Tunnelling process for Safety in design and construction
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The document outlines the essential processes and management strategies for safe tunneling operations, emphasizing the importance of planning, monitoring, and controlling various parameters such as face pressure and ground conditions. It discusses the design input and output requirements, risk assessments, building condition surveys, and instrumentation needed to minimize settlement impacts on existing infrastructure. Overall, it highlights the critical role of thorough geological and geotechnical investigations, systematic monitoring, and contingency planning in ensuring successful tunneling projects.
Tunnelling process for Safety in design and construction
- 1. SAFE TUNNELLING It’s All About Process
- 2. Management Processes Demming Cycle - PDCA Plan – Execute – Monitor/Control - Adjust Inputs – Process(es) – Output
- 3. IDENTIFY & DESIGN PROTECTION WORKS GEOLOGICAL -GEOTECHNICAL MODEL SITE INVESTIGATIONS (All previous data, desk study, other project data.) BUILDING RISK ASSESSMENTS & PROTECTION PLANS. Allowable Limits of Deformation ALIGNMENT OF RAIL TRACK & STATION LOCATION INSTRUMENTATION DESIGN SETTLEMENT ANALYSIS Ground loss, shield loss, tailskin loss, sensitivity TBM OPERATIONAL PARAMETERS & RANGE -Face Pressure, grout pressure/volume SURVEYS FOR UTILITIES, ID NATURE OF MATERIAL & ALLOWABLE LIMITS OF DEFORMATION GEOLOGICAL PROFILE & GEOTECHNICAL PARAMETERS SITE INVESTIGATIONS Supplementary & Instrumentation Installation BUILDING CONDITION SURVEYS, STRUCTURAL SURVEYS, Confirm Extent and magnitude of settlement, correctness of face pressure Confirm /Reassess Geological profile and face pressures required to ensure settlements controlled. Confirm or Revise Building protection Works as required. Revise risk assessment MONITORING TBM Parameters Face Pressure Grout Volume & Pressure Muck Volume Thrust, torque & Advance Speed Instrumentation Drilling Data against geological profile Planned against actual settlement Monitoring of Treated Areas Immediate Actions Reading Frequency Accuracy checks Visual Inspections of surface/buildings SAFE TUNNELLING Controlled settlement, minimal impact on infrastructure, optimised face pressures, controlled progress CONSTRUCTION Tunnelling TBM Operation Face pressure, Grouting Volume & Pressure Muck Volume Thrust Torque Speed of Advance Steering / Survey Control Lining Erection Build Quality / Repars Alignment Ground Treatment Drilling Grouting Verification Immediate Actions Alarm Plans Standard Operating Procedures Emergency Plans DESIGN OF TUNNELADVANCE Horizontal & Vertical Alignment - deeper tunnels have greater pressures, tight curves may require tapered rings Geotechnical Interpretation - possible geological hazards, mixed face conditions, geological boundaries Face Pressures - control of face pressure to avoid stress relaxation & overexcavation Weights / Volumes - assessment of weight based on range of in-situ density, assess likely use of soil conditioning Instrument Plan - types & distribution of instruments based on predicted settlements and location of buildings, frequency of reading Settlement Contours & Settlement Limits - assessment of extent of predicted settlement, allows a check to be carried out during construction Required Consolidation Works - building protection worked to prevent any adverse effects due to settlement. High Risk Areas, Structures & utilities- indicated on drawings to advise of additional care/reporting Anticipated Anomalies & Actions - Loss of face pressure, additional grout, overexcavation Probing - predicted geology, tates of penetration TUNNEL MANAGEMENT PROCESS DESIGN INPUT DESIGN PROCESS DESIGN OUTPUT CONSTRUCTION INPUT CONSTRUCTION PROCESS CONSTRUCTION OUTPUT Input 'field data' &/or correction factors into design TBM - GROUND INTERACTION Compliance with settlement limits Compliance with Face Pressure & Grout requirements Compliance with alignment DAILY/WEEKLY BASISREVIEW OF DATA TBM Design Segment Design/Lining ALIGNMENT VALIDATION - Wriggle survey ALIGNMENTVERIFICATION - Track Work Validation CONFIRM ALIGNMENT - Design modifiaction may be necessary, signalling, route restrictions.
