Application Reference Number: WWO10001 Tunnel and Bridge ... · Form BA: Certificate of Assessment and Checking for „Brunel Thames Tunnel‟ – Detailed Tunnel Assessment Printed

Tunnel and Bridge AssessmentsEastern ZoneForm BA: Certificate of Assessment and Checking ‘Brunel Thames Tunnel’- Preliminary Impact AssessmentDoc Ref: 9.15.119

Folder 111 September 2013DCO-DT-000-ZZZZZ-091500

Form

BA

: Bru

nel T

ham

es T

unne

l

Thames Tideway Tunnel Thames Water Utilities Limited

Application for Development ConsentApplication Reference Number: WWO10001

Transport for London

Form BA : Certificate of Assessment and Checking

Title of Scheme: Thames Tunnel Project

Location: Brunel Thames Tunnel – Rotherhithe to Wapping

ELR: ELL Mileage: N/A OS grid ref.:

TQ 35498 80339

Structure No.: TL163 (Down) /TL164 (Up)

Form BA: Certificate of Assessment and Checking for „Brunel Thames Tunnel‟ – Detailed Tunnel Assessment

Printed 23/09/2011

Thames Tunnel

Form BA: Certificate of Assessment and Checking for ‘Brunel Thames Tunnel’

– Preliminary Impact Assessments

List of contents:

1 Part 1: Assessment Details ............................................................................. 4

2 Part 2: Acceptance by London Overground/ Network Rail Civil Asset Engineer ............................................................................................... 5

3 Appendices .........................................................................................................

4 Bibliography .......................................................................................................






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2 Part 2: Acceptance by London Overground/ Network Rail Civil Asset Engineer

I accept that so far as can reasonably be ascertained from the information submitted, the relevant procedures for Assessment and Check as specified in Network Rail Company Standard NR/SP/CIV/035: Assessment of Structures have been followed properly.

I have considered the Assessment Check statement given in accordance with NR/SP/CIV/035 Clause 9.4.3, and confirm that the method of checking specified was a suitable method to be used.

Signed: Title: Civil Asset Engineer

Name (Print): Mahesh Jethwa Date:

To be signed on behalf of London Overground by the Civil Asset Engineer.






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3 Appendices

Appendix A: Assessment Results






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Appendix A: Assessment Results

The appendix forms part of Form BA which has been produced to certify that the

assessments identified in the Form AA has been undertaken. This appendix presents

the assessment results set out in the method of assessment as described in Form

AA for the Brunel Thames Tunnel.

The following four assessments have been undertaken:

An assessment of the change in track geometry, including an assessment of

the absolute settlement of the tracks and an assessment of the track twist as

the new Thames Tideway: Thames Tunnel is constructed.

An assessment of the twist caused to the track slab and the induced shear

strains.

An assessment of the longitudinal strains in the tunnel caused by the

settlement of the tunnel

An assessment of the impact of the different ground movements on the

stability and stresses in the Brunel Thames Tunnel as the settlement „bow

wave‟ passes through the tunnel.

This document is meant to be a Preliminary Impact Assessment. It is recognised that

a CAT III check will be required at a later stage of the project, but a check is

considered inappropriate at this pre-planning stage when a number of aspects of the

proposed scheme could change. The check is most appropriate once a contractor

has been nominated and assessments have been updated to reflect the specific

proposed method of working.

Note:

The sub-surface ground movement predictions were based on the assumption of a

Ribbon Sink settlement trough (New & Bowers, 1994).

The volume loss (VL) parameter used in the prediction of ground movements at this

stage have been determined based on the context of this assessment. A moderately-

conservative value of 1.0% has been used in the assessments and reflects the

assumed closed-face construction technique. These values should be readily






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achievable provide good construction methods are put in place to ensure good

tunnelling practice (Moss & Bowers, 2005).

The 1% volume loss does not include an allowance for any particular stringent

control of movement caused by the tunnelling at this location. The value is also

expected to have conservatism because the Thames tideway: Thames Tunnel is

founded in Chalk at this location. For the purpose of this assessment, a volume loss

of 1.0% is proposed, which is considered to be moderately conservative as the

settlement caused by tunnelling in Chalk is likely to be less.

