Structural engineering part 2

Technical Report to support Assessment of Environmental Effects (City Rail Link Notice of Requirement): Structural Engineer Assessment.

Appendix B Construction Vibration Receiver Types

B1

Technical Report to support Assessment of Environmental Effects (City Rail Link Notice of Requirement): Structural Engineer Assessment.

a. Built Heritage EBS_ID 709 710 109 19 14 14 27 20 21 22 24 25 25 28 549 719 1 511 34 1118 1117 542 541

St. No 12 2 12-14 3 13 15 46-56 35 37-39 41 51-53 55 57 61 26, 34-36 9-11 98-102 43 83 66 68 24 15-31

Street Queen Street Queen Street Customs Street West Albert Street Albert Street Albert Street Albert Street Albert Street Albert Street Albert Street Albert Street Albert Street Albert Street Albert Street Wyndham Street Durham Lane Albert Street Victoria Street West Albert Street Victoria Street West Victoria Street West Wellesley Street West Wellesley Street West

Building Name/ Description Former Central Post Office Endeans Building Former Customs House West Plaza Yates Building Link House APN NZ Complex Price Buchanan Building Building Prince Albert Apartments Retail and Office building Retail and Office building Retail and Office building Shakespeare Hotel Brewery Former Gas Co Building Bluestone Store Armishaws Building Retail Building Retail and Office building London Dairy J H Hannan Bledisloe House T&G Building B2

Category Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage

Technical Report to support Assessment of Environmental Effects (City Rail Link Notice of Requirement): Structural Engineer Assessment.

EBS_ID 193 517 526 199,198,1022 336 724 724 330 1119 1120 178 333 337 176 212 97 297 458 459 464 464 464 464 465 465 466 467

St. No 11 105 133 290 70-74 1 53 59 283 16-18 251-253 61-65 78 238 9 1 151 215 221 233 235 237 239 241 243 245-247 249-251

Street Mayoral Drive Vincent Street Vincent Street Queen Street Pitt Street Beresford Square Pitt Street Pitt Street Karangahape Road Beresford Square Karangahape Road Pitt Street Pitt Street Karangahape Road Mercury Lane Cross Street Newton Road Symonds Street Symonds Street Symonds Street Symonds Street Symonds Street Symonds Street Symonds Street Symonds Street Symonds Street Symonds Street

Building Name/ Description Former Public Trust Office Auckland Chinese Presbyterian Church Juliette's Aotea Centre The Chatham Building Former Pitt Street Fire Station Old Central Ambulance Station Retail Building Samoa House Office Building Retail and Office building Dentists Chambers Pitt St Methodist Church George Court Building The Mercury - kings theatre George Court Factory Building Commercial Building Edinburgh Castle Building Interface Architecture Building Altezano French Connection Restaurant Retail and Residential Building Retail and Residential Building Retail and Residential Building Retail and Residential Building Retail and Residential Building Retail and Residential Building B3

Category Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage

Technical Report to support Assessment of Environmental Effects (City Rail Link Notice of Requirement): Structural Engineer Assessment.

EBS_ID 468 257 213 1132 1133 1135

St. No 253-255 21 1-13 29 31 33 76-86

Street Symonds Street New North Road Mount Eden Road Brentwood Avenue Brentwood Avenue Brentwood Avenue Albert Street

Building Name/ Description Retail and Residential Building Retail Building Retail and Residential building Residential Building Residential Building Residential Building Historic Toilets/ bluestone retaining wall

B4

Category Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage Built Heritage

Technical Report to support Assessment of Environmental Effects (City Rail Link Notice of Requirement): Structural Engineer Assessment.

b. Residential EBS_ID 33 15 16 31 32 4 8 5 11 515 519 520 528 531 532 201 326 1063 1068 1121 1123 1124 298 144 1129

St. No 8-12 17 22-26 74 76-84 103,105,107 109-125 106-108 128 103 109 113 135 150 156 71-87 29,39,41 22-28 259-281 14 9 A-C 18 153 10 1

