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Structural Performance of ImmersedTunnel Element at Flexible JointJian SunTongji UniversityAugust 4, 2015ISSAEST, Fairbanks, AK, USA, August 2-5, 2015

Immersed Tunnel Fit for underwatertransportation passageproject Prefabricated tunnel tubefloated to construction site,sank and connected Shallow buried Prefabricated instead ofconstructed in site, lightfield construction work, highqualityISSAEST, Fairbanks, AK, USA, August 2-5, 20152

Immersed TunnelTunnel tubes prefabricated in dry docksTunnel tubes floated and transportedto construction siteISSAEST, Fairbanks, AK, USA, August 2-5, 20153

Immersed TunnelTubes in place lowered one at a time into atrench pre-dredged and connected to theprevious tubeISSAEST, Fairbanks, AK, USA, August 2-5, 20154

Connection of Immersed Tunnel Rigid Joint, connect two adjacent tunneltubes as a whole through constructionmeasures, high rigidity, well transmit allinteractions, high internal force, limited jointdeformation, Fit for short distance immersedtunnel Flexible Joint, limited connection mainly torestrict relative displacement between tubes,offer considerable joint flexibility, low internalforce, Fit for long distance immersed tunnelISSAEST, Fairbanks, AK, USA, August 2-5, 20155

Flexible JointExtended shellPrestress AnchorGINA gasketElement tubeTubeShear keyOMEGA gasketElement tubeFire barrierShear keyExtended shellSchematic Drawing of Flexible JointCross Section of Tube at Element JointISSAEST, Fairbanks, AK, USA, August 2-5, 20156

Flexible JointISSAEST, Fairbanks, AK, USA, August 2-5, 20157

Flexible JointCharacteristic Connected mainly by shear key, no rigidconnection Mainly transmits vertical and longitudinal load Relatively low joint rigidity Better bear settlement or earthquake Vertical load transmitted through shear key Longitudinal load transmitted through tunnel endstructureISSAEST, Fairbanks, AK, USA, August 2-5, 20158

Study on Flexible Joint Precise model as part of a total tunnel model,study the local structural performance underdynamic force. Liu et al. (2011), Anastasopouloset al. (2007), Liu (2014) etc. Numerical model universal for immersed tunnelanalysis, Yu et al. (2014), Liu et al. (2014) etc.ISSAEST, Fairbanks, AK, USA, August 2-5, 20159

Extended Shell End of tunnel tubeat element joint Weakened area forinstallation ofwater proof andother facilities Mainly transmitslongitudinal load,transmits limitedvertical load andmomentISSAEST, Fairbanks, AK, USA, August 2-5, 201510

Extended ShellISSAEST, Fairbanks, AK, USA, August 2-5, 201511

Characteristic of Extended ShellSectional dimension relatively smallPoor rigiditySubstructurePart of flexible jointMainly transmit longitudinal load,transmit limited vertical load andmoment (which are main interactionbetween tunnel elements). Mainly bears water pressure ISSAEST, Fairbanks, AK, USA, August 2-5, 201512

Project Background Deeply buried (maximum 44m undersea level) Flexible joint Severe siltation condition (0.5m/monthin 2010, maximum thickness 20m)ISSAEST, Fairbanks, AK, USA, August 2-5, 201513

Analysis Case(1)The element sunk in placeIn this case, two adjacent elements are pulled together forjoining. In the space between two bulkheads, there is a littlewater trapped, still at the pressure corresponding to depth. Thereis longitudinal water pressure on both sides of the newlysubmerged element. The GINA gasket is not compressed andcannot provide waterproof. The joint is unfinished.(2) Depressurize & BackfillIn this case, the water trapped between two adjacent elementsis pumped. The water pressure on the other side of the newlylocated element pushed the element towards the previous one,and the gasket is pressed in the joint. A layer of 2m thick gallet isthen backfilled to provide protection. The construction of anelement is completed.ISSAEST, Fairbanks, AK, USA, August 2-5, 201514

Analysis Case(3)Service ConditionWhen the whole tunnel is completed, no bulkhead is exposed inwater, and there will be no longitudinal water pressure onelements. When the siltation terminates, the silt above the tunnelwill be 20.53m thick.(4)Ultimate ConditionThe ultimate condition is set on basis of service condition, andconsiders all unfavorable loads, including waves, rising of sealevel and sunken load.ISSAEST, Fairbanks, AK, USA, August 2-5, 201515

