Post on 02-Jun-2018
8/10/2019 Tunnel and Bridge Assessments
1/77
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
8/10/2019 Tunnel and Bridge Assessments
2/77
8/10/2019 Tunnel and Bridge Assessments
3/77
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
8/10/2019 Tunnel and Bridge Assessments
4/77
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
8/10/2019 Tunnel and Bridge Assessments
5/77
8/10/2019 Tunnel and Bridge Assessments
6/77
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
8/10/2019 Tunnel and Bridge Assessments
7/77
UKPN Battersea B Power Station Cable Tunnel
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
8/10/2019 Tunnel and Bridge Assessments
8/77
UKPN Battersea B Power Station Cable Tunnel
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.
8/10/2019 Tunnel and Bridge Assessments
9/77
UKPN Battersea B Power Station Cable Tunnel
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.
8/10/2019 Tunnel and Bridge Assessments
10/77
UKPN Battersea B Power Station Cable Tunnel
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.
8/10/2019 Tunnel and Bridge Assessments
11/77
UKPN Battersea B Power Station Cable Tunnel
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.
8/10/2019 Tunnel and Bridge Assessments
12/77
UKPN Battersea B Power Station Cable Tunnel
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
8/10/2019 Tunnel and Bridge Assessments
13/77
UKPN Battersea B Power Station Cable Tunnel
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
8/10/2019 Tunnel and Bridge Assessments
14/77
UKPN Battersea B Power Station Cable Tunnel
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
8/10/2019 Tunnel and Bridge Assessments
15/77
UKPN Battersea B Power Station Cable Tunnel
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.
8/10/2019 Tunnel and Bridge Assessments
16/77
UKPN Battersea B Power Station Cable Tunnel
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
8/10/2019 Tunnel and Bridge Assessments
17/77
UKPN Battersea B Power Station Cable Tunnel
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.
8/10/2019 Tunnel and Bridge Assessments
18/77
UKPN Battersea B Power Station Cable Tunnel
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
8/10/2019 Tunnel and Bridge Assessments
19/77
UKPN Battersea B Power Station Cable Tunnel
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)
Bending Moment (kNm/m)
Permissible lining capacity
Lining forces existing condition based on Duddeck &ErdmannLining forces including distortion due to TTconstruction
8/10/2019 Tunnel and Bridge Assessments
20/77
UKPN Battersea B Power Station Cable Tunnel
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
8/10/2019 Tunnel and Bridge Assessments
21/77
UKPN Battersea B Power Station Cable Tunnel
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
8/10/2019 Tunnel and Bridge Assessments
22/77
UKPN Battersea B Power Station Cable Tunnel
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.
8/10/2019 Tunnel and Bridge Assessments
23/77
UKPN Battersea B Power Station Cable Tunnel
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.
8/10/2019 Tunnel and Bridge Assessments
24/77
Appendices
Appendices
8/10/2019 Tunnel and Bridge Assessments
25/77
Appendices
Appendix A - Drawings
8/10/2019 Tunnel and Bridge Assessments
26/77
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
8/10/2019 Tunnel and Bridge Assessments
27/77
8/10/2019 Tunnel and Bridge Assessments
28/77
Appendices
Appendix BCalculations
8/10/2019 Tunnel and Bridge Assessments
29/77
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
8/10/2019 Tunnel and Bridge Assessments
30/77
Job No. Sheet No. Rev.
215748-20 3.1 0
Member/Location 0
Job Title Thames Tunnel - Battresea B Power Station Tunnel Drg. Ref. 0
Pre- Thames Tunnel construction Made by LN Date 23-Mar-12 Chd. YL
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
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
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
Cast-iron boltedLining Assessment
Spreadsheet
8/10/2019 Tunnel and Bridge Assessments
31/77
Job No. Sheet No. Rev.
