Tunnel and Bridge Assessments Eastern Zone Crossrail Line 1 (Limehouse Basin) Doc Ref: 9.15.120 Folder 111 September 2013 DCO-DT-000-ZZZZZ-091500 Thames Tideway Tunnel Thames Water Utilities Limited Application for Development Consent Application Reference Number: WWO10001
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Tunnel and Bridge AssessmentsEastern ZoneCrossrail Line 1 (Limehouse Basin)Doc Ref: 9.15.120
Folder 111 September 2013DCO-DT-000-ZZZZZ-091500 Cr
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Thames Tideway Tunnel Thames Water Utilities Limited
Application for Development ConsentApplication Reference Number: WWO10001
Table 3: Network Rail limits for track vertical profile and track twist (Network Rail, 2009) ....................................................................................................... 12
Table 4: Material strength of concrete ...................................................................... 15
Table 5: Summary of Results ................................................................................... 16
List of abbreviations
Ch Chainage
CSO Combined Sewer Overflow
CRL Crossrail
NR Network Rail
LUL London Underground Limited
TU021 Thames Tunnel reference for Crossrail (Limehouse Basin) damage assessment
K Trough width parameter
khv Coefficient of earth pressure (horizontal:vertical)
TU021 Crossrail – Assessment Report
TU021 Crossrail Line 1 Page 5 Printed 01/12/2011
1 Executive Summary
1.1.1 Atkins has been appointed by the Thames Tunnel Team to carry out an assessment of the potential effects of the project on the proposed Crossrail running tunnels, to assess if early works are required. The location of the crossing is situated north east of Limehouse Basin in the Borough of Tower Hamlets. The tunnels are yet to be constructed, but will be completed prior to the Thames Tunnel construction. This report describes the assessment of likely effects on the Crossrail tunnels from the proposed Thames Tunnel works - an 8.8m diameter bored tunnel, constructed using a closed face tunnel boring machine.
1.1.2 Atkins has completed the assessments based on semi-empirical methods. The ground movement assessment data is based on „Greenfield‟ ground movement assumptions, together with volume loss assumptions and not accounting for soil-structure interaction, which collectively produce a conservative assessment.
1.1.3 Impact assessments which have been undertaken include an analysis of the ground movement effects on the track geometry, as well as longitudinal and transverse assessments of the Crossrail tunnel linings in response to the ground movement predictions. All assessments have been undertaken in line with Network Rail and London Underground Limited Standards acceptance criteria. The settlement assessment indicates that the predicted track settlements, based on conservative assumptions, are within the „No Mandated Action‟ criteria according to the Network Rail limits for track vertical profile.
1.1.4 Assessment of the risk of damage resulting from the construction of Thames Tunnel on the Crossrail running tunnels suggests that the damage impact is within the acceptance criteria adopted for the ground movement effects on the track geometry. The longitudinal damage assessment indicates that the maximum circumferential joint opening is small (less than 1mm). In the transverse assessment, the results indicate that the increase in radial joint opening due to birdsmouthing is approximately 10%, solely caused by Thames Tunnel construction.
1.1.5 Atkins recommends that monitoring of the Crossrail running tunnels prior, during and after the construction of the Thames Tunnel should be undertaken. If an increase in water ingress into the tunnel is noted, caulking at these locations can be used to manage any significant inflow.
1.1.6 Atkins also recommends that the appointed contractor of Thames Tunnel should undertake a pre-construction survey prior to construction of the Thames Tunnel. If, at the time of the pre-construction survey, Crossrail have a contemporary Clearance & Track survey and information on the circularity („squat‟) geometry of the existing tunnel for this section of the line, we recommend that this is used.
TU021 Crossrail – Assessment Report
TU021 Crossrail Line 1 Page 6 Printed 01/12/2011
2 Description of Works
2.1 Site Description
2.1.1 The Thames Tunnel is planned to cross under the twin bore Crossrail running tunnels to the north east of Limehouse Basin in the Borough of Tower Hamlets. The Crossrail tunnels are yet to be constructed but will have been completed prior to the Thames Tunnel construction. The site location is shown in Figure 1.
Figure 1: Thames Tunnel – Crossrail crossing at Limehouse Basin
2.2 Asset Description
2.2.1 The Crossrail project which is shortly due to commence construction, will be a major new heavy-rail suburban service for London and the South-East, connecting the City, Canary Wharf, the West End and Heathrow Airport to commuter areas east and west of the capital. The main civil engineering construction works for Crossrail are currently underway and are planned to be completed in 2017.
2.2.2 The location of the Thames Tunnel – Crossrail crossing at Limehouse Basin is along Crossrail “Drive Y”, between Limmo and Farringdon. The construction of the Crossrail running tunnels at this location is expected to begin in the third quarter of 2012 and completion is expected in the third quarter of 2014.
Thames Tunnel
Crossrail Westbound
Crossrail Eastbound
Limehouse Basin
TU021 Crossrail – Assessment Report
TU021 Crossrail Line 1 Page 7 Printed 01/12/2011
2.2.3 The Crossrail running tunnels at this location are to be constructed of 6.20m I.D. bolted segmental concrete lining using an earth pressure balance tunnel boring machine. The tunnel rings will consist of 7 segments and a key. The thickness of the lining will be 300mm and the width of the segments is 1.6m (Atkins, 2011).
2.2.4 The tunnel lining will be constructed of precast steel fibre reinforced concrete segments. The circumferential joints of the standard segments have been designed as flat joints connected by plastic dowels. The radial joints have a convex-convex joint detail connected with spear steel bolts (Crossrail Ltd, 2011).
2.2.5 There are two proposed Crossrail cross passages within the vicinity of the crossing – CP10 and CP11, located approximately 341m northwest and 171m southeast of the Thames Tunnel crossing. There are no proposed Crossrail shafts nearby in accordance with the latest alignment provided (Crossrail Ltd, 2011).
2.3 Proposed Thames Tunnel Works
2.3.1 Information received from the Thames Tunnel team (Thames Water Utilities Ltd, 2011) indicates that the excavated Thames Tunnel diameter is 8.8m, inclusive of overcut. The Westbound and Eastbound Crossrail crossings are skewed by approximately 56o and 53o respectively (an angle of 90o signifies a right angle crossing of the Thames Tunnel to the Crossrail tunnel). See Appendix B for details.
2.3.2 The tunnel crown (extrados) of the Thames Tunnel is at 43.127m ATD and the invert (extrados) of the Crossrail Westbound running tunnel is 68.027m ATD. See Figure 2.
2.3.3 The tunnel crown (extrados) of the Thames Tunnel is at 43.086m ATD and the invert (extrados) of the Crossrail Eastbound running tunnel is 67.839m ATD. See Figure 2.
2.3.4 The minimum extrados-to-extrados clearance between the Thames Tunnel and Crossrail is approximately 24.9m and 24.8m on the Westbound and Eastbound running tunnels respectively.
2.3.5 There are no proposed CSO structures or shafts associated with the Thames Tunnel in the vicinity of the Crossrail running tunnels. If subsequently other structures are identified which may have potential effect on any tunnel under assessment these will be separately considered.
2.3.6 At the time of putting together this assessment report, the current revision of the Thames Tunnel project anticipates passing under the Crossrail Line 1 running tunnels in 2018 to 2019, with the Thames Tunnel TBM driving North East towards Abbey Mills.
TU021 Crossrail – Assessment Report
TU021 Crossrail Line 1 Page 8 Printed 01/12/2011
2.4 Ground Conditions
2.4.1 The typical geological sequence at the location of the crossing comprises Made Ground, London Clay Formation, Lambeth Group, Thanet Sand Formation and Chalk Group.
2.4.2 The following geology has been assessed based on a geological section for the area undertaken by the Thames Tunnel team (see Appendix B for more details):
Table 1: Summary of ground stratigraphy
Top of Stratum Approximate ground level
Made Ground 107.696 m ATD
London Clay Formation 100.138 m ATD
Lambeth Group 88.352 m ATD
Thanet Sand Formation 69.343 m ATD
Chalk Group 56.590 m ATD
2.4.3 A separate geological desk study has been undertaken by Atkins (Appendix B), which indicates that the geology at the location of the crossing is similar to that presented in Table 1.
