tunnel asdas

7/21/2019 Tunnel asdas

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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



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P)ssib!e +auses )- -ai!ure

0oor construction Kuality

Ine'ective instrumentation and monitoring

system Failure to implement risk management



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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



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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



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Thank you

tunnel asdas

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