Introduction to Soft Ground Introduction to Soft Ground Introduction to Soft Ground Introduction to Soft Ground Tunnelling in Urban Tunnelling in Urban

EnvironmentEnvironmentDr. Noppadol PhienwejDr. Noppadol Phienwej

Geotechnical and GeoGeotechnical and Geo--environmental Engineeringenvironmental EngineeringSchool of Engineering and TechnologySchool of Engineering and Technology

Asian Institute of TechnologyAsian Institute of Technologygygy

ITA Wh T l?ITA- Why Tunnel?• A country’s infrastructure is one of its main assets• A country s infrastructure is one of its main assets• Developed countries require a modern infrastructure

• Roadsil• Railways

• Power• Communications• Water• Wastewater• Gas• Gas

• Congestion above and at surface level in urban metropolis, where space is at a premium, means

i d h d i h l i bl igoing under the ground is the only viable option

Infrastructures in Modern Urban Area

Underground Space Utilization in Urban Business Area

For Better Environment

Characteristics and Constraints of Characteristics and Constraints of Urban Tunnelling

• Tunnelling at shallow depth – Mostly soft ground tunnelling• High risk due to soft ground and groundwater

Construction in congestion area Traffic disturbance• Construction in congestion area – Traffic disturbance• Tunnelling at close proximity to existing buildings and

utilities- space constraints• Need to minimize damages to existing structures and third

parties• Need to control minimize movementsNeed to control minimize movements• Many parties involving- Work coordination

TUNNEL GROUNDS

•• ROCK TUNNELROCK TUNNEL

•• SOFT GROUND TUNNELSOFT GROUND TUNNEL

Rock Tunnelling

Rock Tunnelling

Rock Tunnelling – Investigation, Design & Construction

W EW E Geotechnical Longitudinal Section

-0,40

-0,30GG+

F

0 0 0 0 0 0 0 0 0 0 0

-0,20

-0,10

0,00

EDCBA

1150

1170

1190

1210

1230

1250

1270

1290

1310

1330

1350

Station [m]

Egnatia Motorway, Anilio Tunnel (Greece)

Rock Tunnel Excavation

Drill & BlastDrill & Blast

Rock Tunnel Boring Machine

Rock Tunnel Boring Machine

Soft Ground Tunnelling

Soft Ground TunnellingWhat is soft ground?

gg

Soft ground consists of various mixtures of sand, silt d land clay.

It can be described as firm raveling squeezing runningIt can be described as firm, raveling, squeezing, running flowing or swelling.

In all types of tunnelling, face stability is the primary goal, this is followed by ground movement controlcontrol.

Ground Movement

Soft Ground TunnellingGround Movement

Face StabilityFace Stability

Tunnel Collapse

M4 metroline crossing Huangpu River in Shanghai

Methods of Tunnel Methods of Tunnel Construction in Soft Ground

• Cut & Cover Construction• Tunnelling

–Shield Tunnellingg–Non-Shield Tunnelling – Shotcrete &

steel arch• Pipe Jacking (Micro Tunnelling)

Methods of Tunnel C t ti i S ft G dConstruction in Soft Ground

Cut and Cover for MRT

Singapore Hong Kong

Stuttgart, Germany

CUT AND COVER TUNNELCUT AND COVER TUNNEL

DIAPHRAGM WALLDIAPHRAGM WALLDIAPHRAGM WALLDIAPHRAGM WALL

BANGKOK MRT

PILE SUPPORTED STRUCTURE

SHIELD SHIELD TUNNELINGTUNNELING

Shield TunnellingShield Tunnelling

Shield TunnellingShield Tunnelling

Reinforced Concrete Segmental Lining

RC S t l RiRC Segmental Rings

Pipe Jacking (Micro Tunnelling)Pipe Jacking (Micro Tunnelling)

Thrust Shaft

S Control Container

Lubricant Preparation Plant

Th t W llITE

Control Container Thrust Wall

Jacking

LAYO

gPipeEntrance Ring

(Soft Eye)

OUTE Base SlabE

Jacking FrameTBM

PPIPEJJACKING

TBM and first pipe placed on jacking frame and ready to commence excavation through the soft eye

PPIPEJJACKING

TBM commences excavation and both pipe and machine togetherboth, pipe and machine together are pushed through the soft eye into the ground by the jacking cylinders