2.4.4 The geological desk studies indicate that the Crossrail running tunnels are situated in a mixed face of London Clay and Lambeth Group at the location of the crossing.
2.4.5 At the location of crossing, the Thames Tunnel TBM will encounter the Chalk formation, with the crown a distance of approximately 4.2m beneath the bottom of the Thanet Sand formation.
2.4.6 Whilst the assessment engineers have attempted to determine the most appropriate geology at the tunnel crossing, there is still a possibility of variation in geology along the length of the tunnel. Nevertheless, this stratigraphy is generally consistent with that found elsewhere in London and significant variation over the length of the tunnel can be considered to be unlikely.
TU021 Crossrail – Assessment Report
TU021 Crossrail Line 1 Page 9 Printed 01/12/2011
3 Assessment
3.1 Ground Movement Assessment
3.1.1 Sub-surface ground movement assessments have been undertaken along the Thames Tunnel alignment. Ground deformations along the alignment of Crossrail have been calculated assuming „Greenfield‟ conditions which do not account for soil-structure interaction or the stiffness of the Crossrail running tunnels.
3.1.2 The presence of Crossrail cross passages CP10 and CP11 noted in Section 2.2.5 have not been considered for the purpose of this phase of assessment as they are beyond the zone of influence of the Thames Tunnel construction.
3.1.3 The ground movement assessments are solely based on short term movement predictions. The impact of long term consolidation movements have been assumed to have negligible impact on the basis that the rate of change of ground slope caused by long term settlement are usually no worse than the „Greenfield‟ settlement trough. The impact of long term settlement increases the apparent trough width factor K such that although the magnitude of settlement increases, the impact of damage is not greater than the short term settlement.
3.1.4 The impact of the pressurised EPB face from the construction of the Thames Tunnel has not been considered in the analysis as it is unlikely to cause significant heave. This will need to be clarified once the final method of tunnel construction has been determined, ensuring that the effects of the face pressure will not be detrimental to the existing tunnel.
3.1.5 The assessment is based on Thames Tunnel Alignment AJ.
Figure 2: Sketch shows levels used in Ribbon Sink ground movement assessment
TU021 Crossrail – Assessment Report
TU021 Crossrail Line 1 Page 10 Printed 01/12/2011
3.2 Modelling Assumptions
3.2.1 The volume loss (VL) parameter used in the prediction of ground movements at this stage has been determined based on the context of this assessment. A moderately-conservative value of 0.90% for this pre-planning phase has been used in the assessments and reflects the assumed closed-face construction technique. A literature review of the documented recent case histories of tunnel construction in Chalk in the UK is presented in Appendix F, and indicates that this value should be achievable, provided good construction practices are in place. The literature review indicates that the highest value found during review for tunnelling in Chalk in the UK is 0.53%.
3.2.2 Based on our preliminary assessments, a volume loss parameter of 0.9% for the ground movement assessments should ensure that the track geometry in the Crossrail tunnels fall within the “No Mandated Action” criteria. The limiting volume loss value between the “No Mandated Action” criteria and the “Planned Maintenance” criteria is 0.94%. However, it should be noted that the volume loss parameter is not the only factor; the effects of Thames Tunnel construction on the Crossrail track geometry can be attributed to a combination of factors including the trough width parameter and consideration of soil-structure interaction.
3.2.3 Thames Tunnel will also ensure that a specification for the tunnel boring machines (TBM) contract documentation will include a requirement that the TBMs should limit volume loss to 0.90% at the Crossrail-Thames Tunnel crossing.
3.2.4 A trough width parameter, K, of 0.5 is proposed in the assessment of ground movements as being representative of typical ground conditions expected at this site. Experience in London reveals that „K‟ is seldom less than 0.40 (O'Reilly & New, 1982), and also indicates that where VL values of less than 1.0% are achieved, a „K‟ value above 0.50 may be appropriate. The „K‟ value of 0.50 has been adopted for ground movement predictions, and is a conservative assumption.
Table 2: Assumed modelling parameters
Modelling Parameters Value
Volume Loss (VL) % 0.90%
Trough width parameter (K) 0.50
TU021 Crossrail – Assessment Report
TU021 Crossrail Line 1 Page 11 Printed 01/12/2011
3.3 Analytical Method
3.3.1 The sub-surface movements from bored tunnels were calculated using the semi-empirical „Ribbon Sink‟ method (New & Bowers, 1994).
3.3.2 Horizontal movements were calculated assuming undrained ground conditions, and assume that ground movement vectors are directed towards a „Ribbon Sink‟ at the invert of the Thames Tunnel.
3.3.3 The predicted tunnel-induced ground movements in the x, y and z-directions at the asset location were generated on MathCAD.
3.3.4 From the predicted ground movements, the following impact assessments were undertaken on both the Crossrail Eastbound and Westbound running tunnels:
Track Geometry and Induced Shear Stress
An assessment of the track geometry has been undertaken and includes a check on the vertical profile and track twist. No stiffening effect of the existing structures has been considered and therefore the movement predictions are solely based on the “Ribbon Sink” trough assumptions.
In addition, a check on the track twist induced shear stresses has also been undertaken. Higher rates of rotation are analogous to higher torsional stresses in the slab. The torsional stress has been calculated using the rate of change of rotation and by assuming that the track slab is a simple rectangular beam.
The limit criteria have been based on the values set out in Network Rail Track Geometry and Gauge Clearance (Network Rail, 2009). The assessment assumes that the Crossrail speed range is 100 kph (62.1 mph) along this section of the crossing.
TU021 Crossrail – Assessment Report
TU021 Crossrail Line 1 Page 12 Printed 01/12/2011
Table 3: Network Rail limits for track vertical profile and track twist (Network Rail, 2009)
Atkins notes that the criteria set out in Tables 2 and 3 assume perfect existing track geometries. If the Crossrail tracks are in place prior to the Thames Tunnel TBM entering the zone of influence, then a Clearance and Track Survey will be undertaken to confirm the track geometry. If a clearance concession is required then all other avenues will need to be explored. The condition of the track will inform the track movement trigger levels.
Figure 3: Illustration of longitudinal and transverse assessment
TU021 Crossrail – Assessment Report
TU021 Crossrail Line 1 Page 13 Printed 01/12/2011
Longitudinal Assessment of Crossrail tunnels
The longitudinal behaviour of the Crossrail tunnels caused by the transverse settlement trough of the Thames Tunnel has been assessed by calculating the sub-surface movements from bored tunnels using the semi-empirical “Ribbon Sink” method (New & Bowers, 1994). Skew of the tunnel crossing and dip of the Crossrail tunnel alignment have also been taken into account.
The longitudinal tensile strains (combined axial tensile and bending) in the circle bolts and in the skin are calculated by apportioning strains based on the respective relative stiffness. This is done by distributing strains based on the stiffness of a jointed model to the stiffness of a monolithic model. The flow chart below is an indication of the calculation method adopted.
From the resultant longitudinal tensile strains in the circle bolts, an equivalent joint opening has been calculated. A check is also undertaken to determine the effect of the induced tensile stresses in the concrete lining.
Figure 4: Calculation flow chart for longitudinal strain assessment
Calculate „instantaneous‟ radius of curvature from Greenfield assessment
Calculate rotation of joint (for 1.6m segment width) from Greenfield assessment
Calculate bending moments at joint Calculate rotational stiffness of joint
Calculate equivalent EI for jointed system from Engineers‟ Bending Theory
Calculate EI from monolithic structure
Apportion strains based on jointed-to-monolithic structure
TU021 Crossrail – Assessment Report
TU021 Crossrail Line 1 Page 14 Printed 01/12/2011
Transverse Assessment of Crossrail tunnels
The transverse assessment of the Crossrail running tunnels caused by the longitudinal settlement trough of the Thames Tunnel is detailed in this section.
An initial assessment of the in-situ earth pressure on the tunnel cross section in the existing condition was undertaken based on the closed form solution proposed by Duddeck and Erdmann (Duddeck & Erdmann, 1985) to obtain bending moments and hoop forces. A coefficient of earth pressure (horizontal-to-vertical), khv, of 0.50 has been used in the analysis. The analysis considers both full bonding between lining and ground, and with tangential slip along the lining.
