talk on ‘permanent works shotcrete in hong kong...
TRANSCRIPT
50 Jurutera, July 2008
report
the talk on ‘Permanent Works Shotcrete in Hong Kong tunnels’ was delivered
by David Salisbury, an associate Director of Ove arup & Partners, Hong Kong with 20 years’ experience in tunnel design and construction, on 19 October 2007 at the IeM lecture hall in Petaling Jaya at 5.30 p.m.
the past ten years has seen rapid advances in sprayed concrete technology for use in underground construction works. In Hong Kong, the recent development of a number of large underground infrastructure projects has led to increasingly imaginative uses of sprayed concrete technology and in particular its use for permanent works.
Spray concrete has made great advances in recent years and is increasingly used in permanent works. In fact, sprayed concrete is better than cast concrete in terms of strength and quality. Salisbury started the lecture by introducing the tunnelling activities in Hong Kong.
at present, there are over 380km of bored tunnels in Hong Kong, 59km in the next seven years and at least another 50km has been planned by 2015. traditionally tunnels are constructed in hard rock but there is an increasing demand for large diameter soft ground tunnelling.
the presentation started with the review of tunnelling case studies on several projects in Hong Kong where alternative and innovative proposals for using sprayed concrete in the permanent works have been adopted. these include:• onepassshaftlining;• cavernsinexcessof20mspan;• complexjunctionsandirregularshapes;• formed surface finishing to provide
smoothhydraulicflow;• fullyreinforcedshotcrete;• application of shotcrete directly onto
waterproofingmembranesand;• drainagereliningworks.
Both dry and wet mix spray concrete (shotcrete) are used in permanent shotcrete applications ini) Caverns and tunnelsii) Shafts andiii) Other applications
Dry Mix ShotcreteFigures 2 and 3 show the examples of dry mix shotcrete used in Hong Kong.
Wet Mix Shotcreteadvantages:• Higheroutput(30m3/hr)• Qualitycontrol• Pumpoverlongdistances• Lessrebound(5-10%)• Steel&polymerfibres• Moreadvancedequipment
• Advancedmixdesign• Anothermethodofconcrete
placement
Figures 4 and 5 show the application of wet mix shotcrete.
Mix DeSign Dry MixOPCement………….......................….480kg10mm aggregate..........................…...600kgCrushed rock.…….............................1200kg
Figure 1: Use of shotcrete in engineering
Figure 2: Use of dry mix shotcrete in slope protection
Figure 3: Use of dry mix shotcrete in tunnel in Hong Kong
talk on ‘permanent Works Shotcrete in Hong Kong tunnels’ ...........................................................................................................................................................................................................................................................................
By: Engr. Dr Ooi Teik Aun, FIEM., P.Eng.
Tunneling and Underground Space Technical Division
51 Jurutera, July 2008
report
accelerator.……….......................…….15kgWater (added at nozzle)
high PerforMance Wet MixOPCement……….................………...400kgPFa…………………….................…….60kgSilica fume……………...................…...40kg 10mm aggregate…….................……450kgCrushed rock.……...................……..1230kgWater…………...……................….…200ltrsrB561 (Superplasticiser)…....................6ltrsSteelfibresRL45/35……..................…30kgFibermesh 150…………...................…0.9kg
PerManent Shotcrete aPPlicationScaverns • IslandWestTransferStation-EPD• PakShingKokTunnels–MTRC• DisneylandResortline–MTRC• QueenswaySubway–Swire/MTRC
Shafts• KaiTakTransferScheme–DSD
non-Standard tunnel Sections• Corners-KwaiChungCable Tunnel–CLP• CrossPassages–LokMaChau SpurLine–KCRC
other applications• Hydraulicprofiling-KaiTakTransfer
Scheme–DSD• ReliningofNullah-KaiTakTransfer
Scheme–DSD
caverns – island West transfer Stationenvironmental Protection Department (ePD)• WastetransferstationonHKIsland
located within a hillside waterfront cavern
• Excavationinrock• Primaryshotcreteandpermanent
rockdowels• Concreteliningonlyatportals• Engineer’sdesign175,000m3• ShotcreteFinaldesign30,000m3• HK$200millionsaving
caverns – Pak Shing Kok crossoverMtr tseung Kwan O extension• 6.1kmofrunningtunnels• Standardtunnelliningbymovingform• Unreinforcedcastin-situconcrete• Not suitable forCrossings, Junctions,
FanNiches.