- 4. Basic Inputs – Purpose of the Tunnel GEOLOGICAL -GEOTECHNICAL MODEL SITE INVESTIGATIONS (All previous data, desk study, other project data.) ALIGNMENT OF RAIL TRACK & STATION LOCATION DESIGNINPUT
- 7. Purpose and Alignment -(Why and Where) Tunnel – pedestrian, road, rail, metro, sewer, water, utilities, drainage, hydropower, gas/oil storage, district cooling/heating, ventilation, military installations Alignment – proximity to existing infrastructure, land take, access, cover, future development
- 8. Ground Conditions Geological Survey – regional geology, pre-existing tunnels, foundations, local knowledge, site investigations, desk studies, topographical maps, aerial photographs, literature searches Engineering geological considerations Geotechnical engineering aspects Previous Tunnelling Experience
- 9. Design Process – Holistic & Integrated IDENTIFY &DESIGN PROTECTION WORKS BUILDING RISK ASSESSMENTS & PROTECTION PLANS. Allowable Limits of Deformation INSTRUMENTATION DESIGN SETTLEMENT ANALYSIS Ground loss, shield loss, tailskin loss, sensitivity TBM OPERATIONAL PARAMETERS & RANGE -Face Pressure, grout pressure/volume SURVEYS FORUTILITIES, IDNATURE OFMATERIAL & ALLOWABLE LIMITS OFDEFORMATION GEOLOGICAL PROFILE &GEOTECHNICAL PARAMETERS SITE INVESTIGATIONS Supplementary &Instrumentation Installation BUILDING CONDITION SURVEYS, STRUCTURAL SURVEYS, DESIGNPROCESS TBMDesign Segment Design/Lining
- 10. Existing Infrastructure – Future Development Building Condition Surveys Utility Surveys Building Risk Assessments Allowable Settlement / Tolerable Settlement Protection Works – ground treatment, underpinning, future provision works Planning permission
- 11. Ground Conditions - Facts Site Investigations (before, during and possibly after) All too often BHs, followed by profiling followed by lab tests etc. & which proves to be ‘inadequate’ Proper planning and hazard ID – parameters for design and distribution, geological profile, info for construction (abrasion, swelling ground, mineralogy, GWater chemistry, gas) sampling required, lab tests, in-situ measurements (Ko), SI techniques (geophysics/BH/Pits/In-situ tests, spatial distribution/frequency of boring/depth. Rock structure/rockhead/geological interfaces Cost benefit – skilled persons can often provide more value than an expensive in-situ test
- 12. Extent / Cost of Investigation
- 14. “You paY for Your site investigation whether you have one or not”.
- 17. Site Investigation: It isn’t over till it’s over If there is a problem then the site investigations may continue with a ‘forensic’ stage and related official enquiry…
- 18. Ground Conditions - Interpretation Geotechnical Interpretative Report Design parameters, construction considerations, a prediction Strength, Permeability, Deformability, Distribution, Variability, Abrasivity, Hazards (voids, boulders, faults, geological hazards, interfaces, stresses, water inflows) Soil – Weak Rock – Hard rock
- 20. “GBR” Geotechnical Baseline Report for the settlement of disputes as to what is and what is not foreseeable and what the Contractor takes on as risk, and what the Employer takes on. What the Contract says about the ground and how ‘varied ground’ is paid for
- 21. eg Abrasion
- 22. Tunnelling Method / Selection Type of tunnel and tunnel size Ground Conditions Contractor experience / preference Risk perception Tunnel length Time available
- 23. Conventional – NATM – Hand - D&B
- 24. EPBM
- 25. Open Shield
- 26. Slurry Machine
- 27. Lining Design – Temporary / Permanent Two Pass system One pass system Segment design
- 28. Settlement / Ground Movement Expected deformation Iteration with existing infrastructure Determines type and extent of any ground treatment
- 31. Instrumentation Based on settlement Building sensitivity Utility sensitivity “Trigger levels’ and what must be done if levels are breached; resetting levels is NOT recommended (Nicoll Highway)
- 32. Tunnel Parameters Depends on type of tunnel NATM – partial headings and type of ground support EPBM – face pressure, weight of ground, hazards, grout pressure Protocol to Advance a Tunnel – PAT Contingencies if parameters cannot be controlled or are exceeded (Void Mitigation Plan)
- 33. …and coordination, iteration IDENTIFY & DESIGN PROTECTION WORKS BUILDING RISK ASSESSMENTS & PROTECTION PLANS. Allowable Limits of Deformation INSTRUMENTATION DESIGN SETTLEMENT ANALYSIS Ground loss, shield loss, tailskin loss, sensitivity TBM OPERATIONAL PARAMETERS & RANGE -Face Pressure, grout pressure/volume SURVEYS FOR UTILITIES, ID NATURE OF MATERIAL & ALLOWABLE LIMITS OF DEFORMATION GEOLOGICAL PROFILE & GEOTECHNICAL PARAMETERS SITE INVESTIGATIONS Supplementary & Instrumentation Installation BUILDING CONDITION SURVEYS, STRUCTURAL SURVEYS, DESIGN PROCESS TBM Design SegmentDesign
