Pinheiros station
• Cologne (Germany) – 03.03.2009. –Deadly collapse at the crossover link of the new tram line at the city’s historical archives building
• Delhi (India) – 12.07.2009. – Deadly collapse of New Airport line near Dhamrudpur
• Cairo (Egypt) – 04.09.2009. –Collapse of New Line3
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Sao Paulo (Brazil) - 12.01.2007. - New metro 4 line in the platform tunnel of Pinheiros station
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Cologne (Germany) – 03.03.2009.Deadly collapse at the crossover link of the
new tram line at the city’s historical archives build ing
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Cairo (Egypt) – 03.09.2009. Metro Line3 construction causes
30x20 m wide sinkhole in Geish Street
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Cairo (Egypt) – 03.09.2009. Metro Line3 construction causes
30x20 m wide sinkhole in Geish Street
No injuries were reported, but two parked cars fell into the 20 meter deep pit at the time of the collapse.
Ten buildings, home to 80 families, have been evacuated.
The drilling work is a major factor, together with excessive amounts of groundwater that had weakened the subsoil structure.
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Delhi (India) – 12.07.2009. – Deadly collapse (six workers killed) of DMRC
new airport line’s rail bridge
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Delhi (India) – 12.07.2009. – Deadly collapse (six workers killed) of DMRC
new airport line’s rail bridge
•Officials said: a pillar supporting the carriageway suddenly collapsed.
•Problem was linked to a design fault in the pillar of the bridge.
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Collapse of the ventilation tunnel of Budapest DBR Metro Line 4 at Tétényi station at 2007.09.04.
The cross-section after the collapse
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Collapse of the ventilation tunnel of Budapest DBR Metro 4 Line at Tétényi station
• After the start of dismantling the subdivided top heading of the shotcrete wall, the collapse took place.
• Large quantity of fractured soil (saturated Kiscelli clay which was mosaic-like joint pattern) was falling down into the tunnel.
• It was intensified by the water ingress from the broken water and sewer pipes.
• The adequate and prompt actions of the site management in the emergency situation mitigated damages, and no casualtiesoccurred.
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The collapsed crater and the debris flown into Rákóczi tér station at 2008.04.08.
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Collapse of the ventilation tunnelat DBR Metro 4 Line Rákóczi station
• A geotechnical exploration boring of 8.5 m depth was made during the construction of the pilot tunel.
• Following the application of the primary shotcrete layer and installation of the first welded wire mesh and the curved truss girders, unexpectedly high-pressure water ingress mixed with clay started in the top heading without any previous indications
• If after completion the exploration boring had immediately been closed the collapse probably would not have occurred,
• However, the preparations for and the management of the actual emergency situation were appropriate.
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Good example: the crossing of Line 3 -Line 4 at Kálvin square at 2009.11.08.
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Good example: the crossing of Line 3 and Line 4 at Kálvin square
• One of the most critical part of the tunneling the crossing of the existing Line 3
• The distance between the two tunnels structure is only 1.5 meter
• Due to the careful TBM drive and protective preparatory measures there was no nameable structural shifting
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Lessons learnt
• Stricter checking is required in the design stage.
• Deviations from the previously specified technical requirements should be allowed only after a thorough consideration of all circumstances, or
• in the case of favourable results provided by convincing additional investigations and calculations.
• In many cases the variations aimed at simplification or acceleration may finally entail delay of the works and increase of costs.
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CONCLUSIONS
•Could all the occurrences have been avoided?
• Since the reasons of the occurrences in all cases originate from defects in the design, method or construction, or human errors, consequently these events could have been avoided by more careful and thorough design, stricter control.
• Unforeseeable natural phenomena, deemed as vis-major, have not been encountered so far (and based on professional experience, such event is usually not typical).
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Sharing responsibilities amongall major project participants
Applying a Multilevel Safety Net.
• The Employer’s responsibility before letting the contracts and during the construction.
• The Contractor’s responsibility.
• The Engineer’s responsibility.
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EMPLOYER’S RESPONSIBILITIES BEFORE LETTING THE CONTRACTS:
• Feasibility study
• Geological investigation
• Detailed risk analysis
• Settlement calculations
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EMPLOYER’S RESPONSIBILITIES DURING THE CONSTRUCTION:
• Ground water monitoring system
• Automatic settlement measurements
• Monitoring the influence of the TBM tunnel drive by inclinometer and extensometer instrumentation
• Manual settlement measurements
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The Employer’s responsibility before letting the contracts and during the construction
Settlements of Building Ch recorded on 20-02-2009.
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The Employer’s responsibility before letting the contracts and during the construction
Settlements of Building Ch recorded on 20-02-2009.
The critical points of the construction along the Metro 4 Line are monitored by an automated measurements system.
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Additional measurements if necessary for safe construction form part of the
responsibilities of the Contractors
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Additional measurements if necessary for safe construction form part of the
responsibilities of the Contractors
•For the monitoring of the influence by the TBMs a so called dynamic mask was developed which was the basis for the manual leveling.
•One measurement per day is done in a zone 50 meters ahead and 100m behind the TBM in the directly affected zone.
•Further out and behind that zone the measurement frequency is reduced according the dynamic mask that is always moving along with the TBM’s progress.
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The Contractor’s responsibility
•Preservation of evidence and analysis of influenced buildings•Preparation of detailed method statements•Preparation of Emergency and Alert Plans
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The Contractor’s responsibility
•Additional soil investigation for critical locations•Design and static analysis showing expected settlements•Provision of an up-to-date tunnel convergence measurement system and additional settlement measurements•Ensuring the presence of a safety engineer responsible for the safety of the construction works and site security•Ensuring the presence of a compulsory geotechnical engineer
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The Engineer’s responsibility.
• Review and approval of design and method statements
• Supervision of construction works
• Checking of work safety measures
• Independent monitoring of settlements and tunnel convergence
• Control of the preparation and checking of Emergency and Alert plans
• Supervision and coordination of risk assessment activities
• Operation of a risk management system
• Delegate special disciplines to independent experts
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MAJOR LESSONS LEARNT
• Even in the case of a complex, large and hazardous project comprising various sub-systems, such as the implementation of a metro line, it is possible to ensure safe realization, which shall be managed solely based on comprehensive thorough design and organization measures, and strict control.
• Project management shall be provided on the basis of a centralized professional hierarchy system.
• Risk management shall form an important part of project management.
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MAJOR LESSONS LEARNT
• Preparations for unexpected events are an important element for ensuring compliance with deadline and avoiding extra costs.
• The implementation of Stage 1 of the Budapest Metro 4 Line has been completed so far under circumstances considered to be safe, which is inter alia due to the fact that the project management was prepared to also deal with unexpected events as far as practicable.
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