tunnel and bridge assessments

8/10/2019 Tunnel and Bridge Assessments

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Tunnel and Bridge AssessmentsCentral Zone

Battersea B Power Station Cable Tunnel

Doc Ref: 9.15.27

Folder 96

Thames Tideway TunnelThames Water Utilities Limited

Application for Development ConsentApplication Reference Number: WWO10001


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Table of contents

Page number

1 Executive summary ......................................................................................................... 32 Introduction ..................................................................................................................... 4

2.1 Site Description ..................................................................................................... 4

3 Structure Details ............................................................................................................. 6

3.1 Asset Details ......................................................................................................... 6

3.2 Asset Condition ..................................................................................................... 6

3.3 Thames Tunnel Details ......................................................................................... 7

4 Material Properties ......................................................................................................... 8

4.1 Lining Details ........................................................................................................ 84.2 Ground Conditions ................................................................................................ 8

5 Assessment Criteria ...................................................................................................... 10

5.1 Ground Movement Assessments ......................................................................... 10

5.2 Analytical method ............................................................................................... 10

5.3 Assessment assumptions ..................................................................................... 10

5.4 Ground movement estimates for structural assessment ...................................... 11

6 Structural Assessment .................................................................................................. 14

6.1 General ................................................................................................................ 146.2 Cast iron lining details ........................................................................................ 14

6.3 Analytical method ............................................................................................... 14

7 Conclusion ..................................................................................................................... 21

Appendices .............................................................................................................................. 22

Appendix A - Drawings .................................................................................................. 23

Appendix B Calculations ............................................................................................. 24

Appendix C - Risk Register ............................................................................................ 25

Appendix D Inspection Report .................................................................................... 26


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List of figures

Page number

Figure 1: Plan of the Thames Tunnel and the crossing with the UKPN Battersea B Cable

Tunnel. ..................................................................................................................... 4

Figure 2: Section on interface of UKPN Battersea B Cable Tunnel and Thames Tunnel ......... 5

Figure 3: Tunnel crown and invert vertical movement ............................................................ 11

Figure 4: Imposed incremental radius of curvature ................................................................. 12

Figure 5: Assessment procedure transverse direction ........................................................... 14

Figure 6: Interaction diagram of existing conditions ............................................................... 16

Figure 7: Interaction diagram including Thames Tunnel works .............................................. 17

Figure 8: Assessment procedure Longitudinal direction ....................................................... 18

List of tables

Page number

Table 1: Asset information ......................................................................................................... 6

Table 2: Tunnel lining geometry and assumed key parameters ................................................. 8

Table 3: Summary of Ground Conditions .................................................................................. 9Table 4: Ground movement assessment parameters ................................................................ 10

Table 5: Calculated distortion .................................................................................................. 12

Table 6: Calculated imposed radius of curvature ..................................................................... 13

Table 7: Assumed key parameters ........................................................................................... 15

Table 8: Imposed bolt and lining stresses ................................................................................ 19


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UKPN Battersea B Power Station Cable Tunnel

2 Introduction

2.1 Site Description

The interface of the proposed Thames Tunnel and the Battersea B cable tunnel is locatedbelow the River Thames, close to Battersea Power Station. The interface of the Thames

Tunnel with the Battersea cable tunnel is at approximate Thames Tunnel chainage 11400mand UKPN chainage 575m (assuming 0m chainage starts at the shaft on the northembankement).

The river bed level at the interface is at approximately 95.8mATD (ATD = Above TunnelDatum: 100mATD = 0 Ordnance Datum OD).

At the interface, the proposed 8.8m diameter Thames Tunnel will pass directly beneath theBattersea B cable tunnel with a vertical clearance of approximately 18.5m. The ThamesTunnel crosses the UKPN tunnel at an angle of approximately 40with 90 being a

perpendicular interface.

Drawings obtained from the Thames Tunnel project team indicates that the Battersea B tunnelconsists of a 2.44m internal diameter tunnel. Photographic evidence suggests that the liningconsists of bolted cast iron segments and this was confirmed during the visual inspection.

The site location and position of the Thames Tunnel interface is shown in Figure 1 andFigure 2.

Figure 1: Plan of the Thames Tunnel and the crossing with the UKPN Battersea B Cable

Tunnel.

Battersea B

Cable Tunnel

Thames Tunnel


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Figure 2: Section on interface of UKPN Battersea B Cable Tunnel and Thames Tunnel

34.36

Thames Tunnel

Battersea B Power Station

Cable Tunnel

(2.44m ID)

18.5m clearancebetween Battersea B

cable tunnel and

Thames Tunnel crown


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3 Structure Details

3.1 Asset Details

The Battersea B cable tunnel was constructed after the end of the Second World War, whenconstruction began on the second phase of the power station, the B station. The station came

into operation gradually between 1953 and 1955, and it is believed that the tunnel wascompleted no later than 1955.

The Battersea B cable tunnel is owned and operated by UKPN. The tunnel runs between theBattersea B power station and a remote shaft on the north embankment at Chelsea BridgeRoad

Limited information about the asset has been obtained from archive drawings and ThamesTunnel alignment drawings received from the Thames Tunnel project team. Furtherinformation was also gathered from a visual inspection undertaken on the 15 March 2012.The information is summarised below inTable 1.

Table 1: Asset information

Classification Description

Asset Name Battersea B Cable Tunnel

Asset Owner UKPN

Built 1953-1955

UKPN Chainage at interface Approximately 575m

Dimensions 2.44m ID

Type Bolted cast iron segments

River Bed Level 95.8m ATD

Crown Level 87.3m ATD

Invert Level 84.3m ATD

Available/received Surveys Visual inspection carried out by Arup on the

15 March 2012.

The material properties of the lining cannot be determined based on the available information.In order to undertake the structural assessment, parameters are based on data for standardLUL cast iron segmental linings of the same diameter as specified in Section 4.

A risk register included in Appendix B outlines assumed lining assumptions.

3.2 Asset Condition

The visual inspection indicated that cast iron segments are in a good condition and the tunnelwas dry at the time of the inspection. There are however a large number of stalactites ofvarying sizes throughout the tunnel which may indicate that water has been present at some

point. The segments also show signs of corrosion but it is considered that the corrosion ismainly superficial with only minimal loss of structural section and the structural capacity.Findings from the inspection have been summarised in the inspection report in Appendix D.


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3.3 Thames Tunnel Details

3.3.1 Construction programme

A detailed construction programme for the bored tunnel is yet to be confirmed, however, it isunderstood that construction work is due to start in 2016.

3.3.2 Thames Tunnel main tunnel

The main Thames Tunnel at the Battersea B cable tunnel interface is currently planned to be7.2m internal diameter with a primary and secondary lining giving an effective 8.5m externaldiameter and an excavated cut diameter of 8.8m.

The Thames Tunnel in this location is anticipated to be constructed using an Earth PressureBalance (EPB) style or Slurry style Tunnel Boring Machine (TBM), using a precast segmentallining. The tunnel axis is at approximately 61.0m ATD and the TBM is anticipated toencounter the London Clay strata from crown to axis and Lambeth Group strata from axis toinvert, at the interface with the UKPN tunnel.


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4 Material Properties

4.1 Lining Details

Since no as-built information has been provided at the time of the assessment, certain key

parameters are based on typical material properties for standard cast iron tunnel linings. The

assumed parameters will have to be confirmed by the asset owner. Available data fromdrawings and from the visual inspection are summarised in Table 2 below.