- 34. Design to Construction DESIGN OUTPUT CONSTRUCTION INPUT
- 35. Tunnel Advance – Design to Execution DESIGN OF TUNNELADVANCE Horizontal & Vertical Alignment - deeper tunnels have greater pressures, tight curves may require tapered rings Geotechnical Interpretation - possible geological hazards, mixed face conditions, geological boundaries Face Pressures - control of face pressure to avoid stress relaxation & overexcavation Weights / Volumes - assessment of weight based on range of in-situ density, assess likely use of soil conditioning Instrument Plan - types & distribution of instruments based on predicted settlements and location of buildings, frequency of reading Settlement Contours & Settlement Limits - assessment of extent of predicted settlement, allows a check to be carried out during construction Required ConsolidationWorks - building protection worked to prevent any adverse effects due to settlement. High Risk Areas, Structures & utilities- indicated on drawings to advise of additional care/reporting Anticipated Anomalies & Actions - Loss of face pressure, additional grout, overexcavation Probing - predicted geology, tates of penetration
- 36. Horizontal & Vertical Alignment deeper tunnels have greater pressures tight curves may require tapered rings Articulated machines
- 37. Geotechnical Interpretation - Getting the stratigraphy, structure and distribution right. geological boundaries mixed face conditions possible geological hazards
- 38. Face Pressures Control of face pressure to avoid stress relaxation & over- excavation Earth pressure Compressed air / interventions
- 40. Weights / Volumes - assessment of weight based on range of in-situ density, assess likely use of soil conditioning Bulking factors Measurement methods (balances, optical scanner, density, ‘muck skips’)
- 41. Settlement Contours & Settlement Limits Assessment of extent of predicted settlement, allows a check to be carried out during construction
- 42. Instruments & Instrumentation Plan Types & distribution of instruments based on predicted settlements and location of buildings, frequency of readings Settlements points, prisms, targets Inclinometers, extensometers Piezometers Automated monitoring / Real Time / Automated Communications
- 43. Required Consolidation / Treatment Works building protection worked to prevent any adverse effects due to settlement. Compensation grouting Underpinning Spiling rods / forepoling / canopy tubes
- 44. Specialist Works
- 47. High Risk Areas, Structures & Utilities- Indicated on drawings to advise of additional care/reporting Third Party involvement (step in rights)
- 48. Combined view of buildings, geology, tunnel, investigation points
- 49. Probing / Looking ahead predicted geology, rates of penetration Difficult ground / proximity to interfaces Geophysical techniques (EM, seismic)
- 50. Anticipated Anomalies & Actions Unexpected Conditions & Actions Contingencies, Emergency Plan Loss of face pressure, additional grout, overexcavation Surface settlement, chimneys, ground loss Collapse
- 52. Construction CONSTRUCTION Tunnelling TBM Operation Face pressure, Grouting Volume & Pressure Muck Volume Thrust Torque Speed of Advance Steering / Survey Control Lining Erection Build Quality / Repars Alignment Ground Treatment Drilling Grouting Verification Immediate Actions Alarm Plans Standard Operating Procedures
- 55. Monitoring (Can’t manage/control what you don’t measure) MONITORING TBM Parameters Face Pressure Grout Volume & Pressure Muck Volume Thrust, torque & Advance Speed Instrumentation Drilling Data against geological profile Planned against actual settlement Monitoring of Treated Areas Immediate Actions Reading Frequency Accuracy checks Visual Inspections of surface/buildings
- 56. Records of Tunnelling Tunnel parameters that must be controlled to ensure minimum impact on the ground and existing infrastructure.
- 59. CONTROL OF THE GROUTING VOLUMES 0 2 4 6 8 10 12 14 16 18 20 334 338 342 346 350 354 358 362 366 370 374 378 382 386 390 394 398 402 406 410 414 418 422 426 430 434 438 442 446 450 454 458 462 466 470 474 478 482 486 490 494 498 502 506 510 514 518 522 526 530 Grouted ring number Secondarygroutvolume(m3) -10 -8 -6 -4 -2 0 2 4 6 8 10 334 338 342 346 350 354 358 362 366 370 374 378 382 386 390 394 398 402 406 410 414 418 422 426 430 434 438 442 446 450 454 458 462 466 470 474 478 482 486 490 494 498 502 506 510 514 518 522 526 530 Longitudinalgroutvolume(m3) Secondary grout volume Longitudinal grout volume lower limit NOTE: the lower limit is defined in the "Folha da Escavaçâo".