An assessment of the transverse related distortion of the tunnel has been undertaken, caused by the longitudinal cumulative probability S-curve related ground movements as the construction of the Thames Tunnel progresses beneath the Crossrail running tunnels. In order to obtain a comprehensive understanding of the distorted shape of the Crossrail tunnels, the transient effects as the Thames Tunnel passes beneath and ground movements were calculated for a number of points on the tunnel perimeter. The maximum (and transitory) distortion of the tunnel occurs on a diagonal axis as the new tunnel passes beneath the assessed tunnel.
A birds-mouthing assessment of the segmental concrete lining was undertaken by assuming an elliptical deformation of the tunnel. To account for a certain degree of construction (as-built) tolerance, a diametric deviation of 50mm was assumed in the calculations (Crossrail Ltd, 2011), resulting in the presence of some inherent joint rotation immediately after the rings have been erected. By applying a deformation and resulting joint rotation, the increase in joint rotation was determined when distortion due to Crossrail construction tolerance and Thames Tunnel construction is applied. This assessment has been undertaken without consideration of the beneficial effects of the radial spear bolts.
It is our understanding that the Crossrail bored tunnel linings have been designed using finite element analytical substantiation. Whilst this preliminary assessment focuses on the serviceability effects of joint rotation, only the increases in birdsmouthing angle at the radial joints due to Thames Tunnel construction have been presented in this report for the purpose of obtaining Approval in Principle (AiP) for planning purposes.
The eccentricity of the bearing stresses on the radial joint was also calculated and a corresponding moment was obtained. These results are plotted on an M-N diagram to verify that they are within the capacity of the tunnel lining.
TU021 Crossrail – Assessment Report
TU021 Crossrail Line 1 Page 15 Printed 01/12/2011
The capacity of the steel fibre reinforced concrete (SFRC) segments has been checked in accordance with the RILEM σ-ε design method for SFRC (RILEM, 2003). The table below presents the material properties of the concrete segments used in the assessment:
The Young‟s Modulus value assumed for this assessment has been taken as a long term stiffness value.
TU021 Crossrail – Assessment Report
TU021 Crossrail Line 1 Page 16 Printed 01/12/2011
3.4 Ground Movement Results and Impact Assessment
3.4.1 The sub-surface ground movements and trough widths along the alignments of the Crossrail Westbound and Eastbound running tunnels are presented in Appendix C.
3.4.2 The results of the assessments for both the Crossrail Westbound and Eastbound running tunnels are summarised in the table below:
Table of Results
Part 1: Track Geometry Westbound Tunnel Eastbound Tunnel
Maximum settlement 17.2 mm “No Mandated Action”
17.3 mm “No Mandated Action”
Trough width (2 x 3 K z) 74.7 m 74.3 m
Min radius of curvature Sagging
13.68 km
Hogging
29.87 km
Sagging
14.50 km
Hogging
31.64 km
Max gradient of
transverse curve
1:1471 1:1510
Track Twist (per 3m) 0.12 mm “No Mandated Action” 0.12 mm “No Mandated
Action”
Part 2: Longitudinal Assessment
Max tensile strain (instantaneous)
494με 427με
Max tensile strain in segment
(based on 1.6m segments)
0.3με 0.3με
Max tensile strain in joint
(based on 1.6m segments)
494με 467με
Max opening of circle joint 0.79 mm 0.75 mm
Part 3: Transverse Assessment
Max diametric distortion due solely to TT construction
4.1 mm 4.1 mm
Birdsmouth angle at radial joint
Due to CRL tolerance 0.93o (3.4mm) 0.93o (3.4mm)
Due to CRL tolerance + Thames Tunnel construction
1.01o (3.8mm) 1.01o (3.8mm)
Table 5: Summary of Results
TU021 Crossrail – Assessment Report
TU021 Crossrail Line 1 Page 17 Printed 01/12/2011
3.4.3 On the Westbound running tunnel, the maximum predicted „Greenfield‟ settlement is 17.2, the settlement trough width (6 K z) is approximately 74.7m and the corresponding maximum instantaneous gradient is 0.68mm/m (1:1471). On the Eastbound running tunnel, the maximum predicted „Greenfield‟ settlement is 17.3mm, the settlement trough width (6 K z) is approximately 74.3m and the corresponding maximum instantaneous gradient is 0.66 mm/m (1:1510). The predicted settlement falls into the „No Mandated Action‟ category based on design criteria figures in Table 3.
3.4.4 In the longitudinal assessment of the Crossrail running tunnels, the assessment indicates that the maximum circumferential joint opening at the crown/invert is 0.79mm and 0.75mm in the Westbound and Eastbound running tunnels respectively. These values are caused solely by Thames Tunnel construction.
3.4.5 In the transverse assessment of the Crossrail running tunnels, the maximum distortion of the tunnel rings occurs on a diagonal axis as the Thames Tunnel passes beneath. The maximum diametric distortion due solely to Thames Tunnel construction is approximately 4.1mm on both the Westbound and Eastbound running tunnels.
3.4.6 The birdsmouth analysis indicates that, on the Westbound and Eastbound running tunnels, the radial joint opening is approximately 0.93o or 3.4mm when subjected to Crossrail construction tolerance and 1.01o or 3.8mm when the additional effects of Thames Tunnel construction are taken into account. This is equivalent to an increase of approximately 10% or 0.4mm solely due to Thames Tunnel construction.
3.4.7 Given the geometry of the convex-convex radial joints of the Crossrail segments, it has been determined that at these values of birdsmouth opening (for both cases before and after Thames Tunnel construction), the radial joints have a reduced bearing area as a consequence of hinging about the segment edge. This assessment is based solely on contact mechanics between cylinders assuming elastic behaviour of the concrete radial joints, without accounting for non-linear material behaviour such as elasto-plasticity or development of cracks.
3.4.8 As noted in Section 3.3.4, an analysis of the bearing and bursting stresses in the Crossrail tunnel segments have not been undertaken in this damage assessment. Whilst it is our understanding that the Crossrail bored tunnel linings have been designed using finite element analytical methods, we believe that the analytical methods carried out in accordance to the current scope of works for Thames Tunnel are sufficient to gain AIP for planning unless otherwise directed.
3.4.9 It should also be noted that the transverse effect is a transitory condition as the TBM face passes beneath the crossing and assumes that the tunnel deforms to the shape of the settlement trough without any consideration of soil-structure interaction.
TU021 Crossrail – Assessment Report
TU021 Crossrail Line 1 Page 18 Printed 01/12/2011
3.4.10 The loads on the tunnel lining from the transverse analysis (for in-situ condition and birds-mouth effect) are within the section capacity and are presented in the figure below:
where W/B and E/B refer to the Westbound and Eastbound running tunnels respectively, and 1.0 and 1.4 are partial load factors applied to the axial force (F) and bending moments (M).
Crossrail : SFRC M-N Diagram for Induced Birdsmouth
Bending Moments (kNm)
Ax
ial F
orc
e (k
N)
TU021 Crossrail – Assessment Report
TU021 Crossrail Line 1 Page 19 Printed 01/12/2011
4 Conclusion
4.1.1 The impact assessments of the potential damage to the Crossrail running tunnels which have been undertaken include an analysis of the ground movement effects on the track geometry, as well as longitudinal and transverse assessments of the Crossrail tunnel structure.
4.1.2 Based on the results of the assessment, the damage impact of the construction of the Thames Tunnel on the Crossrail running tunnels is within the acceptance criteria adopted for the ground movement effects on the track geometry. The settlement assessment indicates that the predicted track settlements, based on conservative assumptions, are within the „No Mandated Action‟ criteria according to the Network Rail limits for track vertical profile.
4.1.3 The longitudinal damage assessment indicates that the maximum circumferential joint opening is small (less than 1mm). In the transverse assessment, the results indicate that the increase in radial joint opening due to birdsmouthing is approximately 10%, solely caused by Thames Tunnel construction.
4.1.4 Atkins recommends that monitoring of the Crossrail running tunnels prior, during and after the construction of the Thames Tunnel should be undertaken. If an increase in water ingress into the tunnel is noted, caulking at these locations could be used to manage any significant inflow.