Street Albert Street Albert Street Albert Street Albert Street Albert Street Albert Street Albert Street Albert Street Albert Street Vincent Street Vincent Street Vincent Street Vincent Street Vincent Street Vincent Street Mayoral Drive Pitt Street Beresford Square Karangahape Road East Street Mercury Lane East Street Newton Road Flower Street Akiraho Street

Building Name/ Description Quay West Hotel Cohesive Technology House The Stamford Chifley Suites City Gardens Apartments Manhattan Apartments Sky City - Grand Hotel & Convention Centre Elliot Tower (Proposed) Crown Plaza YWCA Accommodation The Rodney Apartments Winsun Heights Apartments Dynasty Gardens Hotel The City Lodge Eclipse Apartments Rendezvous Grand Hotel Hopetoun Delta Apartments The Beresford Retail and Residential building Residential Building Residential Building Residential Building Beatnik Eden Terrace Apartments Eden Oaks B5

Category Residential Residential Residential Residential Residential Residential Residential Residential Residential Residential Residential Residential Residential Residential Residential Residential Residential Residential Residential Residential Residential Residential Residential Residential Residential

Technical Report to support Assessment of Environmental Effects (City Rail Link Notice of Requirement): Structural Engineer Assessment.

c. Commercial EBS_ID 707 23 38 17 424 26 29 30 552 36 35 37 39 13 10 546 534 113 189 1126 1127 1128

St. No 21 7 9-11 23-29 12-26 58 63 65-69 38 92-96 85 87-89 99 135 120 44-52 67-101 22 3 32 3 101

Street Queen Street Albert Street Albert Street Albert Street Swanson Street Albert Street Albert Street Albert Street Wyndham Street Albert Street Albert Street Albert Street Albert Street Albert Street Albert Street Wellesley Street West Vincent Street Dundonald Street Flower Street Normanby Road Enfield Street Mount Eden Road

Building Name/ Description Zurich House (Anzo Tower) Retail and Office building Food Alley ANZ Centre Affco House Carpark APN NZ Complex AMI House Auckland District Court Wyndham Towers Former Telecom Tower Retail and Office building Albert Plaza AA Building ASB Building BDO Tower Wellesley Centre Auckland Police Station Soundcraft Ltd TV3 Building Commercial Building Horse and Trap Hometune

B6

Category Commercial Commercial Commercial Commercial Commercial Commercial Commercial Commercial Commercial Commercial Commercial Commercial Commercial Commercial Commercial Commercial Commercial Commercial Commercial Commercial Commercial Commercial

Technical Report to support Assessment of Environmental Effects (City Rail Link Notice of Requirement): Structural Engineer Assessment.

Appendix C Settlement Contours

C1

Technical Report to support Assessment of Environmental Effects (City Rail Link Notice of Requirement): Structural Engineer Assessment.

C2

Technical Report to support Assessment of Environmental Effects (City Rail Link Notice of Requirement): Structural Engineer Assessment.

C3

Technical Report to support Assessment of Environmental Effects (City Rail Link Notice of Requirement): Structural Engineer Assessment.

C4

Technical Report to support Assessment of Environmental Effects (City Rail Link Notice of Requirement): Structural Engineer Assessment.

C5

Technical Report to support Assessment of Environmental Effects (City Rail Link Notice of Requirement): Structural Engineer Assessment.

C6

Technical Report to support Assessment of Environmental Effects (City Rail Link Notice of Requirement): Structural Engineer Assessment.

C7

Technical Report to support Assessment of Environmental Effects (City Rail Link Notice of Requirement): Structural Engineer Assessment.

Appendix D Indicative Settlement Profiles

D1

Technical Report to support Assessment of Environmental Effects (City Rail Link Notice of Requirement): Structural Engineer Assessment.

