Analysis of the main points of wet spraying technology
The wet spraying operation technology needs to be fed in the order of sand-crushed stone-cement-water, etc. The mixing process can be fully automatic metering forced mixer, construction and ingredients must be operated strictly in accordance with the mix ratio, and a compound pump must be added Come to stir, the stirring time is more than 2 minutes, but not more than 4 minutes, so as to ensure the quality of the concrete.
Wet sprayed concrete should be sprayed from bottom to top in an S shape from the lowest point of the tunnel. This can prevent the rebound material from contaminating the rock surface and affect the quality of sprayed concrete. The last shot can be performed after the last concrete set. If the delay time is too long, it can be sprayed after cleaning with water, sprayed to the position of the centerline of the vault, then closed, and sprayed after completion.
In the process of spraying, it is necessary to be able to control the wind pressure well. If the wind pressure is too small, the spraying capacity will be weakened, which cannot meet the requirements of the compactness of sprayed concrete. Not even meet the design requirements and specifications. If the wind pressure is too large, the rock surface of the concrete will be sprayed, which will be blown away by the subsequent strong impact force, which can increase the rebound ability of the aggregate, which directly results in an increase in rebound. In the process of spraying without steel mesh, the spray head should be able to make a 90-degree angle with the vertical rock surface, and it should be biased to the part that is just sprayed, and maintain a distance of about 2 meters to ensure that the concrete is dense. . After the wet spraying, spray with water for one hour after the final setting to keep the spray surface moist and maintain good quality.
Precautions for construction
Before spraying, the cement slurry needs to be washed with water. It is necessary to strictly control the pressure of the working machine within the range of 0.15-0.2. The water-cement ratio is controlled, and the freshly sprayed concrete surface has a faint gloss. Treat the water seepage section. When the amount of water is not large, you can purge. If the amount of water is large, reduce the amount of water spray. After the water is stopped, use normal accelerator to spray the concrete. In the wet spraying process, pay attention to the condition of the nozzle at all times, and once it is blocked, take measures to solve it immediately. After the concrete has set, the strength of the sprayed concrete needs to be checked. When performing the strength check, it is necessary to take a cutting drill core to take samples to approximate the true condition of the sprayed concrete. If the concrete cannot meet the design requirements, timely measures must be taken .
Through the construction application of wet shotcrete technology in tunnels. The application of wet sprayed concrete technology in the tunnel not only makes the construction of the tunnel more convenient, fast and safe, it also makes this technology accumulate rich experience for us in the process, but also improves economic and social benefits. The development of this technology is a heavy stroke.
