Tunnel Construction Technology

for Soft Ground

Prof. Mitsutaka Sugimoto

Nagaoka University of Technology

Japan

EJEC/AIT seminar, 14, June, 2016

2

CONTENTS

I. Introduction of tunnelling method

II. Shield tunnelling method

III. Tunnelling in Bangkok

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I. Introduction of tunnelling method

1. TUNNELLING METHODS

2. HISTORY OF TECHNOLOGY

4

1. TUNNELLING METHODS

(1) Mountain tunnelling method (NATM)

Drilling Mucking Shotcrete Rock bolts Concrete lining

5

(2) Shield tunnelling method

6

(3) Cut & cover method

7

(4) Immersed tunnelling method

Survey target

GravelGasket

8

9

SummaryTunnelling m ethod

C ondition

N A TM Shield T . C ut & cover

T .

Im m ersed T .

D esign stage

C lassification:

-soil

-soft rock

-hard rock

△

◯

◯

◯

△

×

◯

△

×

◯

△

×

G round w ater:

-under ground w ater

-over ground w ater

△

◯

◯

◯

△

◯

◯

－

G round

condition

Self-stability of face:

-unexpected

-expected

×

◯

◯

◯

◯

◯

－

－

Structure Location:

-near ground surface

-shallow

-deep

×

△

◯

△

◯

◯

◯

△

×

◯

×

×

C onstruction stage

Excavation:

-general

-other

blast

rotary cutter

(TBM )

excavator

rotary cutter

excavator

m anual

excavator

dredging

rotary cutter

C onstruction

m ethod

Support shotcrete

rock bolt

segm ent

EC L

box culvert steel box

concrete box

Environm ent Influence to traffic

N oise/v ibration

◯

×

◯

◯

△

△

×

△

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II. Shield tunnelling method

1. Technology

2. Advanced technology

3. Recent topics

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1. TECHNOLOGY

TBM

Segment

Interaction between tunnel & ground

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1.1 TBM

Classification

EP

BS

Partially open shield

Shield typeOpen shield TBM

Dual mode

Slu

rry sh

ield

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Closed shield vs. Open shield

Item C losed shield O pen shield

A pplicable ground

condition

C an cope w ith a w ide range of

ground conditions, i.e., from soft

clay, loose sand, gravel to soft

rock.

In principle, the face m ust be

stable.

Face stability R elatively easy, since the shield

system have the function to

stabilize the face.

R elatively difficult.

E fficiency of

construction

A dvances in m echanization have

resulted in increasing efficiency

and labor saving. Excavation

rate is faster.

It is difficult to increase

efficiency or save labor, since it

depends on labor. Excavation

rate is slow er.

G round stabilization

w orks

In principle, no auxiliary w orks

are required for tunnelling.

A ground stabilization w ork is

essential to secure the face

stability.

C onstruction cost The unit cost per volum e is about the sam e, depending on the ground

condition, som etim es cheaper w ith closed shield .

T roubles in construction Few er troubles M any troubles

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Slurry shield vs. EPBS

Item Slurry shield Earth pressure balanced shield

A pplicable ground

condition

M ainly sandy soils. A lso can

cope w ith clay and sand-gravel

layers. Particularly excellent

against high ground w ater

pressures.

M ainly clayey soils. U sing m ud

pressure shield, can cope w ith

sandy soils and sand- gravel.

Particularly excellent for handling

larger gravel size. M any

construction records.

A pplicable diam eter U sed for m edium -and sm all

diam eter tunnels and som e large-

diam eter tunnels.

M any construction records for

m edium - and sm all-diam eter

tunnels.

S ize of facilities S lurry treatm ent plant is

necessary, then larger space is

required.

R elatively sm all.

C utter torque Sm all Larger

C utter driving m ode E lectric pow er increasingly H ydraulic pow er in m any cases

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Flow of shield selection

1 . design condition (1) shapes

(2) dim ension

(3) length

(4) tunnel depth

(5) curve radius

(6) gradient

(7) lining m ethod

2 . ground condition (1) com position and variation of ground

(2) soil condition

(3) ground w ater level

(4) pore w ater pressure

(1) face stability

(2) perm eability

(3) ventage ratio (air perm eability)

Supplem ental m ethod is necessary or not

3 . environm ental condition (1) river, sea lake

(2) underground structure

(3) structure at ground surface

(4) neighboring structure

(5) road, traffic

(6) condition of the w ork area

(7) pow er supply

4 . construction capability (1) construction schedule

(2) safety

(3) w orking condition

(4) transportation condition

5 . econom ics (cost saving)

6 . selection of shield type

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1.2 Lining

Segment

RC segment Plate type Steel segment

RC segment Box type Ductile segment

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Joint

M aterial Section configuration Joint type

Reinforced concrete Plate type Straight bolt joint type

Steel Curved bolt joint type

D uctile cast iron Box type Pin joint type

Com posite H inge type

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Classification of structure model

(1) Lining model1) Bender beam without the reduction of EI.2) Bender beam with the reduction of EI.3) Multi-hinge without rotation spring and shear spring.4) Multi-hinge with rotation spring at hinge.5) Multi-hinge with rotation spring at hinge and shear spring

between neighbor ring.