The trough width parameter (K) used in the assessment of ground movements has

been based on tunnel construction in cohesive soil (eg. Lambeth Group). Experience

in London reveals that „K‟ is seldom less than 0.40 (O'Reilly & New, 1982), and also

indicates that where VL values of less than 1.0% are achieved, a „K‟ value above 0.50

may be appropriate. The „K‟ value of 0.50 has been adopted for ground movement

predictions, and is a conservative assumption.

Following discussions with London Overground (London Overground, 2011), it is

agreed that the 1% volume loss parameter may be considered “moderately

conservative” provided that the specification and management of the TBM tunnelling

confirms to current best practice. However, London Overground will expect to review

both the TBM specification and tunnelling methodology and method statements.

The proposed assessment methodologies have not intended to be undertaken using

detailed soil structure interaction modelling and therefore parameters such as soil

stiffness have not be considered.

Table 1: Assumed modelling parameters

Modelling Parameters Value

Volume Loss (VL) % 1.0%

Trough width parameter (K) 0.50

Track geometry and track slab

The absolute settlement and change in track geometry were calculated based on the

Ribbon Sink trough assumptions with no stiffening effect of the existing structures

and no soil-structure interaction, as described in Section 1.9.1 in Form AA.






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The change in track geometry was calculated by assessing the difference in ground

movements for points 3m apart along the line of the tracks (track twist).

The limit criteria have been based on values set out in Network Rail Track Geometry

and Gauge Clearance (Network Rail, 2009). We understand that the criteria set out in

the Network Rail Standard assumes perfect track condition which is seldom the case,

and a Clearance and Track Survey will be required prior to the TBM entering the

zone of influence. If London Overgound has a recent survey for this section of the

line, we recommend that this is used. The condition of the track based on the survey

will then inform the track movement trigger levels and tolerance.

The effects of the ground movements causing a twist in the track slab was

considered without taking into account the beneficial effect of the stiffness of the

track slab. Higher rates of rotation are analogous to higher torsional stresses in the

slab. The stress was calculated using the rate of change of rotation and by assuming

the track slab is a simple rectangular beam.

Table 2: Results of Track Geometry and Shear Stress in Track Slab

Settlement Predictions Assessed

Value

Limit

Criteria

(Network Rail, 2009)

Action

Absolute settlement at invert level of Brunel Thames Tunnel

13.0mm 20mm No mandated action

Trough width (2 x 3Kz) 110.6m - -

Track Geometry

Maximum track twist (per 3m) 0.03 mm /3m 12mm /3m No mandated action

Track Slab

Maximum ground movement induced shear stress

0.03N/mm2 - -

The resultant shear stress in the track slab caused by the predicted ground

movements is small and is considered to be insignificant.






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Longitudinal strains

The longitudinal assessment of the effects on the Brunel Thames Tunnel due to the

transverse settlement trough caused by driving the Thames Tideway: Thames

Tunnel has been determined from the Greenfield settlement predictions. The bending

strains derived from the instantaneous radius of curvature, and the instantaneous

axial strains are calculated from the change in length, reduced by an axial tensile

reduction factor of 0.20 (Bracegirdle et al., 1996).

The limiting tensile strain category (Burland & Wroth, 1974) was taken as „Very

Slight‟ with a limiting tensile strain value of 750με, which is one category below the

normal limiting category of „Slight‟ to reflect the sensitivity of the listed status of the

Brunel Thames Tunnel

Table 3: Longitudinal Tensile Strains

Assessed Value Limit Criteria

(Burland & Wroth, 1974)

Longitudinal tensile strain 147με 750με

Damage Category “Negligible” “Very Slight”

As the assessment predicts a damage category within the acceptance limits, a more

detailed assessment of the predicted damage has not been pursued.

Transverse deformation

The transverse deformation of the Brunel Thames Tunnel has been assessed based

on a multi stage process to account for the distortion of the tunnel as the Thames

Tideway: Thames Tunnel is constructed beneath.

The impact of the ground movements on the Brunel Thames Tunnel have been

assessed by considering the difference in ground movements either side of the base

slab. If the differential ground movements are nominal (<5mm) and the existing

structure is shown to have significant residual capacity (37%) then no additional

assessments have been undertaken.