PPIPEJJACKING

Excavation is stopped, jacking pp , j gcylinders are moved backward so that the next pipe can be placed behind the string

PPIPEJJACKING

Then the jacking cylinders are again

d ti htl i tpressed tightly against the pipe end, ready to push the whole line forward

PPIPEJJACKING

PPIPEJJACKING

PPIPEJJACKING

PPIPEJJACKING

Jacking Operation - EPB 1500, 2600 and AVN 1200

PPIPEJJACKING

Shields for Pipe JackingShields for Pipe Jacking

World Record Breaking Pipe Jacking World Record Breaking Pipe Jacking Works in BangkokWorks in Bangkokgg

Shield TunnellingShield TunnellingShield TunnellingShield Tunnelling

Shield TypesShield Types

Slurry ShieldSlurry Shield

EPB Shield

General arrangement – EPB Shield Machine

Non-Shield TunnellingC ti l M th dConventional Method

Non-Shield Tunnelling

Shotcrete + Steel latticeSoil ImprovementSoil Improvement

NATM

FIRST ROAD TUNNELFIRST ROAD TUNNEL

BETONG YALABETONG, YALA

TUNNEL WITH SHOTCRETE AND STEEL ARCH

Invert Shotcreting

SEQUENTIAL EXCAVATIONSEQUENTIAL EXCAVATION

SEQUENTIAL EXCAVATIONSEQUENTIAL EXCAVATION

UNSTABLE GROUND

ROOF SPILINGROOF SPILING

FOREPOLING

When there are stability problem of ground

Umbrella Roof Method

PIPE JACKED ROOFPIPE JACKED ROOF

Freezing method was used to remove the old structure and build new structureand build new structure

Freezing pipes needed toneeded to freeze the ground under the pre-

Old structure

the preexisting tunnel. It could not be installed from

New structurethe road.

Therefore, the curve boring

Extent of frozen

curve boring method was adopted.

ground

INTERVENTION SHAFT EXCAVATION

Soft Clay

Stiff Clay

Sand

TUNNEL PORTALS AND SHAFTS

TUNNEL PORTAL TUNNEL PORTAL –– Slope StabilitySlope Stability

Permanent Shaft Sinking

Completed Shaft from tunnel level

Irregular Shape Shaft

TUNNEL SUPPORTTUNNEL SUPPORT

Cross section showing primary and secondaryCross section showing primary and secondary lining, after Hughes (1987)

DESIGN PRINCIPLESPRIMARY LINING OF SHOTCRETE INSTALLED CLOSE BEHIND

FACE AS EXCAVATION PROCEEDS TO MINIMISE GROUND RELAXATIONRELAXATION

•thin shell design approach ( limited moment capacity)

•applied loads less than full overburden due to negative pore pressure leading to arching support

•time dependent build up of loads

•allow for stress concentrations from nearby tunnels

•limited duration of use before secondary lining cast

includes load factor of 1 4•includes load factor of 1.4

•structural analysis using bedded beam model

Installed Segmented Rings Behind Shield Tail Skin

Segmental Lining

Primary Grouting After Segment Erection

Cement / Bentonite

Sodium Silicate

Grouting Material gels within 8 Sec.

Ring Deformation+Pressure

OBSTRUCTIONOBSTRUCTION

Difficulties in Tunnelling and Effects on Building Foundation

BUILDING PROTECTION PRINCIPLESBUILDING PROTECTION PRINCIPLESBUILDING PROTECTION PRINCIPLESBUILDING PROTECTION PRINCIPLES

DESIGN & CONSTRUCTION METHODSDESIGN & CONSTRUCTION METHODS DESIGN & CONSTRUCTION METHODS DESIGN & CONSTRUCTION METHODS TO MINIMISE GROUND MOVEMENTS TO MINIMISE GROUND MOVEMENTS PREDICTION OF MOVEMENTS REQUIREDPREDICTION OF MOVEMENTS REQUIRED BUILDING CONDITION SURVEYBUILDING CONDITION SURVEY 22nd & nd & 33rd STAGE ASSESSMENT IF REQUIREDrd STAGE ASSESSMENT IF REQUIRED ALERT LEVELS IDENTIFIED BEFOREHANDALERT LEVELS IDENTIFIED BEFOREHAND BUILDING PROTECTION IF REQUIREDBUILDING PROTECTION IF REQUIRED