Table 2: Tunnel lining geometry and assumed key parameters

Dimension/property Value Notes

Internal diameter 2.44m (8ft) 1

No. of segments Ring 1-77: 7 (6 + 1Key)Ring 78 - to shaft: 7 segments

1

Ring width 508mm 1

Flange depth 95mm 1Flange thickness 28mm 1

Plate/skin thickness 26mm 2

Cast iron Youngs Modulus 100,000MPa 12.5% 3

Cast iron compressive strength 150 N/mm 3

Cast iron tensile strength 38 N/mm 3

Number of radial bolts per joint 3 1

Number of circumferential bolts

per joint5 1

Bolt length 135mm 1

Bolt diameter 25mm 1

Notes:

1. Visual inspection carried out on the 15 March 2012 as part of the Thames Tunnelproject.

2. Assumed dimensions based on similar size cast iron segmental tunnel linings.

3. Segment properties based on LUL standards for cast iron lined tunnels.

4.2 Ground ConditionsA review of available borehole logs has been undertaken in order to establish groundconditions at the Thames Tunnel interface. The review has also assessed whether geologicalfeatures such as scour hollows are likely to be present that may affect the tunnel construction.It is important to establish whether geological anomalies are present since it can impact ontunnelling construction and the volume loss which can be achieved.

The geological sequence at the proposed main Thames Tunnel / Battersea cable tunnel

crossing is based on borehole SR2065 and SR2066 located in the River Thames on either side

of Grosvenor Bridge, to the west of the cable tunnel. These boreholes were drilled by Fugro in

June 2010 as part of the Thames Tunnel Phase 2 Project.


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A summary of the borehole logs indicates that the geological sequence comprises River

Terrace Deposits, London Clay Formation, Harwich Formation, Lambeth Group Formation,

Thanet Sand Formation and Seaford Chalk Formation.

The Battersea cable tunnel, with a crown level at 87.3m ATD and an invert level at 84.3mATD lies entirely within the London Clay stratum. The Thames Tunnel, with an axis level atapproximately 61.0m ATD lies with the crown in the London Clay strata and the invert in theLambeth Group strata.

Even though there are no indications of scour features in the reviewed boreholes, it should benoted that deep scour features have been recorded at Battersea Power Station. However, therisk of tunnelling through a scour feature is considered low and the Thames Tunnel projectteam have carried out an assessment of the risk of construction intersection from scourfeatures (doc no: 100-RG-GEO-00000-00017). These features have been surveyed to projectto depths above 85 mATD in the Battersea area. It is therefore unlikely that they will extenddown into the proposed tunnel corridor as there is over 20m of clay cover to the ThamesTunnel soffit anticipated where the tunnel crosses beneath TU003. The anticipated extent of

scour features is presented in Appendix A.The geological cross-section is shown inFigure 2 and the stratigraphy is summarised in

Table 3.

Table 3: Summary of Ground Conditions

Geological formation and stratigraphySR2065 SR2066

approximate level (mATD)

Made Ground

Quaternary River Terrace Deposits 96.1-94.6 96.5-94.7Palaeogene Eocene Thames

Group

London

ClayFormation

94.6-60.3 94.7-60.8

HarwichFormation

60.3-60.2 60.8-60.7

Palaeocene LambethGroup

WoolwichFormation

UpperShellyBeds

60.2-58.6 60.7-58.3

ReadingFormation

UpperMottledBeds

58.6-53.5 58.3-53.2

Woolwich

FormationLaminated

beds53.5-52.3 53.2-52.3

ReadingFormation

LowerMottledBeds

52.3-45.4 52.3-44.2

UpnorFormation

45.4-42.7 44.2-42.3

Thanet SandFormation

42.7-29.9 42.3-30.6

BullheadBeds

29.9-29.7 30.6-30.5

Cretaceous White Chalk Subgroup SeafordChalk

Formation

WhiteChalk

Subgroup

29.7 -(END)

30.5 -(END)

The above assessment confirms that the borehole data is in agreement with Thames Tunnelsground model, which has been used in the assessment.


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5 Assessment Criteria

5.1 Ground Movement Assessments

The ground movement assessment of the UKPN tunnel has assessed end of construction

displacements caused by construction of the Thames Tunnel. The magnitude and distribution

of these ground movements are a function of many factors such as geotechnical properties ofthe ground, construction sequence and program, and the overall standard of workmanship.

The assessment of ground movement assumes that a high standard of workmanship is

adopted by the Contractor. This is assured by review and approval by all relevant parties of

the contractors method statements. Nonetheless, a conservative approach has been adopted in

the selection of input parameters, with the result that this assessment represents a moderately

conservative estimate of ground movement effects.

5.2 Analytical method

Sub-surface greenfield ground movements are calculated using empirical methods (Mair et

al., 1993 and Taylor, 1995) where a settlement trough perpendicular to the new tunnel can be

estimated using an inverted normal probability curve (Gaussian curve). The three dimensionalform of movement is calculated using the Attewell & Woodman (1982) methodology.

Unless otherwise stated ground movements discussed in this report represent greenfield

values that is, it is assumed that overlying or adjacent structures have no influence on the

magnitude or distribution of the estimated movements at foundation level. This is a

conservative, simplifying assumption and the stiffness of individual structures and their depth

of embedment may reduce structural deformations.

The estimated ground movements at the asset location are derived from the Oasyssoftware

Xdisp.

5.3 Assessment assumptions

The borehole review, described in Section 4.2, confirms that the UKPN cable tunnel is

located within the London Clay. The Thames Tunnel is located within both the London Clay

and the Lambeth Group stratum. Since there is no evidence from the borehole review that

scour hollows or other geological anomalies are present, the moderately conservative

volume loss parameter as specified by the Thames Tunnel project team is deemed appropriate

for the ground movement assessment.

Table 4: Ground movement assessment parameters

Assessment parameters Value

Volume Loss (Thames Tunnel main tunnel)1.0%

Trough width parameter (K) at ground

surface0.5


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5.4 Ground movement estimates for structural assessment

In order to determine the imposed deformation of the UKPN cable tunnel for the structural

assessment in Section6,greenfield vertical ground movements have been calculated along

the tunnel at levels corresponding to the crown and invert. These levels are intrados positions

of the tunnel. The estimated settlement along the UKPN tunnel is presented graphically in

Figure 3.

Figure 3: Tunnel crown and invert vertical movement

The estimated ground movements have been used to assess the following tunneldeformations, assuming the tunnel moves freely with the ground:

Maximum tunnel squat/elongation in the transverse direction; and

Worst case radius of curvature imposed on the tunnel in the hogging and saggingzones in the longitudinal direction.

5.4.1 Maximum tunnel squat/elongation

The diametrical distortion, i.e. the change in diameter divided by the original tunnel diameter,of a tunnel lining due to ground loading will result in either an increase of the verticaldiameter and a decrease of the horizontal diameter (elongation) or an increase of the

horizontal diameter and a decrease of the vertical diameter (squat).

-2

0

2

4

6

8

10

12

14

16

18

0 200 400 600 800

Sub-surfacedisplacement[mm]

Offset from TT centreline [m]

TU003 Battersea BVertical displacement at crown and invert

Tunnel Crown Tunnel Invert


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The maximum vertical displacement at levels corresponding to the tunnel crown and invertare summarised inTable 5.The distortion of the UKPN tunnel is calculated by dividing themaximum differential ground movement (i.e. the difference between crown and invertsettlement) by the diameter of the tunnel.

Table 5: Calculated distortion

Maximum vertical displacement

Invert Crown Max. differential Diametrical

distortion

17.8mm 16.6mm 1.2mm 0.04%

The effect of elongation/squat is a potential change in bending moment of the segmentallining that may cause rotation of the joints. The calculated value will form part of thestructural assessment (see Section6.3.4).

5.4.2 Tunnel imposed radius of curvature

The worst case imposed radius of curvature in the longitudinal direction, R imposed, has beencalculated based on the Greenfield settlement profile along the tunnel invert level.

The critical mode of longitudinal deformation is where the tunnel deforms (bends) within asagging or a hogging zone. The radius of curvature has been calculated consideringincremental radii of curvature between the points of inflection. The tightest imposed radius ofcurvature, Rimposedhas been calculated as the minimum of these values, as illustrated inFigure 4below.

L is the cumulative distance between the incremental intervals and is the magnitude ofdisplacement between the points.