4.1.5 Atkins also recommends that the appointed contractor of Thames Tunnel should undertake a pre-construction survey prior to construction of the Thames Tunnel. If, at the time of the pre-construction survey, Crossrail have a contemporary Clearance and Track survey and information on the circularity („squat‟) geometry of the existing tunnel for this section of the line, we recommend that this is used.
TU021 Crossrail – Assessment Report
TU021 Crossrail Line 1 Page 20 Printed 01/12/2011
5 Bibliography
Atkins. List of assumptions for Crossrail Line 1 - Thames Tunnel Assessment (Approved by TT). Atkins, London. Rev 02 (2011). British Standard. BS8110-1-1997: Structural use of concrete - code of practice or design and construction. BS8100-1:1997 (1997). Crossrail Ltd. 6.2m ID Standard Precast Concrete (PCC) Lining Segment Details. Crossrail Ltd, London. C122-OVE-C4-DDD-CR001_Z-23160 (2011). Crossrail Ltd. Crossrail response to Atkins RFI 315-OQ-TPI-TU000-000017. Section KT 10 (KT10.4219) (2011). Crossrail Ltd. Crossrail Running Tunnel Alignment (Limehouse). Crossrail, London. CRL1-XRL-R4-DMA-CR142_Z-00001 (2011). Duddeck, H. & Erdmann, J. On Structural Design Models for Tunnels in Soft Soil. vol 9 (1985). Eurocode 2. Design of concrete structures. General rules and rules for buildings.. BS EN 1992-1-2004 (1992). Guyon, Y. Limit State Design of Prestressed Concrete. (1972). Moss, N.A. & Bowers, K.H. The effect of new tunnel construction under existing metro tunnels. Proceedings of the 5th International Symposium TC28 (2005). Network Rail. Inspection and Maintenance of Permanent Way - Track Geometry and Gauge Clearance. Network Rail, London. NR/L2/TRK/001/C01 (2009). New, B. & Bowers, K. Ground movement validation at the Heathrow Express Trial Tunnel. Tunnelling '94 - Chapman & Hall, London. (1994). O'Reilly, M.P. & New, B.M. Settlement above Tunnels in the United Kingdom - Their Magnitude and Prediction. (1982). RILEM. Test and design methods for steel fibre reinforced concrete. σ-ε design method - Final Recommendation. RILEM TC 162-TDF (2003). Thames Water Utilities Ltd. Crossrail Line 1 interface with Thames Tunnel. (2011).
Appendices
TU021 Crossrail Line 1 Printed 01/12/2011
Appendices
Appendix A Drawings
A.1.1 Sketch and archive drawings
Appendix B Geology
B.1.1 Geological information at the Thames Tunnel – Crossrail Crossing
Appendix C Extract of Assessment Calculations
C.1.1 Graphical output of impact assessment calculations
Appendix D List of Assumptions
D.1.1 List of assumptions for Crossrail Line 1 – Thames Tunnel Assessment (approved by Thames Tunnel)
Appendix E Transverse Cross-section Movements
E.1.1 Cross-section distortion analysis as requested by Crossrail to investigate the systems tolerance between the top of rail and overhead line conductor
Appendix F Technical Note on Settlement Parameters in Chalk
F.1.1 Literature review of documented case studies of tunnel construction in Chalk
CH2M HILL accept no responsibility for any circumstances,which arise from the reproduction of this map after alteration,amendment or abbreviation or if it issued in part or issuedincomplete in any way.
The Point, 7th Floor,37 North Wharf Road,Paddington, London W2 1AF
Thames Water Utilities
This is an indicative working draft plan which has been produced for the purpose of confidential discussions only. Accordingly, the draft plan must not be copied, distributed or shown to any third party without the express written permission of Thames Water Utilities Limited. It provides an indication of sites that, following discussions with local authoritiesand other stakeholders, may be confirmed as being on the shortlist of construction sites for the proposed Thames Tunnel. Inclusion of a site on this draft plan should not be taken to mean that such site will be selected as a construction site to form part of the Thames Tunnel scheme.
PROJECT REF: TU021 LOCATION: London (Section: Along Thames Tunnel) CLIENT: THAMES TIDEWAY
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TITLE: TU021 - Crossrail Line 1 Tunnel
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ENGINEER: RA
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Chalk
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Thanet Sand
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Lambeth Group
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Harwich Formation
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London Clay
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Terrace Gravels
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Made Ground
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Appendices
TU021 Crossrail Line 1 Printed 01/12/2011
Appendix C
Project: Thames Tunnel Job ref5100812
Part of structure: TU021 Crossrail Line 1 W/B Calc sheet no rev4 AB
Calc ref Calc by Date Check by Date002 MY 16-11-2011
Ref Calculations Output
Greenfield Settlement, Radius of Curvature & Longitudinal StrainsReferences:1. Settlements above tunnel in the United Kingdom - their magnitude and prediction; O'Reilly MP, New BM; Tunneling '82; p.173-1812. " Tunneling in Soil" Ground Movements and their Effects on Structures., P.B.Atwell, R.K. Taylor, eds., Surrey University Press, Champman and Hall, New York, NY, 133-2153. Crossrail Line 1, Interface with Proposed Thames Tunnel, 100-DA-TPI-TU021-810000-AA
CROSSRAIL WESTBOUND TUNNEL
[3] Plan Angle between CRL Tunnel and Thames Tunnel β 56deg
[3] Gradient of CRL Tunnel Gradient 1.0%
Slope α atan Gradient( )
[3] External Diameter of Thames Tunnel Dext 8800mm
[4] Volume loss (%) VL 0.90%
[4] Trough width parameter K 0.5
[3] Invert Level of CRL Tunnel (mATD) ILCT 68.0268m
[3] Invert Level of Thames Tunnel (mATD) ILTT 43.127m ILTT 43.127 m
Depth to Thames Tunnel Invert(from CRL Tunnel Invert)
z ILCT ILTT 24.90 m
Volume loss Vs VL πDext
2
2
Vs 0.547 m2
Plan Section
Output:
S(x,y,z) : The settlement of each point
U(x,y,z) : The x direction-displacement of each point
V(x,y,z) : The y direction-displacement of each point
[1,2] s x y z( )Vs
Dext1 cnorm
x
K z
cnorm2y Dext
2 K z( )
cnorm2y Dext
2 K z( )
u x y z( )Vs K
Dext 2πexp
x( )2
2 K z( )2
cnorm2y Dext
2 K z( )
cnorm2y Dext
2 K z( )
v x y z( )Vs K
Dext 2πcnorm
x
K z
1
exp2y Dext( )
2
8 K z( )2
exp2y Dext( )
2
8 K z( )2
Minimum Radius of Curvature
Calculates minimum radius of curvature (long term) by tracking 3 consecutive points
Setting out calculation points
ystart 6 K z yend ystart calculation length lcalc 10mm
intervalyend ystart lcalc sin β( )
interval 18020.75 i 0 interval Yi
ystart i lcalc sin β( )
xstart
ystart
tan β( ) xstart 50.39 m xend
yend
tan β( ) xend 50.39 m
xinterval
xstart xend
interval X
ixstart i xinterval 500m The -500m considers long term settlement
when settlement trough has fully developed
zstart z ystart tan α( ) zstart 25.65 m zend z yend tan α( ) zend 24.15 m
zinterval
zstart zend
interval Z
izstart i zinterval
Si
s Xi
Yi
Zi
Ui
u Xi
Yi
Zi
Vi
v Xi
Yi
Zi
100 80 60 40 20 0 20 40 60 80 10010
5
0
5
10
15
20
Si
mm
Ui
mm
Vi
mm
Yi
m
Max settlement
max S( ) 17.18 mm
Bending Strains
Note:
lcalc is the distance between calculation points. Set this to very small to calculate instantaneous curvature.
H is the vertical offset between three consecutive calculation points.
From similar triangles, the rotation of the alignment over the three points is 2 γi
Assuming lcalc = lhor, the half angle of rotation γi can be calculated.The sensitivity of this assumption has
been checked and is considered negligible wrt H.
The radius of curvature Radi is then calculated from geometry.