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Table 4: Existing condition check


Maximum compressive stress (Mean High Water Spring)

1.4N/mm2 1.92N/mm2

Maximum compressive stress (Mean Low Water Spring)

1.0N/mm2 1.92N/mm2

Table 5: Transverse Assessment Results


Differential settlement of base slab 3.3 mm 5 mm

Conclusion

The results indicate that the damage impact of the construction of the Thames

Tideway: Thames Tunnel on the Brunel Thames Tunnel is within the design criteria

adopted in these assessments.

No further work is recommended to mitigate the potential damage to the Brunel

Thames Tunnel in the section of interest.

Atkins recommends that the appointed contractor of Thames Tunnel should

undertake a pre-construction and alignment survey prior to the construction of the

Thames Tideway: Thames Tunnel.

The monitoring of the Brunel Thames Tunnel during the construction of the Thames

Tideway: Thames Tunnel is a requirement of London Overground and agreement will

be sought for the proposed instrumentation and monitoring plan (London

Overground, 2011). Details of the monitoring strategy will be provided at a later

stage. We believe that the monitoring strategy is most appropriate once a contractor

has been nominated and assessments have been updated to reflect the specific

proposed method of working.






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Appendix B: Extract from Calculations

Project: Thames Tunnel Job ref5100812

Part of structure: TU015 East London Calc sheet no rev4 AB

Calc ref Calc by Date Check by Date002 IN 07-07-2011 MY 07-07-2011

Ref Calculations Output

Greenfield Settlement, Radius of Curvature & Longitudinal StrainsReferences:1. Settlements above tunnel in the United Kingdom - their magnitude and prediction; O'Reilly MP, New BM; Tunneling '82; p.173-1812. " Tunneling in Soil" Ground Movements and their Effects on Structures., P.B.Atwell, R.K. Taylor, eds., Surrey University Press, Champman and Hall, New York, NY, 133-2153. London Overground ELL Thames Tunnel, Interface with Proposed Thames Tunnel, 100-DA-TPI-TU015-810000-AB

[4] Plan Angle between Existing Tunnel and Thames Tunnel β 70deg

Slope angle of Railway Line α 1.5deg

[3] External Diameter of Thames Tunnel Dext 8800mm

[4] Volume loss (%) VL 1.00%

[4] Trough width parameter K 0.5 Conservativelyassume track is atinvert level

[3] Invert Level of East London Line Tunnel (mATD) ILBT 82.265m

Axis Level of Thames Tunnel (mATD) ALTT 49.794m

[3] Invert Level of Thames Tunnel (mATD) ILTT ALTT 0.5 Dext ILTT 45.39 m

Depth to Thames Tunnel Invert(from Existing Tunnel Invert)

z ILBT ILTT 36.87 m

Volume loss Vs VL πDext

2

2

Vs 0.608 m2

8

Plan Section

Output:

S(x,y,z) : The settlement of each point

U(x,y,z) : The x direction-displacement of each point

V(x,y,z) : The y direction-displacement of each point

[1,2] s x y z( )Vs

Dext1 cnorm

x

K z

cnorm2y Dext

2 K z( )

cnorm2y Dext

2 K z( )

u x y z( )Vs K

Dext 2πexp

x( )2

2 K z( )2

cnorm2y Dext

2 K z( )

cnorm2y Dext

2 K z( )

v x y z( )Vs K

Dext 2πcnorm

x

K z

1

exp2y Dext( )

2

8 K z( )2

exp2y Dext( )

2

8 K z( )2

Maximum Radius of Curvature

Calculates maximum maximum radius of curvature (long term) by tracking 3 consecutive points

Setting out calculation points

ystart 6 K z yend ystart calculation length lcalc 10mm

intervalyend ystart

lcalc

interval 22122.60 i 0 interval Yi

ystart i lcalc

xstart

ystart

tan β( ) xstart 40.26 m xend

yend

tan β( ) xend 40.26 m

xinterval

xstart xend

interval X

ixstart i xinterval 500m The -500m considers long term settlement

when settlement trough has fully developed

zstart z ystart tan α( ) zstart 39.77 m zend z yend tan α( ) zend 33.97 m

zinterval

zstart zend

interval Z

izstart i zinterval

Si

s Xi

Yi

Zi

Ui

u Xi

Yi

Zi

Vi

v Xi

Yi

Zi

9

100 50 0 50 10010

0

10

20

Si

mm

Ui

mm

Vi

mm

Yi

m

Max settlement

max S( ) 13.04 mm

Bending Strains

Note:

lcalc is the distance between calculation points. Set this to very small to calculate instantaneous curvature.

