TBM Design meeting notes_20090716.pdf - SCATnow

Alaskan Way Viaduct and Seawall Replacement Program - Central Waterfront Viaduct ReplacementTBM Design / Technologies MeetingDate: July 16, 2009Time: 10:00 AM – 12:00 PMLocation: 23 rd Floor Conference Room SmallLead: Don PhelpsMEETING NOTESAttendees: Eldon Abbott, Stuart Warren, Randy Essex, Don Richards, John Townsend, Bill Hansmire,Greg Korbin, Ed Kennedy, Brenda Bolhke, Mike WongkaewCC:Harvey Parker, Susan EverettDiscussions:I Opening Don PhelpsThe objective of the meeting was to solicit opinion on the following topics:• TBM type: Earth Pressure Balanced or Slurry Shield• Implications of increasing tunnel diameter from TBM design perspective• Upper limit of tunnel diameter from TBM design and risk perspectiveII Machine Type Selection and Design Considerations All• Design and manufacturing of bearings for large diameter tunnels• Design to address overturning moment and rolling for large diameter tunnels. Discussed MadridM30 project in which the Herrenknecht machine used two counter-rotating cutter headswhereas the Mitsubishi machine used single cutter head with other stabilizing techniques.• Torque – slurry shield machines require less torque than EPB machines. Polymer additive couldbe used to reduce torque demand for EPB machine.• Ability to maintain face pressure which is critical to control surface settlement. For largediameter tunnels, the face pressure would also have high gradient top to bottom.• Presence of sticky clay will adversely impact slurry shield machine and slurry treatment plantand reduce the advance rate. Polymer additive could be used to lessen this impact.III Suggestions for TBM Specifications All• Evaluate potential need and benefits of hybrid TBM (EPB and Slurry Shield)• Ability to monitor the tunnel face – physical probes and geophysical probes.• Ability to grout in front of machine faceIV Upper Limit of Tunnel Diameter All• It is the collective perception that the risks will be unacceptable when the TBM diameterbecomes 60 ft or larger. To mitigate this, design deviations could be considered to reduce thetunnel diameter.• A tunnel with liner OD of about 55 ft (TBM diameter of about 59 ft) should be doable; however,risks are significant.9/28/2010 KW

Alaskan Way Viaduct and Seawall Replacement Program - Central Waterfront Viaduct ReplacementMEETING NOTESV Risks Associated with Increasing Tunnel Diameter* AllRisks of various tunnel diameter were discussed ; the following summarizes the initial thoughts on riskfactors and subjective assessments:Risk Factors 48 ft OD 54-55 ft OD(state of (CEVPpractice) Baseline)Production rate +10 to 20% ~ 36 ft/day(Probablyoptimistic. 25 to30 ft / day morerealistic)TBM mechanical requirements (buildabilty, reliability, Baseline 20% increase instep change in technology)probability ofdifficulty.58 ft OD-10%-20%30%increase inprobabilityof difficulty.Number of bidders - if Lump Sum / Unit Price contract-if Target Price/ Target Fee contract1-33-40-12-3Settlement (routine) and third party issues -20% Baseline +20%Extraordinary ground loss Medium Medium HighPhysical space requirements / constraints Improvement Baseline HighMachine type feasibility - Slurry- EPBYesYesYesPossibly (torquelimited)Probably 01-2YesPossibly(torquelimited)Cost (of tunnel only) - TBM- Muck handling- Internal structuresBaselineBaselineBaseline+20%+20%+20%Geology (more boulders, more variable ground) -20% Baseline 10 toRisk of transfer of TBM ownership and associatedproblems to WSDOT+20%No Possibly Probable* Ouside diameter of liner; TBM diameter will be about 3 to 4 feet larger, accommodating thickness ofshield and boring tolerance.9/28/2010 KW