- 60. MANAGEMENT OF FACE SUPPORT PRESSURES DURING THE ADVANCE 0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 336 340 344 348 352 356 360 364 368 372 376 380 384 388 392 396 400 404 408 412 416 420 424 428 432 436 440 444 448 452 456 460 464 468 472 476 480 484 488 492 496 500 504 508 512 516 520 524 528 532 Mounted ring number P7averagepressures(bar) 0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 631,6 637,2 642,8 648,4 654,0 659,6 665,2 670,8 676,4 682,0 687,6 693,2 698,8 704,4 710,0 715,6 721,2 726,8 732,4 738,0 743,6 749,2 754,8 760,4 766,0 771,6 777,2 782,8 788,4 794,0 799,6 805,2 810,8 816,4 822,0 827,6 833,2 838,8 844,4 850,0 855,6 861,2 866,8 872,4 878,0 883,6 889,2 894,8 900,4 906,0 Head chainage (m) P7averagepressures(bar) P7 average value upper limit lower limit NOTE: Lower and upper limits are the ones defined in the "Folha da Escavaçâo".
- 61. CONTROL OF THE EXCAVATED WEIGHTS 0 50 100 150 200 250 300 336 340 344 348 352 356 360 364 368 372 376 380 384 388 392 396 400 404 408 412 416 420 424 428 432 436 440 444 448 452 456 460 464 468 472 476 480 484 488 492 496 500 504 508 512 516 520 524 528 532 Mounted ring number Weight(t) 0 50 100 150 200 250 300 631,6 637,2 642,8 648,4 654,0 659,6 665,2 670,8 676,4 682,0 687,6 693,2 698,8 704,4 710,0 715,6 721,2 726,8 732,4 738,0 743,6 749,2 754,8 760,4 766,0 771,6 777,2 782,8 788,4 794,0 799,6 805,2 810,8 816,4 822,0 827,6 833,2 838,8 844,4 850,0 855,6 861,2 866,8 872,4 878,0 883,6 889,2 894,8 900,4 906,0 Head chainage (m) Weight(t) Actual excavated weight upper limit lower limit NOTE: Lower and upper limits are defined using the in-situ densities after the face surveys.
- 63. Key Parameters Pulse Blood pressure, temperature – NOT intensive care all the time Too much data can result in analysis paralysis and prevent timely decisions from being made. Keep your finger on the pulse!
- 64. Settlement – physical measurement of performance Settlement Profile across the Tunnel Section at GF1 Settlement Profile along the Tunnel Alingment -350 -300 -250 -200 -150 -100 -50 0 Settlement(mm) West Bound East Bound T ot alL1247 EB WB -300 -250 -200 -150 -100 -50 0 -100-80-60-40-20020406080 Distance away from Tunnel face Maximumsettlement(mm) West bound East bound L1257 15 m
- 65. Purpose of Instrumentation Confirm assumptions and apply a ‘field factor’ if required Revisit building assessments and need for possible remediation works
- 66. Instrumentation & Monitoring Instrumentation and Monitoring (I&M) does NOT stop risk I&M allows risk to be seen Murphy’s Law – “accidents tend to happen where there are no instruments”
- 69. Coordination & Collaboration SAFE TUNNELLING TBM - GROUND INTERACTION Compliance with settlementlimits Compliance with Face Pressure & Grout requirements Compliance with alignment DAILY/WEEKLY BASISREVIEW OF DATA
- 70. Construction Performance Reviews Shift Engineer Monitoring Team for each area Site Engineers Design Staff Construction Manager KTRC/C3C ? Handover Meeting Daily Monitoring data collation Review data & prepare Tunnel/Excavation Performance Meeting Issue Agreed Record Issue Weekly Review Report Internal Coordination Meeting Project Manager's Review Meeting Tunnel / Excavation Construction Review Process D A I L Y W E E K L Y Information Information Information Information Information Information Review and identify actions if required M O N T H L Y
- 71. Breaches of Limits – Escalation process Red Amber Green Green - Business as usual. Operating within expected norms and no impact on outside world. Amber – working outside of anticipated norms and potential for adverse effects – tunnel teams and implementation of remedial works on ‘alert’ and standing by. Increased vigilance, scenarios reviewed and plans revised based on situation, Red – adverse effects likely, Action plans implemented; stop tunnelling and implement plans formulated during amber.
