Effects of tunnel construction on nearby pile foundations c

- Tham & Deutscher 2000 Empirical method for calculating greenfield soil movement was translated into pile settlement and pile stresses according to some assumptions made through observa

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Table 2.1 Summary of reported case histories

Reference Development /

Project

Soil Type

Tunnel Type Pile Type In-pile

monitoring

Xpile /

Dtun

Lp /

Htun

Xpile

(m)

Htun

(m)

Dtun

(m)

Dpile

(m)

Lp

(m)

VL

(%) Jacobsz et al

(2005) CTRL 2, London LC EPB shield tunnel

Driven pile &

bored pile No N/A < 1.0

Above tunnel Varied 8.15 Varied Varied

0.28 to 1.0 Takahashi et al

(2004) Rinkai Line, Tokyo

Very dense sand

Slurry shield

Above tunnel 33.2 7.1 0.6 17 0.5 Selemetas et al

(2002)

New London Bridge House, London LC

Sprayed concrete lining tunnel

Bored pile (under-reamed) No 1.23 0.91 10.7 22 8.7 1.4 20 N/A Coutts & Wang

(2000)

MRT North-East Line C704, Singapore

Weathered Granite EPB shield tunnel Bored pile Yes 0.85 > 1.0 5.3

16 to

20 6.2 1.2 N/A N/A Tham &

Deutscher

(2000)

MRT North-East Line C705, Singapore

Old Alluvium EPB shield tunnel Bored RC pile No 0.83 1.07 5.2 14 6.3 0.45 15 0.4

Powderham et

al (1999)

Jubilee Line Extension, London LC

Sprayed concrete lining tunnel Bored pile No N/A 0.67

Above tunnel 30 8.7 N/A 20 N/A Forth & Thorley

(1996)

MTR Island Line, Hong Kong

Weathered Granite

Compressed air shield tunnel Bored pile No 1.01

1.58

to 2.46

8.0 26 7.9 2.0 41 to

64

1.0 to 1.4 Ikeda et al

(1996)

Underground Railway, Japan Soft clay EPB shield tunnel Timber pile No N/A 0.33

Above tunnel 15 7.35 0.25 5 N/A Moroto et al

(1995)

Electric power tunnel, Japan

Very soft silty clay EPB shield tunnel N/A No > 2.18 2.23 > 8.5 18.8 3.9 N/A 42 N/A Mair (1993),

Lee et al (1994)

Angel Underground

Bored pile (under-reamed) Yes 0.69 > 1.0 5.75 Varied 8.25 1.2 28 2.0 Nakajima et al

(1992)

Nanboku Line, Tokyo

Alluvial and Diluvial

Slurry shield tunnel Bored pile No

0.74 &

0.66 N/A

4.9 &

6.5 N/A

6.6 &

9.8 1.2 Varied N/A Inose et al

(1992)

Nanboku Line, Tokyo

Soft silt &

sandy gravel

Slurry shield tunnel Bored pile No N/A N/A

Above tunnel N/A 10 N/A N/A N/A

N/A = Not reported, LC = London Clay

Trang 2

Reference Soil Type In-pile

measurement Xpile / Dtun Lp / Htun

xpile (m)

Htun

(m)

Dtun

(m)

Dpile

(m)

Lp (m)

VL (%)

* Within zone of influence

Pre-loading

Pile group

Lee & Chiang

(2004)

Dense saturated sand

Pile head settlement, pile axial force & pile bending moment

0.83

3.0, 1.8, 1.3 &

1.0

4.98

9, 15,

21 &

27

6.0 0.96 27.0 Up to 3 No Yes No

Ran et al

(2003) Soft clay

Pile axial force &

bending moment 1.00 1.6 6.00 15 6.0 1.26 23.5 28.2 No No No Feng et al

(2002)

Dense dry sand

Pile axial force &

bending moment 1.50 1.6 9.00 16 6.0 1.26 25.0 N/A No No No Jacobsz et al

(2002)

Dense dry sand

Pile head settlement &

axial force

1.43, 2.27, 3.10, 3.93

& 4.77

0.7 &

0.9

6.45, 10.20, 13.95, 17.70

& 21.45

21.45 4.5 0.9 15.0 &

18.75 Up to 20 Yes & No Yes No

Loganathan

(1999)

Stiff clay Test 1 Test 2 Test 3

Pile head settlement, pile axial force & pile bending moment

0.92 1.2, 1.0

& 0.9 5.50

15

18

21

6.0 0.8 18.0 Up to 10

No

No Yes

Yes 2 x 2

Bezuijen &

Schrier

(1994), and

Hergarden et

al (1996)

Clay overlying dense sand Test 1 Test 2 Test 3

Settlement and axial force at pile head

0.70, 0.93, 1.39 & 1.84 1.0

0.8 1.2

4.90, 6.50, 9.70 &

12.90

18.0 23.0 14.5

7.0 0.4 18.0 Up to 10 Yes

& No Yes No

* Zone of influence – defined as the zone within 45o from tunnel springline Table 2.2 Summary of reported centrifuge tests (in prototype unit)