-

CH350 Albert Street Open Cut and Cover

CH350 - Albert Street Open Cut and Cover -30.0

-20.0

Settlement (mm)

-40.0

Offset from Downtrack Centreline (m) -10.0 0.0 10.0 20.0 0.0

30.0

40.0

50.0

2.0 4.0 6.0 8.0

CH620 Albert Street Open Cut and Cover

CH620 - Albert Street Open Cut and Cover -50.0

Settlement (mm)

-

-40.0

-30.0

Offset from Downtrack Centreline (m) -20.0 -10.0 0.0 10.0 20.0 30.0 0.0 4.0 8.0 12.0 16.0

D2

40.0

50.0

60.0

Technical Report to support Assessment of Environmental Effects (City Rail Link Notice of Requirement): Structural Engineer Assessment.

-

CH740 Albert Street Open Cut and Cover

CH740 - Albert Street Open Cut and Cover Offset from Downtrack Centreline (m) -60.0 -50.0 -40.0 -30.0 -20.0 -10.0 0.0 10.0 20.0 30.0 40.0 0.0

50.0

60.0

70.0

80.0

Settlement (mm)

3.0 6.0 9.0 12.0 15.0 18.0

CH1000 Aotea Station

CH 1000m - Open Cut and Cover Aotea Station -40

-30

-20

Offset from Downtrack Centreline (m) -10 0 10 20 0 5

Settlement (mm)

-

10 15 20 25

D3

30

40

50

Technical Report to support Assessment of Environmental Effects (City Rail Link Notice of Requirement): Structural Engineer Assessment.

-

CH1150 Mayoral Drive TBM

CH 1150m - Mayoral Drive TBM -30

-20

-10

Offset from Downtrack Centreline (m) 0 10 20 0

30

40

Settlement (mm)

5 10 15 20 25

CH1450 Vincent Street TBM

CH 1450m - Vincent Street TBM -30

-20

-10

Offset from Downtrack Centreline (m) 0 10 20 0 5

Settlement (mm)

-

10 15 20 25

D4

30

40

Technical Report to support Assessment of Environmental Effects (City Rail Link Notice of Requirement): Structural Engineer Assessment.

-

CH1800 Pitt Street TBM

CH 1800m - Pitt Street TBM -50

-40

-30

-20

Offset from Downtrack Centreline (m) 0 10 20 30 40 50

-10

60

70

80

90

100

90

100

0

Settlement (mm)

2 4 6 8 10

CH1850 Karangahape Road Station

CH 1850m - Karangahape Road Station -50

-40

-30

-20

Offset from Downtrack Centreline (m) 0 10 20 30 40 50

-10 0

Settlement (mm)

-

5

10

15

20

D5

60

70

80

Technical Report to support Assessment of Environmental Effects (City Rail Link Notice of Requirement): Structural Engineer Assessment.

-

CH1900 Karangahape Road Station

CH 1900m - Karangahape Road Station -50

-40

-30

-20

Offset from Downtrack Centreline (m) 0 10 20 30 40 50

-10

60

70

80

90

100

0

Settlement (mm)

10

20

30

40

CH2200 Central Motorway Junction

CH 2200m - Central Motorway Junction -40

Settlement (mm)

-

-30

-20

Offset from Downtrack Centreline (m) -10 0 10 20 30 0

5

10

15

20

D6

40

50

60

Technical Report to support Assessment of Environmental Effects (City Rail Link Notice of Requirement): Structural Engineer Assessment.

-

CH2650 Symonds Street TBM

CH 2650m - Symonds Street TBM -50

-40

-30

-20

Offset from Downtrack Centreline (m) 0 10 20 30 40 50

-10

60

70

80

90

100

70

80

90

100

0

Settlement (mm)

3 6 9 12 15

CH2800 Newton Station

CH 2800m - Newton Station -50

-40

-30

-20

Offset from Downtrack Centreline (m) 0 10 20 30 40 50

-10 0 5

Settlement (mm)

-

10 15 20 25 30 35

D7

60

Technical Report to support Assessment of Environmental Effects (City Rail Link Notice of Requirement): Structural Engineer Assessment.

