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    SECTION 02726

    TUNNELING

   PART 1 GENERAL

   1.1 SUMMARY

   This item shall include the furnishing and installation of tunnels with steel liner plates and carrier pipe as indicated on the drawings and specified herein.

   1.2 UNIT PRICES

   Measurement for payment shall be by the linear foot as named in the Contract Documents. The quantity to be paid shall be the actual number of linear feet of tunnel measured from face of tunnel to face of tunnel. The carrier pipe to be installed inside the tunnel shall be included in the unit price for tunnel at all tunnel locations, and no separate payment will be made therefore. The tunnel costs shall include the liner plates installed in place complete with all appurtenances including grouting, bulkheads, sandfill, unclassified excavation, carrier pipe, strapping, vent pipe assemblies, and all other items required to complete the tunnel.

   PART 2 PRODUCTS

   2.1 TUNNEL LINER PLATE

   The tunnel liner shall be constructed of galvanized, four flanged or two flanged steel plates bolted together unless the Engineer approves the use of an alternate material. Reference the Contract Drawings or chart in these specifications for plate gauge size. The space between the liner and the edge of excavation shall be filled with grout placed under pressure.

   The steel lining shall consist of plates, not to exceed 18 inches wide. Each circumferential ring shall be composed of the number and length of plates to complete the required diameter. Liner plate shall be fabricated from structural quality, not-rolled carbon-steel sheets or plates conforming to ASTM Specification A569. The flat plate (before cold forming) shall conform to the following minimum mechanical properties. The Contractor shall submit details of the lining for approval.

    Tensile Strength 42,000 psi

    Yield Strength 28,000 psi

   All plates shall be punched for bolting on both longitudinal and circumferential seams and shall be so fabricated as to permit complete erection from the inside of the tunnel. The longitudinal seam shall be of the lap type with offset equal to gage of metal for full width of plates including flanges, and shall have staggered bolt construction, so fabricated as to allow the cross-section of the plate to be continuous through the seam. All plates shall be of uniform fabrication and those intended for one size tunnel shall be interchangeable.

   The material used for the construction of these plates shall be new and unused and suitable for the purpose intended. Workmanship shall be first-class in every respect.

   After the plates are formed to shape and after all holes are punched, the plates shall be galvanized on all surfaces by the hot-dip process. A coating of prime western spelter, or equal, shall be applied at the rate of not less than 2 ounces per square foot of double exposed surface. If the average spelter coating as determined from the required samples is less than the amount specified above, or if any one specimen shows a deficiency of 0.2 ounce, the lot shall be rejected. Spelter coating shall be of first-class commercial quality free from injurious defects such as blisters, flux and uncoated spots.

   All nuts and bolts shall be galvanized.

    Bolts and nuts used with lapped seams shall be no less than 5/8 inch in diameter. The bolts shall conform to the specifications of ASTM A 449 for plate thickness equal to or greater than 0.209 inch, and A 307 for plate thickness less than 0.209 inch. The nut shall conform to ASTM A 307, Grade A.

    Bolts and nuts used with 4-flanged plates shall be no less than 1/2 inch in diameter for plate thicknesses to and including 0.179 inch, and no less than 5/8 inch in diameter for plates of greater thickness. The bolts and nuts shall be quick acting coarse thread and shall conform to ASTM A 307, Grade A.

   Plates shall be fabricated with grout holes to facilitate grouting above and around the tunnel liner. These grout openings shall be 2" I.P.T. half couplings welded into a hole in the center corrugation of a plate and a galvanized C.I. plug shall be provided for each opening to permit tight closure after grout is pumped. All rings are to be provided with grout holes so that the spacing of holes will be on a maximum spacing of 18" centers at the top of the tunnel and at the top quarter points, each course staggered with the holes at the top.

   Field coating material shall be asphalt mastic, Trumbull 5X, or approved equal, and shall be applied with hydraulic spray equipment using a minimum of 2,400 pounds pressure at the nozzle tip. The material shall be supplied at spraying consistency and shall be applied both to the outside and inside of the liner plates. In lieu of spraying asphalt mastic, plates may be hot-dipped in asphalt mastic to produce a similar coating.

   Alternative liner design may be submitted, but Contractor's bid shall be based upon galvanized, four flanged steel liner plates.