Figure 4: Imposed incremental radius of curvature


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Table 6: Calculated imposed radius of curvature

Minimum imposed radius of curvature, Rimposeddue to vertical movement

Sagging

UKPN Battersea B Cable Tunnel 17.5km

The radius of curvature will be used to assess the structural impact on the UKPN tunnel in thelongitudinal direction (see Section 6.3.6). This will include assessing bolts and the size of the

gap which may open up between two segments.


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6 Structural Assessment

6.1 General

The structural assessment of the bolted cast iron lined UKPN tunnel considers existingconditions and additional conditions due to construction of the Thames Tunnel.

The estimated vertical distortion (difference between crown and invert maximum verticalmovements) is considered when assessing the change in lining stresses while the imposedradius of curvature is considered when assessing the potential for opening up of tunnel jointsand bolts.

6.2 Cast iron lining details

The structural assessment is based on assumed material properties and tunnel geometry since

no as-built information has been provided at the time of writing of this assessment. The

assumed parameters are summarised in Section 4.1.

6.3 Analytical method

6.3.1 Change in lining stresses due to squat/elongation of tunnel section

An outline of the assessment procedure is presented below inFigure 5.Calculations are

included in Appendix A.

Figure 5: Assessment procedure transverse direction

PERMISSIBLE TUNNEL LININGCAPACITY ENVELOPE

From lining material and section properties

DETERMINE EXISTING HOOP FORCES

IN LINING

Using Elastic Continuum method after

Duddeck and Erdmann (1985)

DETERMINE CHANGE IN BENDING

MOMENT IN LINING DUE TO THAMES

TUNNEL CONSTRUCTION

Apply predicted distortion to tunnel and use

Morgan (1961) method to calculate change in

BM

CHECK THE AXIAL FORCE/BENDING

MOMENT REMAINS WITHIN THEPERMISSIBLE CAPACITY ENVELOPE


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6.3.2 Permissible tunnel lining capacity envelope

The lining capacity envelope is determined by plotting an interaction diagram. The interaction

diagram can be plotted, by computing the bending moment and hoop force values. This

provides an envelope which defines the limit of the cast iron lining capacity. Lining

dimensions and cast iron grade are parameters that impact on the capacity envelope. Theinteraction diagram for the Battersea B tunnel is based on the parameters summarised in

Section 4.1.

6.3.3 Determine existing lining stresses

The existing stresses, which do not include the effect of the Thames Tunnel works, arecalculated using Duddeck and Erdmann (1985). Tunnel stresses using Duddeck and Erdmannare assumed to be in a continuous elastic environment and therefore, it does not take intoaccount any volume lost or relaxation of the ground. However, the number of assumptionsmade in this report, collectively produce a conservative assessment of the stresses in the

tunnel lining.The existing stresses are calculated in accordance with a number of assumed parameters.These are presented inTable 7.

Table 7: Assumed key parameters

Assumed key parameters

Earth pressure coefficient at tunnel location K0=0.7

Surface surcharge No additional surcharge since interface is

located below the River Thames

Existing diametric distortion of the tunnel See below

For the calculations presented in this report two ground water pressure profiles has beenassumed, a hydrostatic ground water pressure profile and zero pore water pressure at thetunnel axis. The result included in Appendix B is for the most conservative case assumingzero pore water pressure at the tunnel axis.

Changes in horizontal stress and a reduction of K0following tunnel construction are likely to

have resulted in the UKPN cable tunnel having a squatted tunnel profile. Since no

dimensional survey records have been obtained, the existing distortion is calculated from the

maximum radial displacement derived from the Duddeck and Erdmann equations. Based on a

maximum radial displacement of 2.76mm, the existing diametrical distortion equates to

0.23% using the Duddeck and Erdmann equations. The Thames Tunnel will then impose

0.04% ovalisation (elongation, i.e. crown to invert distance increases) as discussed in Section5.4.1.

The maximum bending moment, and hoop force derived from the Duddeck and Erdmannequations are 8.73kNm/m and 442kN/m respectively and these are plotted in the interactiondiagram to confirm that design assumptions are reasonable as the plotted values should fallinside the diagram, seeFigure 6.


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Figure 6: Interaction diagram of existing conditions

6.3.4 Determine change in bending moment in lining due to Thames Tunnelconstruction

The tunnel cross-sectional distortion calculated from vertical greenfield ground movementsequates to a maximum of 0.04% ovalisation as specified inTable 5.Since the existing UKPNtunnel is likely to have a non-perfect build lining, i.e. the ring may have squattedduring/since construction; the calculated ovalisation will potentially counterbalance the squat

and will therefore not superpose any additional adverse effect on the lining structuralcapacity.

This is assessed by using the calculated ovalisation as an input to determine the change inbending moment in the UKPN tunnel. The calculated ovalisation of 0.04% is subtracted fromthe existing diametrical distortion of 0.23%. Using Morgans equations (1961), the finalmaximum factored bending moment in the tunnel lining will be 7.5kNm/m. For the purposeof the structural assessment the ovalisation due to the Thames Tunnel works is considered tooccur in any plane of the tunnel.

6.3.5 Check that the axial force/bending moment remains within the capacity envelope

The factored hoop force calculated by Duddeck and Erdmann and the factored bendingmoment described in section6.3.3 are plotted together in the interaction diagram. If the

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

5.00

-60.00 -40.00 -20.00 0.00 20.00 40.00 60.00

Axia

lForce(MN/m)

Bending Moment (kNm/m)

Permissible lining capacity

Lining forces existing condition based on Duddeck &Erdmann


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moment / hoop thrust plots inside the capacity envelope, this indicates that the lining is withinthe section capacity while a moment / hoop thrust outside the capacity envelope indicates thatthe tunnel lining will not meet the safety requirements for the code of practice specified forthe calculations.

As shown inFigure 7,the calculated ovalisation will counterbalance the squatted tunnel

profile and the existing bending moment will effectively reduce i.e. move to the left in theinteraction diagram. This is indicated in the interaction diagram below where the plots whichrepresents the existing condition have a greater bending moment than the plots whichrepresents the UKPN tunnel after construction of the Thames Tunnel works. It should also benoted that even if the lining distortion would be added to the existing bending moment andhoop force, the lining is still within but close to the structural capacity. This covers thescenario in the hogging region where the crown to invert dimension will reduce as aconsequence of ground movement (ref Figure 3).

Figure 7: Interaction diagram including Thames Tunnel works

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

5.00

-60.00 -40.00 -20.00 0.00 20.00 40.00 60.00

AxialForce(MN/m)



Lining forces existing condition based on Duddeck &ErdmannLining forces including distortion due to TTconstruction


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6.3.6 Longitudinal deformation of the tunnel lining

In the longitudinal direction, the UKPN tunnel lining is assessed based on the procedurepresented inFigure 8.

Figure 8: Assessment procedure Longitudinal direction

6.3.7 Bolt and lining stress check (1stcheck)

The method is based on calculating the extreme fibre strains at the extrados of the lining andthe resulting bolt stress using beam bending theory. This method assumes bending mode onlyand does not account for shearing due to horizontal axial movement. It should be noted thatthe imposed radius of curvature is predominately used for an initial screening assessment toestablish whether the bolts and lining needs further analysis. If the factor of safety of the boltsand lining is greater than 1, no further assessment is proposed at this stage. However, if thefactor of safety is less than 1, further analysis will be undertaken to look at the performance ofthe bolts and flanges in more detail.