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Method Descriptions Soil model Advantages / disadvantages Pertinent findings Reference

Risk of damage to a piled building was assessed

using method by Mair et al (1996) The method

categorises the damage according to the tensile

strain computed at the building

-

1) Pile response cannot be computed and unknown Only overall building damage can be assessed

2) The method was derived for building supported on shallow foundation

-

Tham &

Deutscher (2000)

Empirical method for calculating greenfield soil

movement was translated into pile settlement and

pile stresses according to some assumptions

made through observations in centrifuge tests

and field study

-

1) Simple & less time consuming

2) Can be used for pile with its base within zone of influence

3) Only pile axial response particularly settlement can be assessed

At small volume loss, end bearing pile settles equally to greenfield settlement at pile base Friction pile settles equally to Greenfield surface settlement

Jacobsz et

al (2005)

1) Bearing capacity was checked via the

comparison of pile base moment with resistance

moment due to face pressure from shield

machine

2) Bearing capacity was checked via the

comparison of reaction force at pile base with

grouting or face pressure in tail void

-

1) Simple hand calculation

2) Only pile bearing capacity can

be assessed

3) Can be used for pile with its base above tunnel

-

Nakajima

et al

(1992) Empirical

Bearing capacity of pile during the shield

advancement was investigated through

assumption of an imaginative cone around pile

base and compared to the face pressure from

shield machine

-

1) Simple hand calculation to determine the need for mitigation work at pile base

2) Can be used for pile with its base above tunnel

- Inose et al

(1992)

Table 2.3 Summary of reported prediction and design methods

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Table 2.3 Summary of reported prediction and design methods (continue)

FE analysis was used to compute pile

settlement A row of piles was modelled as a

sheet pile wall with reduced properties

Mohr-Coulomb (Drained)

1) Less time consuming

2) Accuracy of pile properties reduction method adopted is unknown

Pile settlement followed the settlement of bearing layer where the pile base was founded

Vermeer &

Bonnier (1991) 2-D finite

element FE analysis was used to predict the piles

lateral deflections at Angel Underground

Development Piles were not modelled and

assumed to deform with soil

Linear elastic (Undrained)

2) Pile stiffness was not considered

3) Soil model used is too simple

Pile lateral deflection was well predicted and provided an upper bound value compared to measured data

Lee et al

(1994)

A 3-D model to simulate shield tunnel

advancement on adjacent single pile and 2x2

pile group Pile-soil-tunnel interaction was

taken into account No physical data was

back-analysed to verify the model’s reliability

Mohr Coulomb (Drained)

1) More time consuming compared to 2-D analysis

2) Unified approach towards the study of pile axial and bending responses

Significant axial force and lateral deflection were induced in pile particularly when the pile base was below tunnel invert Positive pile group effect was observed

Mroueh &

Shahrour (2002)

A 3-D model to simulate open face tunnel

advancement on adjacent single pile

Centrifuge test results from Loganathan

(1999) was compared

Drucker-Prager (Consolidation)

1) More time consuming

2) Unified approach

3) The simulation not represent any type of tunnelling system

FOS in pile was reduced significantly from 3.0 to 1.5 Axial force and BM were not significant Transverse BM was three times longitudinal BM

Lee & Ng (2005)

3-D finite

element

A 3-D model to simulate plane strain tunnel

adjacent to single pile Parametric studies were

carried out The data from MRT NEL C704

was also briefly back-analysed

Non-linear elastic (Undrained)

1) Tunnel advancement was not simulated

2) Unified approach

BM in pile is negligible when

Xpile/Dtun>2 Cracking moment exceeded when Xpile/Dtun<1 Axial force depends

on VL, soil stiffness & pile base position

Cheng et

al (2004)

Trang 5

A two-stage approach where greenfield soil

movement computed from 2-D FE was

imposed on pile in soil-spring model Design

charts were prepared

Linear elastic 1) Less time consuming

2) No pile-soil-tunnel interaction

Max BM was found near pile cap level and relatively low BM near tunnel springline

Broms &

Pandey (1987)

A two-stage approach where the greenfield

soil movements computed from analytical

solution were imposed on pile in boundary

element analyses

Linear elastic

3) Pile lateral and axial responses were computed separately

The pile responses were influenced significantly by tunnel-pile geometry, volume loss, soil stiffness and strength

Long and short piles responded differently

Chen et al

(1999)

soil movements computed from 3-D FE were

imposed on pile in boundary element analyses

Linear elastic

1) Less time consuming Only one 3-D FE analysis required

The approach used is exactly the same

as Chen et al (1999) except 3-D FE was used to compute greenfield soil movement instead of analytical method

Surjadinata et

al (2005)

soil movement computed from analytical

solution was imposed on pile in soil-spring

model The approach used is similar to Broms

& Pandey (1987)

Non linear hyperbolic

1) Only pile bending moment can

be computed

2) More rigorous hyperbolic non linear soil model

3) Allow only single pile analysis

If Lp < Htun-R, BM in single curvature

If Htun-R < Lp < Htun+R, BM in double curvature

If Lp > Htun+R, BM in triple curvature

[R = pile radius]