    J. Liner plate thickness shall be as tabulated below:

    Minimum

    Gage Flange

    8 (0.1644) 4

    K. Nominal plate dimensions shall provide the sectional properties shown in Article 1.13.9 of the AASHTO Standard Specifications for Highway Bridges. Thickness tolerances shall conform to Paragraph 14 of AASHTO M 167.

    Liner plate design shall be in accordance with the design criteria for joint strength, stiffness, buckling and deflection as defined in the AASHTO Standard Specifications for Highway Bridges, latest revision.

    L. The tunnel strength shall be designed for AREA railroad E80 loading at railroad locations at the depth of cover on the contract drawings. Design notes shall be submitted to the Engineer with shop drawings for review.

    The inside and outside of the plates shall be given a bituminous coating meeting the American Railway Engineering Insulation (AREA) Specification for Coated Corrugated Metal Pipe and Arches, Chaper 1, Part 4.

   2.2 GROUT

   The grout shall consist of Portland cement, water, sand and 2% approved additive (Bentonite, Septamine Seaex, Hydrocide liquid, etc.). One part Portland cement with additive shall be combined to four parts clean sand and sufficient water added to provide a grout having the consistency of thick cream when well mixed.

   2.3 CARRIER PIPE

   The carrier pipe shall be as indicated on the drawings.

   PART 3 EXECUTION

   3.1 EXCAVATION

   Excavation shall be unclassified and no distinction shall be made between rock and other materials excavated. The cost of excavation shall be merged in the unit price per linear foot of the tunnel. Blasting for the tunnel is acceptable only with explicit written approval from The Tennessee Department of Transportation, CSX Railroad or other jurisdictional entity.

   Construction of the tunnel shall be carried on in such a manner that settlement of the ground surface above the tunnel shall be held to an absolute minimum. Where ground conditions are unstable, poling plates or poling boards shall be used to prevent caving of material above the tunnel before the liner plates can be installed. Steel liner plates shall be installed as soon after the excavation is removed as possible and excavation shall not be removed more than 24" ahead of the installed liner plates. Excavation shall be carried on in such a manner that voids behind the liner plates will be held to a minimum. However, should any boulders larger than 1' in diameter be encountered, they shall be removed so that none are closer than 6" to the outer face of the liner plate. Where boulders are excavated below the invert of tunnel liner plates, the holes shall be backfilled with crushed stone (#57 or 67).

   3.2 LINER PLATE

   When installing liner plate by the tunneling method, the excavation shall be performed in such a manner that voids between the undisturbed earth and the liner plate shall be maintained at a minimum. Any void occurring shall be filled with a Portland cement and sand grout pumped under pressure through grouting openings in the liner plate.

   The minimum provision for grouting openings shall be one opening in a top plate of the tunnel at locations not to exceed 54" apart. Additional plates with grouting openings are to be installed at the top quarter points on each side between the top openings. The opening shall be staggered, but shall not exceed 54" in any one line. Grout vent pipes will be required at a minimum of one per monolithic pour.

   3.3 GROUTING

   A pump shall be provided for placing the grout which shall be capable of exerting sufficient pressure to assure the filling of all voids between the liner plate and the undisturbed ground. Minimum acceptable pressure to fill voids will be five pounds per square inch.

   Pumping of grout shall be done (1) at the completion of the installation of approximately each 9' of liner plate, (2) at more frequent intervals than 9' if conditions indicate the necessity, and (3) at the end of a work shift or for stopping of work for any reason.

   3.4 CARRIER PIPE

   The carrier pipe shall be pulled into place on a concrete invert within the tunnel with wooden skids strapped or banded to it in order to protect the pipe and the liner plate flanges. The carrier pipe shall be adequately strapped to the tunnel flanges behind each bell with 2" x 1/4" stainless steel straps bolted to the liner plate flanges with 1/2" stainless steel bolts and nuts. Bulkheads will be placed at each end of the tunnel; thickness and placement of which shall be subject to the Engineer's approval.

   Sand or pea gravel shall be blown into the tunnel to fill the void between the inside wall of the tunnel and outside edge of the carrier pipe to a depth of not less than 2/3 of the outside diameter of the carrier pipe. Care shall be exercised to not completely fill the tunnel to prevent the external loads from being transmitted to the carrier pipe.

    END OF SECTION