With the continuous improvement of wet spray equipment and technology and the continuous improvement of construction requirements, wet spray technology of wet shotcrete machine has become the mainstream of the development of spray technology in various countries around the world.
Wet shotcrete machine concrete spray technology has a history of nearly 100 years in the world. It started in Austria, and Switzerland, Germany, France, Sweden, the United States, the United Kingdom, Canada, and Japan have successively adopted this technology. Tunnel concrete spraying is widely used in tunnel engineering with simple technology, timely support and lower cost. In the composite lining structure system of the tunnel, sprayed concrete can seal the rock surface on the one hand, and effectively prevent the collapse of the surrounding rock on the arch top after the stress is released, and the leakage of water and gas gas can be prevented to ensure the construction safety. Form a concrete supporting structure with the surrounding rock and actively make the surrounding rock of the tunnel become a part of the ring-shaped bearing structure, which can bear important loads during the design life cycle of the tunnel. Sprayed concrete can be divided into dry spray (referred to as dry spray) and wet spray (referred to as wet spray) from the construction process. Therefore, its corresponding equipment is also divided into dry spray machines and wet spray machines. With the continuous improvement of wet spray equipment and technology and the continuous improvement of construction requirements, wet spray technology of wet shotcrete machine has become the mainstream of the development of spray technology in various countries around the world.
Compared with the dry spraying process, the wet shotcrete machine wet spraying technology has the following four obvious advantages: First, it can greatly reduce the concentration of construction dust and eliminate the harm to workers' health. The second is high productivity. The third is low rebound. When dry sprayed, the concrete rebound can reach 15% ~ 50%. With wet spray technology, the rebound rate can be reduced to less than 10%. Fourth, the construction quality is high. In wet spraying, because the water-cement ratio is easy to control, the homogeneity of concrete can be greatly improved, and the quality of dry spraying depends to a large extent on the skill and responsibility of the operator.