DETERMINE THE MAXIMUM IMPOSED RADIUSOF CURVATURE FROM GREENFIELD

VERTICAL MOVEMENTS

As described in section 5.4.2

USE THIS IMPOSED RADIUS OF CURVATURETO DETERMINE GAP WHICH OPENS UP

BETWEEN TWO RINGSAssume no circumferential bolts between rings (i.e.

loosened or missing)

CHECK WHETHER THE GAP WILL PRESENT ARISK TO THE TUNNEL BASED ON

GROUND/GROUNDWATER CONDITIONS

USE THIS IMPOSED RADIUS OF CURVATURETO CALCULATE EXTREME FIBRE STRAIN OF

TUNNEL

Use beam bending theory, = r / R

CHECK THE BOLT AND LINING STRESS WITHTHEIR ULTIMATE CAPACITY

Assume extension of bolt and lining at extremefibre. The limiting stress in the lining is determined

by the bolt stresses

1st

CHECK

2n

CHECK


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The analysis can be summarised in the expression for overall limiting extreme fibre strainfrom:

= +

Where:

skin= skin strain at limiting allowable bolt stress

bolt= bolt strain at limiting allowable bolt stressLbolt= length of bolt under tension

Lskin= circumferential width of tunnel segment

Based on the critical imposed radius of curvature in the sagging mode of 17.5km, the bolt

lining stresses required to accommodate this curvature is as follows:

Table 8: Imposed bolt and lining stresses

Distortion mode Sagging

Imposed radius of curvature R (m) 17500

Imposed bolt stress (N/mm) 77.1

Bolt stress factor of safety1 4.0

Imposed lining stress (N/mm) 6.2

Lining stress factor of safety2 22.1

Notes:1 The existing stresses in the bolts are unknown and the analysis is based on

comparing the imposed stress with the ultimate bolt tensile stress. The ultimatetensile stress (including a condition factor) is 342 N/mm2 x 0.9= 307.8N/mm2

2 The ultimate lining tensile stress = 4 x permissible stress with a lining conditionfactor of 0.9 = 4 x 0.9 x 38 = 136.8N/mm

The imposed stresses on the bolt inTable 8present the limiting case with the calculated bolt

stress, in the sagging mode of distortion, having a factor of safety of 4 in relation to the

ultimate bolt stress of 307.8 N/mm2(this relates to bolts at the extreme fibre in the invert).

Since the factor of safety is greater than 1, the impact on the discharge tunnel lining and bolts,

due to the Thames Tunnel works, is considered to be minor and no further assessment will be

undertaken.

6.3.8 Gap opening up between rings (2nd check)

The tunnel lining is assessed by examining the maximum gap that can occur between tworings. The imposed radius of curvature is used to calculate the maximum gap due to bendingwhich may open up between rings.

Gap = (bxR)/(R-) - b

Where b = overall width of section

R = imposed radius of curvature

= External diameter


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The maximum gap from bending at the Battersea B interface is 0.08mm. However, themaximum gap from bending as explained above together with maximum imposed gap due tohorizontal displacement gives a maximum combined gap of 0.12mm. This gap is consideredsmall and since the Battersea B tunnel is founded in the relatively impermeable London Clay,there is no significant risk associated with opening up of the tunnel joints.

6.3.9 In house structures

The Battersea B tunnel houses in tunnel structures such as brackets and a limited number of

communication cables. Based on the calculated ground movement, the impact on any in

tunnel structures is considered likely to be negligible.


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7 Conclusion

The assessment described in this report is based on PBA/Arups understanding of the

proposed Thames Tunnel project. Any recommendations should be considered holistically by

the Thames Tunnel project team within the detailed context of the proposed works onsite.

The UKPN Battersea B cable tunnel is located directly above the Thames Tunnel with a

vertical clearance of approximately 18.5m. Results from the ground movement assessment in

the longitudinal and transverse direction have been used to calculate the resulting stresses

imposed on the tunnel lining. The assessment is based on a number of conservative

assumptions regarding lining material properties and geometry.

The current assessment indicates that the impact on the UKPN cable tunnel in both transverse

and longitudinal direction is within the lining capacity. The maximum gap of 0.12mm which

may open up between two segments is considered to present low risk to the integrity of the

tunnel structure since the tunnel is located within the relatively impermeable London Clay

strata. The impact on the bolted segments is also considered to be low.

A visual inspection was carried out on the 15thMarch 2012 in order to validate assumptions

relating to this assessment report and to confirm the likely behaviour of the tunnel. The visual

inspection indicates that the cast iron tunnel segments are in good condition. The tunnel was

dry at the time of the inspection and even though there were limited signs of water ingress, a

number of stalactites may indicate that water has been present at some point. The tunnel

lining and bolts exhibits varying degree of corrosion but it is considered that the corrosion is

mainly superficial with only minimal loss of structural section and the structural capacity.

Maintenance checks of the bolted segments during excavation of the Thames Tunnel may be

appropriate and it is also recommended that a condition survey is carried out after theproposed construction of the Thames Tunnel. This will confirm whether any adverse changes

in the condition of the tunnel have occurred as a result of the Thames Tunnel construction.


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Appendices

Appendices


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Appendices

Appendix A - Drawings


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NOTE:

1. VERTICAL SETTLEMENT IS SH

EXAGGERATED BY A FACTOR2. DO NOT SCALE FROM DRAWI

DATE ISSUED: 21.03

TUNNEL SETTLEMENT

TUNNEL CURVE KEY:

GEOTECHNICAL KEY:

UKPN BATTERSEA B P

STATION CABLE TUNN

GREENFIELD GROUNSETTLEMENT 1.0% VL

307-SK2-TPI-TU003-81

SUPERFICIALDEPOSITSAND MADE GROUND

LONDON CLAYFORMATION

LAMBETH GROUP

THANET SAND FORMATI

CHALK GROUP

10m 20m0m

* THE EXCAVATED TUNNEL DIAMET

ADOPTED IN THE GROUND MOVEASSESSMENT IS 8.8M.

LONGITUDINAL SECTION THAMES TUNNEL AT BATTERSEA B POWER STATION CABLE TUNNEL (TU003)

84.29

87.29

(3.0MID)

34.8

1

17.8mm

ID

BATTERSEAB POWERSTATION CABLE TUNNEL

*

APPROXIMATELY 120m OF TUNNEL TO BE INSPECTED


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Appendices

Appendix BCalculations


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Job No. Sheet No. Rev.

215748-20 1.0Member/Location

Job Title Thames Tunnel - Battresea B Power Station Tunnel Drg. Ref.

Pre- Thames Tunnel construction Made by LN Date 23-Mar-12 Chd. YL

1.0 Input Data

Materials Young's Modulus of cast iron, Ecast iron= 112 500 MPa

Poissons ratio of cast iron, ncast iron= 0.26

Permissible compressive strength of cast iron Rp in c.= 150 N/mmPermissible tensile strength of cast iron, Rp in t= 38 N/mm

Material safety factor for cast iron = 1.00

Elastic Modulus of ground,Ec= 40 MPa

Poissons ratio of ground, n= 0.20

Tunnel geometry internal diameter, D= 2 438 mm ext. dia, ED= 2 680 mm

overall depth of section, h= 121 mm

internal depths for gaskets: internal,iint= 0 mm, external, iext= 0 mm

depth of skin, hf= 26 mm

length of centre rib, hr= 0 mm

overall width of section, b= 508 mm

total width of ribs, bw= 51 mm from: rib 1, t1= 25 mm

rib 2, t2= 0 mm

Density of cast iron = 7 200 kg/m rib 3, t3= 25 mm

number of segments, n= 6

angle subtended by segment, = 60

Condition factor Fc= 0.9 from LU G-055

Loading

GL= 95.84 mTD Factored Loads Unfactored Loads

GWL = 61.02 mTD 344.323 286.94 (vert. tot stress)

Tunnel axis level = 85.79 mTD 0 0 (pwp)

Unit weight of soil = 20 kN/m3

344.323 286.94 (vert eff. Stress)

K = 0.7 241.026 200.85 (hor. eff. stress)

Surface surcharge = 85.936 kPa 241.026 200.85 (hor. tot. stress)

Partial factor on overburden = 1.2

Partial factor on surcharge = 1.2

Vertical Pressure at the Axis Pfv= 344.32 kPa Puv= 286.94 kPa

Horizontal Pressure at the Axis Pfh= 241.03 kPa Puh= 200.85 kPa

Duddeck and Erdmann analysis

The continuum model derived by Duddeck and Erdmann is use to derive the forces and moments in the

lining. This model gives different equations for (a) full bond between the lining and the ground, and

(2) tangential slip. The type of analysis used in this spreadsheet need to be input in the box below.