INSTRUMENTATION & MONITORINGINSTRUMENTATION & MONITORING INSTRUMENTATION & MONITORINGINSTRUMENTATION & MONITORING

BUILDING DAMAGEBUILDING DAMAGE

Building response to ground movement

6.3 m outer-diameterSingle TrackSingle Track

TUNNEL–PILE RELATIVE POSITIONSUMMARYSUMMARY

Angel Underground Station, LondonExisting MRT North-East Line C704, Singapore

MTR Island Line, Hong KongMRTA Subway, BangkokElectric Power Tunnel, Japan

Existing super-

structure

Type 1

Tunnel45o

Type 2

MRT Circle Line C825, SingaporeC bl T l L dType

3Type

4

Tokyo Subway Line 7, JapanJ bil Li E t i L d

North/South Metroline, Amsterdam

Cable Tunnel, London

Jubilee Line Extension, LondonChannel Tunnel Rail Link 2, LondonMRT Circle Line C825, Singapore

TUNNELLING NEAR TO PILE FOUNDATION

Columns

BuildingNegative skin friction (NSF)

Downdrag

Pile cap

Tunnelling in progress

Soil movementNSF

Resisting force

Lateral

Pilesdeflection

Transverse Settlement Trough due to Tunnel BoringLocation:Settlement Array, CS-9A (SS-9-1A-T )

Underground South Structures : Petchaburi Station to Rama IX Station

10

-5

0

5 9-1- 9-1- 9-1- 9-1- 9-1- 9-1-F 9-1- 9-1- 9-1-I 9-1-J 9-1- 9-1-L 9-1- 9-1- 9-1- 9-1- 9-1- 9-1- 9-1- 9-1-T

-25

-20

-15

-10

t, m

m

Instrumentation or Reading Error

-40

-35

-30

Sett

lem

ent

PeckNB i factor 9 22 m

-55

-50

-45

NB SB

1st 2ndNB i-factor = 9.22 mSB i-factor = 9.62 mVs = 2%

-600 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105

Distance, m

-8m(NB) 0m(NB) +8m(NB) +38m(NB)79 (NB)/0 (SB) 90 (NB)/ 30 (SB) 122 (NB)/ 67 (SB) 172 (NB)/ 125 (SB)

Figure 5.18: Transverse Settlement Trough due to Tunnel Boring (Parallel Running)

+79m(NB)/0m(SB) +90m(NB)/+30m(SB) +122m(NB)/+67m(SB) +172m(NB)/+125m(SB)+688m(NB)/+430m(SB) +715m(NB/SB) Peck's

Vertical Movement Contour for Twin Tunnels (Case 3)

Loganathan and Poulos (1998)’s method

E=5,000 kNlm^2 E=5,000 kNlm^2

E=4,300 kNlm^2 E=4,300 kNlm^2

E=68,170 kNlm^2 E=400,000 kNlm^2

Plastic PointPlastic Point

Yield Point

RESPONSE OF PILE FOUNDATION TO TUNNELLINGTO TUNNELLING

• Pile lateral deflection and bending moment– Transversely (Perpendicular to tunnel advancing

direction)– Longitudinally (Parallel to tunnel advancing direction)

• Tensile force in pile– Possible near pile head depending on the type of restraint

• Dragload (additional axial force) in pile– Above tunnel springline or invert level

• Pile settlement– Due to downdrag

• The type of response depends on the tunnel-pile relative position

Bangkok Tunnelling Experiences

RISK IN TUNNEL CONSTRUCTIONRISK IN TUNNEL CONSTRUCTION

Causes of Soft Ground Tunnel CollapsesCauses of Soft Ground Tunnel CollapsesCauses of Soft Ground Tunnel CollapsesCauses of Soft Ground Tunnel Collapses

RISK IN TUNNEL CONSTRUCTIONRISK IN TUNNEL CONSTRUCTION

• Considerably High• Inherent Uncertainty in Geological • Inherent Uncertainty in Geological

Condition (Variability in Ground Type & Groundwater)& Groundwater)

• Potential of Large-scale accidentsD t Thi d P t (U b • Damages to Third Party (Urban tunnelling)

Th k YThank You