-

Ch3030 Newton Open Cut and Cover

CH3030 - Newton Open Cut and Cover -30.00

-10.00 0

Settlement (mm)

-50.00

Offset from Downtrack Centreline (m) 10.00 30.00 50.00 70.00

90.00

110.00

130.00

3

6

9

Ch3100 NAL West Open Cut and Cover

CH3100 - NAL West Open Cut and Cover -50.00

Settlement (mm)

-

-30.00

Offset from Downtrack Centreline (m) -10.00 10.00 30.00 0.00 4.00 8.00 12.00 16.00

D8

50.00

70.00

Technical Report to support Assessment of Environmental Effects (City Rail Link Notice of Requirement): Structural Engineer Assessment.

Ch3100 NAL East Open Cut and Cover

CH3100 - NAL East Open Cut and Cover -60.0

Settlement (mm)

-

-40.0

-20.0

Offset from Downtrack Centreline (m) Alber 0.0 20.0 40.0 60.0 0.0

4.0

8.0

12.0

D9

80.0

100.0

Appendix E Settlement Principles Report

Project: Auckland City Rail Link

Reference: 228072

Settlement Principles Report

Prepared for: Auckland Transport Revision: 1 10 August 2012

In association with

Document Control Record Document prepared by: Aurecon New Zealand Limited Level 4, 139 Carlton Gore Road Newmarket Auckland 1023 PO Box 9762 Newmarket Auckland 1149 New Zealand

T F E W

+64 9 520 6019 +64 9 524 7815 auckland@aurecongroup.com aurecongroup.com

A person using Aurecon documents or data accepts the risk of: a) b)

Using the documents or data in electronic form without requesting and checking them for accuracy against the original hard copy version.

Using the documents or data for any purpose not agreed to in writing by Aurecon.

Report Title

Settlement Principles Report

Document ID

228072-AC-WPP-012

File Path

C:\Users\David.Mockett\Documents\228072 City Rail Link\Settlement Principles Report\228072-AC-RPT-012[0]Rev1.docx

Client

Auckland Transport

Client Contact

Rev

Date

Revision Details/Status

Prepared by

0

12 July 2012

Issued Draft

DRM

1

10 August 2012

Issued Draft

DRM

Current Revision

228072

Project Number

Steve Hawkins Author

Verifier

Approver

Bill Newns as part of CDR Bill Newns as part of CDR

1

Approval Author Signature

Approver Signature

Name

Name

Title

Title

Aurecon | Mott MacDonald | Jasmax | Grimshaw

Project 228072 | File Appendix E Settlement Principles Report.docm | 10 August 2012 | Revision 1

Contents 1.

Overview

5

1.1

General

5

1.2

Settlement Caused by Excavation

5

1.3

Settlement Caused by Groundwater Drawdown

6

1.4

Potential Seismic Effects

6

2.

Buildings

7

3.

Utilities

9

3.1

Pipelines

9

Settlement Prediction

10

4.1

Tunnels

10

4.2

Cut and Cover Tunnels and Shafts

4.

5.

Error! Bookmark not defined.

Interim Conclusions

11

5.1

Condition Surveys

11

5.2

Surface and Structural Settlement Monitoring

11

5.3

Groundwater Levels and Pressures

11

5.4

Response Plans

11

E4

Aurecon | Mott MacDonald | Jasmax | Grimshaw

Project 228072 | File Appendix E Settlement Principles Report.docm | 10 August 2012 | Revision 1

Overview

1.

1.1

General

Settlement observed at surface resulting from tunnelling and excavation can be divided into those occurring as a result of ground deformations (volume loss or immediate settlements) or from effective stress changes, as a result of soil pore water pressure decreases in compressible soils (consolidation).

Tunnel shaft and cut and cover excavations reduce groundwater levels and soil pore water pressures via drainage over the design life such that settlements will occur where there are compressible soils.

Settlement trough curvature induced by excavation (volume loss/immediate settlements) is the principal factor in determining the potential for adverse effects upon existing buildings and structures.