If full bond is to be used type F, if not type Tfor tangential slip F

Full bond has been specified

Ovalisation due to Thames Tunnel construction - from XDISP or other calculations

maximum "squat" = 0 of internal radius

\maximum radial displacement, u2 = 0.00 mm

Bolt geometry

Diameter of bolt, Dbolt= 25 mm Ult. Tensile, Ubolt= 342 N/mm

Length of bolt, Lbolt= 135 mm Ult. Shear, Sbolt=0.4Ubolt= 137 N/mm

Cross sectional area, Abolt= 490.87 mm2

Young's Modulus, Ebolt= 190 GPa

Number of circumferential bolts = 35 Material factor Mbolt= 1.2

Cast-iron boltedLining Assessment

Spreadsheet


30/77


215748-20 3.1 0

Member/Location 0

Job Title Thames Tunnel - Battresea B Power Station Tunnel Drg. Ref. 0


3.1 Duddeck and Erdmann analysis (Ie) - consider the effect of panels for lining stiffness

Input parameters:

Ground: Elastic Modulus Ec= 40 MPa

Poisson's Ratio = 0.20Lining: Radius of Centroid ro= 1.31075 m

Elastic Modulus E= 120656 MPa E=Ecast iron/(1-ncast iron2) - Muir Wood

Effective Moment of Inertia Ie= 1.50E-05 m /m

Sectional Area A= 0.03547 m2/m

Loading: Factored Loads Unfactored Loads



Theory:

The loading on the lining is calculated using the Duddeck and Erdmann analysis. These equations allow

either full bond between the lining and the ground, or tangential slip. This is selected below based on an

appreciation of the behaviour of the ground Full bond specified F

Duddeck and Erdmann Formulae

Full Bond Tangential Slip

(Derived from Nav)

Results Factored UnfactoredBending Moment+/- M= 8.73 kNm/m M= 7.28 kNm/m

Average Hoop Thrust Nav= 382.06 kN/m Nav= 318.60 kN/m

Variable Hoop Thrust+/- Nvar= 59.33 kN/m Nvar= 49.44 kN/m

Constant Radial Displacement Uo= 0.12 mm Uo= 0.10 mm

Max, Radial Displacement Umax= 2.76 mm Umax= 2.30 mm

Relative Flexibility Factor Q2= 3.45 Q2= 3.45

Design Shear(Lining/Ground) T= 80.37 kPa T= 66.97 kPa

Moments and Hoop Stresses Induced in the Lining

factored maximum hoop load, Nfmax= 441 kN/m (or 0.441 MN/m)

factored minimum hoop load, Nfmin= 323 kN/m (or 0.323 MN/m)

unfactored maximum hoop load, Numax= 368 kN/m (or 0.368 MN/m)

unfactored minimum hoop load, Numin= 269 kN/m (or 0.269 MN/m)factored maximum moment, Mfmax= 8.7 kNm/m 8.73 -8.73

unfactored maximum moment M = 7 3 kNm/m 7 28 -7 28

(sv-s

h)R

2+ 4nEcR3/EJ

(3-4n)(12(1+n)+EcR3/EJ)

0.5(sv+sh)R2

(1-u)(1-K0)EcR3 + EA

(1-2u)(1+u)

(sv-sh)R4/EJ

12+ 3-2n EcR3

(1+n)(3-4n) EJ.

(sv-sh)R2

4+ 3-2n EcR3

3(1+n)(3-4n) EJ.

(sv-sh)R2

10-12n + 2 EcR3

3-4n 3(1+n)(3-4n) EJ.

(sv+sh)R

2+ 2(1-n)(1-K0) EcR

(1-2n)(1+n) EA.

(sv-sh)R

10-12n + 2 EcR3

3-4n 3(1+n)(3-4n) EJ.

(sv-sh)R4/EJ

6(5-6n) + 2 EcR3

3-4n (1+n)(3-4n) EJ.

Averagehoop thrust

Nav

Variablehoop thrust

Nvar

Constant radialdisplacement

u0

Maximum radialdisplacement

u2y

Maximumbending

moment,M


Spreadsheet


31/77


215748-20 5.1 0

Member/Location 0



5.1 Comparison of actual loads with lining capacity: consider the effect of panels

The capacity graph from section 2.0 is reproduced here, with the loads calculated plotted on.

All loads are factored.

0.00

1.00

2.00

3.00

4.00

5.00

6.00

-60.00 -40.00 -20.00 0.00 20.00 40.00 60.00

AxialForce(MN/m)



Lining forces existing condition based on Duddeck & Erdmann

I=Ie

Cast-iron bolted

Lining AssessmentSpreadsheet

using Duddeck &Erdmann equation tocalculate existing BM


32/77


215748-20 1.0Member/Location

Job Title Thames Tunnel - Battresea B Power Station Tunnel Drg. Ref.

Post- Thames Tunnel construction Made by LN Date 23-Mar-12 Chd. YL

1.0 Input Data

Materials Young's Modulus of cast iron, Ecast iron= 112 500 MPa

Poissons ratio of cast iron, ncast iron= 0.26

Permissible compressive strength of cast iron Rp in c.= 150 N/mmPermissible tensile strength of cast iron, Rp in t= 38 N/mm

Material safety factor for cast iron = 1.00

Elastic Modulus of ground,Ec= 40 MPa

Poissons ratio of ground, n= 0.20

Tunnel geometry internal diameter, D= 2 438 mm ext. dia, ED= 2 680 mm

overall depth of section, h= 121 mm

internal depths for gaskets: internal,iint= 0 mm, external, iext= 0 mm

depth of skin, hf= 26 mm

length of centre rib, hr= 0 mm

overall width of section, b= 508 mm

total width of ribs, bw= 51 mm from: rib 1, t1= 25 mm

rib 2, t2= 0 mm

Density of cast iron = 7 200 kg/m rib 3, t3= 25 mm

number of segments, n= 6

angle subtended by segment, = 60

Condition factor Fc= 0.9 from LU G-055

Loading

GL= 95.84 mTD Factored Loads Unfactored Loads

GWL = 61.02 mTD 344.323 286.94 (vert. tot stress)

Tunnel axis level = 85.79 mTD 0 0 (pwp)

Unit weight of soil = 20 kN/m3

344.323 286.94 (vert eff. Stress)

K = 0.7 241.026 200.85 (hor. eff. stress)

Surface surcharge = 85.936 kPa 241.026 200.85 (hor. tot. stress)

Partial factor on overburden = 1.2

Partial factor on surcharge = 1.2



Duddeck and Erdmann analysis

The continuum model derived by Duddeck and Erdmann is use to derive the forces and moments in the

lining. This model gives different equations for (a) full bond between the lining and the ground, and

(2) tangential slip. The type of analysis used in this spreadsheet need to be input in the box below.

