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

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Lee Tunnel, Contract No. 6LYG/A1 PT – Particular Tunnelling Specification - PT200 PT239.5 PT239.6 PT239.7 PT240 PT240.1 a) Primary grout shall be injected by positive displacement. Consideration shall be given to providing a ring main system with the incorporation of approved retarders and accelerators to control the setting of the grout. The grout pump system shall incorporate a safety pressure by-pass arrangement, with means of reading the grout pressure at the point of injection. b) Primary Grouting shall commence in a manner such the cavity is completely filled with grout and all excess air and water is displaced and the grout is retained under pressure until the first set takes place. Records Records at each stage of the grouting process shall be kept, to include quantity and pressure applied at each injection point. These records shall be submitted to the Project Manager daily. Grout Performance The minimum compressive strength requirement of all grouts as measured from testing cubes shall be:-1.5N/mm² at 24 hours and have an initial set within 10 seconds with Marsh Flows between 45 and 60 seconds at a base temperature of 20°C. Testing Three sample cubes of the grout shall be taken daily to an approved testing facility to verify the minimum strength requirement. The results of these tests shall be forwarded to the Project Manager. Tests shown in Table below to be carried out on the grout. item Specification Test method Frequency On ground Bleeding Less 3%(1hour) Bleeding test Every day Consistency 8 to 11 sec Flow test Every day Gel time 5 to 12 sec Mix test Every day 1 hour Compressive Every test with 4cm month 24 hour 1.5 N/mm 2 cube sample Every day 7 day Every month 28 day Every month In each tunnel Every week Every week Every week Every month Every week Every month Every month INSTALLATION, MONITORING AND CONTROL FOR SEGMENTAL LINING Installation of Tunnel Lining Remark Solution -A Solution -A A+B Referen ce only Referen ce only Referen ce only a) Construct rings to correct line and level, in true circular form to preserve the circularity of the tunnel. b) Select combinations of tapered segment rings to provide specific tunnel geometry, and for making corrections as necessary during construction. c) Inspect concrete segments and gaskets before transport into the tunnel nd the building of the segments in the tailskin. No damaged segments are to be taken in to the tunnel and prior to build. Thames Water Utilities Limited August 2008 Page 30 of 38
Lee Tunnel, Contract No. 6LYG/A1 PT – Particular Tunnelling Specification - PT200 PT240.2 PT241 PT241.1 PT241.2 PT241.3 PT241.4 PT241.5 PT241.6 PT241.7 d) The Contractor shall tighten bolts across the joints to ensure gasket compression in accordance with gasket manufacturer recommendations. e) Do not add packings or materials to circumferential joints to adjust line and grade unless accepted by the Project Manager. f) Stagger radial joints in adjacent rings. Rings may be rotated one or two equidistant bolt locations to meet line and grade and curve requirements, provided that only T joints result between adjacent rings. g) Hangers for utility lines necessary for construction of the tunnel may be connected to concrete segments with the Project Manager’s acceptance. Monitoring of Segments a) The Contractor shall take measurements of the horizontal and vertical diameters for each tunnel ring following installation within the tail skin. Measurements shall be forwarded to the Project Manager on a daily basis. b) Installation tolerances to be as per BTS specification. c) The deviation from the true inside diameter of the completed ring shall not exceed ± 15mm. SURFACE DISPLACEMENT MONITORING Preliminary assessments have been made of the settlement resulting from the construction of the Works and are shown on drawings 6LYG-A1-02131 to 6LYG- A1-02141. These are provided for information only, with no warranty given by the Employer. to its accuracy or completeness, and the Contractor shall provide his own assessment of the settlement as required under Section 4 Schedule 2 of the Works Information. The Contractor shall carry out a detailed settlement assessment based on the proposed methods of working, proposed alignment, ground conditions and ground support details and submit detailed supporting calculations and a full set of revised settlement contour drawings for the Project Manager’s acceptance. The Contractor shall monitor the effects of tunnel construction, ground treatment or dewatering at the surface, including all ground movements and the effects on all structures, including the Works. For the purposes of this clause structures include buildings at Abbey Mills Pumping Station and Beckton STW, utility services including the Northern Outfall Sewer(See Clause PT242.a), railway tracks, bridges, railway furniture and all other structures identified as at risk of settlement damage by the construction of the Works. The Contractor shall submit to the Project Manager, within 60 days of award of Contract, a Method Statement detailing his proposal for the monitoring and control of surface displacement in accordance with the contract. The Contractor shall incorporate, where applicable, the requirements in the clauses below for agreement by the Project Manager and interested third parties where appropriate. The Employer shall serve notice where required by statute and provide letters detailing the Works to third parties which may be affected by the construction but do not require formal issue of Statutory notices. Monitoring shall be referenced to stable survey stations located outside the zone of influence of the works and not subject to ground movement. Such benchmarks and co-ordinated stations shall be established and agreed with the Project Manager before any ground is excavated and before any ground treatment or dewatering takes place. They shall be checked at intervals during the duration of the works. Surface displacement monitoring for the construction of the bored tunnel shall be carried out to ensure that the maximum allowable surface (vertical) settlement is Thames Water Utilities Limited August 2008 Page 31 of 38
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080731 6LYG A1 Particular Tunnelling Specification ... - SCATnow

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