That is, the potential for damage arises largely from tensile strains associated with the settlement trough gradient as opposed to the magnitude of the settlement itself.

The potential for adverse effects arising from settlement is directly related to settlement curvature, relative to the dimensions of the structure at risk and the resulting strains induced in the buildings. A greater magnitude of consolidation settlement has a much lower potential for adverse effects in comparison to settlement associated with ground deformation (volume loss).

Many methods for mitigating settlement effects are possible. More detailed assessment of the vulnerability of existing buildings and structures may result in further consideration of such settlement mitigation measures.

1.2

Settlement Caused by Excavation

Settlements observed at surface are typically in the form of a settlement trough. The ratio between the volume of the settlement trough and the excavated volume is called the volume loss. This parameter depends predominantly on the type of ground, tunnelling method and standard of workmanship.

For a TBM tunnel with a segmental lining, the volume loss has the following components:   

Face Loss – Elastic deformation of the ground towards the advancing tunnel could be up to 1/3 of the final unsupported radial convergence.

Shield Loss – Convergence occurring due to the annulus surrounding the shield. This is affected by TBM advance.

Post shield / pre-grout & post grout loss – convergence that occurs before the grout is either injected or gains sufficient strength to interact with the ground and lining.

The initial ground surface settlement and lateral displacement due to the tunnelling induced volume loss have been assessed based on the widely used Gaussian distribution form.

For the platform tunnels and launch adits volume loss is associated with face loss and deformation of the excavated periphery which is a function of the interaction of the ground with the installed temporary support. Given that this is typically installed at the face this often a smaller percentage of the excavation than for TBM tunnelling.

E5

Aurecon | Mott MacDonald | Jasmax | Grimshaw

Project 228072 | File Appendix E Settlement Principles Report.docm | 10 August 2012 | Revision 1

In shaft excavations and those for cut and cover tunnels, the support offered by the walls is also largely passive in nature. Deflection of the walls will create a corresponding volume loss to the side of the shaft excavation that will be translated at the surface as a settlement trough.

Settlements associated with ‘volume loss’ have the greatest potential to cause adverse effects upon existing buildings and structures as described above. As the volume loss component of tunnel excavation occurs almost contemporaneously with tunnel excavation.

Consolidation effects have a time dependence which is related to the permeability of the ground.

‘Volume-loss’ cannot be measured directly, and is only established from back-analysis of the surface settlement data.

Good construction practices will assist in the reduction of volume losses.

1.3

Settlement Caused by Groundwater Drawdown

Depending on geological and hydro-geological conditions at or near the excavation and the timing of and degree of water-tightness of excavations there may be additional settlements due to consolidation of soils arising from groundwater drawdown. This is also dependent upon the relationship between geological history and consequent geotechnical characteristics of the soils experiencing the groundwater pressure changes and the actual groundwater pressure changes.

During tunnelling operations the period for which the ground may drain to the tunnel is limited, as the permanent lining will be installed and grouted into place close behind the advancing TBM. Based on the project assumptions for advance rate this is likely to be within 3 days of excavation although TBM delays may extend this period. The lining must be opened to form the pedestrian cross passages, which provides a further opportunity for groundwater diversion for approximately 2 months.

Should detailed condition surveys and monitoring results indicate the need, pre-treatment of the ground (i.e., prior to segmental lining breakout) with grouting may reduce the potential for groundwater flows at these locations. Various methods exist for sealing tunnel lining joints that are likely to provide significant water ingress.

1.4

Potential Seismic Effects

The tunnel structures will be designed in accordance with established industry practice and in accordance with New Zealand Standards such as NZS 1170.5. Although underground structures perform much better than surface structures during earthquakes, it is conceivable that local increases in groundwater ingress may occur to the tunnels as a result of lining joint displacement at fault or shear zones. Such increases in groundwater ingress will not significantly increase the potential for ‘damage’ to existing buildings and structures (not already damaged by the seismic event itself).