Design model

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(2) Ground model

1) Continuous medium 2) Spring 4) Nothing

3) No-tension spring

(Winckler's ground model)

Classification of load model

(3) Resistance earth pressure

1) calculated by displacement. 2) given.

(4) Earth pressure

1) sV 2) sH + sV

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Classification of boundary

(5) Boundary condition between ground and lining

1) Slide in tangential direction

a. is allowed b. is not allowed

2) Initial displacement of ground

a. is considered.

b. is not considered.

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Design loads (1)C ategory D esign load C om m ent

Earth pressure 1 . V ertical earth pressure at crow n , sVU

1) Soft clay or

stiff clay w ith H /D <1 or

sand w ith H /D <1

sVU = (effective) overburden load

2) S tiff clay w ith H /D >3 or

sand w ith H /D >3

sVU = Terzaghi's loosening (effective) earth pressure

2 . H orizontal earth pressure , sH

sH = sV

sV = sVU + h

:lateral earth pressure ratio

:(subm erged) density of ground

h :depth from crow n

H :overburden depth

D :d iam eter of tunnel

H ydraulic pressure 1 . Sandy ground

C onsider effective earth pressure and hydraulic pressure

separately.

2 . C layey ground

C onsider total earth pressure, w hich m eans the use of density (not

subm erged density) in the calculation of earth pressure.

R esistance earth pressure 1 . V ertical resistance earth pressure

A ssum e vertical resistance earth pressure at the bottom of tunnel

so as that vertical force has balanced.

2 . H orizontal resistance earth pressure

This pressure is generated due to the deform ation of lin ing.

O verburden load This load is generated due to the structures on the ground surface.

M ain load

Self-w eight The w eight of lin ing

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Design loads (2)C ategory D esign load C om m ent

Inner-w eight The w eight of facilities in tunnel.

Tem porary load under

construction

This load is caused due to follow ing item s;

1)Jack thrust

2)G routing pressure

3)Earth pressure at c rown just behind tail

4)H andling

Secondary

load

D ynam ic load in earthquake This load is considered in the follow ing conditions;

1)The boundary of layers crosses the tunnel.

2)Tunnel connects w ith the vertical shaft.

3)O verburden depth changes rapidly.

4)Soft ground

5)Liquefaction

A dditional load due to tw in

tunnel

G eom etric shape of tw in tunnel causes this load. Special load

A dditional load

due to ground settlem ent

1)A dditional vertical earth pressure is loaded on tunnel due to

ground settlem ent.

2)D ifferential settlem ent in longitudinal direction causes the

bending m om ent in the lining.

Stiff sand Soft clay

Tunnel

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Design load & models

Pe :vertical earth pressure : lateral earth pressure ratiog : self weight of segment per unit length

resistance earth pressurepg : due to self weight of segmentqH : in horizontal directionqV : vertical directionqr : radial direction

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Moment and axial force on each analysis model

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Flow of of segment designSTA RT

(1) decide segm ent type, design load

(2) decide the segm ent dim ension (thickness, reinforced steel)

(3) decide the physical properties ( ,. spring constant etc.)

(4) calculate sectional force

(5) calculate stress

(6) stress < allow able stress ?

(7) design the detail of segm ent

(8) check ?

EN D

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1.3 Ground movement

Concepts

Ground surface settlement in longitudinal direction

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Ground surface settlement in transverse direction

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Three dimensional displacement around face

(a) Clay (b) Sand

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Measurements examples

1979 Mexico 1985 Mexico

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Analysis method

(1) Empirical method: error function form

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(2) Conventional 2D FEM analysis

E

α

a: Stress release ratio

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(a) t=t0

Jack thrust

Ground

Shield

Exca. E

(b) t=t0+dt

Ground

Shield

Exca. E

(c) t=t0+dt

Ground

Shield

Exca. E

Excavation elements & remesh of ground (Akagi & Komiya)

(3) 3DFEM analysis: Akagi – Komiya model

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Vertical Disp. at 1.0m above crown (Akagi & Komiya)

0.03514 day

0.21924 day

0.40494 day

0.52266 day

1.12640 day

1.64357 day

Measurement point

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2. ADVANCED TECHNOLOGY

Technology for

safety,

high quality,

economy,

high speed.

