Introduction to Soft Ground Introduction to Soft Ground Introduction to Soft Ground Introduction to Soft Ground Tunnelling in Urban Tunnelling in Urban Environment Environment Dr. Noppadol Phienwej Dr. Noppadol Phienwej Geotechnical and Geo Geotechnical and Geo- -environmental Engineering environmental Engineering School of Engineering and Technology School of Engineering and Technology Asian Institute of Technology Asian Institute of Technology
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Introduction to Soft Ground Introduction to Soft Ground Introduction to Soft Ground Introduction to Soft Ground Tunnelling in Urban Tunnelling in Urban
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
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
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