Construction Technology of Tunnel Waterproof Membrane Made of Polyvinyl Chloride (PVC)
[Summary description] Construction tools: self-propelled hot-melt welding machine, welding torch, impact drill
Construction tools:
Self-propelled hot melt welding machine, welding torch, impact drill
Preparation:
1. First check whether the tunnel profile and sprayed concrete surface meet the design requirements. If there is over-excavation or under-excavation, it should be repaired. The ratio of the pit depth to the span of the rock drilling base should not be greater than 1/6, and sharp objects such as over-convex rocks and bolt heads should be removed.
2. The power supply and voltage of the construction site should be stable, and the circuit and electrical connections should be firm without leakage. Construction personnel should be familiar with the knowledge of safe use of electricity and how to use electrical appliances and clarify the construction quality standards.
3. Before construction, take a small amount of waterproof coiled material for trial welding, debug the welding machine, and adjust the temperature of the welding machine to the optimum temperature.
Laying waterproof membrane:
1. Mark the center line along the longitudinal direction of the tunnel on the arch, and determine the position of the hanging point on the base surface. The vertical hanging point spacing is the same as that of the waterproof coil ring, and the circumferential hanging point spacing: 85cm for the arch and 90cm for the side wall. Reserve a low sag of the waterproof board in the arch to ensure the thickness of the poured concrete and prevent voids in the arch.
2. Use an impact drill to drill holes at the marked hanging points and pre-embed plastic expansion tubes and wood screws.
3. Gradually unfold the waterproof board from the center of the arch to both sides along the ring direction, fix the suspension rings in sequence, fasten the wood screws, fix other suspension rings to both sides in sequence, and complete the suspension.
4. Lay and hang the adjacent waterproof boards according to the above method, and reserve 10-13cm overlapping edges and the overlapping surfaces must be smooth.
5. During construction welding, use a self-propelled hot-melt welding machine to carry out double-seam welding from one side along the ring direction. The temperature of the hot-melt welding machine can be controlled at the temperature during commissioning. After each weld is welded, an inflation inspection must be carried out. When the pressure reaches 0.1-0.2Mpa, keep it for 1min, and check whether the waterproof board is welded firmly. If the weld seam and the waterproof membrane are not damaged, it indicates that the welding quality is good.
6. The overlapping width of the waterproof membrane is 8-10cm, and the width of each weld is 1cm. The double seam welding should be welded firmly at the same time, and there should be no virtual welding, missing welding, or burning. If there is a burn-through, repair it with a waterproof membrane and welding torch. The size of the repaired waterproof board should be determined by referring to the width of the lap joint greater than 8-10cm.
Precautions:
When laying steel mesh, supporting arches, and formwork, attention should be paid to the protection of waterproof boards.