If full bond is to be used type F, if not type Tfor tangential slip F

Full bond has been specified

Ovalisation due to Thames Tunnel construction - from XDISP or other calculations

maximum "squat" = 0.00039 of internal radius

\maximum radial displacement, u2 = -0.48 mm

Bolt geometry

Diameter of bolt, Dbolt= 25 mm Ult. Tensile, Ubolt= 342 N/mm

Length of bolt, Lbolt= 135 mm Ult. Shear, Sbolt=0.4Ubolt= 137 N/mm

Cross sectional area, Abolt= 490.87 mm2

Young's Modulus, Ebolt= 190 GPa

Number of circumferential bolts = 35 Material factor Mbolt= 1.2


Spreadsheet


33/77


215748-20 3.1 0

Member/Location 0



3.1 Duddeck and Erdmann analysis (Ie) - consider the effect of panels for lining stiffness

Input parameters:

Ground: Elastic Modulus Ec= 40 MPa

Poisson's Ratio = 0.20Lining: Radius of Centroid ro= 1.31072 m

Elastic Modulus E= 120656 MPa E=Ecast iron/(1-ncast iron2) - Muir Wood

Effective Moment of Inertia Ie= 1.50E-05 m /m

Sectional Area A= 0.03515 m2/m

Loading: Factored Loads Unfactored Loads



Theory:

The loading on the lining is calculated using the Duddeck and Erdmann analysis. These equations allow

either full bond between the lining and the ground, or tangential slip. This is selected below based on an

appreciation of the behaviour of the ground Full bond specified F

Duddeck and Erdmann Formulae

Full Bond Tangential Slip

(Derived from Nav)

Results Factored UnfactoredBending Moment+/- M= 8.73 kNm/m M= 7.28 kNm/m

Average Hoop Thrust Nav= 382.04 kN/m Nav= 318.58 kN/m

Variable Hoop Thrust+/- Nvar= 59.33 kN/m Nvar= 49.44 kN/m

Constant Radial Displacement Uo= 0.12 mm Uo= 0.10 mm

Max, Radial Displacement Umax= 2.76 mm Umax= 2.30 mm

Relative Flexibility Factor Q2= 3.45 Q2= 3.45

Design Shear(Lining/Ground) T= 80.37 kPa T= 66.97 kPa

Moments and Hoop Stresses Induced in the Lining

factored maximum hoop load, Nfmax= 441 kN/m (or 0.441 MN/m)

factored minimum hoop load, Nfmin= 323 kN/m (or 0.323 MN/m)

unfactored maximum hoop load, Numax= 368 kN/m (or 0.368 MN/m)

unfactored minimum hoop load, Numin= 269 kN/m (or 0.269 MN/m)factored maximum moment, Mfmax= 8.7 kNm/m 8.73 -8.73

unfactored maximum moment M = 7 3 kNm/m 7 28 -7 28

(sv-s

h)R

2+ 4nEcR3/EJ

(3-4n)(12(1+n)+EcR3/EJ)

0.5(sv+sh)R2

(1-u)(1-K0)EcR3 + EA

(1-2u)(1+u)

(sv-sh)R4/EJ

12+ 3-2n EcR3

(1+n)(3-4n) EJ.

(sv-sh)R2

4+ 3-2n EcR3

3(1+n)(3-4n) EJ.

(sv-sh)R2

10-12n + 2 EcR3

3-4n 3(1+n)(3-4n) EJ.

(sv+sh)R

2+ 2(1-n)(1-K0) EcR

(1-2n)(1+n) EA.

(sv-sh)R

10-12n + 2 EcR3

3-4n 3(1+n)(3-4n) EJ.

(sv-sh)R4/EJ

6(5-6n) + 2 EcR3

3-4n (1+n)(3-4n) EJ.

Averagehoop thrust

Nav

Variablehoop thrust

Nvar

Constant radialdisplacement

u0

Maximum radialdisplacement

u2y

Maximumbending

moment,M


Spreadsheet


34/77


215748-20 4.2 0

Member/Location 0



The drawings below show the typical deflected shapes and the envelopes of shear force and bending

moment:

Typical displacements for Pv>Ph, KoPh, Ko


35/77


215748-20 5.1 0

Member/Location 0



5.1 Comparison of actual loads with lining capacity: consider the effect of panels

The capacity graph from section 2.0 is reproduced here, with the loads calculated plotted on.

All loads are factored.

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

5.00

-60.00 -40.00 -20.00 0.00 20.00 40.00 60.00

AxialForce(MN/m)



Lining forces existing condition based on Duddeck & Erdmann

Lining forces including distortion due to TT construction

I=Ie

Cast-iron bolted

Lining AssessmentSpreadsheet

using Duddeck &Erdmann equation tocalculate existing BM


36/77


215748-20 6.0 0

Member/Location 0



6.0 Longitudinal curvature

CHECK 1

s= M yextreme/ I yextreme= dist. between neutral axis and extreme fibre 1875.8 mme= M yextreme / E I I = Second moment of area of tunnel section

Three modes of tensile strain are considered:

a) The strain assuming the lining only deforms and reaches its permissible stress.

The radius of curvature, R', can be calculated as:

R' = EI /MR' limiting= E yextreme/ spermissible Lining spermissible = 34 N/mm

2

a) assume lining failure only, y extreme= external radius of the tunnel

lining, limiting= spermissible/E= 2.83E-04 where E= 120656 MPa (for lining)

R' limiting= r/ lining, limiting= 4727 m (for information)

b) assume strain of lining at bolt allowable stress, yextreme= external radius of the tunnel

assume working bolt stress sbolt= 85.5 N/mm (= Ult ten./4 (BCIRA))

Cross-section area of bolt = 490.874 mm2 Maximum force per bolt = 41.97 kN

Skin area = 213868 mm2

Number of circumferential bolts = 35 Skin area per bolt = 6110.5 mm2

Stress on the lining from a single bolt (at the bolts allowable stress) = 6.8684 N/mm2

From above lining, limiting= slimited by bolt stress/E= 5.69E-05 where E= 120656 MPa (for lining)

R' limiting= r/ lining, limiting= 23537 m (for information)

c) consider the strain along the extreme fibre bolt and lining and calculate required bolt stressusingetotal = elining+ ebolt* Lbolt/ Llining and yextreme= 1875.8 mm

where lining= lining strain at limiting allowable bolt stress

bolt= bolt strain at limiting allowable bolt stress

Lbolt= length of bolt under tension assume 0.07 m, between the nut and head of bolt

Llining= circumferential width of tunnel segment = 0.508 m

imposed radius of curvature = 17500 m Manual inputetotal = 0.0001

Ebolt = 190 GPa

Elining = 121 GPa

Required bolt stress = 77.056 N/mm

Imposed lining stress = 6.19 N/mm

CHECK 2

calculate the size of gap if the circumferential bolts are not considered (i.e. missing or loosen bolts)

gap = b * Rimposed/ (Rimposed - ED) - b

= 0.0778 mm

b) The strain assuming the lining deforms based on the limiting stress caused by the bolt reaching its allowable

stress

c) The required bolt stress at the imposed radius of curvature assuming that both the lining and bolt deform

Assume the tunnel is a continuous flexible tube, the extreme fibre stress and strain of a tunnel section can be

calculated as follows:


Spreadsheet

Rimposed

2 panelswidth

Diameter ofthe tunnel

gap


37/77

Appendices

Appendix C - Risk Register


38/77

Hazard Risk Register

\\GLOBAL.ARUP.COM\LONDON\G_E\JOBS\200000\215748-00\50_DESIGN_ANALYSIS\PACKAGE 2C\TU003\DETAILED ASSESSMENT\APPENDIX C\HAZARD RISK REGISTER_TU003.DOCX

Page 1 of 5Arup | F18.2a | Rel 14.2 23 March 2012

Register reference

Project Thames Tunnel Detailed Assessment package 2c Job number 215748-20

Package/Topic TU003Battersea B Power Station Cable Tunnel Design stage

Remember: Avoid Reduce Control and communicate relevant information to others (CDM Regulation 11)

DateArea/Location of RiskExposure

Description of Hazard andRisk Exposure

Mitigation of Risk(Potential or Achieved)

A R C Further Action byStatus

(+ initials) Active/closed

23/03/12 Thames Tunnel(TT) excavation

below Battersea B

Power Station

Cable Tunnel

Unidentified geologicalanomalies may cause

higher volume loss during

excavation than

anticipated and the risk of

ground movement at theabove discharge tunnel

increases.

TT has carriedout a desk studyto identify

geological

anomalies.

Arup hasreviewed

existing boreholedata to confirm

strata at TT face

and TT/UKPN

interface.

TT is planning to drill anumber of additional deep

and high level boreholes

in this area.

23/03/12 Thames Tunnel

(TT) excavationbelow Battersea B

Power Station

Cable Tunnel

The London Clay strata is

more permeable thananticipated and water

ingress could occur

through the gap which

may open up between

segments.