External diameter of CRL tunnel DE 6.8m DE 6.800 m
εbending_hogging
DE
Minhogging
0.000228εbending_sagging
DE
Minsagging
0.000497
εbendingi
DE
Radi
Axial Strains
Xfi
Xi
Ui
Yfi
Yi
Vi
Zfi
Zi
Si
Lfi
Lfi
Zfi
Zfi 1
2 Xfi
Xfi 1
2 Yfi
Yfi 1
2 1 i interval 1if
Lfi
1 1010
m otherwise
Lfi
Li
Li
Zi
Zi 1 2 X
iX
i 1 2 Yi
Yi 1 2 1 i interval 1if
Li
1 1010
m otherwise
Li
Compression Tension
εaxiali
Li
Lfi
Li
max εaxial 0.000455 min εaxial 0.000211
Combined Strains
Reduction Factor for axial tensile strains RF 0.20
εtotali
εtotali
εbendingi
RF εaxiali
εaxiali
0if
εtotali
εbendingi
otherwise
εtotali
100 50 0 50 1006 10
4
4 104
2 104
0
2 104
4 104
6 104
εtotali
εaxiali
εbendingi
Yi
mMaxstrain min εtotal 497.0 10
6
Project: Thames Tunnel Job ref5100812
Part of structure: TU021 Crossrail Line 1 E/B Calc sheet no rev4 AB
Calc ref Calc by Date Check by Date012 MY 16-11-2011
Ref Calculations Output
Greenfield Settlement, Radius of Curvature & Longitudinal StrainsReferences:1. Settlements above tunnel in the United Kingdom - their magnitude and prediction; O'Reilly MP, New BM; Tunneling '82; p.173-1812. " Tunneling in Soil" Ground Movements and their Effects on Structures., P.B.Atwell, R.K. Taylor, eds., Surrey University Press, Champman and Hall, New York, NY, 133-2153. Crossrail Line 1, Interface with Proposed Thames Tunnel, 100-DA-TPI-TU021-810000-AA
CROSSRAIL EASTBOUND TUNNEL
[3] Plan Angle between CRL Tunnel and Thames Tunnel β 53deg
[3] Gradient of CRL Tunnel Gradient 1.0%
Slope α atan Gradient( )
[3] External Diameter of Thames Tunnel Dext 8800mm
[4] Volume loss (%) VL 0.90%
[4] Trough width parameter K 0.5
[3] Invert Level of CRL Tunnel (mATD) ILCT 67.8393m
[3] Invert Level of Thames Tunnel (mATD) ILTT 43.0862m ILTT 43.086 m
Depth to Thames Tunnel Invert(from CRL Tunnel Invert)
z ILCT ILTT 24.75 m
Volume loss Vs VL πDext
2
2
Vs 0.547 m2
Plan Section
Output:
S(x,y,z) : The settlement of each point
U(x,y,z) : The x direction-displacement of each point
V(x,y,z) : The y direction-displacement of each point
[1,2] s x y z( )Vs
Dext1 cnorm
x
K z
cnorm2y Dext
2 K z( )
cnorm2y Dext
2 K z( )
u x y z( )Vs K
Dext 2πexp
x( )2
2 K z( )2
cnorm2y Dext
2 K z( )
cnorm2y Dext
2 K z( )
v x y z( )Vs K
Dext 2πcnorm
x
K z
1
exp2y Dext( )
2
8 K z( )2
exp2y Dext( )
2
8 K z( )2
Minimum Radius of Curvature
Calculates Minimum radius of curvature (long term) by tracking 3 consecutive points
Setting out calculation points
ystart 6 K z yend ystart calculation length lcalc 10mm
intervalyend ystart lcalc sin β( )
interval 18596.54 i 0 interval Yi
ystart i lcalc sin β( )
xstart
ystart
tan β( ) xstart 55.96 m xend
yend
tan β( ) xend 55.96 m
xinterval
xstart xend
interval X
ixstart i xinterval 500m The -500m considers long term settlement
when settlement trough has fully developed
zstart z ystart tan α( ) zstart 25.50 m zend z yend tan α( ) zend 24.01 m
zinterval
zstart zend
interval Z
izstart i zinterval
Si
s Xi
Yi
Zi
Ui
u Xi
Yi
Zi
Vi
v Xi
Yi
Zi
100 50 0 50 10010
0
10
20
Si
mm
Ui
mm
Vi
mm
Yi
m
Max settlement
max S( ) 17.28 mm
Bending Strains
Note:
lcalc is the distance between calculation points. Set this to very small to calculate instantaneous curvature.
H is the vertical offset between three consecutive calculation points.
From similar triangles, the rotation of the alignment over the three points is 2 γi
Assuming lcalc = lhor, the half angle of rotation γi can be calculated.The sensitivity of this assumption has
been checked and is considered negligible wrt H.
The radius of curvature Radi is then calculated from geometry.
Subject: List of Assumptions for Crossrail Line 1 – Thames Tunnel Assessment
In order to undertake a damage assessment of Crossrail Line 1 due to the construction of Thames Tunnel, the following assumptions are proposed owing to the lack of detailed information received to date:
Item No. Description Assumption
1 Level of Crossrail Eastbound running tunnel - Information received from CRL gives chainage and proposed rail levels in
section – but no chainage makers on plan (Dwg No. CRL1-XRL-R4-DMA-CR142_Z-00001). Insufficient information.
- LTTDT Doc Ref: 315-OQ-TPI-TU000-000017 (15 July 2011) states that
“An updated CAD Crossrail route plan & profile for the tunnels in the vicinity is being updated to include chainages and cross-passage details in profile”
Assume level of Crossrail Eastbound running tunnel is the same as Westbound running tunnel, ie CRL invert extrados 67.350mATD. Thames Tunnel (Alignment AH) levels:
The location of the section cut at the intersection point is based on the drawing provided by Thames Tunnel (Dwg No. 100-DA-TU021-810000)
2 Dimensions of Crossrail running tunnel - Atkins have so far only received information (LTTDT Doc Ref: 315-OQ-TPI-
TU000-000017) on the key segments and radial/circle joint detail from CRL (Dwg No. C122-OVE-C4-DDD-CR001_Z-23160, 161 & 163). These drawings do not give specific information on internal/external diameter of CRL tunnels, segment type, no. of segments per ring, length of ring etc at the location of crossing.
Assume the CRL running tunnels at the location of crossing have the following dimensions:
- I.D. = 6200mm - O.D. = 6800mm - No of segments/ring = 7 segments + 1 key - Length of ring = 1600mm - No. of circle bolts/ring = 22 - No. of radial bolts/segment = 2
3 Properties of concrete segments & reinforcement - No information available on concrete properties (Young’s modulus, poisson
ratio) or reinforcement details
Assume segmental concrete lining has the following properties:
- Young’s Modulus = 16000 N/mm2
Memo
Assumptions for TU021 Assessment (IT)_15.07.2011.docx
Item No. Description Assumption
- Poisson Ratio of concrete =0.30 - Assume steel fibre reinforced segments - The characteristic flexural strength of the concrete at the
limit of proportionality (LOP) is assumed to be 5.0 MPa when tested in accordance with BS EN 14651. This Standard describes the method of calculating the flexural tensile strength of steel fibre reinforced concrete (SFRC) and in accordance with RILEM. The method provides for the determination of the LOP and of a set of residual flexural tensile strength values;
- The characteristic residual flexural tensile strength, as defined by a crack mouth opening displacement (CMOD) of 0.5mm, (fR1) is assumed to be 4.8 MPa;
- The characteristic residual flexural tensile strength, as defined by a crack mouth opening displacement (CMOD) of 3.5mm, (fR4) is assumed to be 3.4 MPa
4 Radial Joint Connection – Properties of bolt - Strength (Class) of bolts unknown - From Dwg No C122-OVE-C4-DDD-CR001_Z-23160, bolts are M24 coarse
5 Longitudinal Joint connections - Information provided in C122-OVE-C$-DDD-CR001_Z-23160 indicates that
plastic dowel connector to be proposed by contractor. Insufficient information.
Assume flat circumferential joints with 3No. plastic dowel Assume Bucklock (or similar) connectors to longitudinal joints http://www.buchanconcrete.com/pdf/BCS_BUCLOCK.pdf
6 Gasket tolerance and movements - Information provided in LTTDT Doc Ref: 315-OQ-TPI-TU000-000017 but
information on material properties is insufficient.