Consolidation effects associated with a driven tunnel do not contribute greatly to settlement trough gradients, as they influence a wide zone of ground above the tunnel.

E6

Aurecon | Mott MacDonald | Jasmax | Grimshaw

Project 228072 | File Appendix E Settlement Principles Report.docm | 10 August 2012 | Revision 1

Buildings

2.

Tension induced in buildings as a result of settlement may be caused by two separate effects: 



Direct Tension which is the result of the horizontal displacement field predicted by the Gaussian method, such that if one corner of the building experiences more horizontal displacement than the opposite corner, the building will experience tensile strain.

Flexural Tension which is caused by the building being forced to sag or hog, inducing tensile strain in the building at the extreme fibre of the building represented as a beam, or diagonal tension due to shear effects.

Table 2 - 1 – Classification of Visible Damage to Walls with Particular Reference to Ease of Repair of Plaster and Brickwork or Masonry Source: Mair, Taylor and Burland (1996) Category of Damage

Normal Degree of Description of Typical Damage Severity (Ease of repair is in bold type)

0

Negligable

Hairline cracks less than about 0.1 mm.

1

Very slight

Fine cracks which are easily treated during normal decoration. Damage generally restricted to internal wall finishes. Close inspection may reveal some cracks in external brickwork or masonry. Typical crack widths up to 1 mm.

2

Slight

Cracks easily filled. Re-decoration probably required. Recurrent cracks can be masked by suitable linings. Cracks may be visible externally and some repointing may be required to ensure weathertightness. Doors and windows might stick slightly. Typicial crack widths up to 5 mm.

3

Moderate

The cracks require some opening up and can be patched by a mason.

Repointing of external brickwork and possibly a small amount of brickwork to be replaced. Doors and windows sticking. Service pipes may fracture.

Weathertightness often impaired. Typical crack widths are 5 to 15 mm or several greater than 3 mm.

4

Severe

Extensive repair work involving breaking out and replacing sections of walls, especially over doors and windows. Windows and door frames distorted, floor sloping noticably1. Walls leaning1 or bulging noticeable, some loss of bearing in beams. Service pipes disrupted. Typical crack widths are 15 to 25 mm but also depends on the number of cracks.

5

Very Severe

This requires a major repair job involving partial or complete rebuilding. Beams lose bearing, walls lean badly and require shoring. Windows broken with distortion.

Danger of instability. Typical crack widths are greater than 25 mm but depends on the number of cracks.

E7

Aurecon | Mott MacDonald | Jasmax | Grimshaw

Project 228072 | File Appendix E Settlement Principles Report.docm | 10 August 2012 | Revision 1

Category of Damage

Normal Degree of Description of Typical Damage Severity (Ease of repair is in bold type)

Note: Crack width is only one factor in assessing category of damage and should not be used on its own as a direct measure of it. Local deviation of slope, from the horizontal or vertical, of more than 1/100 will normally be clearly visible. Overall deviations in excess of 1/150 are undesirable.

The terms “slight”, “moderate”, etc in Tables 2 – 1 do not necessarily correspond to building owners’ perceptions. Such terminology is widely accepted and the classification system illustrated by Table 2 1 has been adopted by organisations such as the Institution of Structural Engineers London, the Institution of Civil Engineers and the Building Research Establishment (BRE).

The division between category 2 and 3 is considered particularly significant, with damage up to category 2 resulting from a variety of sources within the building itself.

Because the above process incorporates the effects of distortion and deflection of the building, the tensile strain can be used directly with Table 2 - 1 without reference to angular distortion of the ground surface.

E8

Aurecon | Mott MacDonald | Jasmax | Grimshaw

Project 228072 | File Appendix E Settlement Principles Report.docm | 10 August 2012 | Revision 1

3.

Utilities

3.1

Pipelines

The treatment of pipelines is similar to that for buildings, whereby pipelines and duct banks are modelled as circular tubes. It is then assumed that the settlement profile of the ground beneath the pipe is the same as the deformation induced in the pipe. This is a conservative assumption as there will be some slip at the soil pipe interface causing a smaller deformation in the pipe.