Boreholes at

tunnel interfaceto identify sandlenses in the

London Clay

strata.

TT is planning to drill a

number of additional deepand high level boreholes

in this area.

23/03/12 Battersea B Power

Station CableTunnel Lining

The assumed lining

thickness is incorrect andthe structural capacity is

Use archivedrawings for the

assessment.


39/77



Page 2 of 5Arup | F18.2a | Rel 14.2 14 February 2011

Register reference









overestimated. Adoptconservativethickness for the

detailed

assessment.

23/03/12 Battersea B PowerStation Cable

Tunnel Lining

The assumed cast ironstrength is incorrect and

the structural capacity is

overestimated. Theinduced impact on the TS

tunnel may exceed the

lining capacity.

Use conservativecast iron strength

parameters.

Use LondonUnderground

recommendedparameters for

the assessment.


Station CableTunnel Lining

The assumed Youngs

modulus for cast iron isincorrect and the structural

capacity is overestimated.

Use London

Undergroundrecommended

parameters for a

conservative

YoungsModulus.


40/77




Register reference









23/03/12 Battersea B PowerStation Cable

Tunnel Bolts

The existing tensile forcesin the circumferential

bolts are not known. If

there is significant pre-

existing force in the bolt,

then small increments oftensile stress caused by

ground movement may

potentially caused the bolt

or flange to break.

Case studiesreferenced in thereport highlight

several instances

where cast iron

tunnels have

been subjected tolarger distortions

and no damage

has been noted.

There is noreason to believethat significant

torque was

applied to boltswhen fastened.


Station Cable

Tunnel Bolts

For assessing the

longitudinal distortion,

only initial screening

assessments have beencarried out. These use of

an index parameter

(radius of curvature) to

The effects on thecircumferential

bolts indicate that

the stresses do

not result in aFOS of less than

1.


41/77


42/77




Register reference









deformation shouldbe considered in

greater detail.


43/77

Appendices

Appendix DInspection Report


44/77

307-RI-TPI-TU003-000001| AA| 21 March 2012

UKPN Battersea B

Power Station CableTunnel

Inspection report


45/77


46/77

Table of contents

Page number

1 Executive summary ......................................................................................................... 32 Introduction ..................................................................................................................... 4

3 Tunnel construction ........................................................................................................ 5

4 Tunnel inspection ............................................................................................................ 6

4.1 Scope of inspection ............................................................................................... 6

4.2 Access and limitations .......................................................................................... 7

5 Observations .................................................................................................................... 8

5.1 General condition .................................................................................................. 8

5.2 Tunnel geometry ................................................................................................... 8Appendices ................................................................................................................................ 9

Appendix D1 Figures .......................................................................................................

Appendix D2 - Ring observations ......................................................................................

Appendix D3 Photographs ...............................................................................................


47/77

List of tables

Page number

Table 1 - Inspection team ........................................................................................................... 6Table 2 - Tunnel geometry ......................................................................................................... 8


48/77

UKPN Battersea B Power Station cable Tunnel

1

Executive summary

Thames Water is currently progressing with its planned Tideway improvements. Theimprovement works consists of the construction of two new tunnels, the Thames Tunnel andthe Lee Tunnel, together with a programme of sewer upgrades. Construction of the proposed

Thames Tunnel (TT), an 8.1m 8.8m excavated diameter tunnel, stretching approximately23km for much of its route under the River Thames from West London to Abbey Mills is dueto commence in 2016.

The proposed interface between the Thames Tunnel and the UKPN Battersea B cable tunnelis located in the middle of the River Thames by Battersea Power Station, in the borough ofWandsworth. The Thames Tunnel main tunnel will be constructed with a clear distance ofapproximately 18.5m between the two tunnels.

To date, an interim detailed assessment report has been prepared to assess the likely impact onthe Battersea B cable tunnel due to the construction of the Thames Tunnel works. The interimreport is based on a number of assumptions regarding the tunnel lining geometry and tunnel

condition. In order to confirm these assumptions and to record the condition of the tunnel, avisual inspection of the cable tunnel was undertaken on Thursday 15thMarch 2012.

The inspections indicate that the cast iron segments are in a good condition. Segments arebolted and one part of the rings has a key segment while the other part does not have a keysegment. There are signs of condensation on the segments; however, there are limited signsof active seepage. The segments and bolts do show a slight degree of corrosion but it isconsidered that the corrosion is superficial with no significant impact on the structuralcapacity.


49/77


2

Introduction

The Battersea B cable tunnel runs from Battersea Power Station on the south embankment toa shaft located at located on Chelsea Bridge Road on the north embankment. The interface is

between the Thames Tunnel and the cable tunnel is in the middle of the River Thames. TheUKPN tunnel is located approximately 8.5m below river bed level and the clear distance tothe Thames Tunnel connection tunnel is approximately 18.5m.

The Battersea B cable tunnel is owned by UKPN and is used for carrying communicationscables cables beneath the River Thames. There are currently only a small number of cables inthe tunnel and it is unclear whether UKPN will install more cables in the future.

As part of the assessment of the Battersea B cable tunnel, a visual inspection has beenundertaken to confirm assumptions made in the detailed analysis and to record the generalcondition of the tunnel lining. The tunnel inspection was limited to a zone, extendingapproximately 60m on either side of the Thames Tunnel interface. This zone represents thelength of the Battersea B cable tunnel which is subject to ground movement greater than1mm; see Sketch 1 in Appendix D1.


50/77


3

Tunnel construction

The Battersea B cable tunnel was constructed after the end of the Second World War, whenconstruction began on the second phase of the power station, the B station. The station cameinto operation gradually between 1953 and 1955, and it is believed that the tunnel wascompleted no later than 1955.

The tunnel consists of bolted cast iron segments. Some of the rings are composed of 7segments and 1 key segment while some rings did not have a key segment.


51/77


4

Tunnel inspection

The inspection of the Battersea B cable tunnel was carried out on Thursday 15thMarch 2012between 8.00am and 2.00pm. The inspection team consisted of Arup Tunnel Engineers andpersonnel from ABA Engineering Limited. ABA Engineering Ltd was appointed by UKPN toassist and manage the confined space procedures.

Table 1 - Inspection team

Name Company Role

Linn Nordstrom Arup Tunnel Inspector

Yung Loo Arup Tunnel Inspector

5x ABA Engineering Ltd

Personnel

ABA Engineering

Ltd

2x Tunnel escort,

top man andrescue team

A method statement had been prepared for the tunnel entry protocol and safety, and this wasfully complied with by all parties.

The weather on the morning of the inspection was foggy flowed by sunshine. It had been aclear night and there had been limited rain fall in the days prior to the inspection.

The inspection was undertaken from a north to south direction along the tunnel. However, theinspection team only used the south shaft located at Battersea Power Station, for access andegress.

4.1 Scope of inspection

The scope of the inspection was to undertake a visual observation of the tunnel lining toconfirm the lining geometry and to determine the presence of any signs of distress or damagethat may compromise the structural capacity of the tunnel. Such features include but are notlimited to: cracking of tunnel segments; corrosion of tunnel segments; water ingress; and

birdsmouthing of segments.

The visual inspection consisted of a walkthrough with notes and photographs taken where

necessary to flag up any potential areas of concern.It should be noted that the inspection was not intended to be a full structural survey or anintrusive investigation. The following information was recorded as a minimum:

Tunnel details including;

Location

Lining Type

Tunnel Lining

Segment and key position

Segment dimensions


52/77


53/77


5

Observations

The findings of the inspections are summarised below. Recorded observations for each ringare included in Appendix D2 whilst Appendix D3 contains photographs of some of thedefects observed.

5.1 General condition

The survey started approximately 215m northwest along the UKPN cable tunnel from theshaft at Battersea Power Station. The tunnel was inspected back towards this shaft in a south-easterly direction. The location of the first ring was 22m north of the signage boardindicating: 193m to the shaft at the Power Station. It should be noted that the tunnel wasnaturally ventilated during the inspection.