Assumption about tolerance of gaskets to movements - assume the same compression curve as is used in the Bucklock brochure http://www.buchanconcrete.com/pdf/BCS_BUCLOCK.pdf
7 Assessment criteria for track geometry, twist, cant limits - As the Crossrail tunnels are not in operation, there are no assessment
criteria standards. - Atkins have requested from CRL the track performance requirements, but
have yet to receive them as promised.
Assume track geometry, twist and cant limits based on Network Rail Geometry and Gauge Clearance (NR/L2/TRK/001/C01)
8 Fire mains or the catenaries No information on requirements of performance provided therefore a check will not be undertaken.
Assumptions for TU021 Assessment (IT)_15.07.2011.docx
Item No. Description Assumption
9 Geology Assumptions on geology based on geological desk study and verified against Thames Tunnel assumed geological cross section
10 Internal structures within tunnel Assume internal features within the tunnel do not significantly affect the stiffness of the tunnel for assessment purposes. (see description for Item No 11)
11 Cross passages - LTTDT Doc Ref: 315-OQ-TPI-TU000-000017 (15th July 2011) states that
“There are no shafts in the vicinity; Cross passage 10 is nearby at approx. Chainage 12580 Eastbound. (evident on the CAD drawing that you have already received)”
Atkins will verify if Cross Passage 10 is within the zone of influence of the assessment to determine if assessment of the cross passage is required. .
Appendices
TU021 Crossrail Line 1 Printed 01/12/2011
Appendix E
Technical note on Transverse Movements Rev 2.docx
Technical note
Project: Thames Tideway To: Crossrail
Subject: Response to Comment
- 'Regarding Volume loss'
From: Michael Yap
Date: 25 Nov 2011 cc:
Following the submission of the Damage Impact Assessment of Crossrail Line 1 (Limehouse Basin) due to
the construction of Thames Tideway, Crossrail raised the issue regarding the systems tolerance between the
top of rail and the overhead line conductor, which is particularly sensitive to distortion once installed
(Crossrail, 2011). Discussions with Crossrail have indicated that further work on the prediction of the cross
section distortion of the Crossrail tunnel is required to address this issue, hence the purpose of this technical
note.
Method of Assessment
The same semi-empirical method of ground movement prediction (New & Bowers, 1994) and parameters as
described in the Design Report (Thames Tunnel, 2011) has been adopted in this analysis (VL=0.9% and k-
0.50). The transverse related distortion of the tunnel is assessed by tracking the 3D ground movements of a
number of points on the Crossrail tunnel extrados, taking into account the angle of skew of the crossing.
By monitoring a series of points on the perimeter of the tunnel, the following assessments have been
undertaken:
Assessment of the predicted deformed cross-section shape of the Crossrail tunnel
Gross bulk movement of each point on the perimeter of the tunnel extrados, which gives the
resultant vertical and horizontal movements on each point subjected to Thames Tunnel ground
movements
Net movement of each point on the perimeter of the tunnel extrados, where the net movement is the
difference between the gross bulk movement and the averaged movement at a point on the centre of
the tunnel
Crossrail Eastbound
Crossrail Westbound
Thames Tunnel
+ve V
+ve U -60m
+60m 53o
Figure 1: Sign convention for graphical output in Figure 2
Technical note on Transverse Movements Rev 2.docx
Technical note
Vertical and horizontal movement plots of the Crossrail tunnel extrados are presented in the results section.
Four cross sections have been analysed, 8m apart from the point of crossing. (ie. Y = 0m, 8m, 16m and
24m). This is to take into account the effects of the lateral displacements and to enable the results to be
extrapolated, once the systems of the OLE and spacing of the centenary equipments have been determined.
Figure 2: Ground movement predictions along Crossrail Eastbound
It should be noted that this assessment is based solely on the assumption that the Crossrail tunnel lining
deforms to the shape of the predicted ground movement profile, without any consideration of soil-structure
interaction. The ground is also assumed to behave in an elastic manner, and deformations considered are
caused by the Thames Tunnel with a fully developed settlement trough after the TBM face has passed. The
transient effects of the TBM advance have not been considered in the analysis. Although maximum
distortions could occur in this transient phase as the settlement trough develops, this effect is temporal
based on the assumptions set out above.
60 50 40 30 20 10 0 10 20 30 40 50 6020
15
10
5
0
5
10
SAi
mm
UAi
mm
VAi
mm
8 16
Yploti
24 0
Technical note on Transverse Movements Rev 2.docx
Technical note Deformed Cross-Section Shape of Crossrail Tunnel
– Magnification x100 on both vertical and horizontal movements
4 2 0 2 46
4
2
0
2
4
Distorted Shape
Distorted Shape
Original Crossrail Tunnel
Original Crossrail Tunnel
4 2 0 2 46
4
2
0
2
4
Distorted Shape
Distorted Shape
Original Crossrail Tunnel
Original Crossrail Tunnel
4 2 0 2 46
4
2
0
2
4
Distorted Shape
Distorted Shape
Original Crossrail Tunnel
Original Crossrail Tunnel
Min diametric distortion -2.48mm
Ma
x d
iam
etr
ic
dis
tort
ion +
3.6
2m
m
Min diametric distortion -2.54mm
Max diametric distortion 3.46mm
Figure1b: Deformed shape of Crossrail Tunnel at Y = 8m
Figure1a: Deformed shape of Crossrail Tunnel at Y = 0m
Technical note on Transverse Movements Rev 2.docx
Technical note
– Magnification x100 on both vertical and horizontal movements
4 2 0 2 46
4
2
0
2
4
Distorted Shape
Distorted Shape
Original Crossrail Tunnel
Original Crossrail Tunnel
4 2 0 2 46
4
2
0
2
4
Distorted Shape
Distorted Shape
Original Crossrail Tunnel
Original Crossrail Tunnel
4 2 0 2 46
4
2
0
2
4
Distorted Shape
Distorted Shape
Original Crossrail Tunnel
Original Crossrail Tunnel
Figure1c: Deformed shape of Crossrail Tunnel at Y = 16m
Max diametric distortion +3.17mm
Min diametric distortion -2.60mm
Figure1d: Deformed shape of Crossrail Tunnel at Y = 24m
Min diametric distortion -2.88mm
Max diametric distortion +2.96mm
