Parsons - 2010 Construction Management for AWV.pdf - SCATnow

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ground surface and structure damage. Consequently, a TBM capable of balancing external groundwater and soil pressuremust be used to control excavation rates and groundwater inflow, as well as maintain stability of the tunnel face.It is understood that the successful design-builder has selected the earth pressure balanced TBM (EPBM). Our teamevaluated all available pressurized-faced machine technologies and all of the associated risks as related to the SR 99Design-Build project. While all technologies have their share of risks and benefits, EPBM technology has many benefits andeconomies for soft ground tunnels; however, this is generally for smaller diameters, not in the mega sizes, primarily dueto higher risks. EPBM function is compromised in the loose granular soils, which will require a high volume of polymer soilconditioners to improve face support. Our soil evaluation indicates several areas of soils with high stickiness potential thatwill require additional soil conditioning to prevent plugging of the cutterhead, increased wear, critically increased torque,and face support issues.The mega-diameter of the EPBM creates issues not experienced with smaller TBMs. The pressure differential between thetop and bottom of the EPBM is significant and will require special procedures and conditioners to maintain stable facepressure. Unusually high thrust and power requirements for the cutterhead is a tremendous risk and concern in variableface conditions. This project has an unprecedented diameter using EPBM mode tunneling, considering the difficult groundconditions. Our job will be to confirm that the EPBM operations are synchronized with the ground conditions and theproper mitigation measures are implemented and monitored.TBM maintenance, if not performed at proper intervals, can cause excessive wear, extended hyperbaric interventions, andunnecessary delays. Routine maintenance will generally minimize the need for significant repairs. A robust TBM designedto reduce wear and extend component life must be provided.In Portland, Greg Colzani and Jan Babenderderdeevaluated TBM cutter wear and recommendedafter-market cutters that would double the distancebetween cutter changes.For most of the alignment, the cutterhead will requireaccess through the plenum under hyperbaric conditions tomaintain face stability. Wear plates, wear indicators, highperformance cutting tools, and unprecedented soilconditioning must be part of the risk reduction plan. Theproper amount of face pressure must be applied in theinspection area so as not to leak air to the surface. Depending on ground conditions, additional face support throughgrouting may need to be performed to prevent face collapse. When mining is resumed, the evacuated plenum must berecharged with bentonite or a bentonite rich inert backfill material to ensure that over-mining is prevented.To ensure the long-term performance, the segmental liningmust be transported and erected in the tunnel withoutdamage to exacting tolerances. Subsequently, the annulargap between the liner and surrounding soil must be filledwith grout, concurrent with TBM advance, to preventovalization and ground loss. Our team researched andevaluated segment installation and annular space groutingprocedures to address the unique risks associated with the‘mega-diameter’ tunnel.Bored Tunnel Alternative Design-Build ProjectDesign-Build Construction Management Services SR 99The TBM cutterhead must be designed to handle all conditions represented in the Geotechnical Baseline Report (GBR). Thedesign-builder’s TBM design tunnel excavation plans must include operational guidelines for mining through changes inmaterial, boulders, granular soils, and soils with high stickiness potential.Our team has the understanding and demonstrated experience to manage the tunneling risks of the SR 99 project. TableE.1 provides representative examples of our methodology, acting as CM support to WSDOT, to manage these and similarproject risks.34
Bored Tunnel Alternative Design-Build ProjectDesign-Build Construction Management Services SR 99Table E.1 Risk CM Role - Design and Pre-construction CM Role - ConstructionTBM Design/Operation:• Loss of control of the face pressuresdue to high pressure gradient betweencrown and invert level• Inability to provide for a homogenousmixture of excavated materialsgiven the extremely high probabilityof mixed face or variable soil andgroundwater conditions• Failure of critical TBM components• Immobility of cutterhead• Unexpected inundationWater-Bearing Running SandsLoss of face pressure/poor mixingin the earth plenum triggersuncontrolled flow of running sand/water into the plenumGround Loss at The Face• Surface settlement is caused by loss ofground at the face, above and aheadof the face, and if shunt flow occursbehind the face, especially for re-startafter stop and interventionGround Loss Around the Tail Skinand Segmental Lining• Surface settlement occurs by excessiveground loss around the shield orimperfect grouting of the annularbehind the tunnel liningThe CM team must confirm that the design-builder’sdesign provides:• Redundant safety factors for the design of TBM componentsdedicated to control the pressure balance• Redundant sensors to monitor face pressures• A supply of bentonite fully available to fill up the chamber inthe event of pressure loss after manned interventions• Numerical/physical model of mixing in the plenum• Additional wear plates, wear detectors, and redundantcutters to minimize interventions• Proper sizing of TBM components to take into account thelarge-scale tunnel• Mechanisms for keeping the cutterhead from becomingimmobile in sticky soil• Adequate ports for lubrication and conditioning for pressurebalance and control of water pressureThe CM team must confirm that the design-builder’sdesign provides:• Designs TBM and procedures to withstand added facepressure• Provides soil conditioning and additional bentonite supplyfor injection, as requiredThe CM team must confirm that the design-builder’sdesign provides:• Selects and designs the TBM to provide soil conditioningincluding bentonite injection, if necessaryThe CM team must confirm that the design-builder’sdesign provides:• Designs grout for anticipated ground conditions• Designs a robust grouting system and a redundant back-upsystemThe CM team must monitor the design-builder’sactivities to confirm:• Extensive factory testing of the TBM• TBM is maintained in accordance with manufacturers’recommendations• Face pressure is maintained at all times• Proper conditioning program is tested and used• Monitoring of all machine and operational functions• Plenum filling is completed prior to re-mining• Redundant systems are in place and operational• Backfill grouting system is operating as designedThe CM team must monitor the design-builder’sactivity to confirm:• Fabricates and operates the TBM to increase control of theface in high pressure areas• Uses soil conditioning and additional bentonite injection asrequired.The CM team must confirm that the design-builder:• Refills the chamber with bentonite or other material ascompressed air is lowered• Performs cutter changes in partially evacuated plenum,refilling and mining ahead and repeating, conducting workin partially filled chamber to reduce the pressure differentialfrom top to bottomThe CM team must confirm that the design-builder:• Controls grout injection with the TBM advance• Provides a robust grouting system and a back-up system• Injects bentonite in the annular space around the TBM shield• Verifies grout by coring and performs secondary grouting2One-Pass Pre-Cast Bolted Gasketed Segmental Concrete Lining SystemsBenefits to WSDOT• Large diameter segment design, fabrication, and inspectionexperience• In-depth understanding of project-specific geotechnicalconditions as related to lining designOur team members and companieshave designed, fabricated, installed, andinspected over 100 miles of segmentlinedtunnels, including the 10.84-meterDublin Port Tunnel and the 11.34-meterinterior diameter Brisbane Airport Link.35
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* Key Staff(C) CMTS, Inc.Firm(CRS)
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ARCHITECT-ENGINEER QUALIFICATIONSPA
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HealthForce Partners, LLC
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Additional Staff ResumesTab 1 Addit
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Tim Daley, Vent Building Mechanical
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Prime and Sub Information Packet Fo
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Submittal Information FormProject N
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Washington StateDepartment of Trans
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