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TUNNEF A I L U R ESubmitted by :
Karan Desai AP 14299
Manan Desai AP 14300aynei! Desai AP 1430"
aimin Pate! AP 1439"
Ab#ina$ A%ar&a! AP 1439'
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Hard Rock Tunnels
Deep tunnels above sea level,
predominantly on rock and generallywithin less developed areas
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S o f t / m i x e d g r o u n d T u n n e l s
hallow tunnels !"#$m below ground%
generally below water table in urbanareas
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Types of failure
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Soil flowing in tunnel
&wo di'erent diameter o( tunnels Une)pected ground (ailure
*ap e)isting between two stages o(
tunnels
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Failure due to water
+ater inow into the tunnel(eas)ns &he tunnel intersected the bottom o( an
abandoned well &he tunnel passed through a shallow
anticline and intersected a -ssure
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Water flowing into Tunnel
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Sinkholes
(eas)ns
.verstressing o( the sprayed
concrete temporary lining &hin weathered rock cover
Inow o( soil and groundwater
/igh groundwater pressure
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/igh permeability soil
Layer o( marl separating
groundwater bearing layers wasmuch thinner than originallyassumed
0ossible 1rock slippage2
Under designed rock bolts due toincreased span
Sinkholes
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Failure due to Sinkholes
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Failure due to Sinkholes
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Sinkholes
(emedia! Measures
3oid was back-lled with crushed rock andcement and pressure grouted
4ack-lling the crater with soil (ollowed bycement grouting and chemical grouting
4ored5pile wall to (orm a sha(t
E)cavation inside the sha(t (or rescue
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Sinkholes
(emedia! Measures
&unnel driven using compressed air
teel rings installed in tunnel either side o(
the collapse Road resur(acing
A curtain o( piles ahead o( the collapsed
(ace &he void was back-lled with o( glass5sand
!recycled glass%
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Deformation
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Deformation
&unnel subsidence at sur(ace +ater 6 soil ! can lead to 7899 liters:min into the
tunnel%
(eas)n
Fluctuation o( groundwater level caused by tidale'ects results in vertical movement o( thetunnel tube causing opening o( ;oints
(emedia!
*round (ree
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Ground freeing
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!low out crater
Insu=cient overburden above thetunnel
/igh pressure within tunnel causingblow out (ailure
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Failure of diaphragm wall
Rapid uctuation o( groundwater levelcaused movement o( unidenti-ed graveland sand strata
Additional loading on diaphragm notconsidered in design
(emedia!
4ack-lling o( e)cavation pit
ubsoil grouting
Diaphragm wall strengthening
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Failure of Diaphragm WallSingapore MRT, 20 April 20
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*a+,%r)und> An open cut tunnel e)cavated (or ingapore
?R&@s new ircle Line
> E)cavated trench o( B$m wide and CCm deepmainly in marine clay with some uvial claysupported by 95B9m thick diaphragm wallwhich is C$5$m deep without rock socket
> teel strutsG 5$m hori Het grouted base slabs
> Layer B5B$m thick at #$m below ground
> Layer #5Cm thick at CC$m below ground
Singapore MRT, 20 April 20
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T#e -ai!ure th level o( struts being installed when
collapse took place
Unusual cracking and groaning noisesheard early in the morning !8 hours%
Loud cracking noise heard in thea(ternoon, B$minutes be(ore collapse
ollapse plan area was B99m by BC9m ettlement up to B$m
Diaphragm walls displaced
teel struts mangled
Singapore MRT, 20 April 20
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P)ssib!e +auses )- -ai!ure
0oor construction Kuality
Ine'ective instrumentation and monitoring
system Failure to implement risk management
Singapore MRT, 20 April 20
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(emedia! measures
Rescue and back-lling
tructurally disconnected the ?erdeka
4ridge All contracts o( the ircle Line put on hold
All contracts to carry out checks and
review o( design and construction o(temporary works
Singapore MRT, 20 April 2
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(emedia! measures
All 0ro(essional Engineers to con-rm inwriting the adeKuacy o( their designs
All designs to be independently checkedby the 4uilding
onstruction Authority
Singapore MRT, 20 April 2
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Thank you
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