These results have also proven in the past to be conservative for larger pipes because of the effects of pipe stiffness and joint release. For smaller pipes, the reduction in strains from these effects will reduce strains by 50%.

Figure 3 – 1 shows how deflection of utilities due to the settlement of the ground follows the settlement trough. It can be seen that the utility does not deflect to the extent of the settlement trough, with this difference in deformation due to the stiffness of the pipe material and the joint types.

Ground Surface

x

Settlement Profile at Surface

Settlement Profile at Pipe

Smax

Pipe Deflection H

Differential settlement between pipe and ground results in stress within pipe

D Tunnel

Z

Figure 3 – 1 – Pipe Deflections due to Settlement of Ground from Tunnelling

The potential damage to utilities will be assessed on a case by case basis. The utility owner should be notified of the potential settlement and slope induced in utilities and advice sought on the requirements for each service.

Assessment of utilities in conduit, such as electricity and telecommunications, and pipes <200 mm diameter are considered to be sufficiently flexible to absorb the effects of settlement without damage.

Utilities like these may only be assessed for damage where they lie within proximity to shaft excavations.

E9

Aurecon | Mott MacDonald | Jasmax | Grimshaw

Project 228072 | File Appendix E Settlement Principles Report.docm | 10 August 2012 | Revision 1

4.

4.1

Settlement Prediction Tunnels

Initial surface settlements attributed to stress redistribution in rock due to tunnel excavation have been predicted utilising the computer program â&#x20AC;&#x153;XDISPâ&#x20AC;?.

XDISP is a 2-dimensional settlement analysis program which applies the method for determining immediate settlement troughs. XDISP identifies tunnels as tubular sections, with each section assigned a face-loss parameter which accounts for the proposed ground support to be installed, the tunnelling method and the quality of the rock mass.

E10

Aurecon | Mott MacDonald | Jasmax | Grimshaw

Project 228072 | File Appendix E Settlement Principles Report.docm | 10 August 2012 | Revision 1

Interim Conclusions

5.

5.1

Condition Surveys

Pre-construction and post construction inspections will be undertaken to establish the condition of structures and utilities within the zone of influence of the works, (defined as the predicted contour for 5mm settlement) to determine whether these properties have been affected by the construction activities and the extent of damage, if any.

Any particularly vulnerable structures, e.g., those with mixed foundation structures would be identified and highlighted for special attention well in advance of construction.

5.2

Surface and Structural Settlement Monitoring

Provision, installation and monitoring of surface settlement makers will be required as a result of the settlement estimations and pre-construction inspections indicated above.

These would be sited along each tunnel alignment at regular intervals to measure settlement directly above the tunnels. Transverse arrays to measure settlements horizontal to the tunnel alignment would be installed at a lesser frequency. This monitoring (in conjunction with piezometers) will enable a route wide monitoring of effects.

At buildings and structures of concern additional monitoring measures may be required which may include settlement monitoring at corners of the buildings and at any points of particular structural concern.

Monitoring will commence 18 months prior to work starting in order to measure natural movement of existing structures from seasonal changes in the water table. Monitoring will also continue for at least 6 months after completion of construction.

5.3

Groundwater Levels and Pressures

Additional boreholes and piezometers are expected to be undertaken to complete regional groundwater monitoring and provide such additional geotechnical investigation as required to complete the detailed design.

5.4

Response Plans

The requirement for ‘mitigation’ should be based on;  

The detailed assessment of the vulnerability of structures within the zone of influence of the tunnels and excavations.

The derivation of limits of settlement for the vulnerable structures according to the vulnerability assessment described above.

Such assessment would be expected to form part of a subsequent submission as part of a Construction and Environmental Management Plan (CEMP), once the CRL moves into a construction phase.

E11

Aurecon | Mott MacDonald | Jasmax | Grimshaw

Project 228072 | File Appendix E Settlement Principles Report.docm | 10 August 2012 | Revision 1