Foreseen Challenges in Underground Tunneling for Mumbai Metro Line 3
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Foreseen Challenges In Underground Tunneling For Mumbai Metro Line 3 S.K.GUPTA Director (Projects)/MMRCL 25.05.2018 CONTENTS OF PRESENTATION • Project Route • Project Overview • Challenges • MML – 3 Geology, Mumbai • Technical challenges • NATM • TBMs selection • Building Condition • Monitoring • Quality Assurance PROJECT ROUTE PROJECT ROUTE Fully Underground • Length: 33.5 Km • Stations: 27 (26 U/G + 1) • Completion Cost: US$ 3.5 Billion • Phase 1: SEEPZ to BKC- June 2021 Phase 2: BKC to Cuffe Parade- Dec 2021 2021 2031 Ridership 1.22 Million 1.70 Million Headway 4 min, 16sec 2 min, 55 sec (CP-BKC) 256 sec 175 sec Coaches 248 (31 x 8 336 (42 x 8 cars) cars) PROJECT OVERVIEW PROJECT OVERVIEW(CIVIL WORKS) Contract Packages – Civil Works Packag Length Stations Limits e No. (K.M.) Cut & Cover NATM Cuffe Parade, Vidhan Bhavan, Hutatma Chowk 1 Cuffe Parade to CST 4.20 Churchgate C.S.T. Kalbadevi, Girgaoan, 2 CST to Mumbai Central 4.05 Grant Road Mumbai Central, Mahalakshami, 3 Mumbai Central to Worli 5.06 Science Museum, Acharya Atre - Chowk, Worli Siddhi Vinayak, Dadar Shitaladevi 4 Worli to Dharavi 6.08 5 Dharavi to Santacruz 4.94 Dharavi, B.K.C., VidyaNagari Santa Cruz Santacruz to CSIA CSIA Domestic, Sahar Road, 6 4.45 - (International) CSIA International Airport CSIA (International) to MIDC, SEEPZ Marol Naka 7 4.16 SEEPZ Total Length of the Corridor 33.5 CHALLENGES The Mumbai city will see such a big scale infrastructure intervention, spanning 33.5 km in the city for the first time in recent history. The project poses number of challenges: Administrative Geological Technical Logistics etc. I will cover only the Geological and Technical Challenge(Topographical and QA related) Mumbai Geology Reclamation History of Mumbai City TOWARDS SEEPZ PAREL MAZGAON B.K.C. LITTLE COLABA GIRGAON CUFFE PARADE DADAR MUMBAI CHURCHGATE RECLAIMED LAND CENTRAL MAHIM WORLI BOMBAY COLABA Mumbai Geology, Historical Background 9 Mumbai Geology • Mumbai : Seven islands with history of reclamation since 1800 • Deccan trap formation – 65 Ma ago • Parent rocks of Mumbai region are volcanic in nature • Basalt, Breccia, Tuff • Intertrappean Sedimentary Rocks like Shale (long period of quiescence in volcanic activity) • Thickness of overburden soil 1.0 m to 14.0 m. • Predominantly: Marine Clay, boulders, filled-up material • Ground Water is close to ground level MML – 3 GEOLOGY, MUMBAI Anticipated Construction Challenges Geological Possible Construction Issues Condition Compact Basalt High degree of jointing, water bearing strata, rock fall, instability Contact Boundary Filling of clay at contact plane, weak rock mass at contact zone between Basalt and Breccia Tuff, Tuff Breccia Clay minerals in rocks produce sticky muck and may jam cutters affecting progress Intertrappean Shale Unstable due to their inherent softness which may be aggravated by their closely spaced laminations, water seepage along bedding planes, rock fall due to softening in contact with water, swelling behaviour MML – 3 GEOLOGY, MUMBAI Varying Geological Conditions Ground Water Table 18.6 STATION m Shale, Breccia, Basalt Grade IV, V Basalt Grade I, TUNNEL II Challenges in TBM Tunnelling - Varying Geological Conditions TECHNICAL CHALLANGES Technical • The corridor passes through densely populated and congested parts of Mumbai • It is practically unavoidable not to have tunnels passing directly underneath or in a close proximity of existing buildings and existing infrastructure. The alignment is in proximity of : • High Rise Buildings (existing) • Proposed Development / Redevelopment • Heritage Buildings • Dilapidated Buildings • Flyovers and Metro Viaduct • Railway Lines • Most of the Stations are on road and very close to buildings • There is limited space for planning and implementing: • Traffic Diversion • Utility Diversion Heritage Buildings HUTATMA CHOWK STATION Arrangement for Cut & Cover Box with One NATM Platform Tunnel outside the Box HUTATMA CHOWK STATION HERITAGE PRECINCT 19 Dilapidated Buildings GIRGAON TBM Tunnel s Girgaon Crossing Railway Lines & Water Bodies Stabling Sidings & Cross- Passages by NATM Tunnel Crown 19.0 m below water Tunnel Crown 15 m below Suburban Railway level Tracks Tunnels under Flyovers A CSIA International A Foundation Details of Sahar Elevated Road based on actual piling records Variation in rock head SECTION A-A Tunnels in Proximity of High Rise Buildings 70 m 4.7 m 2.8 4.9 m m 25 m ROCK LEVEL New Austrian Tunneling Method (NATM) NATM TUNNELING • New Austrian Tunneling Method (NATM) is being employed extensively in stations to excavate where ground access is not available. Seven stations out of 26 have a component of NATM in 4 structural forms • Reversal siding at Cuffe Parade as well as siding at BKC below a large water body are to be done by NATM • NATM