Shotcrete construction technology is an important part of the initial support of tunnel excavation. It uses compressed air and spraying equipment to spray ready-mixed concrete on the supporting surface, and the concrete quickly condenses and hardens, forming the tunnel enclosure structure. The level of shotcrete construction technology directly affects the quality of tunnel support and construction safety.
Construction quality problems of shotcrete in tunnel engineering;
1, concrete cracking.
2, concrete peeling.
3. Concrete layering.
4. Insufficient concrete thickness.
Quality control measures of shotcrete construction in tunnel engineering;
1, site testers and site technicians put raw materials into the site, all materials are tested for various indicators, and unqualified materials are not allowed to enter the site. The fineness modulus of medium and coarse sand is greater than 2.5, and the silt content is less than 3%.
2, the use of high technical level of spray workers, spray workers fixed personnel, shall not be arbitrarily replaced. Operators and on-site technicians should follow the shift and make construction records.
3, check the injection equipment and condition, pressure gauge can be used normally, to ensure that the air pipe does not leak, water pipe does not leak.
4. Spraying concrete means that the sprayed material is transported by high-pressure pipeline with the help of spraying machinery, and is sprayed on the spraying surface at high speed with compressed air as the power, so the spraying surface bears great pressure.
5. Cement hydration but water evaporation loss, the specific surface area of cement gel produced in the process of cement hydration is large, and a large amount of water becomes surface adsorbed water. So as to prevent water from entering the concrete, the water for hydration reaction is less and less, and when the water-cement ratio is less than 0.5, the self-drying phenomenon occurs, which makes the hydration of cement unable to continue and directly affects the strength of concrete. 2 hours after the final setting of sprayed concrete, the curing will begin. Spray water three times a day during the curing period, and the curing period is 14 days.
Tunnel engineering construction should integrate theory with practice, and each working procedure should be step by step, check the quality layer by layer, eliminate hidden dangers, ensure smooth construction and increase benefits. The progress of tunnel construction technology has laid a foundation for the development of long tunnels and the development and utilization of underground space. At the same time, large-scale underground engineering construction will also put forward new and higher requirements for tunnel construction technology.
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