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BASICS OF UNDERGROUND CONSTRUCTION

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IIT-Madras Sep 2015

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Underground Space & ConstructionUnderground Excavations

Deep open excavations

Totally Underground (Tunnels, Caverns)

Access thro’ vertical or inclined shafts

• Geotechnical & Geological conditions pose many challenges for construction.

Metros -Underground

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Metro--Underground

Underground Spaces• Purposes:

– For Buildings - Basements– For Metros- running stretches, stations– For Hydro-electric power projects, Underground

Power Houses– For Services- pipelines, water-conductors, sewage

pipelines,…– For Storage – petroleum strategic storage,

defense-related,….

Underground Spaces - Parameters• Type:

– Trenches: exposed to outside – Tunnels/ caverns: completely underground

(shallow, deep)– Shafts: access (vertical shaft, inclined ramp)

Shaft

Ground Level

Terminology

Different Types of Underground Works• Excavation / Trench – for transition from Ground

level to underground tunnel • Tunnel – Completely below ground- shallow

depths or deeper, below ground/ river/ sea, below other tunnels

• Cavern – Larger tunnel usually with greater heights & shorter lengths; generally rectangular plan shape with vaulted ceiling; for stations/ maintenance facilities/ power houses

• Shaft- For access to underground tunnels/ caverns or for ventilation/ lighting rarely/ emergency escape; generally circular in cross section; vertical or inclined

Geological/ geotechnical Investigations

Geological Log of Tunnel Alignment

TRENCHES

Trench Excavation

Ground Support Methodologies

Cut & Cover – Stabilising the sides

• Soil Nails• Wire mesh• Steel beams/ Lattice girders & Lagging• Guniting/ shotcreting• Rock bolting• Rock anchors/ Soil anchors• Grouting• Sides Covering- shoring (& strutting), sheetpiling,

diaphragm walling, secant piling,….

Cut & Cover- Open Cut Method

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Nailing works carried for Soil Stabilization

Struts

ExcavationD.Wall

Earth pressure

Struts

Ground Level

Rock/ SoilAnchor

GroutedAnchorage

Cut-and-Cover Excvation- Strutted

Construction inside excavation

Shaft in progress

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Underground Metro Project

Various soil / rock supporting

arrangements

Muck removal from Shaft

Cut & Cover excavation - Instrumentation

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Well Point Dewatering System

GCT- Technical Symposium “GEOFEST

’05” - Inaugural dd h

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Visual Modflow -3D Numerical Ground water Modeling

To estimate the numberof deep wells required

To determine the drawdown.

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Reinforced Earth Walls – Simple stem walls– Counterfort walls– Reinforced Earth walls

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Sheetpiling

Sheet piles

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Contiguous/ Secant/ Tangent Piles

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Diaphragm Walls

Diaphragm Walls

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Diaphragm Walling

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Trench Cutter for Diaphragm Wall

Other Methods- Freezing, Grouting

Tunnels

TunnelsThree basic types of tunnel construction in

common use:• Cut and cover tunnels, constructed in a

shallow trench and then covered over.• Bored tunnels, constructed in situ, without

removing the ground above. They are usually of circular or horseshoe cross-section.

• Immersed tube tunnels, sunk into a body of water and sit on, or are buried just under, its bed.

Tunnels - Methodologies

• Drilling & Blasting• Mechanical Methods – Cutters, Road

Headers,…………..• Pipe jacking/ pushing• Tunnel Boring Machines

Tunnel• Completely underground structure• In soil or in rock (hard or soft)• May require to be lined – for preventing side

collapse or water ingress, aesthetics, easy maintenance, etc

• Shapes: usually circular for better design, rectangular also; single tube with side-by-side tracks or one-over-the-other tracks, or multiple tubes; horse-shoe for better strucurals

Tunnels - Advantages• The boring work would not affect the

underground utilities like sewerage, electric cables, telephone cables and water lines since construction of tunnels will run well below surface level, much below the cables and pipes.

• Also, surface structures will not be affected

Tunnel Shapes

CircularD-Shape Horse shoe

Modified Horse-shoe Egg shape

Typ. Highway Tunnel

Half Tunnel

Tunnel with Metro tracks one over another

Drilling – Common Equipment• Jack Hammers; Pusher legs• Drill Jumbos mounted on trucks• Boomers

– Single Boom Assembly;– Twin Boom Assembly;– Multi - Boom Assembly.

• Wagon Drills.

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BOOMERS

Scaling

Tunnel supporting Steel Ribs

Shotcrete - Robot application

Basic Principle of Rock Bolting

Regular testing necessary- Proof Testing& Routine Testing

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BOLTEC MACHINE FOR PLACING ANCHOR BOLTS

Finishing - Tunnel Lining

Ventilation for Tunnels

In-place Tunnels

Box pushing

TBM (Tunnel Boring Machine)

Need for TBM

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TBM- Getting inside Tunnel

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Open type/ Double-shielded TBM

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Cutter Head of a TBM

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TBM being assembled

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Inside the TBM

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Break-out/ day-lighting!

Lined Tunnel

Caverns

Storage Cavern

Isometric View of New Shape

Access Ramp (AR)

Upper Connection (UC)

Intermediate connection (IC)

Upper Shaft Connection (USC)

Access Shaft (AS)

Operation Shaft (OS)

Lower Shaft Connection (LSC)

Water Gallery – Operation Shaft Connection (WOC)

Water Gallery – Access Shaft Connection (WAC)

Water Curtain Gallery (WCG

Sump which houses the submersible pumps

Lower connection (LC)

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Cavern: 2 limbs 200m x 20m x 19m200 m below GL

AS: 6.5 m dia, OS: 4 m dia

4m x 4m, 232 m long

Work inside the Access shaft

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View of the Operation Shaft. The Shaft is

almost 150 meters deep.

The LHD in the Access shaft, at Upper shaft

connection invert level (-170 m)

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Oresund Tunnel

55,000tElementbeing towed!

SAFETY --Personal Protective Equipment, Accessories

Fluorescent Clothing

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Thank you