[Fujian] Tunnel secondary lining construction programme
The construction preparation has gone through the tunnel excavation and initial support in the early stage. The convergence and settlement of the arch crown, arch foot and the surrounding of the tunnel have become stable. The construction conditions for secondary lining have been met, and the mechanical equipment for secondary lining construction has been in place. 2、 Construction scheme 2.1 Waterproof and drainage construction 2.1.1 Waterproof layer construction Tunnel special waterproof coiled material shall be set between shotcrete and formwork concrete. Before laying waterproof layer, buffer layer shall be laid on the surface of shotcrete. The buffer layer shall be 300g/m2 geotextile, and then special waterproof coiled material for tunnel shall be laid. The laying method is as follows: foundation surface inspection: use the working platform to cut off the exposed anchor bolts, steel bar heads and other iron parts of the support, and use mortar to plaster them into a circular surface to prevent them from puncturing the waterproof board. Laying of geotextile lining layer and setting of groove gasket: lay the geotextile lining layer on the surface of sprayed concrete for initial support, and set geotextile fixing strip and groove gasket at the same time. The two shall be fastened with nails. The geotextile lining layer, geotextile fixing strip and groove gasket shall be firmly fixed on the sprayed concrete through nails. Metal gaskets shall be added between the nails and groove gaskets, The nail spacing shall be set according to the design requirements. Waterproof coiled material laying: lift the waterproof coiled material to the working platform, weld the waterproof coiled material symmetrically from top to bottom on the fixed washer, and bond it firmly. Schematic diagram: laying quality inspection: after the construction of waterproof layer is completed, the construction quality shall be inspected, and the construction of the next process can be carried out only after the self inspection is qualified and the supervision engineer approves. If quality problems are found, repair welding shall be carried out to make it reach the acceptance standard. Key points of waterproof layer laying operation: under the premise of meeting the fixed spacing, the fixed points shall be fixed at the concave part of the shotcrete surface as far as possible to make the waterproof layer closely stick to the shotcrete surface as far as possible. The length of the waterproof layer between the fixed points shall be left with a certain margin depending on the flatness of the construction support surface. The principle of "loosening rather than tightening" shall be followed to prevent the lining from being squeezed out during formwork construction. The laying length of the waterproof layer in each cycle is 2.0m longer than that of the corresponding lining section, so as to facilitate the overlapping between cycles, and to stagger the waterproof roll joint and the lining work joint by 2.0m, so as to ensure the waterproof effect. After the waterproof layer is laid, the lining shall be carried out as soon as possible to ensure that the waterproof layer is not damaged and the waterproof effect is guaranteed. 2.1.2 The settlement joints of the tunnel are waterproof with water swelling rubber waterstop. Drill a φ 12mm hole every 0.5m along the axis of the secondary lining on the baffle plate, penetrate a φ 10 steel bar clamp, and clamp one half of the waterstop clamped in the baffle plate, and fold the other half into a 90 ° angle, and cling to the baffle plate. After the concrete is poured and solidified, the baffle plate shall be removed, the other end of the steel bar clamp shall be bent to clamp the exposed part of the waterstop tightly, and the concrete shall be poured. In order to fix the steel bar clamp, the positioning steel bar shall be set in the space to be poured concrete, and the positioning steel bar shall be set every 50cm along the circumferential direction. The steel bar clamp and the positioning steel bar shall be bound with iron wire. After the completion of concrete support, the space between the deformation joints shall be filled with joint filler and sealed with polysulfide sealant within 3cm of the inner edge.