H is the vertical offset between three consecutive calculation points.

From similar triangles, the rotation of the alignment over the three points is 2 γi

Assuming lcalc = lhor, the half angle of rotation γi can be calculated.The sensitivity of this assumption has

been checked and is considered negligible wrt H.

The radius of curvature Radi is then calculated from geometry.

Hi

Hi

Si

Si 1 S

i 1 2

1 i interval 1if

Hi

1 1020

m otherwise

Hi

Set non-zero

γi

asinH

i

lcalc

Radi

lcalc

sin 2 γi

Maxhogging A 109

km

A Radi

Radi

A Radi

0kmif

i 0 intervalfor

A

Maxhogging 55.58 km

Rad

0

01

2

3

4

5

6

7

8

9

12-5.00·106-5.32·106-5.31·106-5.30·106-5.28·106-5.27·106-5.26·106-5.25·106-5.23·10

...

km

Maxsagging A 109km

A Radi

Radi

A Radi

0kmif

i 0 intervalfor

A

Maxsagging 26.52 km

10

Bending strain

Assume bending about base of sewer

Diameter of existing tunnel DE 12ft 9in3

4in DE 3.905 m

εbending_hogging

DE

Maxhogging

7.025846 105

εbending_sagging

DE

Maxsagging

0.000147

εbendingi

DE

Radi

Axial Strains

Xfi

Xi

Ui

Yfi

Yi

Vi

Zfi

Zi

Si

Lfi

Lfi

Zfi

Zfi 1

2 Xfi

Xfi 1

2 Yfi

Yfi 1

2 1 i interval 1if

Lfi

1 1010

m otherwise

Lfi

Li

Li

Zi

Zi 1 2 X

iX

i 1 2 Yi

Yi 1 2 1 i interval 1if

Li

1 1010

m otherwise

Li

Compression Tension

εaxiali

Li

Lfi

Li

max εaxial 0.000306 min εaxial 0.000151

Combined Strains

Reduction Factor for axial tensile strains RF 0.20

εtotali

εtotali

εbendingi

RF εaxiali

εaxiali

0if

εtotali

εbendingi

otherwise

εtotali

100 50 0 50 1002 10

4

1 104

0

1 104

2 104

3 104

4 104

εtotali

εaxiali

εbendingi

Yi

mMaxstrain min εtotal 147.3 10

6

11

Project: Thames Tunnel Job ref5100812

Part of structure: TU015 East London Calc sheet no rev2 AB

Calc ref Calc by Date Check by Date005 IN 07-07-2011 MY 07-07-2011

Ref Calculations Output

Settlements of either side of base slabIn this calculation the difference in ground movements either sied of the base slab is calculated.Then if the maximum of the difference is less than 5mm, no additional assessments will be required forthe impact of the ground movements on Brunel's Thames Tunnel.

References:1. Settlements above tunnel in the United Kingdom - their magnitude and prediction; O'Reilly MP, New BM; Tunneling '82; p.173-1812. London Overground ELL Thames Tunnel, Interface with Proposed Thames Tunnel, 100-DA-TPI-TU015-810000-AB

Plan Angle between Existing Tunnel and Thames Tunnel β 70deg

External Diameter of Thames Tunnel Dext 8800mm

Tunnel excavated diameter of New tunnel D Dext 8.800 m

Width of Existing Tunnel segment D1 11.45m

VL 1.0%

Face loss (%) K 0.5

Trough factorInvert Level of Existing Tunnel IL 82.265m

Axis Level of Thames Tunnel AL 49.794m

Depth to Thames Tunnel Axis (from Existing Tunnel Invert) z IL AL 32.471 m

Volume loss Vs VL πD

2

2

Vs 0.608 m2

Maximum settlement Smax

Vs

2π K z Smax 14.95 mm

30

Plan

x1 x( ) xD1

2sin β( )

y1 y( ) yD1

2cos β( )

z1 zD

2

x2 x( ) xD1

2sin β( )

y2 y( ) yD1

2cos β( )

z2 zD

2

Output: Six(x,y) : The settlement of each point

S1x x y( )Vs

Dcnorm

2 y1 y( ) D

2 K z1

cnorm2 y1 y( ) D

2 K z1

1 cnormx1 x( )