Technical note on Transverse Movements Rev 2.docx
Technical note Bulk Movement of Perimeter Points on Crossrail Tunnel
– Magnification x100 on both vertical and horizontal movements
4 2 0 2 46
4
2
0
2
4
Bulk Vertical Movement
Bulk Vertical Movement
Bulk Horizontal Displacement
Bulk Horizontal Displacement
Tunnel Extrados
Tunnel Extrados
4 2 0 2 46
4
2
0
2
4
Bulk Vertical Movement
Bulk Vertical Movement
Bulk Horizontal Displacement
Bulk Horizontal Displacement
Tunnel Extrados
Tunnel Extrados
4 2 0 2 46
4
2
0
2
4
Bulk Vertical Movement
Bulk Vertical Movement
Bulk Horizontal Displacement
Bulk Horizontal Displacement
Tunnel Extrados
Tunnel Extrados
-13
.66
mm
-13
.71
mm
-13
.85
mm
-14
.15
mm
-14
.65
mm
-15
.38
mm
-16
.24
mm
-16
.98
mm
-17
.28
mm
-16
.98
mm
-16
.24
mm
-15
.38
mm
-14
.65
mm
-14
.15
mm
-13
.85
mm
-13
.71
mm
Figure2a: Bulk movement of perimeter points at Y = 0m
Figure2b: Bulk movement of perimeter points at Y = 8m
0.00 mm
-0.40 mm
-0.77 mm
-1.06 mm
-1.24 mm
-1.26 mm
-1.06 mm
-0.61 mm
0.00 mm
0.61 mm
1.06 mm
1.26 mm
1.24 mm
1.06 mm
0.77 mm
0.40 mm
-1.17 mm
-1.52 mm
-1.84 mm
-2.11 mm
-2.32 mm
-2.44 mm
-2.43 mm
-2.22 mm
-1.80 mm
-1.24 mm
-0.71 mm
-0.36 mm
-0.23 mm
-0.30 mm
-0.51 mm
-0.82 mm
-13
.06
mm
-12
.70
mm
-12
.46
mm
-12
.38
mm
-12
.58
mm
-13
.11
mm
-14
.00
mm
-15
.10
mm
-16
.07
mm
-16
.56
mm
-16
.46
mm
-15
.93
mm
-15
.25
mm
-14
.58
mm
-13
.99
mm
-13
.49
mm
Technical note on Transverse Movements Rev 2.docx
Technical note
– Magnification x100 on both vertical and horizontal movements
4 2 0 2 46
4
2
0
2
4
Bulk Vertical Movement
Bulk Vertical Movement
Bulk Horizontal Displacement
Bulk Horizontal Displacement
Tunnel Extrados
Tunnel Extrados
4 2 0 2 46
4
2
0
2
4
Bulk Vertical Movement
Bulk Vertical Movement
Bulk Horizontal Displacement
Bulk Horizontal Displacement
Tunnel Extrados
Tunnel Extrados
4 2 0 2 46
4
2
0
2
4
Bulk Vertical Movement
Bulk Vertical Movement
Bulk Horizontal Displacement
Bulk Horizontal Displacement
Tunnel Extrados
Tunnel Extrados
Figure2c: Bulk movement of perimeter points at Y = 16m
Figure2d: Bulk movement of perimeter points at Y = 24m
-11
.40
mm
-10
.74
mm
-10
.17
mm
-9.7
7 m
m
-9.6
4 m
m
-9.8
7 m
m
-10
.56
mm
-11
.65
mm
-12
.93
mm
-14
.02
mm
-14
.59
mm
-14
.58
mm
-14
.16
mm
-13
.53
mm
-12
.83
mm
-12
.10
mm
-2.04 mm
-2.25 mm
-2.44 mm
-2.60 mm
-2.74 mm
-2.86 mm
-2.97 mm
-3.01 mm
-2.90 mm
-2.61 mm
-2.21 mm
-1.84 mm
-1.62 mm
-1.57 mm
-1.65 mm
-1.83 mm
-9.0
8 m
m
-8.2
7 m
m
-7.5
4 m
m
-6.9
5 m
m
-6.5
9 m
m
-6.5
7 m
m
-6.9
6 m
m
-7.7
9 m
m
-8.9
9 m
m
-10
.29
mm
-11
.30
mm
-11
.79
mm
-11
.75
mm
-11
.33
mm
-10
.68
mm
-9.9
0 m
m
-2.44 mm
-2.48 mm
-2.50 mm
-2.51 mm
-2.53 mm
-2.59 mm
-2.71 mm
-2.88 mm
-3.03 mm
-3.06 mm
-2.93 mm
-2.72 mm
-2.52 mm
-2.40 mm
-2.36 mm
-2.39 mm
Technical note on Transverse Movements Rev 2.docx
Technical note Net movement of Perimeter Points on Crossrail Tunnel
– Magnification x200 on both vertical and horizontal movements
4 2 0 2 4
4
2
0
2
4
Net Vertical Movement
Net Vertical Movement
Net Horizontal Displacement
Net Horizontal Displacement
Tunnel Extrados
Tunnel Extrados
4 2 0 2 4
4
2
0
2
4
Net Vertical Movement
Net Vertical Movement
Net Horizontal Displacement
Net Horizontal Displacement
Tunnel Extrados
Tunnel Extrados
4 2 0 2 4
4
2
0
2
4
Net Vertical Movement
Net Vertical Movement
Net Horizontal Displacement
Net Horizontal Displacement
Tunnel Extrados
Tunnel Extrados
Figure3a: Net movement of perimeter points at Y = 0m
Figure3b: Net movement of perimeter points at Y = 8m
1.3
9 m
m
1.3
5 m
m
1.2
0 m
m
0.9
0 m
m
0.4
0 m
m
-0.3
2 m
m
-1.1
8 m
m
-1.9
3 m
m
-2.2
3 m
m
-1.9
3 m
m -1
.18
mm
-0.3
2 m
m
0.4
0 m
m
0.9
0 m
m
1.2
0 m
m 1.3
5 m
m
0.00 mm
-0.40 mm
-0.77 mm
-1.06 mm
-1.24 mm
-1.26 mm
-1.06 mm
-0.61 mm
0.00 mm
0.61 mm
1.06 mm
1.26 mm
1.24 mm
1.06 mm
0.77 mm
0.40 mm
1.1
7 m
m
1.5
3 m
m
1.7
8 m
m
1.8
5 m
m
1.6
6 m
m
1.1
2 m
m
0.2
3 m
m
-0.8
7 m
m
-1.8
4 m
m
-2.3
3 m
m -2
.23
mm
-1.7
0 m
m
-1.0
1 m
m
-0.3
4 m
m
0.2
4 m
m 0.7
4 m
m
0.21 mm
-0.14 mm
-0.46 mm
-0.74 mm
-0.94 mm
-1.06 mm
-1.05 mm
-0.85 mm
-0.43 mm
0.13 mm
0.67 mm
1.02 mm
1.15 mm
1.08 mm
0.86 mm
0.56 mm
Technical note on Transverse Movements Rev 2.docx
Technical note
– Magnification x200 on both vertical and horizontal movements
4 2 0 2 4
4
2
0
2
4
Net Vertical Movement
Net Vertical Movement
Net Horizontal Displacement
Net Horizontal Displacement
Tunnel Extrados
Tunnel Extrados
4 2 0 2 4
4
2
0
2
4
Net Vertical Movement
Net Vertical Movement
Net Horizontal Displacement
Net Horizontal Displacement
Tunnel Extrados
Tunnel Extrados
4 2 0 2 4
4
2
0
2
4
Net Vertical Movement
Net Vertical Movement
Net Horizontal Displacement
Net Horizontal Displacement
Tunnel Extrados
Tunnel Extrados
Figure3c: Net movement of perimeter points at Y = 16m
Figure3d: Net movement of perimeter points at Y = 24m
0.28 mm
0.07 mm
-0.12 mm
-0.28 mm
-0.41 mm
-0.54 mm
-0.65 mm
-0.69 mm
-0.58 mm
-0.29 mm
0.11 mm
0.48 mm
0.70 mm
0.75 mm
0.67 mm
0.49 mm
0.19 mm
0.15 mm
0.12 mm
0.12 mm
0.10 mm
0.04 mm
-0.08 mm
-0.25 mm
-0.40 mm
-0.43 mm
-0.31 mm
-0.09 mm
0.11 mm
0.23 mm
0.27 mm
0.24 mm
0.0
3 m
m
0.8
4 m
m
1.5
7 m
m
2.1
6 m
m
2.5
2 m
m
2.5
4 m
m
2.1
6 m
m
1.3
2 m
m
0.1
2 m
m
-1.1
8 m
m -2
.19
mm
-2.6
8 m
m
-2.6
4 m
m
-2.2
2 m
m
-1.5
7 m
m -0.7
9 m
m
0.6
4 m
m
1.3
0 m
m
1.8
6 m
m
2.2
6 m
m
2.4
0 m
m
2.1
6 m
m
1.4
8 m
m
0.3
9 m
m
-0.9
0 m
m
-1.9
8 m
m -2
.55
mm
-2.5
5 m
m
-2.1
3 m
m
-1.5
0 m
m
-0.7
9 m
m -0.0
7 m
m
Technical note on Transverse Movements Rev 2.docx
Technical note
Notes:
Sign convention for Figures 2-3
Calculations undertaken for eastbound Crossrail tunnel which is slightly more critical than westbound tunnel. The maximum predicted settlement is 19.2mm and 19.1mm on the eastbound and westbound respectively.
Cross-section of Crossrail tunnels (Figures 1-3) are looking along direction of traffic (i.e. east) on the eastbound tunnel.
Bibliography
Crossrail. (2011, November 3). Email from Geoff Rankin. Subject: Crossrail - Thames tunnel interface - close out of comments. London: Crossrail. New, B. M., & Bowers, K. H. (1994). Ground movement model validation at the Heathrow Express trial tunnel. London: Tunnelling '94. Thames Tunnel. (2011). Thames Tunnel Project - Preliminary Impact Assessment (Crossrail Line 1). 315-RG-TPI-TU021-000001. London: Atkins.
