080731 6LYG A1 Particular Tunnelling Specification ... - SCATnow

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Lee Tunnel, Contract No. 6LYG/A1 PT – Particular Tunnelling Specification - PT200 PT245 PT246 PT246.1 PT246.2 PT246.3 PT246.4 PT247 PT247.1 PT247.2 TBM LAUNCH FROM OVERFLOW SHAFT The TBM will be launched from the 25m ID Overflow Shaft at Beckton STW. From the Site Information and GBR, the launch of the TBM will be within the Greenwich Fault Zone of the chalk, the Employer views this as one of the highest risks to the success of this Project and the Contractor shall, within 28 days of the award of Contract, submit to the Project Manager a detailed Method Statement of his Means and Methods for the launch of the TBM, including ground treatment and temporary works proposals. A Risk Assessment shall also be provided. CONSTRUCTION TOLERANCES Bored Tunnel Tolerances a) Tunnel shall be constructed to the alignment as defined in the Works Information. b) Maximum tolerances allowed in respect of the departure of any point on the bored tunnel alignment from its designed centreline shall not exceed 50mm horizontally and 50mm vertically. d) No ponding anywhere in the tunnel shall be deeper than 25mm. e) The maximum and minimum measured diameter in any one ring shall be within 0.5% of the theoretical design diameter of the ring. f) The maximum lipping between the edges of the adjacent segments shall not exceed 5mm. Inner Lining Tolerances a) At no point shall the lining thickness be less than that recommended by the designer. b) As stated in PT246.1 the maximum departure of any point on the inner lining shall not exceed 50mm from its designed position. c) No ponding anywhere in the tunnel shall be deeper than 25mm d) The internal diameter of the inner lining measured at any point around the circumference shall depart no more than 10mm from the designed diameter. e) If cast in sections there shall be no lipping between the panel joints. Groundwater Ingress Primary Lining a) The infiltration volume of water for the total length of tunnel shall not exceed 0.1 litre per hour per linear metre of nominal bore. b) Sealing of leaks in the segmental lined tunnel shall be carried out prior to the secondary lining installation Groundwater Ingress Inner Lining There shall be no visible damp patches or running water present on the finished surface of the lining. AS-BUILT TUNNEL SURVEY On completion of the tunnel construction the Contractor shall carry out an As-Built Tunnel Survey in the bored tunnel. The accuracy of the survey shall be to ±20mm for vertical and horizontal alignment. The As-Built Tunnel Survey shall be completed as soon as practical following the completion of the tunnel, the As- Built Survey data is to be finalized and submitted to the Project Manager prior to the final acceptance of the tunnel. Thames Water Utilities Limited August 2008 Page 36 of 38
Lee Tunnel, Contract No. 6LYG/A1 PT – Particular Tunnelling Specification - PT200 PT248 PT248.1 PT248.2 PT248.3 PT248.4 SECONDARY LINING DESIGN AND INSTALLATION The Contractor shall be responsible for the design and installation of a Reinforced Concrete Inner Lining in accordance with the Works Information. The design must allow for the build tolerances in the primary lining. The design life of the Inner Lining shall be 120 years. The Specification for the design and construction will be the British Tunnel Society Specification for Tunnelling and the References as detailed in PT402 Special Clauses are detailed in this Section The Contractor shall submit to the Project Manager for his acceptance in accordance the timescales of Schedule 4 and the requirements of Schedule 6 of the Works Information. This includes, but is not limited to, design calculations and drawings of the proposed Reinforced Concrete Inner Lining. The design submissions shall include as a minimum details of design standards used, loading conditions, design assumptions, design parameters, method of analysis, references and proposals as to how they will meet the water ingress specification PT246.4 and detailed drawings and installation methodology. PT248.5 The Contractor shall submit to the Project Manager for his approval within 90 days of award of Contract a detailed Method Statement of the proposed methodology for the construction of the Inner Lining. This is to include but not limited to details of the location of the Concrete Production, transportation of the concrete to the location of the placement, detailed drawings of the proposed arrangement of the internal formwork, method and timing of the fixing of reinforcement if proposed. PT248.6 PT248.7 PT248.8 PT248.9 PT248.10 PT248.11 The Contractor can work from Beckton and/or Abbey Mills on the installing of the Inner Lining should he so decide as part of the Construction methodology. Account should be taken of any restrictions imposed by the Planning Agreements at either site as described in the Works Information. Concrete Mixes shall be designed and mixed in accordance with the requirements of PT400. Concrete mixes shall be designed to minimise cracking of the lining and to ensure that crack widths do not exceed the permitted width specified in Eurocode 2-part 3:2006 and the National Application Document Concrete shall be compacted by high frequency mechanical vibrators. type shall be used, supplemented in the case of steel formwork by heavy duty formwork vibrators where necessary. Vibrators shall not be used to distribute concrete from the point on placing The Contractor shall submit to the Project Manager for acceptance within 90 days of the award of Contract a concrete placement Method Statement. This shall include the proposed construction joint detail and locations. This shall also include proposals for the testing of the inner lining concrete to ensure that the minimum concrete strength, as specified in the Contractor’s design submission, has been achieved prior to removal of the formwork, and any testing procedures the Contractor proposes to carry out to ensure that there are no voids in the concrete inner lining. The submission shall include a detailed methodology to eliminate air entrapment and voids between the inner lining and the primary lining when placing the concrete and pressure grouting procedures and his proposed method for ensuring the completed lining is free from voids Where encountered the Contractor shall grout any cavities and voids between the inner lining and the primary lining. Grouting will not be allowed until the concrete has been demonstrated as achieving the designed 28 day strength. Temporary grout pipes can be provided in the crown of the lining and used for the elimination of air entrapment and voids, these shall not remain within 40mm of the surface of the finished concrete. Thames Water Utilities Limited August 2008 Page 37 of 38
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