K z1

*

S2x x y( )Vs

Dcnorm

2 y2 y( ) D

2 K z2

cnorm2 y2 y( ) D

2 K z2

1 cnormx2 x( )

K z2

*

DoS x y( ) S1x x y( ) S2x x y( )

Maximum Difference of S1 and S2

x 0m y 5 m

DoSmi Minimize DoS x y( )

DoSmi2.84

7.97

m

DoS DoSmi0

DoSmi1

3.3 mm

x 100 m y 15m

DoSma Maximize DoS x y( )

DoSma117.81

18.65

m

DoS DoSma0

DoSma1

1.7 mm

As is shown above, the maximum of the difference in ground movements either side of thebase slab is less than 5 mm. Therefore the additional assessments will not required.

31






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4 Bibliography

Bracegirdle, A., Mair, R., Nyren, R. & Taylor, R. A methodology for evaluating potential damage to cast iron pipes induced by tunnelling. Balkema, Rotterdam. (1996). pg 659-664.

Burland, J.B. & Wroth, C.P. Settlement of buildings and associated damage. State of the art review. (1974).

London Overground. Comments of Form BA - East London Line (Thames Tunnel Impact Assessment). London Overground, London. LO-IFM-306-5-0011 (2011).

Moss, N.A. & Bowers, K.H. The effect of new tunnel construction under existing metro tunnels. Proceedings of the 5th International Symposium TC28 (2005).

Network Rail. Inspection and Maintenance of Permanent Way - Track Geometry and Gauge Clearance (NR/L2/TRK/001/C01). Network Rail, London. (2009).

New, B.M. & Bowers, K.H. Tunnelling-induced ground movements; predicting their magnitude and effects. (1994).

O'Reilly, M.P. & New, B.M. Settlement above Tunnels in the United Kingdom - Their Magnitude and Prediction. (1982).

Thames Tunnel. Design Standard and Guidance: Impact Assessment of Construction Induced Ground Movements On Third Party Infrastructure And Buildings. 100-PS-DES-00000-000008 (2011).

Copyright notice Copyright © Thames Water Utilities Limited September 2013. All rights reserved. Any plans, drawings, designs and materials (materials) submitted by Thames Water Utilities Limited (Thames Water) as part of this application for Development Consent to the Planning Inspectorate are protected by copyright. You may only use this material (including making copies of it) in order to (a) inspect those plans, drawings, designs and materials at a more convenient time or place; or (b) to facilitate the exercise of a right to participate in the pre-examination or examination stages of the application which is available under the Planning Act 2008 and related regulations. Use for any other purpose is prohibited and further copies must not be made without the prior written consent of Thames Water. Thames Water Utilities LimitedClearwater Court, Vastern Road, Reading RG1 8DB The Thames Water logo and Thames Tideway Tunnel logo are © Thames Water Utilities Limited. All rights reserved.

Copyright notice Copyright © Thames Water Utilities Limited September 2013. All rights reserved. Any plans, drawings, designs and materials (materials) submitted by Thames Water Utilities Limited (Thames Water) as part of this application for Development Consent to the Planning Inspectorate are protected by copyright. You may only use this material (including making copies of it) in order to (a) inspect those plans, drawings, designs and materials at a more convenient time or place; or (b) to facilitate the exercise of a right to participate in the pre-examination or examination stages of the application which is available under the Planning Act 2008 and related regulations. Use for any other purpose is prohibited and further copies must not be made without the prior written consent of Thames Water. Thames Water Utilities LimitedClearwater Court, Vastern Road, Reading RG1 8DB The Thames Water logo and Thames Tideway Tunnel logo are © Thames Water Utilities Limited. All rights reserved.

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Application Reference Number: WWO10001 Tunnel and Bridge ... · Form BA: Certificate of Assessment and Checking for „Brunel Thames Tunnel‟ – Detailed Tunnel Assessment Printed