+ve v
ert
ical
+ve horizontal
Appendices
TU021 Crossrail Line 1 Printed 01/12/2011
Appendix F
Technical note on settlement parameters in chalk.docx
Technical note
Project: Thames Tideway To: Thames Tunnel/Crossrail
Subject: Detailed Damage Impact Assessment
From: Michael Yap / Rob Sizer
Date: 14 Nov 2011 cc:
Ground movement predictions for tunnelling in chalk
Introduction:
Atkins was appointed by Thames Tunnel Team to carry out an assessment of the potential effects of the
Thames Tunnel construction on the proposed Crossrail running tunnels. At the location of the Thames
Tunnel – Crossrail crossing, the Thames Tunnel TBM will encounter the Chalk formation, with the crown a
distance of approximately 4.6m beneath the bottom of the Thanet Sand Formation.
Figure 1: Geological formations at the Crossrail-Thames Tunnel crossing
An initial damage impact assessment has been undertaken based on semi-empirical methods of ground
movement predictions for tunnelling in soft ground. Sub-surface movements from bored tunnels were
calculated using the ‘Ribbon Sink’ method (New & Bowers, 1994), with a volume loss parameter VL=1.0%
and trough width parameter k=0.50. At the time these were considered to be ‘moderately-conservative’
parameters which reflect the assumed closed-face construction technique and have been shown to be
readily achievable when tunnelling in London Clay and Lambeth Group (Moss & Bowers, 2005), provided
that good construction methods are put in place to ensure good tunnelling practice.
However, following discussions with Thames Tunnel, it has been suggested that these assessment
parameters are potentially not appropriate for assessments of ground movements in the Chalk formation,
notably where the Chalk is competent and unweathered. This note is a summary of the literature review
undertaken by Atkins to determine appropriate conservative assessment parameters of volume loss factors
for tunnel construction in Chalk from documented case histories.
Technical note on settlement parameters in chalk.docx
Technical note Case Histories:
One of the challenges in understanding the effect of tunnel-induced settlements from tunnel construction in
Chalk is the limited number of published case histories. The problem of predicting sub-surface ground
movements from tunnel construction in Chalk is complex, and various behaviours have been documented.
For example, a chimney of block ground movements have been noted in shallow cover chalk tunnels
(Watson, Warren, Hurt, & Eddie, 2001), whereas the formation of a stable arch over deep cover chalk
tunnels have been suggested by (Protodyaknov, 1970) and (Terzaghi, 1946).
Owing to the lack of documented case histories and understanding of the behaviour of tunnelling in Chalk, it
is common in the tunnelling industry to adopt the widely recognised semi-empirical method of tunnelling in
soft ground which gives rise to a uniform settlement trough that can be described by an inverted bell-shape
profile. In this technical note, a literature review has been undertaken to determine the appropriate
conservative assessment parameter of volume loss factors for ground movement predictions resulting from
tunnel construction in Chalk formation.
The following case histories of tunnelling in Chalk have been reviewed:
Ramsgate harbour approach tunnel (Bloodworth, Houlsby, Burd, & Augarde, 2002), where a
single bore 11m diameter tunnel was constructed at very low cover in weathered chalk, overlain by
Brickearth and River Gravels
North Downs tunnel (Watson, Warren, Hurt, & Eddie, 2001), where the 8m O.D. CTRL tunnel runs
at depths of up to 100m beneath the chalk hills of the North Downs in Kent
DLR Extension to Woolwich Arsenal (Alder, Dhanda, Hillyar, & Runacres, 2010), where twin 5.3m
diameter running tunnels were constructed through chalk beneath the River Thames
CTRL London Tunnels (Bowers & Moss, 2006), where twin 8.15m excavated diameter tunnels
were driven under east London for the Channel Tunnel Rail Link (CTRL) high speed railway
CTRL Contract 220 (Borghi, 2006) (Wongsaroj, et al., 2006), as above but, in addition, provides
some monitoring data for tunnelling in chalk between Stratford Box and Gifford Street Portal near St
Pancras.
The results from the monitored data from Ramsgate and North Downs are presented in Figure 2. The results
indicate a volume loss of up to 0.4%. Both these tunnels were constructed using the NATM method, and at
Ramsgate, the use of the pre-vaulting technique was adopted where small bores were created and filled with
sprayed concrete prior to tunnel construction.
From the CTRL London Tunnels monitoring, it was noted that throughout much of the route, settlement
volume loss figures averaged around 0.5% (Bowers & Moss, 2006). Where Chalk was encountered at the
tunnel invert, reaching a maximum content of 50% near the Graham Road shaft, volume loss between 0.18%
and 0.53% were encountered (Wongsaroj, et al., 2006).
No specific monitoring data for tunnelling in chalk were provided from Woolwich Arsenal, although the actual
face loss was less than the 1% assumption, with the exception of the drive start-up zone within the
construction worksite
Both the Woolwich Arsenal and CTRL London tunnels were constructed using closed face EPB TBM
machines.
Technical note on settlement parameters in chalk.docx
Technical note
Figure 2: Monitored data from Ramsgate, North Downs and CTRL C220 tunnel construction in Chalk
Conclusion:
Based on our findings from the documented case histories we believe that an ‘appropriately conservative’ assessment parameter of 0.9% volume loss can be achieved in chalk at this location, given that best-practices would be in place during the closed-face mechanised TBM construction.
Atkins would recommend to TT that consideration be given as to how during future design development of the tunnelling proposals the specification of works is prepared to ensure that the 0.9% volume loss can be confidently delivered.
0.00%
0.10%
0.20%
0.30%
0.40%
0.50%
0.60%
0.70%
0.80%
0.90%
1.00%
0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00
Vo
lum
e lo
ss
Normalised tunnel depth (depth / diameter)
Tunnelling in Chalk:Relationship between normalised tunnel depth and volume loss
Technical note on settlement parameters in chalk.docx
Technical note
Bibliography
Alder, A., Dhanda, D., Hillyar, W., & Runacres, A. (2010). Extending London's Dockland Light Railway to Woolwich. London: Proceedings of the Institution of Engineers.
Bloodworth, A., Houlsby, G., Burd, H., & Augarde, C. (2002). 3D Modelling of the Interaction between Buildings and Tunnelling Operations. Response of buildings to excavation-induced ground movements. London: Proceedings of the International Conference at Imperial College.
Borghi, F. (2006). Soil conditioning for pipe-jacking and tunnelling. Cambridge: University of Cambridge.
Bowers, K. H., & Moss, N. A. (2006). Settlemetn due to tunnelling on the CTRL London Tunnels. London: Taylor & Francis Group.
Moss, N. A., & Bowers, K. H. (2005). The effect of new tunnel construction under existing metro tunnels. Geotechnical Aspects of Underground Construction in Soft Ground.
New, B. M., & Bowers, K. H. (1994). Ground movement model validation at the Heathrow Express trial tunnel. London: Tunnelling '94.
Protodyaknov. (1970). Szechy K, The Art of Tunnelling. Budapest: Akademiai Kiado.
Terzaghi, K. (1946). Rock defects and loads on tunnel supports. Youngstown, USA: Rock Tunnelling with Steel Supports.
Watson, P. C., Warren, C., Hurt, J. C., & Eddie, C. (2001). The Design of the North Downs Tunnels. London: Underground Construction 2001.
Wongsaroj, J., Borghi, F., Soga, K., Mair, R., Sugiyama, T., Hagiwara, T., et al. (2006). Effect of TBM driving parameters on ground surface movments: Channel Tunnel Rail Link Contract 220. London: Geotechnical Aspects of Underground Construction in Soft Ground.
Technical note on settlement parameters in chalk.docx
Technical note
Data from Case Studies – Ramsgate and North Downs Tunnels
Location Surrounding
soil
External diameter
(m)
Depth to tunnel
axis (m)
Excavation method
Lining type Quoted volume
loss
Volume loss
(Average) Reference
Normalised depth
Ramsgate Harbour Approach Tunnel
- single bore
Competent Upper Chalk
11 m 11.5 m NATM, Perforex
pre-vaulting method
Sprayed concrete lining with invert slab drilled and grouted sacrificial glass fibre reinforcement