215748-20 5.1 0
Member/Location 0
Job Title Thames Tunnel - Battresea B Power Station Tunnel Drg. Ref. 0
Pre- Thames Tunnel construction Made by LN Date 23-Mar-12 Chd. YL
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)
Bending Moment (kNm/m)
Permissible lining capacity
Lining forces existing condition based on Duddeck & Erdmann
I=Ie
Cast-iron bolted
Lining AssessmentSpreadsheet
using Duddeck &Erdmann equation tocalculate existing BM
8/10/2019 Tunnel and Bridge Assessments
32/77
Job No. Sheet No. Rev.
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
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" = 0.00039 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
Cast-iron boltedLining Assessment
Spreadsheet
8/10/2019 Tunnel and Bridge Assessments
33/77
Job No. Sheet No. Rev.
215748-20 3.1 0
Member/Location 0
Job Title Thames Tunnel - Battresea B Power Station Tunnel Drg. Ref. 0
Post- Thames Tunnel construction Made by LN Date 23-Mar-12 Chd. YL
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
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
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
Cast-iron boltedLining Assessment
Spreadsheet
8/10/2019 Tunnel and Bridge Assessments
34/77
Job No. Sheet No. Rev.
215748-20 4.2 0
Member/Location 0
Job Title Thames Tunnel - Battresea B Power Station Tunnel Drg. Ref. 0
Post- Thames Tunnel construction Made by LN Date 23-Mar-12 Chd. YL
The drawings below show the typical deflected shapes and the envelopes of shear force and bending
moment:
Typical displacements for Pv>Ph, KoPh, Ko
8/10/2019 Tunnel and Bridge Assessments
35/77
Job No. Sheet No. Rev.
215748-20 5.1 0
Member/Location 0
Job Title Thames Tunnel - Battresea B Power Station Tunnel Drg. Ref. 0
Post- Thames Tunnel construction Made by LN Date 23-Mar-12 Chd. YL
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)
Bending Moment (kNm/m)
Permissible lining capacity
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
8/10/2019 Tunnel and Bridge Assessments
36/77
Job No. Sheet No. Rev.
215748-20 6.0 0
Member/Location 0
Job Title Thames Tunnel - Battresea B Power Station Tunnel Drg. Ref. 0
Post- Thames Tunnel construction Made by LN Date 23-Mar-12 Chd. YL
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:
Cast-iron boltedLining Assessment
Spreadsheet
Rimposed
2 panelswidth
Diameter ofthe tunnel
gap
8/10/2019 Tunnel and Bridge Assessments
37/77
Appendices
Appendix C - Risk Register
8/10/2019 Tunnel and Bridge Assessments
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.
8/10/2019 Tunnel and Bridge Assessments
39/77
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 2 of 5Arup | F18.2a | Rel 14.2 14 February 2011
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
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.
23/03/12 Battersea B Power
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.
8/10/2019 Tunnel and Bridge Assessments
40/77
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 3 of 5Arup | F18.2a | Rel 14.2 14 February 2011
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 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.
23/03/12 Battersea B Power
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.
8/10/2019 Tunnel and Bridge Assessments
41/77
8/10/2019 Tunnel and Bridge Assessments
42/77
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 5 of 5Arup | F18.2a | Rel 14.2 14 February 2011
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
deformation shouldbe considered in
greater detail.
8/10/2019 Tunnel and Bridge Assessments
43/77
Appendices
Appendix DInspection Report
8/10/2019 Tunnel and Bridge Assessments
44/77
307-RI-TPI-TU003-000001| AA| 21 March 2012
UKPN Battersea B
Power Station CableTunnel
Inspection report
8/10/2019 Tunnel and Bridge Assessments
45/77
8/10/2019 Tunnel and Bridge Assessments
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 ...............................................................................................
8/10/2019 Tunnel and Bridge Assessments
47/77
List of tables
Page number
Table 1 - Inspection team ........................................................................................................... 6Table 2 - Tunnel geometry ......................................................................................................... 8
8/10/2019 Tunnel and Bridge Assessments
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.
8/10/2019 Tunnel and Bridge Assessments
49/77
UKPN Battersea B Power Station cable Tunnel
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.