2.1 TBMSharp curve

Articulated shield

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Variation of cross section

Rectangular cross section

Swing drum type Fixed drum type

Box type DPLEX

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Double circular cross section

Multi face shield

DOT shield

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3 circular cross section

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H & V shield

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Wing shield

Excavation mechanism

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DPLEX shield

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Docking / Branching

Mechanical docking

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Branching

57

2.2 Segment

Saving work

Pin coupler + Mortise & tenon joint Wedge joint

Pin coupler + Bolt joint

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3. RECENT TOPICS

3.1 TBMLong distance

Wear resistance (cutter bit, seal)

High speed

Continuous excavation

Prediction & control: theoretical model

Kinematic shield model

Docking / Branching

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3.2 Segment

Construction loads

Thinner, wider segment

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Corrosion

Maintenance

Waterproof sheet

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Renewal

Ex. Renewal of cut & cover tunnel

Advance direction

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Ex. Renewal of shield tunnel

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3.3 Ground movement

Neighboring construction

Analysis method

Deep tunnel

Design method (Design loads)

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III. Tunnelling in Bangkok

1. HISTORY OF SHIELD TUNNELLING IN

BKK

2. PROBLEM STATEMENTS

3. COUNTERMEASURES

(The Shoho Magazine, 1996.4, JCC, BKK)

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1. HISTORY OF SHIELD TUNNELLING IN BKK

Year Use Length

(km)

Dia.

(m)

Soil Depth

(m)

TBM

1970 Flood

discharge

1.8 3.3 Soft Clay 5~8 Blind

1975~1979 Water

supply

24.5 2.0~3.4 Stiff clay,

Under river

17~20 Open (Mechanical)

-> Slurry

1981~1983 Water

supply

7.1 2.0~2.5 Stiff clay 17~20 Open

(Semi mechanical)

1986~1988 Water

supply

34.0 2.0~3.2 Soft clay 0~9 C&C, Pipe jacking

1990~1991 Water

supply

2.2 2.0 Stiff clay 18 Open

(Semi mechanical)

1994~ Sewage 9.0 2.5~3.2 Soft/Stiff

clay

10~18 EPBS

1995~ Water

supply

10.5 2.0 Stiff clay 16~18 EPBS

Noppadol Phienwej, “Tunnel lining and cut-and-cover excavation in Bangkok soils”,

Seminar on urban and traffic engineering and geotechnical engineering on delta areas, 1996. 3.

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Master plan of

mass rapid transit

in BKK

“Master plan Bangkok mass rapid transit”,

Executive summary report, 1994.7.

(in Thai language) Area to construct MRT by subway.Area to construct MRT by subway expectedly.

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2. PROBLEM STATEMENTS

(1) Soft soil, ground water

Geological profile (W – E)

ESCAP, “Geological information for planning in Bangkok, Thailand”,

Geology and urban development-Atlas of urban geology, ESCAP,

Vol. 1, 24-60, 1988.

Softclay

Stiffclay Sand

SandyclayLaterite

(2) Ground subsidence

Ground subsidence

Around 1996, the subsidence

speed is around 1 ~ 3

cm/year1).

TP contour (m)

Subsidence V.(cm/y)

ESCAP, “Geological information for

planning in Bangkok , Thailand”,

Geology and urban development-Atlas of

urban geology, ESCAP, Vol. 1, 24-60,

1988.

1) Yordphol Tanaboriboon, “Demand

management and traffic crisis in Bangkok”,

Seminar on urban and traffic engineering

and geotechnical engineering on delta areas,

1996. 3.

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(3) Flood

Depth of water in BKK

at 1983 flood

(by JICA, 1984)

(cm)

ESCAP, “Geological information for

planning in Bangkok , Thailand”,

Geology and urban development-Atlas

of urban geology, ESCAP, Vol. 1, 24-60,

1988.

Max depth of water = 1.1m

In 1995 flood, damage to

BKK is less than that of

1983 flood.

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3. COUNTERMEASURES (Tunnel)Problems Counter measures

Soft ground, ground water

Construction Surface settlement

Face stability

TBM control

Select layers

Adopt a closed type shield

Ex. Protection wall

Operation Leakage Ensure watertight

Set discharging pumps

Ground subsidence

Operation Unequal subsidence Restrict pumping up groundwater

Select layers

Set the flexible connection between station

& tunnel at design

Adjust rail alignment

Flood

Construction

Operation

Flooding Consider the influence of flood on station

& shaft at design

Set discharging pumps

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3. COUNTERMEASURES

(Environment)

Problems Counter measures

Traffic disturbance

Construction Station

Vertical shaft

Adopt a trenchless method

Use a open space around road

Influence on neighboring structures

Construction Structure Adopt a countermeasures

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Thank you for your kind attention !!

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3. CONSTRUCTION RECORDS IN JAPAN

History

Railway

Len

gth

(k

m)

Road

Year

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1. SELECTION OF

TUNNELLING METHODSItem NATM Shield Cut &

coverSoil type

SoilSoft rockHard rock

Ground water levelunderover

Ground

conditon

Face stabilizationunexpectedexpected

Location Depthnear ground surfaceshallowdeep

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Vertical Disp. (Akagi & Komiya)

2

-8

-6

-4

-2

0

0 0.5 1 1.5 2

Time (day)

Ver

tica

l dis

p. (m

m)

1m above crown

Measured

Calculated