requires less land, and are chosen based on the type of locality /land availability/geology • Cross-Overs proposed at CST and Sahar Road • All Cross passages are by NATM Contract Packages – NATM Work Scope Package Limits NATM Work Scope No. Turn back/stabling siding tunnels at Cuffe Parade, UGC-01 Cuffe Parade to CST Hutatma Chowk station Cross Passages Kalbadevi station Girgaoan station UGC-02 CST to Mumbai Central Grant Road station Cross Passages UGC-03 Mumbai Central to Worli Cross Passages Shitaladevi station UGC-04 Worli to Dharavi Cross Passages Santacruz station UGC-05 Dharavi to Santacruz Two stabling siding tunnels at BKC Cross Passages UGC-06 Santacruz to CSIA (International) Cross Passages Marol Naka station UGC-07 CSIA (International) to SEEPZ Cross Passages NATM TUNNELING KALBADEVI -CROSS SECTION Cross Section at Cut & Cover Box Cross Section at NATM TBM For Mumbai Metro Line 3 TBM Design Approval Process - Introduction TBM by Category Design Challenges • Complexity of Geology and Hydrogeological conditions • Heritage, religious, high rise and dilapidated building • Extremely congested city • Fast Track Project Approval Process TBM by Contractor and Supplier • TBM selection by contractors • Standardised Design Approval process o Integrated approach to design approval o Re-iterative design review process as more geotechnical data became available o Collaborative debates and discussions TBM Design Requirements Following TBM design approval parameters were established during Kick-off meetings • Initial TBM design was based on Tender Geotechnical Data, GIR & GFR • Geometric parameters o Alignment, excavation diameter, segmental lining preliminary design, minimum radius of curvature etc. • Geotechnical and hydrogeological parameters o Rock Types and Class, water table, permeability, cohesion etc. • Mechanical requirements of the TBM o Thrust pressure, torque, cutter head design (Particularly on Used TBM) , main bearing loads, thrust pad and annular grouting requirements • Other TBM Design Requirements o Transportation through congested and constrained road network o Geo-statical, dead loads, and erection loads TBM TYPES SELECTED DUAL MODE HARD ROCK TBM ROCK EPB TBM Building Condition Principle Control Process to Protect the Existing Heritage Buildings and Adjacent Structure MML3 Project has established a very stringent process in design and construction stages to safeguard and protect existing heritage buildings, weak buildings and adjacent structures with respect to structures integrity and safety. The control process broadly consists of four(4) stages: 1. Assessment of existing building condition and assigning allowable impact limit categories. 2. Design the station and tunnelling excavation method impacts to be within limits of the adjacent buildings categories 3. Design and installation of protection and mitigation measures where necessary. 4. Close and continuous monitoring duration construction and revising designs as per steps 2 and 3 • Keeping watch on and getting early warning of any excessive and undue movement and/or distortion of adjacent ground and buildings is the underlined principle of the monitoring philosophy. • Instrumentations are installed on the buildings and ground before commencement of work to monitor vital parameters of the building and ground during Construction: • Settlements • Tilting • Distortions • Ground water level • Stress and displacement in excavation and support system • Vibrations Monitoring Mumbai Metro Line 3 Monitoring and TBM Active Control Control System • Controlling of Boring Process: guide parameters from interdisciplinary processing of geotechnical, geodetic and machine data QUALITY ASSURANCE Quality Assurance General Quality Assurance of MML3 is implemented on a well structured state-of-art System, monitored and recorded to ensure 120 years Infrastructure Design Life. • Mainstays for assuring quality: • Contract Documents • ISO, BIS,DIN, EN • Project Quality Plan • Design Quality Plan • Manufacturer Quality Plan • Approved Design and Drawings • Approved Method Statements & ITPs • Instruments used for ensuring quality: • Routine Audits & Construction Monitoring • Approval Process • Assessment Process • Request for Inspection (RFIs) • Contractor’s Surveillance Inspections • Non Conformance Report (NCRs) • Corrective Action Report (CARs) Conclusion Conclusion • Dealing with advance geology within an urban environment, similar to Mumbai, can be problematic, leading to significant tunnelling delays if not foreseen. • In variable ground conditions this can prove demanding depending on Stress State, Rock Competence and Groundwater inflows. Mitigating delays associated with bad ground at significant depth requires foresight, comprehensive design solutions and advance planning. • Tunnelling operations has commenced with 8 TBMs with all TBMs performing satisfactorily. General Consultants Thank you .