8/10/2019 Tunnel and Bridge Assessments
50/77
UKPN Battersea B Power Station cable Tunnel
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.
8/10/2019 Tunnel and Bridge Assessments
51/77
UKPN Battersea B Power Station cable Tunnel
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
8/10/2019 Tunnel and Bridge Assessments
52/77
8/10/2019 Tunnel and Bridge Assessments
53/77
UKPN Battersea B Power Station cable Tunnel
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
8/10/2019 Tunnel and Bridge Assessments
54/77
Appendices
Appendices
8/10/2019 Tunnel and Bridge Assessments
55/77
Appendices
Appendix D1 Figures
8/10/2019 Tunnel and Bridge Assessments
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
8/10/2019 Tunnel and Bridge Assessments
57/77
8/10/2019 Tunnel and Bridge Assessments
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
8/10/2019 Tunnel and Bridge Assessments
59/77
8/10/2019 Tunnel and Bridge Assessments
60/77
Arup
UKPN TU003 Tunnel
Condition survey results
Job No. 215748 Sheet 3/5
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
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
8/10/2019 Tunnel and Bridge Assessments
61/77
Arup
UKPN TU003 Tunnel
Condition survey results
Job No. 215748 Sheet 4/5
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
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
8/10/2019 Tunnel and Bridge Assessments
62/77
Arup
UKPN TU003 Tunnel
Condition survey results
Job No. 215748 Sheet 5/5
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
237
238
239
240 7 Photo taken to the north 23
241 7
242 7
243 7244
8/10/2019 Tunnel and Bridge Assessments
63/77
Appendices
Appendix D3 Photographs
8/10/2019 Tunnel and Bridge Assessments
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.
8/10/2019 Tunnel and Bridge Assessments
65/77
Photo 3 Calcite build-up around bolts at LH axis at Ring 5
Photo 4 Stalactities at crown at Ring 16
8/10/2019 Tunnel and Bridge Assessments
66/77
Photo 5 Photo taken to the north at Ring 20
Photo 6 - Photo taken to the north at Ring 40
8/10/2019 Tunnel and Bridge Assessments
67/77
Photo 7 - Photo taken to the north at Ring 60
Photo 8 - Photo taken to the north at Ring 80
8/10/2019 Tunnel and Bridge Assessments
68/77
Photo 9 - Photo taken to the north at Ring 100
Photo 10 Missing bolt at key segement at Ring 102
8/10/2019 Tunnel and Bridge Assessments
69/77
Photo 11 - Photo taken to the north at Ring 120
Photo 12 Dripping at let shoulder of Ring 123
8/10/2019 Tunnel and Bridge Assessments
70/77
Photo 13 Step between axis joints at Ring 128/129
Photo 14 - Photo taken to the north at Ring 140
8/10/2019 Tunnel and Bridge Assessments
71/77
Photo 15 Caulking visible at circumferentil joints from Ring 160
Photo 16 - Photo taken to the north at Ring 160
8/10/2019 Tunnel and Bridge Assessments
72/77
Photo 17 Segments show more corrosion from Ring 164
Photo 18 step at axis join between Ring 171/172
8/10/2019 Tunnel and Bridge Assessments
73/77
Photo 19 - Photo taken to the north at Ring 180
Photo 20 Stalactites visible along the left hand shoulder starting at Ring 181
8/10/2019 Tunnel and Bridge Assessments
74/77
Photo 21 Photo taken to the north at Ring 200
Photo 22 - Photo taken to the north at Ring 220
8/10/2019 Tunnel and Bridge Assessments
75/77
Photo 23 - Photo taken to the north at Ring 240
Photo 24 Typical segment (5 circumferential bolts, 3 radial bolts)
8/10/2019 Tunnel and Bridge Assessments
76/77
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.
8/10/2019 Tunnel and Bridge Assessments
77/77
Photo 25 Typical key (1 circumferential bolt, 3 radial bolts)