caverns – Pak Shing Kok crossover• One24mwidecrossoverCavern• Seven12mwidefanniches• Fivebifurcations• Two‘T’junctions• Allpermanentshotcretelined
caverns – tai yam teng tunnel nichesMTRDisneylandResortLine• 3kmlongshuttleconnectiontothe
new Disney theme park• 850mlongtunnelsection,5.4m
internal diameter • twofannichecaverns• sixothernon-standardsections• Sheetandsprayedmembrane
caverns – Queensway Subway• 300mlongpedestriansubway• Linkingdeveloperspropertiesand
Mtr station• Cavernenlargementforescalator
connection• Excavatedinrockwithlowcover
below major road• 15mwidex33mlongrockcavern• Constantlyvaryingsection• Constantaccessrequired• Fullytanked• Sprayedmembrane(Masterseal345)• Steelandpolymerfibres• Primarysprayedconcrete• Gunitesmoothinglayer
Figures 4 & 5: Applications of Wet Mix Shotcrete
Figure 6: Queensway Subway
Tunneling and Underground Space Technical Division
52 Jurutera, July 2008
report
• Reinforcedconcreteinvert• Maintunnelunreinforcedcastin-situ• Leaksdivertedtotemporary
invert drain• Mastersealsprayapplied• Severallayersused• Roughsubstrate• 5-6mmthick• Sprayedoversheetmembrane
at intersections• Constructionjointspreparedwith
waterbarandsealant(Masterflex900)• Finalinspectionforleaks• Permanentsprayedconcreteapplied
directly onto Masterseal
• 600mmthickappliedin2-3layers• Minimalrebound(<10%)• Surveycheckthenfinallayer,nofibres• Escalatoraditfullyreinforced
sprayed concrete
Figure 6 shows the completed subway at Queensway.
Shafts – Kai tak transfer Drainage SchemeDrainage Services Department• 1.9kmlongstormwatertransfer
tunnel• Sixshafts
• Fourshaftsbytheone-pass shotcrete method
• Circular:7.0-8.5mI.D.• Depth:Max.21.0m• ShotcreteOnePassTemporaryand
Permanent lining• FoamConcreteBackfillfor
tBM entry• R.C.BaseSlab&RoofSlab• Pipepilesinstalled• Excavate2.0m• Steelringbeaminstalled• Excavate2.0mandshotcrete
Primary layer 200mm x 1.5m• ShotcretePermanentlayer 100mm x 1.0m• FloatfinishPermanentlayer• Pipepilesinstalled• Excavate2.0m• Steelringbeaminstalled• Excavate2.0mandshotcrete
primary layer 200mm x 1.5m• Shotcretepermanentlayer 100mm x 1.0m• FloatfinishPermanentlayer• EarlyStrength16MPaat
12 hours• Excavate1.5m• Fixhydrophilicandgrout
tube strips• Shotcreteprimarylayer 200mm x 1.5m• Shotcretepermanentlayer 100mm x 1.5m• Floatfinishpermanentlayer• Repeatthree-daycycle• Detailofshotcreteoverlapshowing
grout tube hydrophilic strips• Constructionjoint1.3mlong• Nomembrane,noleaks• Floatfinishasgoodascastin-situ
lining form
the talk on permanent work spray concrete was indeed very informative and it attracted some 90 participants.
Figure 7 shows a section of the participants in the IeM hall.
the talk ended at 7.30 p.m. with numerous interesting questions from the floor. Dr Ooi, on behalf of the tunnelling and underground Space technical Division presented Salisbury with a memento as a token of appreciation (see Figure 8). n
Figure 7
Figure 8
Tunneling and Underground Space Technical Division