TBM Design meeting notes_20090716.pdf - SCATnow

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