Proposal for Northern Extension of Northolt Tunnel sift report
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- Figure 2.1 Provision for the Heathrow Spur
- Turnout T1 Turnout T2 Turnout T3
- 3 Scope of the Sift
- 4 Assumptions 4.1 General
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Northern Extension of Northolt Tunnel SIFT Report
Northern Extension of Northolt Tunnel SIFT Report C222-ATK-DS-REP-020-000034 Revision – P06
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Figure 2.1 Provision for the Heathrow Spur 2.1.5
The Proposed Scheme position of the portal to the Northolt Tunnel at West Ruislip is located at chainage 23+480m as indicated on Map No. CT-06-018 from the ES Volume 2 mapbooks, CFA 6 South Ruslip to Ickenham. For Options B and C the inclusion of a tunnel to pass beneath the River Colne, and the associated vertical alignment requirements would remove the need for this. 2.1.6 The principal features of the alternative options are included in Drawing Nos C222-ATK- RT-DSK-020-011303 and C222-ATK-RT-DSK-020-011304. 2.1.7
Similarly, an environmental assessment of the northern extension of the Northolt Tunnel has been undertaken and is reported in C252-ETM-EV-REP-020-000116. 2.1.8 The evaluation has been undertaken in accordance with HS2 Route Development Procedure (HS2-HS2-SA-PRO-000-000007 rev. P07) and utilising HS2 – Route Development Appraisal Template document (HS2-HS2-SA-TEM-000-000004 rev. P03).
Turnout T2 Turnout T3 `Code 1 -
Accepted Uncontrolled when printed INTERNAL INFORMATION
Northern Extension of Northolt Tunnel SIFT Report
Northern Extension of Northolt Tunnel SIFT Report C222-ATK-DS-REP-020-000034 Revision – P06
8 Uncontrolled when printed
3 Scope of the Sift 3.1.1
The assessment of the possible alternative options (Options B & C) will comprise a comparison with different elements of the Proposed Scheme (Option A) in terms of engineering feasibility, environmental impact and cost. 3.1.2
The comparison scheme for the sift tables, drawings and costing is the Proposed Scheme as presented in the Environmental Statement and Hybrid Bill submission, and this comparison has taken into account the HS2 design requirements (civil and rail systems) and the geological conditions along the line of the proposed tunnel. 3.1.3 The Proposed Scheme for the Northolt tunnel, has an overall length of 13.4km. The baseline position of the west portal to the Northolt tunnel is at Ch 23+480m, from which point, continuing westwards, it enters a section of cutting and embankment at about Ch 25+900m and the commencement of the Colne Valley viaduct structure at Ch 26+000m. North-west of the viaduct, the alignment enters a further section of tunnel, the 13.3km long Chiltern tunnel, with its southern portal at Ch 31+363m.
`Code 1 -
Accepted Uncontrolled when printed INTERNAL INFORMATION
Northern Extension of Northolt Tunnel SIFT Report
Northern Extension of Northolt Tunnel SIFT Report C222-ATK-DS-REP-020-000034 Revision – P06
9 Uncontrolled when printed
4 Assumptions 4.1 General 4.1.1
It has been assumed that the Proposed Scheme horizontal (plan) rail alignment would remain applicable to the alternative options. The vertical alignment of the HS2 mainline is included as Drawing Nos. C222-ATK-RT-DSK-020-011301 and C222-ATK-RT-DSK-020- 011302. 4.1.2 For Option B it is assumed that adequate passive provision for the Heathrow Spurs has been made through initial design of turnout caverns, however the alignment of the spurs themselves need not be designed at this stage. The horizontal and vertical alignments of the Heathrow spur connections to the mainline recognise the particular requirements of high speed turnouts and the need for the spur lines to pass either over or beneath the mainline tunnels. Note that the two profiles shown in red and blue (drawings 011301 and 011302) relate to whether the Heathrow spur tunnels indicatively run above or below the mainline (at this stage no preference need be expressed since passive provision only is required). 4.1.3 For Option B it is assumed that the spur tunnels would pass over or beneath the main running tunnels with a minimum clear separation of one tunnel diameter. Similarly minimum ground cover over the tunnel crown should be one tunnel diameter except beneath the lakes where this requirement would increase to a minimum of two tunnel diameters at this stage of design. Indicative vertical alignments are included as Drawing Nos C222-ATK-RT-DSK-020-011303 and C222-ATK-RT-DSK-020-011304. 4.1.4
It is assumed that the Option C rail alignment would be the same as that for Option B mainline, but that there would be no requirement for turnouts to form the Heathrow spur. 4.1.5
Options B and C would require ventilation-intervention shafts for the additional tunnelled length. Due to constraints on the locations of the shafts across the Colne Valley, the maximum distance between shafts would need to be in excess of the general requirement of 3000m, up to a maximum of 3200m. It is assumed that this is acceptable for this study, however this would need to be confirmed at detailed design stage. A key requirement would be the need for a shaft adjacent to Ickenham Auto Transformer Feeder Station (ATFS) to facilitate power supply to the railway. 4.1.6
It is assumed that a temporary connection to the railhead near Harvil Road would be designed for low speed and a maximum gradient of 3.5%, as is permissible within current HS2 design standards 4.1.7
It is assumed that access from the railhead to HS2 would be required in both directions. 4.1.8
It is assumed permissible to operate diesel locomotive hauled trains onto and along HS2 during construction and that suitable ventilation provision can be made within the tunnels. It is assumed that overhead line electrification equipment would not be required on the railhead connection, and it could be constructed to reduced clearances given it would be used by UK loading gauge rail vehicles (having accessed the line from Network Rail). A reduced rail to soffit height of 4500mm has been assumed, which is Yüklə 0,76 Mb. Dostları ilə paylaş:
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