The cast iron segments were generally in a good condition. There was very little sign of activeseepage and the invert was dry, however there were little droplets on the segments due to

condensation. There were also a large number of stalactites in varying sizes throughout thetunnel which may indicate that more water has been present over the years. Physical damageto segments, such as cracking was not encountered.

The configuration of the rings varied over the length of the inspection. The first 77 rings had akey segment while the rest did not. In addition, the first 159 rings did not have any caulkingor grout in the circumferential joint but this did not seem to impact on water ingress.

A description of observations is presented in Appendix D2. Photographs of observations arepresented in Appendix D3.

5.2 Tunnel geometry

The following measurements and observations in regards to the tunnel geometry were madeduring the inspection.

Table 2 - Tunnel geometry

Parameter Value

No segments Ring 1-77: 7 (6 + 1Key)Ring 78 - to the shaft: 7 segments

Segment type Bolted cast ironSegment width 508mm

Internal Diameter 2438.4mm (8ft)Bolts per circumferential joint 5Bolts per radial joints 3Bolt diameter 24-25mmBolt Length 130-135mmDepth of flange 95mmThickness of flange 28mm


54/77

Appendices

Appendices


55/77

Appendices

Appendix D1 Figures


56/77

NOTE:

1. VERTICAL SETTLEMENT IS SH

EXAGGERATED BY A FACTOR2. DO NOT SCALE FROM DRAWI

DATE ISSUED: 21.03

TUNNEL SETTLEMENT

TUNNEL CURVE KEY:

GEOTECHNICAL KEY:

UKPN BATTERSEA B P

STATION CABLE TUNN

GREENFIELD GROUNSETTLEMENT 1.0% VL

307-SK2-TPI-TU003-81

SUPERFICIALDEPOSITSAND MADE GROUND

LONDON CLAYFORMATION

LAMBETH GROUP

THANET SAND FORMATI

CHALK GROUP

10m 20m0m

* THE EXCAVATED TUNNEL DIAMET

ADOPTED IN THE GROUND MOVEASSESSMENT IS 8.8M.

LONGITUDINAL SECTION THAMES TUNNEL AT BATTERSEA B POWER STATION CABLE TUNNEL (TU003)

84.29

87.29

(3.0MID)

34.8

1

17.8mm

ID

BATTERSEAB POWERSTATION CABLE TUNNEL

*

APPROXIMATELY 120m OF TUNNEL TO BE INSPECTED


57/77


58/77

Arup

UKPN TU003 Tunnel

Condition survey results

Job No. 215748 Sheet 1/5

TU003 (UKPN Battersea B)

Legend: 1 = cracking 2 = evidence of water ingress 3 = active Seepage

4 = calcite buildup 5 = staining 6 = damage at bolt hole7 = Stalactite 8 = displacement of segment 9 = missing caulking

10 = open joints 11 = seepage at joints 12 = seepage at bolt holes

13 = damage of lifting socket/grout 14 = corrosion 15 = missing/loose Bolt

Date: 15th March 2012

Surveyor: LN/YL

Ring Number LK LA LS K RS RA RK Notes Photo

1 4Photo 2 taken of caulking between segment joints.

Caulking at radial joints only.1,2

2

3

4 4 4Signs of cacite around bolts. This is the same for

most segments

5 4 4 36 4 4 4 calcite at LK lifting socket

7

8 7 Ring marked 450

9

10

11 4

12 7

13 2/4

14

15 7

16 7 4

17

18 7

19 2/4

20 2/4 7 Photo taken to the north 5

21 4/7 7

22 7

23 4

24

25 4

26 4

27

28 4/7 7

29 7

30 4

31

32 4/7 7

33

34

35

36

37 7

38

39 3/7 Dripping (slow)

40 4 4/7 Photo taken to the north 6

41 7 7

42 7 4/7

43 4 7

44 4 Exit sign: 525m to embankement; 193m to shaft

45 2* 3/7 7 *standing water

46 7 7 4

47

48 7 stalactite around lifting socket

49

50

51 4

52 7 7

53

54 4

55 4

56 4


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60/77

Arup

UKPN TU003 Tunnel









Surveyor: LN/YL


119

120 11

121

122

123 3/4/7 Dripping (slow) 12

124 3/4/7

125126

127 4 4

128Step at left shoulder/axis joint between ring 128/129

13

129

130 7

131

132

133 4 7

134 4/7

135

136

137

138

139 4

140 4 Photo taken to the north 14

141

142

143

144 Exit sign: 575m to embankement; 143m to shaft

145

146

147

148

149

150

151

152

153

154

155 4

156

157 4

158 15

159 4 4

160Ring marked 300. Caulking visible at both radial

and circumferential joints. 16

161

162

163

164 7 Increase of corrosion at flanges (Ring 164-168) 17

165

166 7

167

168

169 * *Missing lifting socket plug170 4 7 Key segment corroded

171 4/7 step in segment 18172 4

173 * 7 *Missing lifting socket plug. Exit sign: (591m; 268m)174 7


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Arup

UKPN TU003 Tunnel









Surveyor: LN/YL


178 4 7 7 7

179 7 7 7

180 4 7 Photo taken to the north 19

181 4 7 7 7 Photo taken of stalactities along the LH shoulder 20

182 7 3/7 3/7 7

183 7

184 3/7 3/7 7 7 Dripping at stalactities185 3/7 3/7 7 7

186 3/7 3/7 7 7corrosion visible at rings, signs of calcitie buildup in

invert from dripping water

187 3/7 3/7 7 7

188 3/7 3/7 7 7

189 3/7 3/7 7 7

190 3/7 3/7 7 7

191 3/7 3/7 7 7

192 3/7 3/7 7 7

193 3/7 3/7 7 7

194 3/7 3/7 7 7

195 3/7 3/7 7 7 21

196 4/7 4/7

197 4/7 4/7

198 4/7 4/7

1994/7 4/7

200 4/7 4/7

201

202 4/7 4/7 7

203

204

205 4/7

206 4Rings show less stalactities and a bit more

rust/corrosion

207

208

209

210 Ring marked 250

211

212

213

214

215

216

217 3/7 Dripping (slow)

218

219

220 Photo taken to the north 22

221

222

223

224

225

226

227

228

229

230

231

232

233


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Arup

UKPN TU003 Tunnel









Surveyor: LN/YL


237

238

239

240 7 Photo taken to the north 23

241 7

242 7

243 7244


63/77

Appendices

Appendix D3 Photographs


64/77

Photo 1 Start of survey at ring 1. Photo is taken to the north.

Photo 2 No caulking/grout at circumferential joint at Ring 1 to Ring 159.


65/77

Photo 3 Calcite build-up around bolts at LH axis at Ring 5

Photo 4 Stalactities at crown at Ring 16


66/77

Photo 5 Photo taken to the north at Ring 20

Photo 6 - Photo taken to the north at Ring 40


67/77




68/77


Photo 10 Missing bolt at key segement at Ring 102


69/77


Photo 12 Dripping at let shoulder of Ring 123


70/77

Photo 13 Step between axis joints at Ring 128/129



71/77

Photo 15 Caulking visible at circumferentil joints from Ring 160



72/77

Photo 17 Segments show more corrosion from Ring 164

Photo 18 step at axis join between Ring 171/172


73/77


Photo 20 Stalactites visible along the left hand shoulder starting at Ring 181


74/77

Photo 21 Photo taken to the north at Ring 200



75/77


Photo 24 Typical segment (5 circumferential bolts, 3 radial bolts)


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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 Limited

Clearwater Court, Vastern Road, Reading RG1 8DB

The Thames Water logo and Thames Tideway Tunnel logo

are Thames Water Utilities Limited. All rights reserved.


77/77

Photo 25 Typical key (1 circumferential bolt, 3 radial bolts)

tunnel and bridge assessments

Documents