- 72. Feedback Loops Alignment – ensure the tunnel is in the correct place and take necessary actions Monitoring and actual performance against design assumptions Change design if required / if possible: ➢opportunities in better ground, ➢ increased risk in poorer ground or sub-optimal equipment selection and workarounds required Changes in ground and possible claims against any contractual baseline
- 73. Construction Output SAFE TUNNELLING Controlled settlement, minimal impact on infrastructure, optimised face pressures, controlled progress
- 74. IDENTIFY & DESIGN PROTECTION WORKS GEOLOGICAL -GEOTECHNICAL MODEL SITE INVESTIGATIONS (All previous data, desk study, other project data.) BUILDING RISK ASSESSMENTS & PROTECTION PLANS. Allowable Limits of Deformation ALIGNMENT OF RAIL TRACK & STATION LOCATION INSTRUMENTATION DESIGN SETTLEMENT ANALYSIS Ground loss, shield loss, tailskin loss, sensitivity TBM OPERATIONAL PARAMETERS & RANGE -Face Pressure, grout pressure/volume SURVEYS FOR UTILITIES, ID NATURE OF MATERIAL & ALLOWABLE LIMITS OF DEFORMATION GEOLOGICAL PROFILE & GEOTECHNICAL PARAMETERS SITE INVESTIGATIONS Supplementary & Instrumentation Installation BUILDING CONDITION SURVEYS, STRUCTURAL SURVEYS, Confirm Extent and magnitude of settlement, correctness of face pressure Confirm /Reassess Geological profile and face pressures required to ensure settlements controlled. Confirm or Revise Building protection Works as required. Revise risk assessment MONITORING TBM Parameters Face Pressure Grout Volume & Pressure Muck Volume Thrust, torque & Advance Speed Instrumentation Drilling Data against geological profile Planned against actual settlement Monitoring of Treated Areas Immediate Actions Reading Frequency Accuracy checks Visual Inspections of surface/buildings SAFE TUNNELLING Controlled settlement, minimal impact on infrastructure, optimised face pressures, controlled progress CONSTRUCTION Tunnelling TBM Operation Face pressure, Grouting Volume & Pressure Muck Volume Thrust Torque Speed of Advance Steering / Survey Control Lining Erection Build Quality / Repars Alignment Ground Treatment Drilling Grouting Verification Immediate Actions Alarm Plans Standard Operating Procedures Emergency Plans DESIGN OF TUNNELADVANCE Horizontal & Vertical Alignment - deeper tunnels have greater pressures, tight curves may require tapered rings Geotechnical Interpretation - possible geological hazards, mixed face conditions, geological boundaries Face Pressures - control of face pressure to avoid stress relaxation & overexcavation Weights / Volumes - assessment of weight based on range of in-situ density, assess likely use of soil conditioning Instrument Plan - types & distribution of instruments based on predicted settlements and location of buildings, frequency of reading Settlement Contours & Settlement Limits - assessment of extent of predicted settlement, allows a check to be carried out during construction Required Consolidation Works - building protection worked to prevent any adverse effects due to settlement. High Risk Areas, Structures & utilities- indicated on drawings to advise of additional care/reporting Anticipated Anomalies & Actions - Loss of face pressure, additional grout, overexcavation Probing - predicted geology, tates of penetration TUNNEL MANAGEMENT PROCESS DESIGN INPUT DESIGN PROCESS DESIGN OUTPUT CONSTRUCTION INPUT CONSTRUCTION PROCESS CONSTRUCTION OUTPUT Input 'field data' &/or correction factors into design TBM - GROUND INTERACTION Compliance with settlement limits Compliance with Face Pressure & Grout requirements Compliance with alignment DAILY/WEEKLY BASISREVIEW OF DATA TBM Design Segment Design/Lining ALIGNMENT VALIDATION - Wriggle survey ALIGNMENTVERIFICATION - Track Work Validation CONFIRM ALIGNMENT - Design modifiaction may be necessary, signalling, route restrictions.
- 75. Holistic View Many specialist areas contribute to the tunnel design Many views and opinions Many data sources Lots of data available Multiple stakeholders along the alignment and through the process One error can be enough to be catastrophic!!