Analysis Analysis Object：roof Software ：ANSYS Load：Water pressure, etc.Interaction between tubes not included Analysis Method：StaticISSAEST, Fairbanks, AK, USA, August 2-5, 201516

Schematic Diagram of LoadingAccidental Load, Wave &Change of sea levelWater pressutre & Earth pressureWater pressutreEarth pressutreGravityLive loadWater pressutre & Reaction of foundationISSAEST, Fairbanks, AK, USA, August 2-5, 201517

Analysis Result – Horizontal Stress Characteristic The existence of extended shell does haveinfluence on horizontal stress of tunnel tube. The top of H-shaped support and mid span ofroof undergo more influence than other partsHorizontal Stress Resultof Service ConditionISSAEST, Fairbanks, AK, USA, August 2-5, 201518

1014121086420-2-4-6-8-10-12-14Element JointSegment Joint8X-component Stress (MPa)Stress (MPa)Analysis Result – Horizontal StressMid ce from Left End of Roof Slab (m)Comparison of Horizontal Stress on ElementJoint and Segment Joint of Tube510152025Longitudinal distance from element joint (m)Variation of Horizontal Stressalong Longitudinal AxisISSAEST, Fairbanks, AK, USA, August 2-5, 201519

Analysis Result – Principal Stress Characteristic The existence of extended shell does haveinfluence on principal stress of tunnel tube. The top of H-shaped support and mid span ofroof undergo more influence than other partsPrincipal Stress PatternISSAEST, Fairbanks, AK, USA, August 2-5, 201520

Analysis Result – Principal Stress Characteristic The existence of extended shell does haveinfluence on principal stress of tunnel tube. The top of H-shaped support and mid span ofroof undergo more influence than other partsPrincipal Stress (MPa)12108642Elemenr JointSegment Joint005101520253035Distance from Left End of Roof Slab (m)Comparison of Principal Stress onElement Joint and Segment Joint of TubeISSAEST, Fairbanks, AK, USA, August 2-5, 201521

Analysis Result - Displacement Vertical Displacement Patternof Service ConditionCharacteristic Vertical displacement of extended shellcoordinates with adjacent tube structure. Vertical displacement difference betweenextended end and adjacent tube structure isnegligible. The existence of extended shell does haveinfluence on displacement of tunnel tube.ISSAEST, Fairbanks, AK, USA, August 2-5, 201522

Analysis Result - Displacement766Displacement (mm)Displacement (mm)55432Element JointSegment Joint1432100051015202530035Comparison of Vertical Displacement onElement Joint and Segment Joint of Tube510152025Longitudinal Distance from Element Joint (m)Distance from Left End of Roof Slab (m)Variation of Vertical Displacementalong Longitudinal AxisISSAEST, Fairbanks, AK, USA, August 2-5, 201523

Conclusion The extended shell at the joint is of lowrigidity, but well supported by adjacent tunneltube. Its deformation and stress are wellcontrolled. The extended shell has limited influence ondistribution of stress and deformation of thewhole element.ISSAEST, Fairbanks, AK, USA, August 2-5, 201524

Conclusion The existence of extended shell does haveinfluence on stress and deformation ofadjacent tunnel element, its adjacent tunnelstructure bears about 10% more stress anddeformation, especially on tunnel roof.ISSAEST, Fairbanks, AK, USA, August 2-5, 201525

Suggestion & Prospect Consideration of the influence of extendedshell on tunnel tube should be taken duringdesign Structural performance of extended shellunder interaction between elements underearthquake or settlement should be studiedISSAEST, Fairbanks, AK, USA, August 2-5, 201526

Thank YouISSAEST, Fairbanks, AK, USA, August 2-5, 201527

Jian Sun Tongji University August 4, 2015 . ISSAEST, Fairbanks, AK, USA, August 2-5, 2015 Immersed Tunnel 2 Fit for underwater transportation passage project Prefabricated tunnel tube floated to construction site, sank and connected Shallow buried Prefabricated instead of