Sawatparnich

& Kulhawy (2004)

Numerical

and

analytical

A program called PRAB developed to analyse

single pile, pile group and pile raft due to

tunnelling The approach used is similar to

Loganathan et al (2001)

Linear elastic

2) No pile-soil-tunnel interaction 3) Unified approach

Single pile analysis can be used to represent piles in a group for BM, lateral deflection and settlement only

Hence, no pile group effect

Kitiyodom et

al (2004), Matsumoto et

al (2005) Design

charts

Design charts were developed from parametric

studies carried out using the two-stage

approach as described in Chen et al (1999)

Linear elastic

1) Only hand calculation required

2) Allow only single pile analysis

2) Limited to some assumptions

Tunnelling induced BM, lateral deflection, settlement and axial forces can be computed

Chen et al

(1999), Chen

et al (2000)

Table 2.3 Summary of reported prediction and design methods (continue)

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Table 3.1 Weathering classification for Granite in Singapore (Dames and Moore, 1983)

Grade Equivalent BS

weathering grade

General description

G1 I and II Fresh to slightly weathered Granite

G2 III and IV Moderately to highly weathered Granite

G3 - Bouldery soil : Boulders of Granite of variable weathering

within completely weathered rock or residual soil G4 V and VI Completely weathered Granite or residual soil

Table 3.2 Details of instrumented pile foundation for bridge viaducts

Pier

no

No

of

pile

Pile diameter , Dpile

(m)

Pile length,

Lp

(m.b.g.l.)

Tunnel depth,

H tun

(m.b.g.l.)

Pile length to tunnel depth ratio, Lp/Htun

XSB

(m)

XNB

(m)

XSB

/Dtun

XNB

/Dtun

XSB = Distance between South bound tunnel axis and the nearest pile centre

XNB = Distance between North bound tunnel axis and the nearest pile centre

Trang 7

Table 3.3 Construction stages of viaduct bridge and tunnels advancement

Year / Month

Pier 11

Piling work

Pile cap construction

Plinth casting

Entire stem pour

Flare head casting

Casting of diaphragm

Starting stub casting

Casting of box girder web and bottom slab - Span P10/P11

Casting of deck slab - Span P10/P11

Casting of inner console slab - P9-P11

SB tunnel at Pier 11

NB tunnel at Pier 11

VWSG reading taken

Pier 14

Piling work

Plinth casting

Entire stem pour

Flare head casting

Casting of diaphragm

VWSG reading taken

Pier 20

Piling work

Plinth casting

Entire stem pour

Flare head casting

Diaphragm casting

VWSG reading taken

Year / Month

Pier 32

Piling work

Plinth casting

Entire stem pour

VWSG reading taken

Pier 37

Piling work

Plinth casting

Entire stem pour

VWSG reading taken

Pier 38

Piling work

Plinth casting

Entire stem pour

NB tunnel at Pier 38

VWSG reading taken

LEGEND :

2000

Day 275 = no of days from 1 January 2000 compared to 1 April 1999 (Day 0 = 1 April 1999 = Start of tunnelling work)

Trang 8

Table 3.4 Volume loss for SB and NB tunnels advancement

Volume loss, VL (%) Pier no

11 0.76 1.23

14 1.45 1.43

20 1.38 1.67

32 0.35 0.32

37 0.34 0.71

38 1.17 0.88

Table 3.5 Maximum dragload measured in piles due to tunnel advancement

Due to southbound Tunnel

Due to southbound + northbound tunnels Pier (Pile)

kN % kN %

Note: % of the structural capacity

-ve : compressive force (dragload)

Trang 9

Table 3.6 Maximum transverse bending moment measured in piles due to tunnels

advancement

SB SB + NB Pier (Pile)

kNm kNm

11 (P6) 142 569

14 (P3) 464 267

14 (P4) 219 227

20 (P1) 401 395

20 (P2) 163 253

32 (P7) 167 142

37 (P9) 1040 1293

37 (P10) 577 841

38 (P11) 1008 1163

38 (P12) 392 798

Table 3.7 Maximum longitudinal bending moment measured in piles due to tunnels

advancement

SB SB + NB Pier (Pile)

kNm kNm

11 (P5) 158 408

20 (P1) 131 129

37 (P9) 536 710

37 (P10) 555 648

38 (P11) 991 1151

38 (P12) 304 915

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Table 3.8 Comparison of the assumptions made in the design charts with C704 problem

Details (Chen & et al., 1999) Design chart MRT NEL C704 problem

Pile head condition Free pile head Pilecap exists (Pier 20 & 38) /

No pilecap (Pier 14) Pile loading condition No load (Stress free) No load (Pier 14, 20, 38) or

partially loaded (i.e Pier 11)

Limiting end bearing

pressure, fb

540kPa Limiting lateral pile-soil

pressure

540kPa

21m (Pier 20) 23.3m (Pier 38) Construction time Undrained analysis Time dependent problem

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